ML20093K469
| ML20093K469 | |
| Person / Time | |
|---|---|
| Issue date: | 03/04/2020 |
| From: | Michael Snodderly Advisory Committee on Reactor Safeguards |
| To: | |
| Snodderly, M, ACRS | |
| References | |
| Download: ML20093K469 (252) | |
Text
Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Reactor Safeguards NuScale Advisory Committee Docket Number: (n/a)
Location: Rockville, Maryland Date: Wednesday, March 4, 2020 Work Order No.: NRC-0837 Pages 1-197 NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers 1323 Rhode Island Avenue, N.W.
Washington, D.C. 20005 (202) 234-4433
1 1
2 3
4 DISCLAIMER 5
6 7 UNITED STATES NUCLEAR REGULATORY COMMISSIONS 8 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 9
10 11 The contents of this transcript of the 12 proceeding of the United States Nuclear Regulatory 13 Commission Advisory Committee on Reactor Safeguards, 14 as reported herein, is a record of the discussions 15 recorded at the meeting.
16 17 This transcript has not been reviewed, 18 corrected, and edited, and it may contain 19 inaccuracies.
20 21 22 23 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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1 1 UNITED STATES OF AMERICA 2 NUCLEAR REGULATORY COMMISSION 3 + + + + +
4 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 5 (ACRS) 6 + + + + +
7 NuSCALE SUBCOMMITTEE 8 + + + + +
9 WEDNESDAY 10 MARCH 4, 2020 11 + + + + +
12 ROCKVILLE, MARYLAND 13 + + + + +
14 The Subcommittee met at the Nuclear 15 Regulatory Commission, Two White Flint North, Room 16 T2D10, 11545 Rockville Pike, at 8:30 a.m., Walter L.
17 Kirchner, Chair, presiding.
18 19 COMMITTEE MEMBERS:
20 WALTER L. KIRCHNER, Chair 21 RONALD G. BALLINGER, Member 22 DENNIS BLEY, Member 23 CHARLES H. BROWN, JR., Member 24 VESNA B. DIMITRIJEVIC, Member 25 JOSE MARCH-LEUBA, Member NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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2 1 DAVID PETTI, Member 2 JOY L. REMPE, Member 3 PETER RICCARDELLA, Member 4 MATTHEW W. SUNSERI, Member 5
6 ACRS CONSULTANTS:
7 MICHAEL L. CORRADINI 8 STEPHEN SCHULTZ 9
10 DESIGNATED FEDERAL OFFICIAL:
11 MIKE SNODDERLY 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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3 1 P R O C E E D I N G S 2 (8:30 a.m.)
3 CHAIR KIRCHNER: We're back in session.
4 This is day three of our NuScale Subcommittee meeting.
5 This is an open session. And we have a little change 6 to the schedule here to kick things off.
7 So, Joe, would you just introduce yourself 8 for the record, and then we're going to go over some 9 information related to instrumentation, and then we'll 10 pick up the schedule with NuScale.
11 So go ahead, Joe.
12 MR. ASHCRAFT: My name is Joe Ashcraft.
13 I'm in the EICA branch, I&C branch, technical reviewer 14 for NuScale.
15 So we had some questions as far as the 16 sensors' classification and where it's shown. And so 17 I'm going to kind of go through that briefly. Charlie 18 had some questions, but I think they're more in the 19 proprietary nature, so we might have to go through 20 closed session on some of his questions.
21 But generally, I'm going to speak first to 22 their sensor report, which is rev two, and that's 23 proprietary. But in that, there's a table 7.1 that 24 shows the level sensors and their classifications and 25 what they are, the ranges, et cetera, and the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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4 1 quantity.
2 MEMBER MARCH-LEUBA: Sorry, this is not 3 proprietary, the one we have on the table?
4 CHAIR KIRCHNER: It has no markings, 5 proprietary.
6 MR. ASHCRAFT: No, what I gave you is just 7 a ---
8 (Simultaneous speaking.)
9 MR. ASHCRAFT: Right.
10 CHAIR KIRCHNER: Okay. Thank you.
11 MR. ASHCRAFT: And this table actually has 12 no markings in their sensor report, but I decided not 13 to give it to you. But anyway, so that table really 14 lays quantity for the pressurizer level and RPV riser 15 level. It shows that it's one sensor, and there are 16 four of them. And it shows the zero to 100 percent, 17 and the pressurizer level span is 130, which is the 18 top part of the riser level span is 554, which would 19 go down lower.
20 And then, just kind of let you know what's 21 going on with the sensor technical report, it's laid 22 out in four phases. So phase one, which is what we 23 reviewed in our SE, or looked to, is really where they 24 -- NuScale was looking for technology selection. So 25 they're confident with what they've selected.
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5 1 Now, they've got phase two, which is proof 2 of concept. And it says in the report that they 3 should have finished at the end of 2019. But I don't 4 know the status of that. But then phase three is 5 where they go into product development. And phase 6 four is the environmental qualification. So, it's 7 similar to all the -- like the ECCS valves, there's a 8 lot of stuff that's going to take place down the road, 9 and we just don't have those answers.
10 So, now, as far as the DCA, so chapter 11 seven, what we do for instrumentation, we look to see 12 that they're qualified for what they're described.
13 But we point to chapter three because that's where the 14 qualifications of the sensors and all components are 15 done. In Section 7.1.1.1, it describes -- this is 16 where they're kind of going through the design-basis 17 for their sensors, but it's pointing to Section 3.2 18 for classification.
19 MEMBER BLEY: I lost the thread, are you 20 -- chapter 7 of the DCA?
22 MEMBER BLEY: All right, so sensor report.
23 Okay.
24 MR. ASHCRAFT: Right. So, I'll put the 25 sensor report -- we may come back to it, but like I NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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6 1 said, it's proprietary in nature. So questions, we 2 may have to close the session to get to.
3 So now I'm in the DCA, and I think that 4 goes more to Joy's concern of where it shows what's 5 going on as far as the sensors. Now, this all came 6 about -- they had that I&C design mod where they took 7 out the RPV level as part of the initiation. But that 8 sensor, which is pressurizer level and RPV riser level 9 were classified A1, and it remains classified A1.
10 And the signal goes to the MPS, and that's 11 where they do the scaling of that. So they take the 12 top part of the analog and say, well, that's 13 pressurizer level in the bottom part. And we don't 14 have that information as far for scaling.
15 So it goes to the MPS, and then after 16 that, as with all their safety-related instruments, 17 the signals go out through isolation and end up in the 18 safety display board for PAM variables, et cetera.
19 Now, that's -- it's called safety display, 20 but it's non-safety, and it's primarily because they 21 don't have any PAM-A variables which would have 22 required, you know, safety-related for the PAM-A 23 variables. But they don't have that, so all they have 24 are B, C, D, and E, or whatever.
25 So that signal goes out of the MPS through NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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7 1 isolation to the safety display. And I think that was 2 a question Joy had asked about. And that's done 3 throughout the industry.
4 DR. CORRADINI: That's what I guess I want 5 to understand. This is not uncommon?
6 MR. ASHCRAFT: No, no.
7 DR. CORRADINI: Okay, fine.
8 MR. ASHCRAFT: I mean, the biggest concern 9 or issue or whatever is these are new-type sensors --
10 or they're not new technology. But they haven't been 11 used in this -- you know, this type of scenario. So, 12 but --
13 MEMBER REMPE: Could I?
14 MR. ASHCRAFT: Sure.
15 MEMBER REMPE: Are you done, Mike, with 16 your question?
17 DR. CORRADINI: I just want to make sure 18 that it was clear that this is -- had been done and is 19 commonly done in industry now.
20 MEMBER REMPE: Okay.
21 DR. CORRADINI: The nuclear industry now.
22 MEMBER REMPE: So just to make sure we're 23 all on the same track because there has been some 24 slight information that maybe wasn't quite accurate.
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8 1 for water level in the containment as well as the 2 pressure riser, which is also the same sensors, just 3 a bit longer for the RPV.
4 MR. ASHCRAFT: Right. And that's on one 5 of these tables.
6 MEMBER REMPE: Yeah, but the function is 7 non-safety related for the RPV and the pressurizer, 8 correct?
9 MR. ASHCRAFT: Right. And that shows up 10 on table of the DCA --
11 MEMBER REMPE: 7.1-9.
12 MR. ASHCRAFT: Right. So what that says 13 -- so the signal --
14 MEMBER REMPE: I get what you're saying.
15 I just am summarizing what you said, okay?
16 MR. ASHCRAFT: Okay.
17 MEMBER REMPE: But now, if during this 18 meeting, Charlie said, hey, the rad levels aren't that 19 high in the -- and the applicant didn't tell me to be 20 clear. Earlier this week, I heard you say that --
21 MEMBER BROWN: Radiation levels aren't 22 high?
23 MEMBER REMPE: I thought though you said 24 that earlier this week.
25 MEMBER BROWN: I don't remember --
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9 1 (Simultaneous speaking.)
2 MEMBER BROWN: I don't think my brain was 3 that fried.
4 MEMBER REMPE: I thought I heard you say 5 that.
6 MEMBER BROWN: I mean, I was awake the 7 whole time.
8 MEMBER REMPE: Okay, well, anyway, in the 9 topical report about the sensors, it acknowledges that 10 the rad levels are higher than what's typically seen 11 in a conventional light-water reactor. That's you're 12 understanding too?
13 MR. ASHCRAFT: Yes, but keep in mind --
14 so, you've got your radar guide tube, which is in the 15 area --
16 MEMBER REMPE: Right.
17 MR. ASHCRAFT: -- and they place the 18 sensors because they're mostly -- they're digital and 19 stuff, they've got to be outside to be able to work.
20 MEMBER REMPE: Absolutely.
21 But, okay, so let's talk about the 22 radar-based sensor, which has changed over time. Even 23 the whole sensor has changed over time. But you have 24 in chapter three, a cumulative rad level, and you have 25 peak temperatures in there. But you do acknowledge NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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10 1 that, hey, thermal expansion might be an issue with 2 the vessel versus the radar-based waveguide.
3 And what I'm wondering is, are the 4 properties of this radar-based waveguide, the ability 5 to have a signal shot through it and come back, isn't 6 that also a function of the properties of the 7 material, which vary with temperature?
8 MR. ASHCRAFT: That is correct. But I 9 mean, that's --
10 MEMBER REMPE: Okay. So is it really 11 temperature, or is it temperature gradient it's 12 exposed to? And is it radiation levels or radiation 13 -- flux gradient in the core?
14 MR. ASHCRAFT: Well, we had thought to see 15 if NuScale can answer that. So that question, I mean, 16 that tube is in the pressurizer levels going down. So 17 it's going to be exposed to whatever, temperature 18 gradient and --
19 MEMBER REMPE: Right. And the speed of 20 sound. Okay, but my brain isn't maybe calibrated to 21 what this particular sensor is. But with an 22 ultrasonic thermometer, you've got to worry about the 23 speed of sound in the material, and that varies with 24 temperature. So the calibration of it isn't just 25 going to be dependent on peak temperature and peak --
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11 1 and cumulative rad levels, it's the actual what it 2 sees. And within a reactor that's going through a 3 transient, that could change with time.
4 MR. ASHCRAFT: So they've selected their 5 centers that they believe it's going to work for their 6 design, and they're doing -- and maybe they completed 7 their proof of concept at this point. They were 8 supposed to be completed at the end of this last year.
9 But that's where they will just, you know, figure that 10 out.
11 MEMBER REMPE: Okay, but you are 12 regulating -- if you don't mind, let me finish, okay?
13 PARTICIPANT: All right.
14 MEMBER REMPE: Okay, but you have in 15 chapter three, some requirements that they have to 16 meet, and you've listed cumulative rad levels, and 17 you've listed peak temperature. What about 18 temperature gradient and flux gradient? Because it 19 may not -- why aren't those things listed in table 20 three -- chapter three of that table?
21 MR. ASHCRAFT: Well, those are not typical 22 qualification aspects. I mean, so when they designed 23 -- just like any other transmitter, whatever, when 24 they go to do their setpoint calc, they will account 25 for any of those types of issues.
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12 1 MEMBER REMPE: Okay, so it's not just what 2 it sees -- okay, those conditions will change. And 3 what I'm trying to get to is, in the sensor 4 development stuff I did in the past, we had not just 5 considered normal operation. We had to consider 6 things that might change during the accident. And so 7 you need to think about the whole situation and all I 8 see your plots of peak temperature and things like 9 that they -- that are included there.
10 And I just am wondering, how do we 11 document? You need to think about calibrating not 12 just for the worst situation but the time-dependent 13 situation. Because, again, if it's changing along its 14 length, it may be a lot more difficult to have a 15 sensor. And so it needs to be carefully looked at by 16 the staff when they come in.
17 MR. ASHCRAFT: Well, I will say for anyone 18 that's seen the scaling for steam generator levels of 19 existing plants, it's, you know, you've got steam, 20 you've got boiling -- you know, you go through the 21 gamut, you've got expansion. So all that will be 22 accounted for in their setpoint count.
23 And you'll see any additional -- I mean, 24 right now, they have what they believe they're going 25 to meet. So, you know, they've defined their NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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13 1 setpoint. And now, they've got to get the 2 instrumentation to fulfill that. And any of those 3 type of process PMA effects or whatever will be 4 accounted for. And it might have to adjust the 5 setpoint, or it may not work, but --
6 MEMBER REMPE: It may need some sort of 7 time-dependent calibration --
8 CHAIR KIRCHNER: Joy, their piece of 9 equipment in that, say, a safety-related sensor going 10 into the module protection system is going to have to 11 be likewise qualified. This is not unique.
12 MEMBER REMPE: This radar-based --
13 CHAIR KIRCHNER: This might be a unique 14 detector, and they're going to have to develop it, and 15 then they're going to have to qualify. But that same 16 range has to be done for every single instrument that 17 feeds into the MPS. So, this is no different.
18 MEMBER REMPE: I guess when we've done 19 instrumentation for the ATR, we had to think about 20 something that is a bit different. If you have a 21 standard thermocouple, you don't have to worry about 22 some of these things. If you have an irradiation --
23 I didn't see anywhere in the discussion on the sensor 24 about any sort of concerns with radiation effects over 25 time with the sensor.
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14 1 It's just this is a little bit different 2 than a DP cell or an RTD, or some of the other things 3 people are --
4 CHAIR KIRCHNER: Every other instrument 5 has to survive the environment and be qualified for 6 that.
7 MR. ASHCRAFT: Let's --
8 CHAIR KIRCHNER: And they're going to see 9 radiation over time. All the other instruments as 10 well.
11 MR. ASHCRAFT: That's part of the phase 12 four qualification.
13 CHAIR KIRCHNER: Yeah, that's part of the 14 EQ.
15 MEMBER REMPE: I didn't see the flux 16 gradient, just the temperature gradient discussed.
17 MR. ASHCRAFT: Well, I don't know that 18 that's part of the EQ qualification.
19 MEMBER REMPE: And, so, how will -- if 20 it's not part of the qualification, how will they have 21 confidence that the sensor is going to be accurate 22 during a transient?
23 MR. ASHCRAFT: Well, so our review, we 24 looked at the ranges, et cetera, to see that they met 25 the GDCs. The rest of it, once they purchase it -- we NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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15 1 don't know what they purchase, we're not even sure 2 what they're looking at, because that's still part of 3 this.
4 But that's the case of any design. I 5 mean, most previous designs, we kind of knew what the 6 instrumentation was, so it wasn't that big a concern.
7 These are new, but still, that's NuScale's issue of 8 putting the equipment to monitor their design.
9 MEMBER REMPE: Okay.
10 MR. ASHCRAFT: Again, if you had an idea 11 of what it was, I would agree with you, and it would 12 be part of the normal concerns, but they brought in a 13 widget that's a little different, and I didn't see any 14 discussion in the report or in the staffs. Because, 15 again, the staff's been kind of thrown something that 16 keeps changing with time, I get it.
17 But some of these widgets, it may bring in 18 new issues that haven't been considered.
19 DR. CORRADINI: But, I guess, I'm not 20 understanding your concern. Is your concern that it 21 is new? Or you're concerned that they have to make it 22 in this current environment, and it's new?
23 MEMBER REMPE: It's because that it's new 24 that it brings in some new issues that I didn't see 25 identified in the topical report or in the staff's NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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16 1 qualifications. And, of course --
2 DR. CORRADINI: So, it's more a matter of 3 documentation from your standpoint?
4 MEMBER REMPE: Yeah. And again, when you 5 bring in a new widget, then you need to be cognizant 6 of it. And so, what's going to happen is -- I would 7 think, again, if they were not a -- which I'm sure 8 they're very concerned and whatever applicant.
9 But an applicant could say, hey, I'm at 10 the peak temperature, I met the peak exposure limits, 11 and they don't even think about is the flux going to 12 be tailored similar to what the flux is in the core?
13 Is the temperature gradient going to be similar to 14 what the temperature gradient in the core is during 15 normal operation as well as accident conditions for 16 DBAs?
17 That's what I am concerned is that the 18 widget's a bit different, and the exposure -- or the 19 qualifications that are listed, which are typical for 20 sensors haven't been thought about enough because this 21 widget's different.
22 CHAIR KIRCHNER: You're presupposing you 23 know the design, and then, you're imposing some 24 additional EQ program on them. I don't see where this 25 is any different than any other instrument.
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17 1 It may be new. It may be novel. We've 2 registered that concern already in one of our letters, 3 but they have to go through this process. And I think 4 they'll --
5 MEMBER REMPE: But the process may need 6 extra rigor because the widget's new.
7 MEMBER SUNSERI: But my experience on the 8 instrument setup is there's going to be a scaling 9 calculation, and it's going to be very detailed. It's 10 going into the manufacturing details of the insurance.
11 It's going to get into the sensitivities of it. It's 12 going to get into the environmental influences on it, 13 and that'll be at an extremely detailed calculation of 14 all those influences resulting in how am I going to 15 calibrate this instrument in the field to support the 16 plant? And there could be a cold calibration. There 17 could be a hot calibration associated with that. It 18 could be -- you know, it just depends on what the 19 technical requirements of the manual are.
20 MEMBER REMPE: So they did not --
21 MR. ASHCRAFT: But those scaling 22 calculations are very detailed.
23 MEMBER REMPE: So they did not consider --
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18 1 which can affect the speed of sound if it were an 2 ultrasonic thermometer in the material as a function 3 of time? You calibrate when you first start up. You 4 might calibrate it sometime, but you don't calibrate 5 that it can change during the exposure?
6 MR. ASHCRAFT: If the manufacturer says 7 they need --
8 MEMBER REMPE: Yes, sir.
9 MR. ASHCRAFT: Trying to turn to the --
10 MR. PRESSON: Matthew Presson with NuScale 11 Licensing. I just want to introduce Brian Arnholt to 12 the conversation if he is available to talk to some of 13 us. And again, with a quick reminder that this is 14 open session, in case any those details are prop.
15 MEMBER REMPE: Okay.
16 MR. ARNHOLT: Yes, good morning, this is 17 Brian Arnholt with NuScale Power, I can answer 18 generalities. But because this is an open session, I 19 can't share, obviously, some of the more detailed 20 information you may be looking for. But we have found 21 vendors who, at this point in time, can meet our 22 accuracy and performance requirements that we've 23 established that Joe Ashcraft had been talking about.
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19 1 and do different kinds of testing to verify that we 2 can meet those performance requirements.
3 MEMBER REMPE: So, I have looked at your 4 topical report, and without talking about any sort of 5 specifics that are proprietary, I didn't see anything 6 that talks about a flux distribution or a temperature 7 distribution. I saw peak values.
8 MR. ARNHOLT: As part of the qualification 9 program, we describe, you know, what we will meet in, 10 in the DCA chapter seven. And then, the qualification 11 criteria are spelled out in chapter three. I guess 12 I'd need more information. I understand your concern.
13 But I don't know where in the qualification program 14 those requirements are spelled out.
15 So I guess I'd maybe need to get some more 16 information on what the question is.
17 MEMBER REMPE: The reason I'm bringing 18 this up is because this device -- again, my experience 19 is extrapolated from ultrasonic thermometers, which 20 I'll acknowledge, this may be different, but you're 21 shooting some sort of electronic signal down through 22 this waveguide. And if you did that with an 23 ultrasonic thermometer, you would be looking at the 24 flux distribution that can be experienced in a test 25 reactor, which is better known because you plan for NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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20 1 that.
2 But in an operating reactor, you've got to 3 consider different conditions, and you need to -- you 4 know, I didn't see anything about you're going to have 5 some material that will not transmute with time.
6 MR. ARNHOLT: Okay, I certainly understand 7 the concern. And again, without going into 8 proprietary details, I don't know that I can share any 9 more. But I can share the particular -- one of the 10 particular sensor manufacturers we've been working 11 with has done -- this technology has been in use over 12 the last 20 to 30 years. In fact, there's been some 13 development in the NRU program back in the 1980s.
14 So we'd just have to follow up with our 15 manufacturers --
16 MEMBER REMPE: Okay.
17 MR. ARNHOLT: -- and, you know, explore 18 those types of questions.
19 MEMBER REMPE: So I'm glad you're aware of 20 it, and verbal stuff's great. I just kind of wonder 21 if maybe some sort of discussion is needed because, 22 again, we've talked throughout this week about that 23 the staff here today may not be the staff that's going 24 to be around to look at what the COL applicant 25 provides. And this is going to be deferred to the COL NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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21 1 applicant eventually, and the staff who is evaluating 2 at that time.
3 MR. ASHCRAFT: Well, similar to Vogtle --
4 so we supported their inspections of their setpoint 5 methodology and calcs. Oh, I'm sorry.
6 So this is similar to Vogtle where the 7 actual calcs because they hadn't specified their 8 equipment when we did our review, we didn't know. But 9 we support the inspectors for those typical ITAAC 10 closeouts, or even, you know, whatever inspections 11 they do on that.
12 So if -- that's when we'll look at their 13 scaling and everything --
14 MEMBER REMPE: I just would feel more 15 comfortable because, we, may be a different person.
16 MR. ARNHOLT: Well, I understand that, but 17 I'd like to think that we're grooming the future.
18 MEMBER REMPE: But if I'd seen something 19 about, you know, radiation resistant, considering 20 gradients in temperature and flux gradients to which 21 the sensor will be exposed during normal operation, as 22 well as accident conditions, I would have more 23 confidence.
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22 1 qualifications, I mean, that's when that'll be taken 2 care of. And we don't review that now. I mean, this 3 is a year or so in the future. I don't know exactly 4 when.
5 MEMBER REMPE: Yeah, I'm just -- I'm 6 saying that it'd be good to see something along those 7 lines in the text somewhere.
8 CHAIR KIRCHNER: That's part of normal --
9 MEMBER REMPE: Charles, how do you feel 10 about this? What would the Navy have done?
11 CHAIR KIRCHNER: This isn't the Navy, I'm 12 going to intervene. We've taken now almost 25 minutes 13 off schedule. There is a process, Joy, that has to be 14 followed. After they do the proof of concept and 15 development, they have to qualify. They're going to 16 have to qualify for the environment. And this is not 17 different than what's done as Joe points out at 18 Vogtle.
19 So, I think the point has been made, and 20 we've flagged it in previous letters, and I think at 21 this point, I'd like to go back to the schedule and 22 thank Joe and get the NuScale up so we can pick up 23 chapter 20.
24 MEMBER REMPE: Thank you.
25 CHAIR KIRCHNER: Thanks, Joe.
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23 1 We've used a lot of time. Matthew, are 2 you going to make the introduction, or are we going to 3 go right to Jim?
4 MR. PRESSON: I think we will go right to 5 Jim for this. Keep it briefly.
6 CHAIR KIRCHNER: Jim, do you have your 7 microphone there on? I can't see you.
8 MR. OSBORN: Yeah, the green light's on.
9 Can you hear me?
10 CHAIR KIRCHNER: Go ahead, Jim.
11 MR. OSBORN: All right. Very good. Good 12 morning.
13 My name is Jim Osborn. I am NuScale 14 Licensing. Chris Maxwell is back on the phone, I 15 believe, and he is the SME related to these issues.
16 MEMBER BLEY: I'm sorry. I don't know 17 your jargon. What's an SME?
18 MR. OSBORN: Oh, subject matter expert.
19 MEMBER BLEY: I got you.
20 MR. OSBORN: Sorry.
21 MEMBER BLEY: I should have known it.
22 MEMBER SUNSERI: Jim is an aggie too, so 23 he's tough as nails.
24 MR. OSBORN: Thank you, man.
25 So, I'm just here to present some of the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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24 1 concerns related to the -- brought up by this 2 committee. So NuScale has revised DCA chapter 20 to 3 include pointers to the three tables at the end of 4 Section 20.1.
5 In addition, footnotes were added to these 6 tables to clarify that instrumentation used to monitor 7 various parameters are not relied upon for the event 8 mitigation but would only be a supplementary 9 capability.
10 So the following slides actually show the 11 actual markup of our DCA, indicating the changes we 12 have made. So this slide just shows section 20.1.3 13 and that pointers were added to the appropriate places 14 to the tables at the end of the section. So you can 15 see the edits there in green and -- or the red/green 16 revisions.
17 And so the next slide shows the markup 18 that a new table footnote was inserted to reiterate 19 that this monitoring instrumentation is not required 20 nor relied upon, right? And you can read the footnote 21 there. It basically copies text from other parts of 22 the DCA and ties it here to clarify that this is not 23 relied upon.
24 The following slide. Two other tables --
25 MEMBER BLEY: I'm sorry.
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25 1 MR. OSBORN: Yes, sir.
2 MEMBER BLEY: It's not relied upon in your 3 safety analysis. If you put it in there, it will be 4 relied upon by the operators. No matter what we say, 5 they're going to use it.
6 MR. OSBORN: If the capability is there --
7 MEMBER BLEY: It seems a little easy to 8 misunderstand what's being said, but I know what you 9 mean.
10 MR. OSBORN: It's not relied upon in the 11 safety analysis, right, or in the actual accident 12 analysis. It's obviously -- if the instrument is 13 available, the operators would be able to use it.
14 MEMBER REMPE: In other parts of somewhere 15 in the documentation, you have the words that it 16 provides additional assurance to the operators even 17 though they don't need it. And that's kind of --
18 again, that's why I cause trouble about this. Without 19 what he's done, it looks like that they were assuring 20 the functions established.
21 But the other text -- and now I've 22 forgotten where that other text is, whether it's in 23 the DCA or the SEs or both, but anyhow, that's I think 24 the way you want to characterize it.
25 MR. OSBORN: Right. So anyway, yeah, so NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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26 1 the footnote says it's a supplementary capability if 2 it's actually available. So that's the --
3 MEMBER BROWN: Can I --
4 MR. OSBORN: Yes.
5 MEMBER BROWN: I'm trying to understand 6 your footnotes. Footnote one says monitoring is --
7 none of this stuff is needed for the mitigation 8 strategies and guidelines. Is that the way I'm 9 supposed to be reading those because that applies to 10 the whole table?
11 MR. OSBORN: Yes, sir.
12 MEMBER BROWN: All of these sensor -- all 13 this data is not relied upon for any of the mitigating 14 strategies?
15 MR. OSBORN: That is correct.
16 MEMBER BROWN: Then notes two and three, 17 or at least two, says, by design, once the function is 18 established, they're maintained indefinitely.
19 I mean, it sounds like somebody is looking 20 for something somewhere that you're going to be trying 21 to establish them. And if they don't, you don't care?
22 Is that --
23 MR. OSBORN: So --
24 MEMBER BROWN: I maybe use the wrong 25 words. When I said, don't care.
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27 1 MR. OSBORN: Yeah, well, it's the 2 functions are established, right? That's not a 3 reference --
4 MEMBER BROWN: But what do we mean by the 5 functions? Like containment water level under ECCS 6 decay heat removal, that one's got the little three, 7 with the red two marked out. Spent fuel pooled 8 provides indication of these things, but if you don't 9 have spent fuel pool level or containment water level, 10 it's not relevant to any of the strategies at all?
11 MR. OSBORN: Yes, sir.
12 MEMBER BROWN: Okay.
13 MR. OSBORN: That is my understanding.
14 Chris, you can correct me if I'm wrong.
15 MEMBER BROWN: No, I just want to make 16 sure we understood the notes. If I turn -- all this 17 stuff is not working at all, when we go into the 18 mitigating -- it's just if we're okay. And I just 19 wanted to make a nice clear declarative statement, 20 that's all.
21 MEMBER REMPE: After ---
22 (Simultaneous speaking.)
23 MEMBER MARCH-LEUBA: Before you go too 24 much down that rabbit hole. You were not here this 25 week. At least I am extremely worried about boron NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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28 1 redistribution during progression of some events. And 2 by now I think there are more people than me that are 3 worried about that.
4 And the solution to those problems is in 5 what we call recovery, where instrumentation is used 6 to prevent bad recovery from going bad. I would 7 almost call that mission-critical.
8 And will the resolution of those issues 9 might affect this? And I guess Matt is ready to 10 answer.
11 MR. PRESSON: Yeah, and the separation 12 between that is more of a kind of listed here the 13 mitigation versus what you would do post-mitigating 14 whatever event that is. So once you reach that point 15 where you're stable for Chapter 15 DBA assumptions, 16 then we're looking to reestablish whatever you need to 17 recover.
18 MEMBER MARCH-LEUBA: We may have to write 19 our letter, at least add the comments to the letter 20 more strongly. You didn't hear the Thelma and Louise 21 analogy, but what he calls a safe, stable situation is 22 Thelma and Louise driving in a dirt road, happily in 23 their car not knowing there is a precipice right 24 there, which comes from the sequel of the movie.
25 So, while you will call -- I will not call NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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29 1 that a safe and stable situation. Recovery is part of 2 getting you out of it. So we need to think clearly 3 about it, but I would not call the situation -- if the 4 boron has redistributed, that is not a safe and stable 5 condition. You have not mitigated the event, then.
6 MR. PRESSON: But if there is nothing to 7 perturb it --
8 MEMBER MARCH-LEUBA: How do you know?
9 You're not looking at the instrument? You don't have 10 an instrument?
11 MR. PRESSON: Well, that's --
12 MEMBER MARCH-LEUBA: You don't know when 13 the level can rise.
14 MR. PRESSON: And that's part of why 15 you're looking to after you've established that, it's 16 post-accident space.
17 MEMBER MARCH-LEUBA: If you rely on some 18 instrumentation for the recovery phase because you are 19 on the border of the precipice, you're driving towards 20 the canyon. And while you're driving towards the 21 canyon, you're safe and stable, but eventually, you 22 may get there.
23 You guys need to think long and hard about 24 -- because if the boron redistribution is not an 25 issue, because you cannot get there, which is one NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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30 1 argument -- one likely argument, I would say. Then 2 you're right.
3 But if it is not, then you're not right.
4 MR. PRESSON: If we are not, then we have 5 additional concerns that we have to work with during 6 recovery, and you would certainly want to have various 7 monitoring options available to you. But so long as 8 you are not, there's not another transient to perturb 9 what your condition is, then you've reached your 10 design-basis accident requirements.
11 MEMBER MARCH-LEUBA: Yeah, I certainly 12 reserve the right to review your condition report. I 13 will certainly like to see what you come up with 14 before we write a letter because I don't think you are 15 in a safe and stable condition when you're driving 16 down a dirt road.
17 MR. PRESSON: Which is understood, 18 definitely.
19 MR. NOLAN: This is Ryan Nolan with the 20 staff. Can I try to provide a little bit of 21 perspective? So chapter 20, and what you're seeing 22 here is really how does the design and the future 23 applicant how will they comply with 50.155? That's 24 the beyond design-basis external-event rule.
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31 1 address maybe chapter 20 is a little bit different 2 than what we would do under chapter 15. What you're 3 seeing here is the mitigation strategies piece of the 4 requirement for 155. Recovery is well beyond that.
5 155 requires indefinite coping and mitigation 6 strategies.
7 A recovery is a much later activity. And 8 that's defined by providing an alternate means of heat 9 removal that can be through commissioning of new SSCs, 10 repairing existing SSCs. And so, if -- the way that 11 I see this as a recovery, you would assume you have 12 the power and the instrumentation available to take 13 those actions and the instrumentation doesn't even 14 have to be permanently installed.
15 According to 155, you could use portable 16 -- you can take remote readings to gather whatever 17 information you need to take appropriate action.
18 MEMBER MARCH-LEUBA: But I can imagine 19 actions not taken by the operator that will get you 20 out of that safe and stable state. So, what you call 21 mitigation -- if the boron resolution happens, which 22 is an if. We have not done the thorough analysis to 23 guarantee what will happen under this condition.
24 Once you have redistributed the boron, and 25 you have cold un-boronated water ready to go into the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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32 1 core. You have to guarantee that the riser will not 2 recover level, or the containment doesn't dump water 3 on top of the outcome and pushes. Or that you don't 4 overheat -- did you reheat the primary and the level 5 rises by itself?
6 There are three ways you can get out of 7 that safe, stable, and I'm using quotes around that, 8 state. The fact that you said that you mitigated it 9 depends on you keeping the level below the riser.
10 MR. NOLAN: Right, this is demonstrating 11 compliance with 155.
12 MEMBER MARCH-LEUBA: I'm not sure. I 13 mean, I've never even read 155, okay? But defining a 14 safe and stable condition that may not be safe and 15 stable is worrisome to me.
16 I've been repeating this for the whole 17 week, so I'll leave it right there.
18 MEMBER BLEY: Well, let me add to it 19 because, in various kinds of analyses, we don't go 20 beyond a certain point in the transient, but recovery 21 can lead you into great troubles. And if you want an 22 example, you don't have to look far back. Look at the 23 Robinson fire.
24 After that whole event was over, they 25 reset the 76 relay and created a new event, in some NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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33 1 ways worse than the original event. It can happen, 2 and thinking about those things ahead of time helps 3 you avoid it.
4 MR. NOLAN: And just I guess one more 5 point to add. The staff's review was only for the 6 first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. And in the safety evaluation, we 7 documented that if there are any credible transient 8 phenomena which could impact the safety functions that 9 would be reviewed during the COL.
10 Another point to add is because this is a 11 beyond-design-basis scenario. The assumptions are 12 different than what was used in chapter 15 when these 13 transients were analyzed. And so that we would look 14 from a realistic nominal all rods in, ultimate 15 heatsink, temperatures would be what we would expect, 16 you know, in the long term which could be boiling 17 conditions.
18 MEMBER MARCH-LEUBA: My goal in life this 19 week was to bring visibility to this issue. And I 20 think that nobody claims to be ignorant about the 21 issue anymore. So I think -- I declare success. And 22 we'll see what you come back with when you analyze the 23 event.
24 MEMBER BLEY: But that last statement, 25 while perfectly reasonable, left a vague if any NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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34 1 situation should exist, we'll look at it later. Well, 2 you've been advised of one situation here. So, it's 3 time to make sure we don't lose it.
4 MEMBER MARCH-LEUBA: I can think of three 5 different situations once you get into this, hitting 6 the vessel by any means, inadvertent actuation of our 7 supply of water like CVCS, or opening the containment 8 with a lot of water level in there like it will happen 9 automatically.
10 So I can think of three things that can 11 get you out of that safe and stable condition. I 12 don't see why we're postponing this to a COL when 13 we're certifying our reactor now.
14 And I say, I've achieved my goal, and I'll 15 shut up.
16 DR. SCHULTZ: And just one more comment.
17 NuScale has set up the CR to investigate other things 18 that we haven't thought about. But they're going to 19 examine to see whether there are other issues that 20 need to be addressed.
21 And if they go into affecting this aspect 22 of the design, then they'll need to follow that too, 23 a corrective response -- action response should be 24 sure to identify that.
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35 1 include any FSAR changes through that.
2 CHAIR KIRCHNER: Jim, I wanted to go back 3 to Charlie's question just to clarify, and then I want 4 to make sure Joy -- this has addressed the issues Joy 5 previously raised.
6 I'm looking at the footnotes. You've got 7 five. It's a good one to use. You say footnote 8 numbers two and three in green now, by design once 9 these functions are established, they are maintained 10 indefinitely.
11 What you are saying here in chapter 20 12 space is that basically, you will indefinitely 13 maintain of capability to measure the spent fuel pool 14 level. Is that how I read the footnote?
15 MR. OSBORN: So, the first column of the 16 table is the function. So, the function that's --
17 once it's established will be maintained indefinitely 18 is that inventory control or activity control, heat 19 removal. Those are the functions.
20 CHAIR KIRCHNER: Yeah, I understand that.
21 But the right-hand column seems to imply to me, and I 22 just wanted to understand the footnote that you will 23 measure spent fuel pool level by whatever means 24 indefinitely.
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36 1 of NuScale Power. I just want to say that's correct.
2 There's a requirement for a 50.155 echo for spent fuel 3 pool level.
4 CHAIR KIRCHNER: Exactly.
5 MR. MAXWELL: What you're saying, it's 6 exactly correct.
7 CHAIR KIRCHNER: Okay. Does that address 8 your question, Charlie?
9 MEMBER BROWN: No, actually between the 10 conversations from staff and NuScale, we toss these 11 terms mitigation and recovery around. So, I went back 12 and read again the chapter 20 lead-ins, where it says 13 there are no mitigation strategies at all were tried 14 for NuScale because they're an applicant, not a COL.
15 Well, I mean, that's in the first two 16 paragraphs of chapter 20. But I'm still kind of lost 17 on something happens you take -- to me, these are my 18 thoughts based on when we did all this, a mitigating 19 strategy tries to try to stop what's going on and put 20 you into a condition where you're safe.
21 Recovery is now what do I do longterm?
22 And do I have to bring certain functions back and 23 stuff like that? And I don't quite understand how 24 that conforms with the wording on the table in terms 25 of mitigating and recovery, so I just kind of got lost NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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37 1 with the words about what's indefinite and what's not.
2 Either that or I'm not reading it properly.
3 MEMBER MARCH-LEUBA: I don't think this 4 table addresses recovery at all, about whether there 5 is it's a different beast.
6 MEMBER BROWN: Well, the indefinite -- I 7 guess, I would have disagreed with -- I'm not 8 disagreeing with you, I'm just saying that's not my 9 understanding when I read the words in notes two and 10 three.
11 MEMBER MARCH-LEUBA: I absolutely --
12 (Simultaneous speaking.)
13 MEMBER BROWN: The words indefinitely mean, 14 indefinitely. That's a long time. That's months.
15 That's not a few hours. And that's not just bringing 16 myself to a safe condition. So that seems to me 17 that's a little bit more all-encompassing than just 18 getting yourself to a safe condition, and nothing else 19 applies to me.
20 So that implies a little bit more need for 21 systems and/or instrumentation to be available or be 22 able to be made available in order to do that 23 longer-term thing, and that sounds like that's --
24 there's committing to that, but yet the words say they 25 -- in the beginning of the chapter say, they don't NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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38 1 have to.
2 That's kind of the way I read it. Now, I, 3 again, I read words as words, not as thought -- not as 4 Gedanken experiments. So, anyway, that's that was why 5 I brought it up. That was all.
6 CHAIR KIRCHNER: Joy?
7 MEMBER REMPE: Well, recall, though, the 8 history of this. They originally wanted 30 days.
9 Even though they don't have to do anything, they did 10 this for regulatory certainty or something. And the 11 staff said, yeah, we're just going to look at for 72 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. So even though they say indefinitely, the 13 staff only bought off, and that's all we care about 14 for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> at this point.
15 So I think your concern is -- or should be 16 rephrased Charlie to do you have confidence that 17 they're going to stay in a stable state for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />?
18 And so that's why I'm okay with all this. There's an 19 underlying assumption for assuring the function is 20 established is that the COL applicant will have 21 procedures that will help them understand how to 22 assure that the function is established, but that 23 underlying assumption has been hard to find repeatedly 24 in the last week about that those procedures don't 25 exist.
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39 1 Maybe they do, but they're not part of 2 this process. But that is there that they have to 3 establish this and how they determine it and how they 4 check off and say, yes, it's good.
5 MEMBER MARCH-LEUBA: Ryan, can I ask you 6 a question? These 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is the position of the 7 staff that a plant is passive and doesn't require 8 operator actions as long as you can do it for 72 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br />? And after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, we go into chapter 19-type 10 rules where the operator is going to do something even 11 if you are in a very outside scenario. There is going 12 to be power even it has to be flex power. Is that the 13 position of the staff, that a passive plant is passive 14 for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, not forever?
15 MR. NOLAN: Yes, that certainly was part 16 of the consideration, mostly as documented in the SECY 17 paper that was drafted on the topic. We wanted to try 18 to maintain consistency with what we did for the other 19 new reactors, as well as make a finding on what we 20 feel we should be making a finding on at this point.
21 MEMBER MARCH-LEUBA: Yeah, from the point 22 of view of setting a precedent for other plants, I 23 think it would be nice if certainly ACRS can take a 24 position on it. But we make it clear that the staff 25 -- that we consider a passive plant and as long as it NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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40 1 can cope for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and afterward we'll give you 2 credit for things that are like Class 1E because you 3 will bring power back.
4 MR. NOLAN: Certainly.
5 MEMBER MARCH-LEUBA: It may take a 6 position from the 14th floor of the other building, 7 okay? But it would be nice to have clarity. Because 8 when you hear Charlie say shutdown means shutdown on 9 GDC 27, it's because he's hearing, I'm going to stay 10 there for the next seven months.
11 MEMBER BROWN: Then that's the way it 12 works.
13 MEMBER MARCH-LEUBA: That isn't the way 14 they say it, but what they mean is I want to stay 15 there for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and then something is going to 16 happen.
17 MR. NOLAN: Right, and it could be less 18 than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
19 MEMBER MARCH-LEUBA: Yeah, sure. But it 20 would be nice to have clarity, not for NuScale but for 21 all the old reactors that are coming along. So we'll 22 have to fight this again.
23 MEMBER BLEY: Well, we ought to talk about 24 that ourselves at some point. You know, the last 25 letter we wrote on this disagreement that Joy spoke NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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41 1 about, I think we just urged the staff and the 2 industry to get together and work it out, and we 3 weren't strong on it, but one thing that affected us 4 was the industry program that led to safer and that 5 ability to bring equipment and support to plants.
6 Now, when we get to talking about it, I'm 7 not sure some of these smaller, newer plants are going 8 to join up in that process, so the assumptions that 9 we've had about where help comes from and how fast are 10 linked to people being part of a larger program, and 11 we don't know yet if these small machines will be 12 included in that, so it's premature for us to decide 13 things, I think, in that area.
14 MEMBER BROWN: Just let me restate if you 15 read the notes, monitoring is not relied on for the 16 mitigating strategies and guidelines, but installed 17 instrumentation provides at least 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of module 18 monitoring and at least 14 days of UHF. Ultimate heat 19 sink monitoring is supplemental.
20 Then the next notes say but they're going 21 to be maintained indefinitely once they're 22 established. There's just --
23 MEMBER BLEY: They're functions.
24 MEMBER BROWN: Well --
25 DR. CORRADINI: You're bothered by the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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42 1 incongruity of the two, of the added statement to the 2 other statement. That's what I hear you --
3 MEMBER BROWN: Yeah, yeah, there just 4 seems to be a dichotomy between the two.
5 DR. CORRADINI: I think the understanding, 6 at least from the staff's explanation, is indefinitely 7 is up to their decided time, or the way Joy said it, 8 I think, is best, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is indefinite up to this 9 point in time.
10 MEMBER BROWN: That's not the way I've 11 heard it said.
12 MEMBER REMPE: I said it doesn't matter 13 what they put in their DCA. What we agreed to, what 14 the staff agreed to is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and we review the 15 staff stuff and it, you know, so what? They could 16 have claimed that they're going to do it until kingdom 17 come, you know.
18 That's kind of where I'm at on it, but, 19 you know, again, I get where you're at, but when they 20 -- you know, if they hadn't added the footnote and 21 changed some of this, I would have gotten -- I did get 22 more concerned.
23 MEMBER BROWN: I'll shut up.
24 MEMBER MARCH-LEUBA: I want to ask a 25 question. Administratively, is this going to be NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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43 1 incorporated on the phase six FSAR, I mean, the final 2 one?
3 MS. OSBORN: So, these changes are planned 4 to be part of Revision 5 of the DCA.
5 MEMBER MARCH-LEUBA: Which would be, from 6 the staff, it would be phase six or is there such a 7 thing?
8 MR. NOLAN: Yeah, so we had an opportunity 9 to look at these changes and they did not alter our 10 understanding of how the instrumentation was being 11 used as part of the mitigation strategies or not being 12 used as part of the strategies, and so we don't see a 13 need for the safety evaluation to change.
14 MEMBER MARCH-LEUBA: Yes, sure, but, so 15 this is a gentleman's agreement then kind of or --
16 MR. NOLAN: The changes don't affect the 17 safety evaluation.
18 MEMBER MARCH-LEUBA: I know, and I 19 completely agree that this is a solution for a concern 20 that we had --
21 MR. NOLAN: Right.
22 MEMBER MARCH-LEUBA: -- that they're 23 fixing for us. So, you have a process to get this 24 thing through and get the final signatures?
25 MR. NOLAN: Yes, yeah, and we'll confirm NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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44 1 that these changes are incorporated.
2 MEMBER MARCH-LEUBA: As long as you have 3 a process, I'm happy.
4 MEMBER BLEY: Well, from what Jose just 5 raised, we will be writing our final letter at some 6 point based on, some point fairly soon based on our 7 understanding and reviews of documents.
8 In the past, it has happened that there 9 has been another revision to a DCA after our letter 10 and I think in all of those cases, the staff has 11 brought that back to us and said, "Does this make a 12 change for you?" and usually it hasn't.
13 It's been, if not editorial or other 14 things, then we just send a note back saying 15 everything is fine, but at least we get a chance to 16 look.
17 CHAIR KIRCHNER: Okay, Jim?
18 MS. OSBORN: Yes, sir?
19 CHAIR KIRCHNER: Do you have any more to 20 present?
21 MS. OSBORN: This is it. Not for this 22 topic, no, sir.
23 CHAIR KIRCHNER: Okay, members, further 24 questions? Joy? Okay, at this point then, does the 25 staff wish to make any -- Omid, any further comments NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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45 1 on this?
2 MR. TABATABAI: Yes, good morning. This 3 is Omid Tabatabai. I'm the project manager for 4 Chapter 20. I think we discussed, as Ryan mentioned, 5 we looked at the changes that NuScale has proposed and 6 they have provided these markups on the docket, so 7 it's already been docketed for March.
8 So, they will be incorporated in phase 9 five, in Rev 5 of the DCA, thank you, and we don't 10 have a need for changing anything in our SE. So, at 11 this point, unless you have any other questions, we 12 have no slides to present.
13 MEMBER MARCH-LEUBA: At least 14 administratively, the SE is a recommendation to the 15 commissioners that they approve it, right? So, it is 16 their final signature that really carries the weight 17 of law. Your SE, your recommendation doesn't change.
18 MR. TABATABAI: That's correct. Our 19 conclusions and recommendations don't change.
20 MEMBER MARCH-LEUBA: But the approval 21 really comes from the commissioners.
22 MR. TABATABAI: Understood.
23 MEMBER REMPE: I guess I have a question 24 now. The process is new. What's my next step? I 25 wrote a memo to Matt saying, "Hey, something ought to NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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46 1 change with Chapter 20," and something changed, do I 2 have to do anything else? Does ACRS have to do 3 anything else or are we just done?
4 MR. SNODDERLY: I don't believe so. It's 5 an individual member comment to the chairman, and now, 6 and the committee is aware of it and they will decide 7 whether to adopt it and do anything further or to let 8 it stand alone as it currently does.
9 MEMBER REMPE: Sounds good. Maybe in the 10 minutes of some full committee meeting or something, 11 you could say that this was done and reviewed or 12 something is all -- I'm kind of wondering how we 13 document this for the public, or if somebody looks at 14 this --
15 MR. SNODDERLY: I think it's on the 16 transcript right now. If we have a transcribed 17 meeting, then the public is having the benefit.
18 MEMBER BROWN: Walt?
19 CHAIR KIRCHNER: Yes, sir?
20 MEMBER BROWN: I wanted to, if I could, I 21 wanted to backtrack to the earlier discussion --
22 CHAIR KIRCHNER: Yes.
23 MEMBER BROWN: -- on instrumentation to 24 make sure, because I heard two different, thought I 25 heard two different statements about the detector. Is NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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47 1 Joe still here?
2 CHAIR KIRCHNER: I think he had to leave.
3 That's why we --
4 MEMBER BROWN: Well, NuScale is here and 5 the other staff is here. I think that will work. The 6 comment was made that the detector for containment 7 water level and/or if it was RPV, a reactor pressure 8 vessel, riser level was safety related. I think Joy 9 said that and everybody said that.
10 CHAIR KIRCHNER: Yeah.
11 MEMBER BROWN: But then the comment was 12 made that the function was non-safety related and I 13 just -- the containment water level sensors feed and 14 trigger ECCS, so they feed the MPS. That means it's 15 a safety-related function.
16 CHAIR KIRCHNER: Yeah.
17 (Simultaneous speaking.)
18 MEMBER BROWN: I'm just trying to make 19 sure you understand that the output of the detector 20 goes through, you know, a categorization and then it 21 goes into the MPS. It's one of the coincidences, you 22 know, redundant coincidences, two out of four sensors 23 for triggering ECCS --
24 CHAIR KIRCHNER: So is the --
25 MEMBER BROWN: -- which is protection NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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48 1 related.
2 CHAIR KIRCHNER: So is the component of 3 the reactor vessel's level sensor in the pressurizer.
4 MEMBER BROWN: Yes, yeah.
5 CHAIR KIRCHNER: Just the pressurizer, so 6 they've dropped the RPV measurement as --
7 MEMBER BROWN: Two different sensors 8 that's --
9 CHAIR KIRCHNER: -- part of their 10 triggering, but the upper part measuring what the 11 pressure level is also does a similar --
12 MEMBER BROWN: Yeah, but pressurizer 13 level, containment, and water level --
14 CHAIR KIRCHNER: Right.
15 MEMBER BROWN: Okay.
16 CHAIR KIRCHNER: Both go into the modular 17 protection system.
18 MEMBER BROWN: Both sensors, they both go 19 into the modular protection system and they're --
20 CHAIR KIRCHNER: Right.
21 MEMBER BROWN: Therefore, that whole 22 function is a protection-related function.
23 CHAIR KIRCHNER: I think that's understood 24 at this point.
25 MEMBER BROWN: So I'm just --
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49 1 PARTICIPANT: That's correct.
2 MEMBER BROWN: I wanted to make sure all 3 of these --
4 MEMBER BLEY: I think the function they're 5 talking about that was not safety related is the 6 instrument panel where you read those --
7 MEMBER BROWN: Well, when you take it out 8 of the MPS, it goes to the main control room and is on 9 the panels. That's a safety related --
10 MEMBER MARCH-LEUBA: Why don't we let Matt 11 clarify?
12 MR. PRESSON: So, yeah, you have the, your 13 two sets of sensors for containment for the reactor 14 vessel. They both have safety-related functions.
15 They are both safety created sensors for the sensors 16 that are within the reactor vessel.
17 They have two functions. One is that 18 pressurizer level, which is a safety-related function, 19 and one if the RPV level and that is no longer a 20 safety-related function, so that's how --
21 MEMBER BROWN: It's still there, but it's 22 not --
23 MR. PRESSON: It is still there.
24 MEMBER BROWN: Yeah, I got that.
25 MR. PRESSON: Correct.
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50 1 MEMBER BROWN: Yeah, it's no longer used 2 to trigger ECCS.
3 MR. PRESSON: Right.
4 MEMBER BROWN: And therefore, it can be 5 decoupled, uncoupled from the safety-related function 6 aspect, but pressurizer level is an all the way 7 through.
8 MR. PRESSON: Yes.
9 MEMBER BROWN: It's safety related clear 10 through the display. I mean, you have multiple 11 channels to be selected from in order to maintain some 12 idea of what the levels are. Okay, I just --
13 MEMBER REMPE: So, there's this table.
14 MEMBER BROWN: I understand that. I was 15 listening to the words that got put into the 16 transcript.
17 MEMBER REMPE: Yeah.
18 MEMBER BROWN: I just wanted to make sure 19 it was certain what was what --
20 MR. PRESSON: Yeah.
21 MEMBER BROWN: -- as we articulate it.
22 That's all.
23 MR. PRESSON: Yeah.
24 MEMBER BROWN: Thank you.
25 MR. PRESSON: That's right. Thanks.
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51 1 MEMBER BROWN: Sorry to backtrack.
2 CHAIR KIRCHNER: Okay, at this point then, 3 I think we're ready to transition topics and go to 4 Chapter 9 and hydrogen and oxygen monitoring. I don't 5 know if you, Matt, are you going to present those 6 together or do you want to break them up?
7 MR. PRESSON: They'll be presented 8 together.
9 CHAIR KIRCHNER: Together, okay.
10 MR. SNODDERLY: This is also for the 11 benefit of the members of the public. There's been 12 some -- it's hard for them to follow, so if you could 13 let them know what slide you're on once in a while?
14 MS. OSBORN: Sure.
15 MR. SNODDERLY: It would really help the 16 members of the public. So, for members of the public 17 on the line, we're now going to begin the NuScale 18 Topic Hydrogen Monitoring Slides.
19 CHAIR KIRCHNER: Jim, are you going to 20 present --
21 MS. OSBORN: Yes, sir.
22 CHAIR KIRCHNER: -- this as well? Okay, 23 we're having us sign. Here they come, Charlie. Okay, 24 go ahead, Jim.
25 MS. OSBORN: All right, we're ready? So, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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52 1 yeah, I was going to introduce -- I'm Jim Osborn again 2 and this is Matt Presson, so we'll be doing the 3 presentations here. So, I'm on the introduction 4 slide, slide three.
5 So, as a way of introductory remarks, one 6 of the issues raised by this body is a concern that in 7 the NuScale design, there is a potential that 8 radionuclides from an accident source term could be 9 processed through a non-safety-related system.
10 It should be recognized that this body has 11 already approved or at least recommended for approval 12 such a concept in many other existing designs. This 13 has been approved because the rules of analysis for 14 beyond design basis accidents allow for the use of 15 non-safety-related SSCs for accident mitigation.
16 This presentation will attempt to explain 17 this regulatory framework under which the hydrogen 18 monitoring system design was developed, and explain 19 some of the details of the design so this body can 20 understand and appreciate how the design is in 21 compliance with the current regulations similar to 22 many other designs in the current fleet.
23 So, we will start with explaining the 24 overall paradigm of the design basis versus beyond 25 design basis framework and the differing rules for NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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53 1 accident mitigation for each category.
2 Then we'll clarify aspects of timing of 3 these severe accident scenarios related to developing 4 combustible mixtures that are detrimental to 5 containment, and then we'll also discuss some of the 6 operational decisions for actually initiating hydrogen 7 monitoring in a beyond design basis event.
8 And then next, we will discuss the 9 implications of this design basis versus beyond design 10 basis framework on radiation protection issues, and 11 then the monitoring equipment's capability to 12 withstand combustion events in containment will be 13 presented, and finally, we'll explore the topic of 14 containment mixing and representative monitoring.
15 Next slide.
16 CHAIR KIRCHNER: Jim?
17 MS. OSBORN: Yes, sir?
18 CHAIR KIRCHNER: May I interrupt and just 19 make an observation? We understand the rules. We 20 understand that this is similar to what was done, is 21 done in the current fleet. What our principal issue 22 was in a risk-informed manner, is this -- let me say 23 it shorthand. Is this the best approach to addressing 24 the issue?
25 So, yes, continue through. Walk through NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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54 1 the framework that you just outlined, but I just 2 wanted to make the point that we understand that 3 framework, but we were looking at it from the 4 perspective, is this the best risk-informed way to 5 operate the system?
6 MS. OSBORN: Okay, and --
7 CHAIR KIRCHNER: That's shorthand, okay?
8 MS. OSBORN: Yes, sir, and --
9 CHAIR KIRCHNER: Please continue.
10 MS. OSBORN: And part of this presentation 11 will address the risk question, as I believe the 12 staff's presentation will also, okay.
13 All right, so, slide four. For the design 14 of a nuclear power plant, including NuScale, there are 15 many events that are required to be evaluated by an 16 applicant.
17 For events that are classified as 18 accidents, there are two broad categories, design 19 basis and beyond design basis. The definitions 20 provided on these slides are just copied from the NRC 21 website.
22 So, as it says, a design basis accident is 23 a postulated accident for which a facility must 24 absolutely be designed to withstand by meeting certain 25 criteria, including radiological consequence criteria.
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55 1 A beyond design basis accident is an 2 accident sequence that is possible, but because it is 3 unlikely, the design process does not fully consider 4 all of the implications and ramifications of such an 5 accident.
6 These accidents are therefore not fully 7 designed for or fully evaluated as is the case in a 8 design basis accident, so when you're considering a 9 beyond design basis accident, there is a different 10 regulatory framework which is to be viewed. Next 11 slide.
12 So, the rules for evaluating a design 13 basis accident include several considerations for a 14 particular SSC that is credited for the mitigation of 15 that design basis accident.
16 For example, a credited SSC might be able, 17 or must be able to withstand a single active failure 18 without a loss of its mitigating function. Therefore, 19 such an SSC might have two trains or have two power 20 supplies in order to maintain its mitigating function 21 upon a single failure.
22 Similarly, an SSC is required to be safety 23 related, a higher quality pedigree to ensure that it 24 has procured, maintained, and installed consistent 25 with 10 CFR 50 Appendix B.
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56 1 The SSC is also required to be seismic 2 category one to ensure that it can perform its safety 3 function upon a design basis seismic event. If that 4 SSC that is being credited requires electrical power 5 to perform its safety function, that power source must 6 be a 1E power source.
7 That is why the NuScale design does not 8 have any 1E power sources, because none of the SSCs 9 credited for the design basis accident mitigation 10 require any electrical power. This is why the power 11 provided for the hydrogen monitoring system is also 12 not 1E power.
13 Therefore, a nuclear facility's safety 14 analysis, an SSC credited in mitigating a design basis 15 accident must be appropriately categorized and 16 designed, else it cannot be credited.
17 That is why the accidents in Chapter 15 18 are evaluated as they are, but beyond design basis 19 accidents are different. Next slide. I'm on slide 20 six.
21 So, there we go. So, because the category 22 of beyond design basis accidents are considered by the 23 NRC to be less likely as a category than design basis 24 accidents, non-safety-related SSCs can be credited for 25 accident mitigation purposes.
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57 1 The SSCs credited for mitigating beyond 2 design basis accidents are not required to be safety 3 related, single failure proof, or seismic cat one.
4 Beyond design basis accidents are a 5 different category because they involve multiple 6 failures often, and the accident evaluations allow 7 realistic assumptions.
8 That is why the distinction between design 9 basis and beyond design basis accident is so 10 important. It's a different paradigm. The evaluation 11 rules are different because the relative risk is 12 different.
13 This is also why the NRC revised the 14 regulation relative to hydrogen monitoring to allow 15 the use of non-safety-related equipment to monitor for 16 containment of hydrogen in post-severe accident 17 scenarios.
18 The NRC decided that it was a low risk 19 system, and therefore allowed it to be non-safety 20 related. The NuScale design has complied with these 21 revised regulations. Therefore, the NuScale hydrogen 22 monitoring SSCs are not safety related. They're not 23 single failure proof. They're not seismic category 24 one, and they have no 1E power supplies.
25 Other designs also utilize non-safety-NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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58 1 related hydrogen monitoring equipment, such as Watts 2 Bar 2, so NuScale is certainly not unique in the 3 industry in this regard.
4 DR. CORRADINI: But I guess just to echo 5 what I think Walt started the whole thing off with, I 6 don't think, at least from my perspective, we disagree 7 with that, but --
8 MS. OSBORN: Okay.
9 DR. CORRADINI: -- your design is unique, 10 so therefore, the evaluation of how you satisfy the 11 requirement, if one wants to satisfy the requirement, 12 is what makes it unique, so I think that's where Walt 13 was going.
14 MS. OSBORN: Okay, all right, so I'll 15 continue to go through and see if it answers -- yeah, 16 all right, very good.
17 All right, so I'm on the, yeah, timing of 18 detrimental mixture. So, I'm using the term 19 detrimental mixture here to mean a combustible gas 20 mixture that is capable of actually threatening 21 containment integrity.
22 In the December 20 letter from the ACRS, 23 it was stated that NuScale has weeks of time before 24 combustible levels of hydrogen and oxygen could be 25 generated. This is true if 100 percent core damage is NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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59 1 assumed as the regulations require, but this is not 2 the most limiting case for the NuScale relative to 3 time.
4 So, to ensure that the analyses are 5 conservative regardless of strict adherence to the 6 regulations, additional analyses were performing using 7 lower, smaller core damage percentages. These 8 analyses showed that there are more limiting cases 9 with respect to time for the NuScale design.
10 So, NuScale performed a bounding 11 evaluation of the maximum possible combustion event at 12 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> because, as we discussed before, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is 13 NuScale's licensing and design basis for passive 14 coping period.
15 After 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, it can be assumed that 16 emerging conditions can be managed by plant operators 17 using non-safety-related equipment under the guidance 18 of severe accident management guidelines and the 19 emergency response organization.
20 But at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the maximum possible 21 combustible mixture is not a detrimental mixture and 22 does not adversely affect containment structural 23 integrity, but under bounding assumptions, bounding 24 case assumptions, there are not weeks of time.
25 So, therefore, NuScale did not pursue an NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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60 1 exemption from the hydrogen and oxygen monitoring 2 regulation because there could be, albeit unlikely, 3 there could be conditions under which such information 4 from the monitoring system could prove useful.
5 NuScale and the NRC staff have discussed this and are 6 in agreement that such an exemption would not be 7 recommended.
8 MEMBER MARCH-LEUBA: Your exemption from 9 what, from the monitoring?
10 MS. OSBORN: Yes, sir.
11 MEMBER RICCARDELLA: Can you explain 12 briefly just physically why it is that smaller amounts 13 of core damage create more of a problem than complete 14 core damage?
15 MS. OSBORN: Yeah, so when you have 100 16 percent core damage, you're releasing from the 17 exothermic reaction, right, a maximum amount of 18 hydrogen from the zirc water, so you're essentially 19 hydrogen inerted because there was no oxygen in 20 containment before and the only source of oxygen is 21 through radiolysis, and it just takes a long time for 22 enough oxygen to be developed to create that mixture 23 when you're assuming that much hydrogen.
24 So, for smaller core damage scenarios, you 25 have less hydrogen, so it takes a smaller amount of NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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61 1 time to build up enough oxygen to create that 2 combustible mixture.
3 MEMBER RICCARDELLA: Thank you.
4 MEMBER BROWN: But still more than 72 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />?
6 MS. OSBORN: Yes, sir.
7 MEMBER BROWN: Okay.
8 MS. OSBORN: Yes, so we did a bounding 9 analysis.
10 MEMBER BROWN: For small versus -- I mean, 11 you're not differentiating between small, low core 12 damage and 100 percent? That's what I was searching 13 for. The 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> bounds the small even though that's 14 more limiting than the --
15 MS. OSBORN: Yes, sir.
16 MEMBER BROWN: -- maximum. That's all I 17 was -- I thought I'd made that point halfway clear.
18 MS. OSBORN: No, I understand.
19 MEMBER BLEY: Also, I think I heard you 20 say that in this shorter time, while you're getting 21 enough oxygen, you're getting oxygen, but I think you 22 said it wouldn't be, in your words, a detrimental 23 mixture. It wouldn't damage the containment?
24 MS. OSBORN: That's correct, yes, so --
25 MEMBER BLEY: So, it's --
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62 1 MS. OSBORN: -- a combustible mixture is 2 possible.
3 MEMBER BLEY: Having this shorter time 4 envelope, you're getting a combustible mixture, but it 5 isn't going to hurt anything?
6 MS. OSBORN: Right, containment will still 7 maintain its structural integrity.
8 MEMBER BALLINGER: So, you're saying you 9 could get a deflagration, but not a detonation?
10 MEMBER BLEY: Or a burning anyway.
11 MEMBER BALLINGER: A burning or whatever 12 --
13 MS. OSBORN: You get some combustion --
14 MEMBER BALLINGER: -- but not a 15 detonation?
16 MEMBER BLEY: And probably not a 17 deflagration either.
18 MEMBER BALLINGER: Okay.
19 MEMBER MARCH-LEUBA: Well, I don't think 20 that's what you said, right?
21 MS. OSBORN: No, I didn't quite go into 22 that detail.
23 MEMBER BALLINGER: You said detrimental.
24 I'm just trying to figure out what detrimental is.
25 MS. OSBORN: Detrimental means that you NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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63 1 fail containment.
2 MEMBER BALLINGER: Oh.
3 MEMBER BLEY: And that means you've got to 4 have a detonation.
5 MEMBER BALLINGER: That means you've got 6 to have a detonation.
7 MEMBER BLEY: A shockwave --
8 MS. OSBORN: Okay.
9 MEMBER BLEY: -- if you will.
10 MEMBER MARCH-LEUBA: Physically speaking, 11 the oxygen is your limiting component.
12 MS. OSBORN: Yes.
13 MEMBER MARCH-LEUBA: And it is produced 14 almost at a constant rate by radiolysis because 15 radiolysis is going by how many high energy gamma rays 16 are coming into the core.
17 MS. OSBORN: That's our assumption, yes.
18 MEMBER MARCH-LEUBA: And if you could 19 change the number of alphas that come out of the core 20 by geometric changes, it would affect something, but 21 it's almost impossible to do, so alpha is not going to 22 continue.
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64 1 of H and O that you have produced in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and 2 that's your maximum explosion. Is that correct? And 3 that does not -- you understood what I said? So --
4 MS. OSBORN: No.
5 MEMBER MARCH-LEUBA: You're producing a 6 constant rate of oxygen every hour.
7 MS. OSBORN: So, again, and hopefully I 8 have some phone support from the subject matter 9 experts that did this work, but the assumption is that 10 oxygen is produced through radiolysis at a bounding 11 rate --
12 MEMBER MARCH-LEUBA: Yeah.
13 MS. OSBORN: -- right? And so there's 14 some discussion that -- you know, radiolysis is a two-15 way -- it's a chemical reaction, right? And so 16 there's a -- or it's a nuclear reaction with a 17 chemical component that --
18 Reactions go both ways, and so, but our 19 assumption is that it's only driven by radiolysis.
20 There's no recombination going the other way.
21 DR. CORRADINI: So you ignore 22 recombination?
23 MS. OSBORN: Yes.
24 MEMBER MARCH-LEUBA: So that's a bounding 25 --
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65 1 (Simultaneous speaking.)
2 MS. OSBORN: It's a bounding case. That's 3 why I called it bounding is it could not be worse.
4 MEMBER MARCH-LEUBA: The most oxygen it 5 can produce is this much, and I assume that's how many 6 grams of oxygen I have in containment. I mean, are 7 you assuming it migrates to the worst point, right?
8 MS. OSBORN: Yes.
9 MEMBER MARCH-LEUBA: Because it likely 10 will stay dissolved in the water and wouldn't do 11 anything.
12 MS. OSBORN: Right.
13 MEMBER MARCH-LEUBA: That's another 14 bounding assumption. And what you do is if you 15 oxidize all of the zirconium --
16 MS. OSBORN: The zirconium, right.
17 MEMBER MARCH-LEUBA: -- in the core, you 18 will produce so much hydrogen that you could not 19 explode that oxygen or hydrogen. I mean, it would not 20 be an explosive mixture.
21 MS. OSBORN: Right, it takes a long time 22 for enough oxygen to become available to create a 23 combustible mixture.
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66 1 many there needs to be, then you could get a proper 2 combination of H and O.
3 MS. OSBORN: Right, so I think what we did 4 at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is figure out how much, what was the 5 maximum amount of oxygen that would be available in 72 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and then back calculated how much hydrogen would 7 create the worst mixture, and that amount of hydrogen 8 corresponds to a percent core damage.
9 DR. CORRADINI: So, now let me get to the 10 next step and maybe you need somebody on the phone.
11 And then you did what? You then assumed it combusted.
12 MS. OSBORN: Yes.
13 DR. CORRADINI: And the pressurize from 14 that determined to be detrimental?
15 MS. OSBORN: Was not detrimental.
16 DR. CORRADINI: It was not detrimental?
17 MS. OSBORN: That's correct.
18 DR. CORRADINI: Okay, that's where I was 19 confused.
20 MS. OSBORN: Okay.
21 CHAIR KIRCHNER: And that was in the 22 containment analysis, Chapter 6.
23 DR. CORRADINI: Right.
24 MS. OSBORN: Yes.
25 DR. CORRADINI: Okay.
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67 1 CHAIR KIRCHNER: And that partially 2 informed our position, Jim, because your analyses 3 demonstrated that you would not fail containment.
4 MS. OSBORN: Right, yeah.
5 CHAIR KIRCHNER: So, keep going.
6 MS. OSBORN: For 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, right.
7 MEMBER PETTI: So, just to be clear, after 8 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the letter that was written said many weeks.
9 You're basically telling us that there were some other 10 events that you looked at that was more on the 72 to, 11 I don't know, you know, a couple hundred hours, not a 12 couple of weeks.
13 MS. OSBORN: Right.
14 MEMBER PETTI: So that's why you didn't go 15 for the exemption.
16 MS. OSBORN: Right.
17 MEMBER PETTI: Because if you can recall, 18 committee members, we had lots of discussions about 19 why didn't they go for the exemption, and I don't 20 think we had this full picture as we deliberated, so 21 this is helpful.
22 MEMBER BLEY: Yeah, but before you leave 23 that, as I understand what you said, this is not an 24 explosion you're talking about.
25 MEMBER PETTI: Correct.
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68 1 DR. CORRADINI: It burns.
2 MEMBER BLEY: It burns.
3 DR. CORRADINI: It makes pressure.
4 MEMBER MARCH-LEUBA: No, wait, wait, is it 5 a burn or does it detonate?
6 MEMBER BLEY: It doesn't detonate. It's 7 not detrimental, so it can't hurt containment.
8 MS. OSBORN: It's a combustion event which 9 includes all kinds of things, right, and I don't know 10 if the mixture that we -- is Colin or Scott Weber on 11 the line?
12 MR. WEBER: Yeah, Jim, hey, this is Scott 13 Weber. Yeah, I wanted to jump in here. So, the 14 analysis that we've been referring to, the 72-hour 15 analysis, that is a deflagration to detonation 16 transition event, so it is eventually a detonation 17 dynamic that is analyzed.
18 It is not just a peak deflagration 19 pressure spike, and what the analysis has demonstrated 20 is, as you said, the maximum amount of oxygen at 72 21 hours2.430556e-4 days <br />0.00583 hours <br />3.472222e-5 weeks <br />7.9905e-6 months <br /> combined with this stoichiometrically determined 22 hydrogen amount, even considering the DDT, did not 23 threaten the structural integrity of the containment, 24 so that's all agreed upon.
25 DR. CORRADINI: So, Scott?
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69 1 MR. WEBER: What we haven't -- yes, 2 please, go ahead.
3 DR. CORRADINI: So, it's not detrimental 4 at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. I think Dr. Petti is asking did you 5 perform analyses as to when it would be detrimental?
6 MR. WEBER: Right, and we did not, no.
7 What we know is the amount of time it would take to 8 reach a combustible mixture with 100 percent fuel 9 cladding oxidation, but we have not specifically 10 determined the amount of time after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> at which 11 you could get a detrimental mixture.
12 That's why we haven't definitively stated 13 or agreed with weeks of time. We know it is some time 14 greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, but we do not have a definitive 15 amount of time past that.
16 CHAIR KIRCHNER: So, Scott, this is Walt 17 Kirchner. I remember in the Chapter 6 in the 18 containment analysis that it was deflagration to 19 detonation, and then you did an equivalence analysis 20 to demonstrate that the containment could withstand 21 this pressure pulse.
22 So, was that -- what wasn't clear to me in 23 reviewing Chapter 6, so that set of assumptions then 24 must have been the 72-hour scenario that you're 25 talking about. I don't think it was -- that was not NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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70 1 footnoted in the analysis.
2 It just was -- which led me to believe 3 reading it that you essentially had 100 percent zirc 4 and then you found an oxygen mixture that would 5 detonate that, lead to a detonation. So, the Chapter 6 6 analysis is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />? I guess that's my question.
7 MR. WEBER: Yes, that is correct.
8 CHAIR KIRCHNER: Okay, that wasn't clear.
9 All right, thank you.
10 MEMBER REMPE: So, I'm getting confused.
11 You have confidence that there are some events that 12 could fail the containment. You just don't know what 13 the timing of it is? Because Dave is asking --
14 At first we were told, "Yeah, we've looked 15 at it," and then I think you said, "Well, we've not 16 really looked at it. We don't have a time," but you 17 still have confidence there are some other events out 18 there that could fail the containment. Where are you 19 exactly?
20 MR. WEBER: What we know for certain is 21 that we've looked at a wide range of severe accidents 22 that can potentially occur for the NuScale design, and 23 not all of them are complete core damage and 24 oxidation. So, we know that there exist accidents 25 whereas you only have partial core damage and less NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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71 1 than 100 percent oxidation.
2 What we haven't ever done is translate 3 that into a specific time and done an analysis to see 4 whether that would be a detrimental mixture. So, we 5 don't know for certainty that we have a specific event 6 that would lead to a failed containment, but we do 7 know that there are severe accidents that do not 8 result in 100 percent cladding oxidation.
9 MEMBER REMPE: Thank you.
10 MEMBER BLEY: So that's less hydrogen is 11 what you're saying, so you need less oxygen. I think 12 you also said for the 72-hour calculation that that 13 was, you called it a transition from deflagration to 14 detonation, but then you said the pressure pulse 15 wouldn't damage the containment. If it really 16 transitioned into detonation, you would have also had 17 a shock wave. Did you look at that?
18 MR. WEBER: Yes.
19 MEMBER BLEY: And the shock wave --
20 MR. WEBER: That was part of the analysis.
21 MEMBER BLEY: It's not just the pressure.
22 It's the --
23 MR. WEBER: No, the pressure pulse 24 dramatically exceeded the containment, you know, 25 failure pressure, but it was such a, you know, micro NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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72 1 seconds duration that that was not threatening, and 2 the shock wave was also analyzed and that was part of 3 the structural dynamic load.
4 MEMBER BLEY: Thank you.
5 MEMBER MARCH-LEUBA: If nobody else has 6 other questions, Scott, if by any way we can oxidize 7 the whole core and release all of the hydrogen, and 8 then you detonate all of the hydrogen, that fails the 9 core, the containment? I think you analyzed that one.
10 MR. WEBER: We did not do a structural 11 analysis of that, so I really can't say definitively 12 that we would fail the containment.
13 MEMBER MARCH-LEUBA: Okay, so you don't 14 know.
15 MR. WEBER: That would need much more 16 hydrogen and oxygen than the analysis that was done.
17 MEMBER MARCH-LEUBA: How long would it 18 take to generate enough oxygen to ignite or to 19 detonate all of the hydrogen that you could possibly 20 produce? Are we talking three months?
21 MR. WEBER: Yes, so we looked at, using 22 our conservative radiolysis production curve, we did 23 look at the time it would take to generate enough 24 hydrogen to reach a combustible mixture for our severe 25 accident that produced the most hydrogen, which was NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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73 1 actually slightly greater than 100 percent cladding 2 oxidation due to some structural field oxidation, and 3 we found that it was approximately 45 days until we 4 produced enough hydrogen to reach that mixture.
5 MEMBER MARCH-LEUBA: Okay, so --
6 MR. WEBER: I think actually Jim has that 7 in a slide, that that was going to be coming up in 8 just a couple of slides, but --
9 MEMBER MARCH-LEUBA: So in summary --
10 MR. WEBER: -- but that would be our 11 maximum.
12 MEMBER MARCH-LEUBA: In summary, we have 13 calculations that show that the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is not a 14 problem for containment, and it builds up to 45, and 15 at 45 days, we are not sure whether it would or would 16 not damage containment.
17 MEMBER BLEY: And I think what he said was 18 --
19 (Simultaneous speaking.)
20 MEMBER BLEY: Well, it would have reached 21 the flammability limit --
22 PARTICIPANT: Right.
23 MEMBER BLEY: -- which is pretty unlikely 24 to --
25 PARTICIPANT: Lead to a detonation.
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74 1 MEMBER BLEY: -- be a problem. I mean, 2 you need a lot more oxygen to get to detonation level.
3 PARTICIPANT: Yeah, to detonation.
4 MEMBER BLEY: Right? That's what I heard 5 him say was it was flammability.
6 (Simultaneous speaking.)
7 MEMBER BLEY: I think that's what I heard 8 you say. Is that right, Scott?
9 MR. WEBER: Yes, what I'm trying to get 10 across is that we know for certain that 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> from 11 any combustion event, that the containment integrity 12 will be maintained, and that we know that if we have 13 our maximum amount of hydrogen produced, that it will 14 be weeks of time until you would reach even a 15 combustible mixture.
16 We have not looked at the specific, on 17 containment of that maximum, nor have we looked at any 18 point in between, and that's why we're only 19 definitively trying to say that we have at least 72 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> until we have a detrimental mixture.
21 Likely if we combusted our 100 percent 22 hydrogen production with a detonation included, I 23 would say it's likely that there would be a threat to 24 containment integrity, but we have not specifically 25 done that analysis.
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75 1 MEMBER BLEY: And you don't have any idea 2 how long it would take to get to a detonation-able 3 mixture of oxygen? That's a lot more oxygen than 4 you'd have when you just reach the flammability limit.
5 MR. WEBER: Well, we would probably 6 continue to assume a deflagration to detonation 7 transition, so we'd just need to reach the 8 deflagration concentrations, which we've taken 9 generally as four percent of the lowest possible, but, 10 no, I don't want to postulate because we haven't done 11 a specific analysis of what that time would be when we 12 could get to a detrimental mixture.
13 MEMBER BLEY: Okay, thanks. Go ahead.
14 MS. OSBORN: All right, so I'm now 15 transitioning out of the timing discussion, so the 16 next topic is operational decisions.
17 So, as mentioned on the previous slide, 18 there is no less than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> before a detrimental 19 combustible mixture could be developed. It should be 20 noted that this analysis is a bounding analysis as 21 we've discussed, and 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is consistent with 22 NuScale's design basis passive coping period.
23 During this 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, decisions regarding 24 hydrogen monitoring can be evaluated, including 25 inspecting and evaluating the hydrogen monitoring NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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76 1 system prior to its actual use to verify the system's 2 integrity and availability.
3 So, Reg Guide 1.7 provides a risk-informed 4 decision process regarding the use of this system. It 5 includes such factors as including the priority of 6 these activities as compared to other post-accident 7 activities, the necessity of the information, and 8 additional insights gained from the specific plant 9 conditions that might have actually occurred.
10 Therefore, if it is actually decided to 11 place the hydrogen monitoring system into service, 12 there is sufficient time to take measures to ensure 13 its integrity and availability.
14 MEMBER BLEY: Well, I want to -- because 15 I don't see any slides that get into this. One thing 16 we had raised and we gave you a set of questions or 17 issues we wanted to hear from, you know, when the 18 evacuation system is normally running, those 19 evacuation pumps are running, and you have, you know, 20 your flow through there is probably representative of 21 the almost nothing that's in the containment, and then 22 if you pull a little bit of that off into the sampling 23 system, that may be a good measure.
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77 1 it up and now you would have a fairly large, and we 2 don't have any idea how large, evacuation system 3 sitting there, and then you would start this little 4 sampling pump pulling off of part of that system.
5 And why do you have confidence you would 6 get a measure of hydrogen and oxygen that was 7 representative of what's in the containment? And I 8 didn't see anything here and I don't see you talking 9 about this.
10 MS. OSBORN: Well, okay, so I do talk 11 about it. That's the last topic, is about containment 12 --
13 MEMBER BLEY: Oh, okay, I couldn't tell it 14 from there, okay.
15 MS. OSBORN: But, so --
16 MEMBER BLEY: Well, you can wait until 17 then if you prefer. That's good.
18 MS. OSBORN: Okay, that's fine.
19 MEMBER BLEY: As long as you have it.
20 MS. OSBORN: Well, and so that particular 21 question, I don't have it particularly addressed in 22 the slides.
23 So, I think it's important to understand 24 that the normal pathway used in the containment 25 evacuation system for during normal operations is a NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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78 1 different flow path than is used for post-accident 2 hydrogen monitoring.
3 MEMBER BLEY: Not the inlet side. The 4 outlet side is different. The incoming side is the 5 same.
6 DR. CORRADINI: What I thought Dennis is 7 asking is you're connected to the evacuation piping.
8 MEMBER BLEY: Yes.
9 DR. CORRADINI: That's the inlet side.
10 MEMBER BLEY: That's the inlet side, but 11 you don't have the outlet side open anymore. Well, 12 they have a return path that they use under sampling.
13 MS. OSBORN: So what I'm saying is the 14 part of the containment evacuation system that has 15 the, I don't know what they call it, the pump, right, 16 the hogging pump that is pulling the suction off 17 containment, part of that system is not in use for --
18 MEMBER BLEY: The pumps aren't turned on, 19 but the pipe's connected and the valve alignment is 20 the same because you're coming off after the pump. I 21 have to go back and look again.
22 MS. OSBORN: I think it's a different 23 pathway. I don't --
24 MEMBER BLEY: That's what we asked, to 25 show us the pathway. What's the valve lineup? And I NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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79 1 don't think you're -- well, all we have is a cartoon 2 of the system, so we don't know for sure.
3 MEMBER MARCH-LEUBA: Our concern, Jim, I 4 raised it first, is that the volume of the -- that 5 once you open the isolation valves and you dam 6 containment environment into the CES, from then on, 7 you sample what's in the CES. Now, what we're asking 8 is what is the flow rate that goes from CES to the 9 sampling system in the PAS --
10 MS. OSBORN: Yes.
11 MEMBER MARCH-LEUBA: -- compared to the 12 volume of the CES? And my gut feeling is five hours' 13 worth of volume, but if you tell me it's only two 14 minutes, then I will be happy with that.
15 MS. OSBORN: Okay, so, yeah, so I can't 16 answer the specifics of that question because those 17 details of the system have not been designed.
18 MEMBER MARCH-LEUBA: They're critical.
19 MS. OSBORN: What I'm saying --
20 MEMBER MARCH-LEUBA: This includes your 21 parameter.
22 MS. OSBORN: Well, what I'm saying is --
23 CHAIR KIRCHNER: We know going in, it's a 24 four-inch pipe.
25 MS. OSBORN: True.
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80 1 CHAIR KIRCHNER: That's a big opening in 2 containment bypass space.
3 MEMBER MARCH-LEUBA: On the PAS, it's not 4 on the top of the containment.
5 (Simultaneous speaking.)
6 CHAIR KIRCHNER: And then as Dennis is 7 asking, you know, how much volume? How much pipe run 8 before you start sampling, and then how much 9 throughput do you have, and how representative of 10 that, how representative --
11 MS. OSBORN: Okay.
12 CHAIR KIRCHNER: -- is that of what's in 13 the containment?
14 MS. OSBORN: I understand. So, all right, 15 I'll get to a slide and we'll talk about this. I'm 16 just saying that the particular pathway used for the 17 two scenarios are different, and parts of the system, 18 of the CES will be isolated --
19 CHAIR KIRCHNER: Understood.
20 MS. OSBORN: -- such that volume does not 21 come into play in post-accident space.
22 MEMBER BLEY: We'd sure like to see a 23 sketch of that because the picture of the system that 24 we have doesn't show a way to do that.
25 MS. OSBORN: Right, and what you see in NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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81 1 the FSAR for this flow path doesn't picture the rest 2 of the system because it does not come into play.
3 DR. CORRADINI: But I guess, let me make 4 sure we're clear. Those details that Dr. Bley and Dr.
5 March-Leuba are asking don't exist?
6 MS. OSBORN: That's correct.
7 DR. CORRADINI: Okay.
8 MS. OSBORN: Pipe routing has not been 9 done.
10 MEMBER MARCH-LEUBA: But if that is 11 correct, then I have absolutely no confidence that 12 your PAS system is sampling the containment.
13 MS. OSBORN: And we will discuss that.
14 MEMBER MARCH-LEUBA: Well, please do.
15 MS. OSBORN: Like I said, that's my last 16 slide. I saved the best for last, I guess.
17 MEMBER MARCH-LEUBA: Tell me you're 18 sampling it and that you have confidence that you're 19 sampling the containment because I have some tech 20 spec, I have some requirements, I have --
21 PARTICIPANT: Fixed volume, yeah.
22 MEMBER MARCH-LEUBA: Please, go ahead and 23 show us.
24 MS. OSBORN: Well, let me get through the 25 rest of this and then we'll come back to this. Okay, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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82 1 so that's all I had to say about the operational 2 decisions, so the main point to take away from that 3 is, you know, we have time to inspect the system post-4 accident before we would actually place it into 5 service.
6 MEMBER RICCARDELLA: What do you mean by 7 inspect the system? I mean, you're not going to send 8 Section 11 folks out there to do ultrasonic exams 9 obviously.
10 MS. OSBORN: Well, so I guess it had been 11 postulated that, you know, this is a non-seismic 12 system. Well, what if, you know, something failed in 13 a seismic event, right? And so we're looking for --
14 PARTICIPANT: Gross.
15 MS. OSBORN: -- yeah, gross failures.
16 MEMBER MARCH-LEUBA: So basically 17 something severe akin to the recovery phase on the 18 boron dilution. Before an isolated containment, you 19 will make sure that the volume you're dumping the 20 containment into is not leaking.
21 MS. OSBORN: Well, I mean, that's just 22 standard operating practice, right? I mean --
23 MEMBER MARCH-LEUBA: That's not what 24 you're telling us.
25 MS. OSBORN: That's what?
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83 1 MEMBER MARCH-LEUBA: That's not what 2 you're telling us. You're telling us, "We will 3 operate at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, period." That's what the CAR 4 says.
5 (Simultaneous speaking.)
6 MS. OSBORN: No, I'm saying it's an 7 operational decision, right, based on the risk-8 informed decision process provided in Reg Guide 1.7.
9 MEMBER MARCH-LEUBA: Okay, so have you 10 told the staff what would you do if that volume is not 11 available to open the isolation valves because it's 12 leaking?
13 MS. OSBORN: Well, I mean, again, standard 14 operating practice would be you would repair it, 15 right, and that's what we're saying. Post-accident, 16 we have time. That's why we have the 72-hour passing 17 coping period, so, okay.
18 MEMBER MARCH-LEUBA: So, that's implied in 19 your guidelines, or proposal, or design, is that 20 you're going to dam the containment into the CES, but 21 before doing that, you verify it's working either 22 because it didn't fail or because you fixed it.
23 MS. OSBORN: Yes, so we would take 24 measures to ensure that the system was still intact.
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84 1 an ACRS member did not receive that message when we 2 talked about it.
3 MS. OSBORN: Again --
4 MEMBER MARCH-LEUBA: The message we 5 received is that at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, I will open the valve no 6 matter what.
7 PARTICIPANT: No, I don't think we did.
8 MS. OSBORN: No, I don't --
9 PARTICIPANT: I don't remember that, no.
10 MS. OSBORN: So, that's just, I mean, 11 that's life of the plant, right?
12 CHAIR KIRCHNER: But if you were in a 13 severe accident state -- let's go back one slide.
14 Don't go back on the slides --
15 MS. OSBORN: Okay.
16 CHAIR KIRCHNER: -- just to the thought 17 that this is a low probability event. I think we 18 agree with you, but now you've had the event. It 19 might have been seismically initiated. The quality of 20 the piping downstream of the isolation valves is class 21 D for the CES system.
22 MS. OSBORN: Right.
23 CHAIR KIRCHNER: This is not the quality 24 that's at the isolation valves, so it's not 25 seismically qualified, which you pointed out.
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85 1 MS. OSBORN: Right.
2 CHAIR KIRCHNER: I think when the staff 3 presented some of their analysis, they assumed a leak 4 rate, not a very large one, but that could lead to a 5 significant dose both offsite and also to the control 6 room.
7 So, I'm not sure under these conditions 8 how you're going to do an integrity test, a Section 11 9 or not even that. What are you going to do, a visual 10 inspection, and then based on a visual inspection, say 11 it's not going to leak?
12 MEMBER RICCARDELLA: Section 11 has, you 13 know, visual inspection requirements of V2-1 and V2-2 14 --
15 CHAIR KIRCHNER: Right.
16 MEMBER RICCARDELLA: -- and, you know, I 17 think V2-1 is just, if it's still in place is --
18 MS. OSBORN: Yeah, so I don't think we're 19 going to, at this point, dictate to a post-accident 20 operation environment what method and means they might 21 use to verify their system integrity. Again, this is 22 -- again, we have to remember the framework we're in 23 is a post, a non-design basis --
24 PARTICIPANT: I do, I do.
25 MS. OSBORN: -- severe accident of very NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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86 1 low probability, right, and the -- we're trying to, 2 you know, pick out details that are just --
3 CHAIR KIRCHNER: We're trying to avoid you 4 having to pick out the details by not unisolating 5 containment. That's the point.
6 MEMBER RICCARDELLA: Well, but the trade 7 off is how important --
8 CHAIR KIRCHNER: Yeah, how important.
9 MEMBER RICCARDELLA: -- is the hydrogen 10 and oxygen information that you're going to get, and 11 I guess you're coming to that, right?
12 MS. OSBORN: Well, no, I think --
13 PARTICIPANT: We covered it.
14 PARTICIPANT: It's on this slide.
15 MS. OSBORN: Yeah, we said that such 16 mixtures were possible. Although unlikely, they were 17 possible, and so --
18 MEMBER RICCARDELLA: Yeah, so there's a 19 certain time between 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and 45 days where you 20 might need to know.
21 MS. OSBORN: You might need to know.
22 MEMBER RICCARDELLA: Yeah, okay.
23 MS. OSBORN: And so if that time comes, 24 then we would take, the plant would take appropriate 25 measures to ensure that the system is intact, the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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87 1 system is available, and if there are problems, they 2 can take means or take measures to alleviate those 3 problems. So, it leaks, all right, and they can --
4 MR. MELTON: So, this is Mike Melton with 5 NuScale. So, Jim's pointed out the regulatory 6 framework system for the beyond design basis event.
7 I mean, that is the regulatory position.
8 We will make the best operational decision 9 post the event as required, and we have a Reg Guide 10 decision making process that Jim pointed out that will 11 be considered, implemented into procedures and whatnot 12 before this all even happens.
13 So, that is, you know, the regulatory 14 position and operational decision making position 15 going forward, so we're kind of going in circles, but 16 that's where we're at. You know, we understand the 17 concern, but this is our current -- this is the 18 regulatory decision going forward.
19 MEMBER BLEY: You're giving the guys in 20 the plant a system that you say they can sample the 21 hydrogen and oxygen. We're not convinced from what 22 we've seen so far that it will work, number one.
23 Number two is what if it's bad? What have you given 24 them to deal with that? If you're giving them a tool, 25 you ought to have some hint of advice for them when NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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88 1 they get there, again --
2 MR. MELTON: Yes, sir.
3 MEMBER BLEY: -- not a complete procedure 4 and everything, but a good idea of what they would do 5 if they ever get in this spot. What's that?
6 MR. MELTON: Well, I think our position is 7 that the system is tested, operable, and checked 8 before whatever unfortunate beyond design basis event 9 happens. The decision to use that is based on, you 10 know, the safest, most conservative decision making 11 process we set up.
12 I mean, we'll be staffed -- we are staffed 13 with professionals and safety conscious individuals.
14 We'll make the right decisions. I have full 15 confidence in that.
16 MEMBER BLEY: If the hardware is there to 17 let them --
18 (Simultaneous speaking.)
19 MR. MELTON: The hardware is designed as 20 the regulations require.
21 DR. CORRADINI: So, can I just ask a 22 question? I want to make sure we're -- so let's say, 23 let's just say for the moment that what you're 24 proposing is workable, let's just say. What do you do 25 with the information once you've measured it?
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89 1 MEMBER BLEY: Yeah, that's where I was 2 just --
3 DR. CORRADINI: So what? So you measure 4 it and you find out, oh, my gosh --
5 MEMBER BLEY: Yes.
6 DR. CORRADINI: -- that it's one percent 7 instead of the -- Scott calculates that at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, 8 it's not detrimental, but to get it to burn with post-9 DDT, you needed four percent, and you got to four 10 percent, but you measure it and you got one percent, 11 and then you measure it at 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> and you got 1.5 12 percent. What do you do with that information?
13 MS. OSBORN: So I think all of this, the 14 information would lead to inform the decision as to 15 whether you wanted to vent containment or not.
16 (Simultaneous speaking.)
17 DR. CORRADINI: And so there is no other 18 means by calculation procedure to do a bounding 19 calculation. What I'm looking for, is there a 20 bounding calculation you can do based on detrimental 21 combustion that gives you just as much or even better 22 information without having to vent containment early?
23 I'm bothered by the fact that you're 24 opening up your evacuation line and you don't know 25 what you're opening up to, whereas you could do a NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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90 1 calculation. There might be a calculational way to 2 look at an upper bound.
3 MS. OSBORN: Well, that's what we -- I 4 mean, that's what we've done, right? That's what's in 5 the FSAR is a bounding evaluation of these mixtures.
6 DR. CORRADINI: No, but then I'm not 7 making myself clear.
8 MS. OSBORN: Okay, I'm sorry.
9 DR. CORRADINI: What I'm trying to get at 10 is you've done a calculation that says at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, 11 you have some concentration with some conservative 12 assumption that it's not detrimental.
13 You could do that same calculation and 14 move it forward in time and ask when it is detrimental 15 and use that as your decision making point about 16 venting rather than putting in a monitoring system 17 that could potentially release radioactive materials 18 of unknown concentration.
19 MS. OSBORN: So, but we are no different 20 than other designs in this regard.
21 DR. CORRADINI: I'm not disagreeing with 22 you.
23 MS. OSBORN: Okay.
24 MEMBER SUNSERI: Except does your vent 25 harden like a BWR though, I mean, if you'd be NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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91 1 releasing potentially flammable explosive stuff 2 through there?
3 MS. OSBORN: So, it is not hardened.
4 CHAIR KIRCHNER: And it's lower quality.
5 MEMBER BLEY: It's the evacuation system, 6 I assume.
7 CHAIR KIRCHNER: It's the evacuation 8 system, so if you open it and you had the detonation 9 in the system, then what confidence do you have that 10 the system can withstand that event? Probably not 11 very high confidence.
12 MS. OSBORN: So, I have a slide on that, 13 too.
14 CHAIR KIRCHNER: All right.
15 MS. OSBORN: So, yes, we do have 16 confidence.
17 MEMBER BLEY: Well, that's wait for that 18 one then.
19 CHAIR KIRCHNER: Well, then we'll --
20 MS. OSBORN: Okay.
21 CHAIR KIRCHNER: We'd like to see that.
22 MS. OSBORN: All right.
23 MEMBER RICCARDELLA: You know, Mike, the 24 other issue, I mean, suppose they do monitor it and 25 instead of 1.5 percent they find it's four percent?
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92 1 That's going to tell them to do something, right?
2 DR. CORRADINI: But what they choose to do 3 wouldn't change by essentially an early monitoring.
4 What they choose to do --
5 MEMBER MARCH-LEUBA: Do you have a mic?
6 DR. CORRADINI: I'm sorry, excuse me.
7 Unless I misunderstood, what they choose to do is not 8 going to -- it's a timing decision, but you choose to 9 do would be the same result.
10 So, I could do a calculation and not do an 11 early opening of the system, and have an upper bound 12 as to what the concentration is. They did it at 72 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />. They can do it at subsequent times. That 14 would create the shortest time to a worry without 15 having to open the system, unisolate the system.
16 That's all I'm getting at.
17 MEMBER RICCARDELLA: Well, but, you know, 18 we're using the term unisolate. I mean, even if it's 19 not a class one seismic system, I'd say there's still 20 a high probability that it's going to be intact.
21 They're not automatically venting containment just by 22 opening it up to that system.
23 MS. GRADY: Dr. Corradini, this is Anne-24 Marie Grady, the staff reviewer on this topic, and 25 NuScale has already in their generic technical NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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93 1 guidelines decided that a prudent time to consider 2 taking mitigating action, whether it's venting or 3 inerting the containment, is to do it when the oxygen 4 concentration is three percent in containment.
5 But you'd still need to know if you were 6 approaching that and you'd still need to open the 7 containment for any mitigating action you're going to 8 take, whether it's going to be venting and you have to 9 open CES, whether it's inerting and you have to open 10 CVCS and the nitrogen distribution system.
11 So, there are other points of data that 12 would tell you that you could, like three percent, 13 let's say, which does not support combustion, is a 14 safe time to take action or to plan action.
15 DR. CORRADINI: So I think you've made a 16 very good point, so let me counterpoint. So I can do 17 a calculation that gives me the earliest time to reach 18 three percent based on radiolysis and the optimum time 19 to combustion and not monitor, but at that point, make 20 a decision to inject nitrogen at a higher pressure, so 21 I'm not going to leak out. I'm going to leak in, and 22 then I don't go through the worry of having to open up 23 containment and unisolate early, release materials 24 when I don't necessarily need to.
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94 1 want to, if you took the mitigating action, if you 2 opened up the containment and took the mitigating 3 action, you'd want to confirm it was successful.
4 So, you're still going to, I think, need 5 to use hydrogen and oxygen monitoring flow path to 6 convince yourself of that, otherwise you'd have to do 7 a calculation that says how much you have to inert 8 with the nitrogen or how long you'd have to vent, and 9 I don't think those exist right now.
10 DR. CORRADINI: I see your point.
11 MS. OSBORN: Thank you. Okay, so, moving 12 onto the radiation protection issue, this is slide 13 nine. So, if the decision is actually made to place 14 the system into service, we think there is a high 15 degree of confidence that the system's integrity will 16 be intact.
17 First, the system that is used for 18 hydrogen monitoring are included in the leakage 19 control program. This program is one of the post-TMI 20 action items that is intended to minimize potential 21 leakage from systems outside containment that may 22 contain accident source term.
23 Second, these systems are used during 24 normal operations, so system integrity issues would 25 likely be discovered and remedied during normal NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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95 1 operations.
2 And third, as discussed before, the 3 operators have sufficient time post-accident to 4 evaluate and inspect the system prior to its use. So, 5 the analysis of this leakage path is unprecedented 6 among other applicants, and if they were required, 7 could lead to some compliance issues.
8 If the staff thinks this is a safety 9 issue, the generic implications should also be 10 considered, but if it is hypothesized that the 11 hydrogen monitoring system leaks excessively, 12 subsequent actions could be to isolate the leak.
13 This would be an unplanned, ad hoc 14 operator action which would be the responsibility of 15 the emergency response organization as an 16 unanticipated emergency action and would fall under 10 17 CFR 50.47(b)(11) which is the responsibility of the 18 emergency plan and the emergency response 19 organization.
20 But the staff's position, as they have 21 stated, is that there is not enough design information 22 to perform these dose analyses and the so-called carve 23 out of the rule will allow this to be resolved in the 24 future.
25 MEMBER MARCH-LEUBA: Jim?
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96 1 MS. OSBORN: Yes?
2 MEMBER MARCH-LEUBA: I have a favor to 3 ask.
4 MS. OSBORN: Yes, sir?
5 MEMBER MARCH-LEUBA: You just placed in 6 the record all of this document. You just read it and 7 we will have a transcript of it two weeks from now.
8 Is there a way that you can give that to Mike so we 9 can read it because you talk very fast?
10 MS. OSBORN: Oh, do I?
11 MEMBER MARCH-LEUBA: We're going to have 12 to discuss it for the letter. I would love to have 13 that document. I mean, you just placed it on the 14 record by reading it. Can you give us a copy?
15 MS. OSBORN: I don't know.
16 MEMBER MARCH-LEUBA: Can you talk slower 17 and do it again?
18 MS. OSBORN: I can definitely talk slower.
19 MEMBER MARCH-LEUBA: I think you can do 20 it. You placed it on the record.
21 MS. OSBORN: Yes, sir, so would you like 22 me to go through this slide again?
23 MEMBER MARCH-LEUBA: I'm just kidding, but 24 it would be nice if we could read it because we're 25 going to have to argue among ourselves when we write NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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97 1 our letter about this whether we agree with you or 2 not.
3 MS. OSBORN: Yes, sir.
4 MEMBER MARCH-LEUBA: It would be nice to 5 have it in front of us what it is that we are agreeing 6 on.
7 MR. PRESSON: Yeah, I'll check with Mike 8 and see what that process would be, so.
9 MEMBER MARCH-LEUBA: The process for that 10 is we have to wait for the court reporter to do the 11 transcript and then we can read it, but that's going 12 to take a week. I'm just putting it out there.
13 MS. OSBORN: I'm sorry I was talking too 14 fast.
15 MEMBER SUNSERI: We can expedite that 16 transcript. We can get the transcript.
17 MEMBER MARCH-LEUBA: Yeah, yeah, but we're 18 going to write the letter Thursday.
19 MEMBER BLEY: Expedited, it's a week to 20 two weeks, maybe four days once in a while, but it 21 depends on their load offsite, so it's not immediate.
22 MEMBER DIMITRIJEVIC: Well, I was bringing 23 this before because everybody comes with the reading 24 slides, and it would be very useful to have actually 25 reading slides, not the seeing slides.
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98 1 So, I don't see what is the issue of 2 issuing reading slides which they will show in the 3 transcript anyway, so, I mean, I don't understand what 4 is the problem.
5 CHAIR KIRCHNER: It's just the time to get 6 the transcript. That's all.
7 MEMBER DIMITRIJEVIC: No, but why cannot 8 we just have reading slides as a part of the meeting?
9 CHAIR KIRCHNER: That's up to NuScale.
10 That's a personal or corporate decision.
11 MEMBER REMPE: Why don't you go through 12 the slide again?
13 MS. OSBORN: I can, and I will go a little 14 bit more slowly this time.
15 MEMBER RICCARDELLA: He might have some 16 uncomplimentary things about ACRS in his notes.
17 MS. OSBORN: No, I can assure you.
18 MR. OSBORN: Okay, so I will do this 19 again, all right, and I will try to slower. So if the 20 decision is actually made to place the system into 21 service, we think we have a high degree of confidence 22 of the system's integrity and that it will be intact.
23 So, and there are three reasons for that. One, first 24 it listed there is we've included this system as one 25 of the systems in the leakage control program.
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99 1 So leakage control program is one of the 2 post-TMI action items to address this very issue. So 3 it's intended to minimize the potential leakage from 4 systems outside containment that might contain 5 accident source term. So obviously this is a COLA 6 item. We don't have the program written today. But 7 that's, this system and this pathways go into that 8 leakage control program.
9 The second reason we think it's, will be 10 of, the system will be intact is that we use this 11 during normal operations. And so any systems 12 integrity, system issues would be discovered and 13 remedied during normal operations.
14 And then third, as we discussed before, 15 the operators have time post-accident to evaluate the 16 system, inspect the system, and ensure that it's 17 intact and that the system is, has integrity.
18 So the analysis of presuming a leak path, 19 right, from the hydrogen monitoring system, is 20 unprecedented in other applications. And we think 21 that if that was required of other applications, that 22 they also might have dose criteria compliance issues.
23 And so, but that hasn't been looked at in other 24 designs.
25 MEMBER MARCH-LEUBA: Yeah, but in most NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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100 1 applications, you put the hydrogen monitoring inside 2 containment and nothing leaks.
3 MR. OSBORN: No, sir, not always.
4 MEMBER MARCH-LEUBA: Not always, but --
5 MR. OSBORN: So a case in point, as I 6 pointed out before, is Watts Bar II. They have a 7 hydrogen monitoring system outside containment that 8 non-safety. And so this is not unprecedented from a 9 design standpoint. And so NuScale we don't think is 10 unique in that regard.
11 So we just think that if this is a safety 12 issue concern, that the generic implications of this 13 ought to be looked at as well. It's not unique to 14 NuScale.
15 DR. CORRADINI: So I don't want to 16 interrupt you, but I wanted to get to your last 17 bullet. So if you do a carve-out, does that mean you 18 can come back later and ask for an exemption?
19 MR. OSBORN: That would be up to the COLA 20 applicant, right.
21 DR. CORRADINI: Because now back to unique 22 features. You have a, I think is allowed to say on 23 public, you have 1050 psi containment.
24 MR. OSBORN: Yes, sir.
25 DR. CORRADINI: That makes it unique that NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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101 1 you inert and stay under a combustion mixture of any 2 sort and then sample it, rather than taking the chance 3 of any sort of sampling and having a combustion.
4 So there is unique features on how your 5 containment is strong enough that you could actually 6 take calculated estimates of an upper bound of 7 concentrations that are combustible, inert it so it's 8 not combustible, and then do the sampling. And that 9 would require an exemption, because it's not doing 10 monitoring after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. But to me, from the way 11 your containment, the way your system is designed 12 makes it a lot more advantageous --
13 MR. OSBORN: So there may be more 14 flexibility on the mitigation side.
15 DR. CORRADINI: Yeah.
16 MR. OSBORN: Right? So when you say 17 sampling, so you inert it and then sample, what's the 18 difference between sampling and monitoring in your 19 mind?
20 DR. CORRADINI: Because now I have no 21 chance of combustion.
22 MR. OSBORN: Right.
23 DR. CORRADINI: Once I start sampling, I'm 24 taking out a mixture that can't combust. I don't have 25 to worry about a hardened vent, I don't have to worry NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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102 1 about venting combustion. I basically take a sample, 2 which will take time, but I have it mixed with 3 nitrogen, so I can't, I don't have to worry about it 4 being combusted, combustible.
5 MEMBER MARCH-LEUBA: No, if you pacify 6 the containment so it cannot detonate, you don't need 7 to sample it.
8 DR. CORRADINI: Eventually you're going to 9 have to know what's there, because now I have this, 10 I'm in this residual risk zone of assuming a severe 11 accident, and I will understand its situation going 12 forward in perpetuity.
13 MEMBER PETTI: But the decisionmaking 14 process is completely different at that point than if 15 you hadn't inerted.
16 DR. CORRADINI: Right.
17 MEMBER PETTI: Because you have to worry 18 about the risk of detonation.
19 CHAIR KIRCHNER: The detonation could come 20 with the unisolating --
21 DR. SCHULTZ: Correct.
22 CHAIR KIRCHNER: Of the containment.
23 MR. OSBORN: Again, these are going to be 24 --
25 CHAIR KIRCHNER: That's the worst possible NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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103 1 way to do it.
2 DR. CORRADINI: But the reason I started 3 off with the bullet --
4 CHAIR KIRCHNER: Because containment is 5 designed for --
6 DR. CORRADINI: Is if that if the COL 7 applicants seize an advantageous way of doing this, 8 they can ask for an exemption and a different path 9 forward in terms of how they do the mitigation, 10 assuming a severe accident. How do they do the 11 monitoring? During a severe accident, excuse me.
12 MR. OSBORN: So yeah, obviously the COL 13 application has lots of options, right. And we 14 wouldn't presume to impose what those options may or 15 may not be, if I understand your question right.
16 Operationally, those kinds of choices of what do I do 17 in mitigation space, those kinds of -- that's what 18 emergency response organizations are for. And so 19 post-72 hours, this is, you know, in SAMG space, as we 20 say, severe accident mitigation guidelines.
21 MEMBER SUNSERI: I just want to push back 22 on your statement about hydrogen monitors being 23 external, a generic issue. We don't disagree that 24 there are plants that have external hydrogen 25 monitoring systems. But that's exactly what they are, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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104 1 systems designed specifically for monitoring hydrogen, 2 all equipped, all the engineering worked out. Not a 3 you know, what I'll can --
4 CHAIR KIRCHNER: An appendage.
5 MEMBER SUNSERI: Appendage, yeah. You 6 know, this, it started out with a four-inch line. I 7 mean, nobody has sampling system that has a four-inch 8 line as its starting point.
9 CHAIR KIRCHNER: No one would design a 10 sampling system with a four-inch line. It's like you 11 not to second-guess your design, but it's like an 12 appendage that's put on an existing system just to 13 minimize the penetration for containment. But boy, a 14 four-inch line to do a sample?
15 MR. OSBORN: So I understand the negative 16 perspective that you bring to that. The positive 17 aspect of that same perspective is that the system is 18 used normally. So a dedicated hydrogen sampling 19 system is not used normally, right.
20 So to me, the systems that leak more often 21 are the systems that are not used versus the systems 22 that are routinely used. And so I think the fact that 23 we used a system that was in normal operation for a 24 different purpose for post-accident purposes has its 25 advantages as well.
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105 1 Okay, so where was I? All right, so we 2 talked about the generic implications. But if, so 3 what I was going to say, if the, we hypothesized that 4 the hydrogen system leaks excessively. Again, this 5 will be emergency response organization type of action 6 to ameliorate that leak.
7 So, but that would be an unplanned, ad 8 hoc, operator action, which would be the 9 responsibility of the emergency response organization.
10 And it's an unanticipated emergency action would fall 11 under the emergency plan rules and guided by the 12 emergency response organization, so.
13 But the staff's position is that there's 14 not enough design information to perform these 15 specific dose analyses, either off-site or operator 16 dose. And so the carve-out would allow this to be 17 resolved in the future. All right?
18 MEMBER MARCH-LEUBA: My main concern 19 obviously is an isolated containment and dumping all 20 the isotopes out there. But after your presentation, 21 I still don't know if the PAMS will work for the 22 concerns that we're talking about.
23 MR. OSBORN: Okay, I --
24 MEMBER MARCH-LEUBA: This is probably a 25 question for the staff, but I think my philosophy will NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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106 1 be before I certify this design, I have to know that 2 there is at least one instance of this pipe running 3 that will work. I mean, it's upon you to say I don't 4 know where the PAM system going to be mounted on my 5 third plan installation. They'll have to look at it.
6 But I could run it this way, and it will work. And I 7 don't think you've done that.
8 MR. OSBORN: Okay, I've got a slide on 9 that, and like I said, I think that's my last slide, 10 so we will get to that.
11 So now I'm on the slide having to do with 12 equipment capability, slide 10. So this is, again, 13 regarding this committee's statement related SSCs 14 being able to withstand a hydrogen combustion event.
15 So it is correct that containment is designed to be 16 able withstand without loss of structural integrity, 17 any hydrogen combustion event for the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
18 However, it is also true that the hydrogen monitoring 19 path, pressure boundaries, can also withstand such a 20 hydrogen combustion event in containment.
21 In fact, the design capability's already 22 included in FSAR table 3.2-1, and it states, quote, 23 Pressure boundary components of any monitoring path 24 outside of containment shall be designed to withstand 25 combustion events corresponding to the capability of NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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107 1 containment.
2 So therefore the same claim regarding the 3 ability to withstand a combustion event for 4 containment can be made for the hydrogen monitoring 5 system pressure boundaries. NuScale and the NRC staff 6 agree that this design capability has been accounted 7 for.
8 CHAIR KIRCHNER: So the design pressure of 9 the containment evacuation system is 1050 psi?
10 MR. OSBORN: No, sir.
11 CHAIR KIRCHNER: Okay, so -- the isolation 12 valve, I know, I understand that. Okay, so then the 13 table says that it should be designed for that. What 14 is the design spec for the CES system that you can 15 demonstrate that it can withstand such a ---
16 (Simultaneous speaking.)
17 MR. OSBORN: So this analysis of to take 18 a combustion event inside containment and propagate it 19 through lines outside of containment has not been 20 done, and it cannot be done until pipe is routed, 21 system is fully designed. But that --
22 CHAIR KIRCHNER: That's part of our 23 concern. So you're saying that --
24 MR. OSBORN: But the requirement's there 25 --
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108 1 CHAIR KIRCHNER: Table 3.2 will require 2 them essentially -- see, one of our concerns was that 3 if you un-isolated, the detonation could happen at 4 that point. The valves could trigger the, be the 5 energy source for setting off the event. So you're 6 saying that 3.2-1 will require the COLA, the COL 7 applicant to design that system to withstand one of 8 these pressure pulses.
9 MR. OSBORN: That's correct.
10 CHAIR KIRCHNER: That wasn't obvious.
11 MR. OSBORN: No.
12 CHAIR KIRCHNER: But maybe I need to 13 review 3.2-1 again. That was certainly one of our 14 concerns.
15 MR. OSBORN: Yes.
16 CHAIR KIRCHNER: Okay.
17 MR. OSBORN: Yes, and that's why I wanted 18 to address that. That we have accounted for that, you 19 know, possibility that, or that design requirement 20 that we designed the pressure boundary of any 21 monitoring path outside containment to withstand a 22 combustion event inside containment. All right?
23 Now to the last slide, containment mixing 24 --
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109 1 to read it, that's not addressing my question.
2 MR. OSBORN: Well, okay, so let talk 3 through it and see if we can get there. So 4 containment, mixing, and sampling, this is another 5 issue raised by this body regarding hydrogen 6 monitoring and being able to obtain representative 7 monitoring. First of all, ANSI N13.1, to which 8 NuScale has committed, requires the sampling of this 9 type be representative.
10 Second, representative sampling is 11 dependent upon drawing upon a mixed, a well-mixed 12 fluid. So regulations require that post-accident 13 containment atmospheres be well mixed. So that 14 representative sampling can occur, and it prevents 15 pockets of combustible mixtures being developed 16 earlier than expected.
17 The containment mixing is described in 18 FSAR 6.2.5 and was further explained in the response 19 to RAI 8862. And NuScale has demonstrated that the 20 containment is well mixed, neglecting any mixing 21 contributions from, induced by ECCS flows through 22 containment.
23 This mixing inside containment is driven 24 by the delta T between the reactor pressure vessel 25 wall and the containment vessel wall. And this delta NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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110 1 T is driven by the core's decay heat against the 2 cooler environment outside of containment, which is a 3 condition that will persist longterm.
4 So NuScale and the NRC staff are in 5 agreement that NuScale is in compliance with the 6 regulations regarding mixing and representative 7 sampling. The quote on this slide is from the NRC 8 safety evaluation report regarding this compliance.
9 DR. CORRADINI: But I don't mean to 10 interrupt, but what Dr. March-Leuba's asking for is 11 the, I'll call it timing, from the time you decide to 12 open the isolation valve to the time you're actually 13 going to take a representative sample that represents 14 containment.
15 MR. OSBORN: So it's a flushing time, 16 right?
17 DR. CORRADINI: Right.
18 MR. OSBORN: Yes.
19 DR. CORRADINI: So are you committing to 20 a flushing time?
21 MR. OSBORN: We don't know that time, 22 because --
23 DR. CORRADINI: Well, reverse the problem.
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111 1 a time and by your design, it will not be longer than 2 an hour, two hours, whatever? That's what I thought 3 you were, he's asking.
4 MEMBER MARCH-LEUBA: That's exactly -- I'm 5 telling you your flushing time is 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />. Prove me 6 wrong.
7 CHAIR KIRCHNER: This Chapter 6, wait a 8 minute. Yeah, before we even get there, let's get to 9 the source that you're going to draw. The containment 10 extraction system takes suction from the top of the 11 containment essentially, right?
12 PARTICIPANT: Yes.
13 CHAIR KIRCHNER: This quote is during the 14 blowdown phase and such. Our concern isn't during 15 this time period, this part from Chapter 6, well 16 mixing. This had to do with condensation and other 17 effects during the cooldown period. Let's assume 18 you've cooled and melted the -- not melted, but you've 19 got a zirc oxide reaction, whether there's melting or 20 not.
21 So you've got a hydrogen source. The 22 hydrogen is going to migrate to the top of the 23 containment, and that mixing may continue well below 24 the hydrogen level, but that's not what you're taking 25 out. You're going to take out hydrogen first.
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112 1 This mixing is the steam mixing during the 2 blowdown phase when the RRV -- the RVVs or the RRV, 3 the ECCS system goes into play. But we're out now 72 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or so. And yes, there will be buoyance and 5 turbulence probably inside that containment. But the 6 hydrogen's going to go right up to the top. You're 7 going to pull off hydrogen first.
8 MR. OSBORN: So I think this part of the 9 FSAR that the SER is referring to has to do with this 10 whole issue of combustion --
11 CHAIR KIRCHNER: Even way out at --
12 because we're now 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or more, and now you're 13 going to consider ---
14 (Simultaneous speaking.)
15 MR. OSBORN: No, this is for the first 72 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />.
17 CHAIR KIRCHNER: All right, or let's just 18 say we're at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
19 MR. OSBORN: Right.
20 CHAIR KIRCHNER: If you've produced 21 hydrogen, the hydrogen will separate from the steam.
22 MR. OSBORN: Not in a turbulent 23 environment.
24 CHAIR KIRCHNER: It's not clear how 25 turbulent it will be at that point.
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113 1 DR. CORRADINI: Once I mix, I don't unmix.
2 I'll have a different concentration because of 3 condensation. That's what I thought you were getting 4 at.
5 CHAIR KIRCHNER: Yeah, well, the 6 condensation's going to make this more quiescent than 7 turbulent over time. So now we're out there at a 8 significant point in time, the ECCS system has done 9 its job.
10 MR. OSBORN: But it continues.
11 CHAIR KIRCHNER: Static --
12 MR. OSBORN: I know, I know.
13 CHAIR KIRCHNER: There's heat, yeah, 14 there's going to be circulation. But my sense is 15 because of the condensation and other effects, you're 16 going to get separation. You're not going to get a 17 very representative mixture, not initially. And then 18 it depends how much volume is outside containment in 19 the CES system before you get to your tap where you 20 actually do the sample.
21 MR. OSBORN: Which would tend to increase 22 the hydrogen, apparent hydrogen concentration?
23 MEMBER MARCH-LEUBA: Yeah, but we are 24 worried about --
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114 1 representative anymore.
2 MEMBER PETTI: It's really why we're 3 worried about the oxygen. You need to get, and the 4 oxygen --
5 CHAIR KIRCHNER: Yeah, it's the oxygen.
6 MEMBER PETTI: And it won't be in the top, 7 it'll be down in the bottom, and you may -- so you'll 8 get a false measurement is what --
9 MEMBER MARCH-LEUBA: There are two issues.
10 Is the containment mixed or not, that's what Walt is 11 saying. I don't think it is, but let's give you that 12 the containment is well mixed because you have 13 sufficient turbulence, and it was tall and narrow, 14 hard to believe there's going to be that much 15 turbulence.
16 But then when you dump that containment 17 volume into the four-inch pipe, which as far as I know 18 it could be a hundred foot long, maybe more, but I 19 don't know, you tell me how long it is.
20 MR. OSBORN: Yeah, so there is a dedicated 21 system for each module, right. So it's not like 22 there's a long run of pipes.
23 MEMBER MARCH-LEUBA: Dr. Corradini was 24 saying tell me what the ratio is between the mass flow 25 rate in the PAMS pump that is something for there and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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115 1 what the volume is and specify a maximum time delay 2 for this flushing. Because as I tell you, it's 1000 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. I'm as right as you are because none of us 4 know what the answer is.
5 So there should be a specification on the, 6 on your design that says the flushing time for this 7 system cannot be greater than, and you tell me what 8 the number is, two hours, ten hours. And then I'm 9 happy, at least that part works. You still have to 10 worry about all the stratification and where the 11 oxygen goes and where the hydrogen goes.
12 MR. OSBORN: So I'm not an expert on ANSI 13 N13.1 having to do with sampling and monitoring. I 14 don't know if there's a maximum flushing period as 15 part of that ANSI standard or not. I do know the ANSI 16 standard requires us to perform representative 17 monitoring or representative sampling.
18 MEMBER MARCH-LEUBA: Well, the design 19 you're showing me on the drawing does not do it 20 because it has a time delay for flushing. I mean, the 21 design that you're showing me does not satisfy ANSI 22 N13.1-2011. Prove me wrong.
23 MR. OSBORN: Well, I can't because the 24 system hasn't been designed in detail to figure out 25 all the details you're referring.
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116 1 MEMBER MARCH-LEUBA: So if you're not 2 willing to solve the problem now, at least specify 3 what your bounding parameters will be for the design 4 in the COL. You'll say okay, the COL can do whatever 5 routing of pipes they want to do as long as it's 6 represented within a two-hour time constant.
7 MR. PRESSON: Well, and that's part of our 8 FSAR commitment to the ANSI standard for having that 9 representative sampling. That's written into the 10 FSAR. So as we --
11 MEMBER MARCH-LEUBA: What is written?
12 MR. PRESSON: Commitment to N13.1.
13 MEMBER MARCH-LEUBA: Yeah.
14 MR. PRESSON: So as we finalize, well, as 15 the COL finalizes that design.
16 MEMBER MARCH-LEUBA: If you have a 100 17 foot four-inch pipe, and you have an aquarium pump 18 something for it, it might take 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />.
19 MR. PRESSON: And then it's no longer 20 representative, and so you have to go back make sure 21 you meet the FASR.
22 MEMBER MARCH-LEUBA: You or the staff 23 needs to define what representative means. I see a 24 hole here.
25 MR. PRESSON: Understood, yeah.
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117 1 MEMBER MARCH-LEUBA: If you're 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> 2 behind containment, that's not representative, but you 3 will agree on that.
4 MR. PRESSON: Yeah.
5 MEMBER MARCH-LEUBA: If you're 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br />, 6 eh, maybe it's okay, maybe it's okay, maybe it's not.
7 Do we need two hours, what do we need? You need to 8 agree on that before you design it.
9 MEMBER PETTI: Well, the question is 10 whether the ANSI standard has some of that in there.
11 MEMBER MARCH-LEUBA: I don't know.
12 MEMBER PETTI: I mean, I would just be 13 shocked. I mean, anybody who does sampling knows 14 you've got to flush, you know, you got to get an 15 answer in a reasonable amount of time, which means you 16 have to design it. So it's probably worth trying to 17 say what that standard says I'd be surprised.
18 MEMBER MARCH-LEUBA: How can we make a 19 decision if we don't know?
20 MEMBER REMPE: We actually have access to 21 the standards.
22 CHAIR KIRCHNER: Yeah, we can pull up the 23 standards.
24 MEMBER DIMITRIJEVIC: But I would like to 25 make from my risk prospectus how we see, because NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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118 1 everybody has so far discussed that you, how efficient 2 or unefficient or useful or not useful the system.
3 And comes to the risk-informed decision, this is what 4 is currently happening.
5 And I want to tell you why I think that 6 this is not every case which you say exists in the 7 industry. Because the first time when we start 8 thinking about this issue as, you know, purely 9 analyst, I said well, wait a second, everybody has 10 this system, why is this not looked before.
11 The main reason is the coping time here is 12 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. So nobody in the current industry is 13 dealing with anything longer than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The 14 second thing is the here we saw this in the Asian 15 issue which question habitability of main control 16 room, which is not, you know, doesn't exist in other 17 case. And you have a very specific containment when 18 you try to minimize number of the penetrations and you 19 have a large line coming on this.
20 When it comes to the risk prospectus, once 21 when you open this, this is it, you're getting large 22 release how currently model of the PRA setup. They 23 never really question what type of the, you know, the 24 fission --- releases are going to happen in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
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119 1 in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, you directly lead to large release.
2 This containment can only fail if it's 3 bypassed, either by failure of containment isolation 4 or by, you know, steam generator tube rupture or by 5 LOCA outside of containment. So currently, if the 6 operator is going to bypass containment isolation and 7 un-isolate that within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, we go directly to 8 large release.
9 Therefore, they can either make argument 10 that large release is not likely to happen in 72 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br />, they could, I assume. And they, but they have 12 to change how the model is currently the PRA. So what 13 Michael is going to say, if this is really has a 14 potential to, you know, question habitability of main 15 control room leads to releases, and it's not doing any 16 useful function from risk-informed point of view, do 17 you really need this. So that's a main argument.
18 If this has to become part of containment 19 isolation discussion in the PRA if we conclude that 20 this is going to be done within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, okay, the 21 currently it's not.
22 DR. CORRADINI: So I want to summarize 23 what you just said. Your point is that this action is 24 not in the PRA.
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120 1 in the PRA, it's not part of containment isolation 2 function analysis.
3 DR. CORRADINI: So Scott Weber's on the 4 line. I thought he was somehow connected to the PRA.
5 Is that correct, that it's not part of the PRA?
6 MEMBER DIMITRIJEVIC: There is no 7 discussion of this system --
8 MR. WEBER: Yes, I can confirm that un-9 isolated containment for the purpose of hydrogen 10 monitoring is not currently considered in the PRA.
11 DR. CORRADINI: Thank you.
12 MS. NORRIS: This is Rebecca Norris with 13 NuScale. Scott, sorry, this is going back a couple 14 topics, but we got a little bit more of a thorough 15 answer on the mixing RAI question, so Scott, do you 16 want to go ahead and talk about that?
17 MR. WEBER: Yeah, I just wanted to quickly 18 follow up on the conversation that was being had 19 before about whether or not the mixing, the argument 20 that is being presented on this slide is about the 21 steam blowdown period and whether gasses would still 22 remain stratified in the upper CNV.
23 And I pulled up the associated RAI and 24 the, that analysis was done all the way out to 72 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />. It demonstrated well mixing through the entire NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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121 1 duration, so that's well beyond the initial blowdown 2 period. It would also sort of contain the sort of 3 longterm natural, or decay heat driven natural 4 circulation.
5 It also did include combustible gasses in 6 that analysis, and it did demonstrate that they would 7 be entrained by the, what they call a buoyant steam 8 jet that flows into the upper CNV and then down the 9 exterior inside surface of the CNV. So that analysis 10 did demonstrate that all the way through 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, 11 including consideration and combustible gasses, that 12 the containment atmosphere was well mixed. So I just 13 wanted to make sure that that was clarified.
14 MR. OSBORN: Thank you, Scott. So, I did 15 have, I lied, I have one more slide, which is just a 16 summary and conclusions.
17 So I just want to kind of recap where 18 we've been here. So we first discussed the overall 19 paradigm of accident analysis as it relates to the 20 differences between design basis and beyond design 21 basis, and the rules that we as an industry apply 22 related to accident mitigation and using non-safety 23 related systems for that mitigation.
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122 1 accident, it seems to be in the realm of the 2 incredible. And it's hard to see how it can be even 3 considered credible.
4 Second, we discussed the timing aspects of 5 combustible gasses inside containment, and that we 6 have performed a bounding analysis that shows that 7 there is a minimum of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> before a detrimental 8 combustible gas mixture could form inside containment.
9 And third, we discussed the risk-informed 10 decision process in which operators would utilize in 11 actually placing this hydrogen monitoring system into 12 service. And we discussed that there's sufficient 13 time to allow operators to inspect and verify that the 14 system is intact and available.
15 And regarding radiation protection, the 16 staff has stated that there is insufficient design 17 information to perform either an offsite or an 18 operator dose from a leaky monitoring system.
19 Therefore, a carve-out, created a carve-out for the 20 rule so that this issue could be resolved at a future 21 date.
22 Then we discussed the hydrogen monitoring 23 --
24 DR. CORRADINI: Well, just --
25 MR. OSBORN: Sorry.
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123 1 DR. CORRADINI: This is more for my 2 education, but what's the difference between a carve-3 out and a COL item?
4 MR. OSBORN: So a COL item I believe is 5 something we create as part of the DCA.
6 DR. CORRADINI: And the carve-out is 7 something they -- the staff creates.
8 MR. OSBORN: And so the carve-out is more 9 like a COLA item that the staff creates.
10 DR. CORRADINI: But is it treated 11 identically the same? It's essentially the 12 owner/operator's going to have to show compliance with 13 the equivalent of a staff-related COL item?
14 MR. OSBORN: Yes, from my understanding 15 that is, from that perspective they are similar.
16 MEMBER MARCH-LEUBA: And would the 17 difference be a COL item is something we have an 18 agreement on how it's going to be resolved, you just 19 need to do the calculation. Whereas a carve-out, we 20 don't have an agreement on how it's going to be 21 resolved, and that's why it gets postponed?
22 MR. OSBORN: I don't know that you make 23 that generalization.
24 CHAIR KIRCHNER: I think the staff will 25 address that.
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124 1 MR. TESFAYE: This is Getachew Tesfaye.
2 Chapter 9, a Project Manager, carve-out essentially 3 says that the staff has not reached any conclusion on 4 the design of that, this particular design. In other 5 words, we're not making it a finality of the design at 6 this stage.
7 COL item, on the other hand, is the staff 8 reviewed the COL item and makes the determination this 9 is an appropriate COL item for the applicant to, for 10 the COL applicant to handle. So a carve-out is just 11 completely eliminates this portion of the design is 12 not certified.
13 DR. CORRADINI: So it's an open item going 14 to the COL.
15 MR. TESFAYE: Yes, it's, we have not made 16 any determination on this particular aspect like the 17 design because we didn't have any information.
18 MS. GRADY: Not with respect to 19 monitoring, with respect to leakage from the 20 monitoring path. That's the carve-out, it's that 21 narrow.
22 MEMBER REMPE: So in a way it's a bit 23 easier because they don't have to do an exemption, or 24 it's a different approach. They don't do an 25 exemption, it's not been decided, right? Because NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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125 1 earlier we asked, or Mike asked about this, can they 2 get an exemption.
3 MS. GRADY: Finding on the leakage from 4 the path. There is a finding --
5 MR. TESFAYE: Yeah, so I was just going to 6 make some point here. A carve-out was needed because 7 Applicant did not want to submit an interface item in 8 tier one. This could have been handled in a normal 9 way if the applicant agreed to submit this as an 10 interface item that will be tracked in tier one as a 11 COL item.
12 The applicant did not want to have this in 13 the tier one as an interface item, so the staff was 14 forced to carve this out of the regulation. So it's 15 the only we thing we can do to move forward.
16 CHAIR KIRCHNER: Why don't you wrap up 17 here, and then we're going to take a break, and then 18 we'll get the staff up and we can --
19 MR. OSBORN: Okay.
20 CHAIR KIRCHNER: See their, hear their 21 position.
22 MR. OSBORN: All right, so I'm just 23 finishing this slide. So we discussed the hydrogen 24 monitoring pathway and the fact that it will be 25 capable of withstanding a combustion event, just like NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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126 1 containment can. And NuScale and the staff agree that 2 the system will be, is accounted for, will be able to 3 withstand such an event.
4 And the lastly we talked about containment 5 mixing and ensuring representative monitoring, and 6 NuScale and the staff agreed that this has been 7 adequately accounted for, so.
8 MEMBER BLEY: Jim?
9 MR. OSBORN: Yes, sir.
10 MEMBER BLEY: Just a clarification. The 11 ability of a CES to withstand the hydrogen burn event 12 is at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, is that correct? Or any hydrogen burn 13 event.
14 MR. OSBORN: So as the, as table 3.2-1 15 says, it says, as well as containment can, right. So 16 at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, yes, the monitoring pathway would be able 17 to withstand any combustion event like containment.
18 There is a, there --
19 CHAIR KIRCHNER: Let him finish.
20 MR. OSBORN: So yes, the answer to your 21 question is yes. Now, we haven't analyzed, as Scott 22 Weber said, we have not analyzed after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> what 23 might happen.
24 MEMBER BLEY: So if I've bought one of 25 these and I'm operating it, when I get to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, I NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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127 1 know I'm okay if I open it up and sample and filter 2 and vent it if I need to. But if I decide to wait a 3 while, I'm no longer guaranteed that that's the case 4 should a burn happen later on, before I decided to 5 open it up to sampling.
6 MR. OSBORN: Just as in containment you 7 wouldn't know for sure either.
8 MEMBER BLEY: Right.
9 MEMBER RICCARDELLA: I was just going to 10 say I've got the table up if you wanted me to read the 11 statement. Okay.
12 CHAIR KIRCHNER: Thank you, Jim.
13 MR. OSBORN: All right, thank you.
14 CHAIR KIRCHNER: No good deed goes 15 unpunished, so --
16 MR. OSBORN: I've heard.
17 CHAIR KIRCHNER: With that, let's take a 18 break until five after -- better make that ten after 19 11:00. And then we'll have the staff. And I 20 apologize in advance to the staff, we've used more 21 time than we had expected. We are in recess.
22 (Whereupon, the above-entitled matter went 23 off the record at 10:53 a.m. and resumed at 11:10 24 a.m.)
25 CHAIR KIRCHNER: Okay, we are back in NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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128 1 session. We are now going to turn to the staff to 2 hear on Chapter 9 and related topics. So Getachew, 3 are you going to make the start-off?
4 MR. TESFAYE: Yes.
5 CHAIR KIRCHNER: Please go ahead.
6 MR. TESFAYE: Thank you, Chairman. Good 7 morning, everyone, my name is Getachew Tesfaye, I'm 8 the NRC project manager for NuScale design 9 certification application Chapter 9, auxiliary 10 assistance in the accident source term methodology 11 topical report.
12 As you can see on this list, several 13 members of the NRC staff contributed to the Chapter 9 14 review and the accident source term topical report.
15 Key staff members are here in the audience to support 16 this briefing. On December 10, 2019, the staff issued 17 the phase 4 Chapter 9 SER evaluation with no open 18 items for ACRS review.
19 As the Committee pointed out correctly, 20 the phase 4 and phase 2 SER differ in several areas as 21 a result of a new approach the staff adopted by 22 evaluating information on the docket rather than 23 discussing the individual open items and their 24 resolution. As you'll see in our presentation today, 25 all the SER changes in phase 4 of the SER are the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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129 1 result of information submitted to close open items or 2 changes made in other chapters.
3 None of these changes involve a design 4 change to the systems and components evaluated in 5 phase 2.
6 Our other presentation today addresses 7 questions raised by ACRS regarding our presentation to 8 the full Committee in December 2019 on accident source 9 term methodology and areas of focus. The specifically 10 issues involving post-accident hydrogen oxygen 11 monitoring systems and the process sampling system.
12 We'll start off our presentation with the 13 post-accident hydrogen oxygen monitoring and process 14 sampling system. Anne-Marie Grady and Ed Stutzcage 15 will make that presentation, and then Raoul Hernandez 16 and Chang Li will address the major areas of change in 17 Chapter 9 phase 4 SER, and I'll close out the 18 presentation by discussing the remaining open items in 19 Chapter 9.
20 With that, Anne-Marie.
21 MEMBER BLEY: May I ask something now 22 because it --
23 MR. TESFAYE: Did I say something?
24 MEMBER BLEY: No, you, well, you did a few 25 minutes ago, and so did Anne-Marie. I think I heard NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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130 1 you say, and I think that's what I remember reading, 2 that the mixing issue we've talked about is not 3 anything you've challenged, but --
4 MS. GRADY: For 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
5 MEMBER BLEY: Yeah, for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. But my 6 question has to do with ANSI N13.1-2011 and the 7 associated regulation, 10 CFR 5044(C)(1) that was 8 discussed by them. You folks, I assume, would have 9 looked at those. And are you of the opinion that 10 meeting the requirements in the regulation and the 11 ANSI standard will require the COL applicant to ensure 12 that they're getting a representative sample at the 13 time they do sample?
14 MR. TESFAYE: I have a slide on ANSI --
15 MEMBER BLEY: If you're covering it 16 already, that's fine.
17 MR. TESFAYE: Yeah, it's in there.
18 MEMBER BLEY: But since we hadn't asked 19 that, that's why.
20 MS. GRADY: No, Dr. Bley, you're asking a 21 very specific question. First of all, the technical 22 reviewer who evaluated the mixing was Boyce Travis, 23 and he's not here at the moment.
24 MEMBER BLEY: Okay.
25 MS. GRADY: He evaluated it for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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131 1 as I just said. I have not, so I can't answer your 2 question directly, but I'll try to get an answer for 3 you by the end.
4 MEMBER BLEY: That's fine.
5 MS. GRADY: Do you want to know if he 6 considered it? Because I certainly haven't.
7 MEMBER BLEY: Sure, yes.
8 MS. GRADY: ANSI standards?
9 MEMBER BLEY: Yeah.
10 MS. GRADY: I will find out from Boyce by 11 the end of the day.
12 MEMBER BLEY: And if he thinks that 13 requires them to make sure that they do have a 14 representative sample when they open up the PSS.
15 MS. GRADY: But you're not I'm talking 16 about a specified flushing time, you're just talking 17 about representative sample.
18 MEMBER BLEY: Well, that's kind of 19 embedded.
20 MS. GRADY: Uh huh.
21 MEMBER MARCH-LEUBA: Yeah, so both, is the 22 containment mix, and what is the flushing time on the 23 four-inch pipe.
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132 1 mixed in the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
2 MEMBER MARCH-LEUBA: And now the flushing 3 or the four-inch pipe, it's a separate issue.
4 MS. GRADY: I don't know that he looked at 5 that. I will talk to him and get back to you by the 6 end of the day.
7 MEMBER REMPE: Walt, just so we all kind 8 of understand the game plan, we were supposed to have 9 a meeting that some of us, including yourself, is 10 supposed to, and Matt and me, are supposed to attend 11 at noon, and perhaps some other members. Are we going 12 to hold to that firm schedule and take a break if we 13 don't finish? Because we have --
14 CHAIR KIRCHNER: I think we'll have to 15 take a break if we don't finish and ask the staff to 16 come back after lunch.
17 MEMBER REMPE: Okay, I just kind of wanted 18 to make sure. And if some of the staff members that's 19 a problem, it's a good time to let us know. And the 20 meeting goes from 12 to one and we apologize.
21 PARTICIPANT: Yeah, no problem.
22 CHAIR KIRCHNER: Go ahead, Anne-Marie.
23 MS. GRADY: The hydrogen and oxygen post-24 monitoring in the containment is used --
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133 1 your mic's turned on.
2 MS. GRADY: Just turned it off, thank you.
3 The hydrogen and oxygen post-accident monitoring in 4 the containment is used to measure the gas 5 concentrations to identify flammable conditions early 6 enough to prevent the deflagration to detonation 7 transition, the DDT event. The NuScale containment 8 integrity post severe accident following a postulated 9 DDT event has been analyzed to be maintained for 72 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />, we're in complete agreement there.
11 Radiolysis, which produces both hydrogen 12 and oxygen, continues for weeks after a severe 13 accident and could lead to a potential DDT threat at 14 or about 45 days. Now, at 45 days NuScale has 15 determined that conditions for combustion would occur, 16 five percent oxygen, at least four percent hydrogen, 17 and there's much more than that, and establishing the 18 conditions for combustion. They are then postulating 19 a DDT.
20 There's no mechanistic analysis that goes 21 all the way out and proves it would occur at those 22 conditions. They're postulating it for conservatism.
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134 1 recommended that the Commission would approve them.
2 And the exemption request number two, which would have 3 required an active system to control hydrogen 4 concentration and containment, we've deemed it not 5 necessary, and we've approved that.
6 The exemption request for the post-7 accident sampling system, which is really the grab 8 samples from the RCS and the containment, was approved 9 predicated on the fact that hydrogen and oxygen 10 monitoring, monitoring the containment atmosphere with 11 this closed loop flow path we've talked about, that 12 that would be in effect.
13 So these two other exemption requests are 14 somewhat conditional upon or significantly conditional 15 upon having hydrogen and oxygen monitoring. So that's 16 the status of the review as of today.
17 MEMBER MARCH-LEUBA: Anne-Marie, let me be 18 the bad guy. How can the staff decide to credit the 19 capability of monitor H2 and O2 concentrations if you 20 don't know that it works? I keep asking you what is 21 the flushing time, and you tell me I don't know.
22 You're telling me I don't know that the system they're 23 proposing to use actually performs the function they 24 claim.
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135 1 you heard earlier, has not been established yet. But 2 we have time to flush. So as far as I'm concerned, 3 timing to take this action is important but not 4 critical. There are hours if not days to do it. And 5 I don't really care if it takes an hour or two hours 6 at all, as long as you can establish a representative 7 sample.
8 MEMBER MARCH-LEUBA: What if it's 100 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br />?
10 MS. GRADY: Pardon?
11 MEMBER MARCH-LEUBA: What if it's 100 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />? What is your limit?
13 MS. GRADY: Well, we probably -- probably, 14 this is speculation, we probably have 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> past 15 the 72 in order to, if we have to, flush it. So the 16 timing is not that critical. And actually, I was 17 going to get into the timing in a later slide.
18 MEMBER MARCH-LEUBA: All I'm asking, I 19 think we're asking, is does, they're proposing to do 20 something that is very counterintuitive, which is 21 opening a -- counterintuitive, which is opening a 22 four-inch line, de-isolate containment, and put in all 23 your environmental containment out there in a system 24 that is non-safety grade.
25 MS. GRADY: Yes.
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136 1 MEMBER MARCH-LEUBA: All I'm asking is 2 does it work for the intended purpose. And neither 3 the applicant nor the staff tells me I've looked at 4 the functioning of the system they propose and I'm 5 happy with what they're proposing. You don't tell me 6 that.
7 MS. GRADY: The system hasn't been 8 designed in detail. There are no line sizes, there 9 are no flow rates, the sample pump hasn't been 10 specified, well --
11 MEMBER MARCH-LEUBA: What requirements 12 would you require? I mean, there should be some 13 requirements put on the COL --- if it takes 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> 14 to flush it, it won't work. You have to tell me what 15 is the limit, and then I'll shut up.
16 MS. GRADY: What I do know about the 17 containment is that it's going to be under pressure 18 somewhere between 70 pounds and 250 pounds, that's 19 number one. So there's going to be a, there's going 20 to be a back pressure on this sample pump. Then 21 there's going to be a sample pump that's going to take 22 into consideration the line sizes.
23 And I have confidence that any reputable 24 engineering company could come up with a sample pump 25 that would do the job, and it hasn't been done yet.
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137 1 But I'm not concerned that they can't do it, that 2 there would not be, in fact, a flow path established.
3 And it would sample from where they take off in the 4 containment.
5 MEMBER PETTI: So Jose, I'm reading the 6 ANSI -- I'm trying to get it.
7 MEMBER MARCH-LEUBA: You found it?
8 MEMBER PETTI: Well, I'm looking, and I'm 9 finding, I'm not sure if it's bits and pieces, it's 10 kind of weird. But there is, again, it's for sampling 11 stacks.
12 MEMBER MARCH-LEUBA: Yes.
13 MEMBER PETTI: So these are really large 14 diameter with small, so you know, four inches is, a 15 stack is bigger than four inches. So there's some 16 commonality, but again, they're worried about a 17 slightly different issue, particulates and isokinetic 18 sampling. But there is discussion in here about the 19 transmission efficiency, the considerations in the 20 design of the transport line to maximize the 21 transmission efficiency. So you know, that in my mind 22 means so it doesn't take forever.
23 PARTICIPANT: Minimize the flushing.
24 MEMBER PETTI: Right, right. I mean, you 25 know, I'll keep digging, but I see stuff that if NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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138 1 you're going to follow the standard, there may be some 2 guidance in here that could be helpful.
3 MEMBER MARCH-LEUBA: I'm ecstatic that you 4 have found it, but I don't think the staff has 5 reviewed it, have you?
6 MS. GRADY: I don't know. And just as a 7 clarification, this isn't a four-inch line size. The 8 CES is four at the CIVs, it necks down to two inches.
9 And then going through the sample pump and the line 10 monitor, it's three-eighths of an inch. We don't know 11 the lengths of each of those dimensions, but it's not 12 a four-inch flow path.
13 And then going back in through containment 14 flooding and drain, that's a two-inch line at the 15 CIVs. So there's a lot of line size changing and we 16 don't know the lengths, so we don't know the volume 17 yet. It will be known. Okay, next slide.
18 Now, we have discussed this topic -- no 19 that's good. We have discussed this topic before with 20 the ACRS, and we have understood, not only in 21 discussions but also in your accident source term 22 letter, that you have two major concerns, I would say.
23 One of them is do we really need to 24 monitor hydrogen and oxygen. And the second is, if we 25 need to, is the design going to work. So these first NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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139 1 two slides I have explain to me, at least, to my 2 satisfaction that we do need to monitor post-accident 3 hydrogen and oxygen.
4 We need to do it in order to be, to inform 5 the timing of the following actions. Whether or not 6 the mitigating action is going to inert the 7 containment with nitrogen using CVCS and the nitrogen 8 distribution system. Or if we take action that's in 9 the GTGs, which is to vent the containment, routing 10 the gas either through the stack or into a radioactive 11 gas waste.
12 And we also need the hydrogen and oxygen 13 monitoring to confirm that either of those two 14 mitigating actions have been successful, whether or 15 not we might need to repeat the action or we're good 16 for a while.
17 And we also, because there are going to be 18 EOPs and there are going to be SAMGs, and we've 19 already seen, we have already seen the GTGs that are 20 intended to be the basis of that, we realize that the 21 concentration of hydrogen and oxygen has already been 22 identified by NuScale as being an important data point 23 for in fact taking a mitigating action.
24 MEMBER BLEY: Can I ask you a question 25 about the venting?
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140 1 MS. GRADY: Yes.
2 MEMBER BLEY: That's in the GTG, as you 3 said.
4 MS. GRADY: Yes, that's the action to 5 take.
6 MEMBER BLEY: On our boiling water 7 reactors a couple years -- several years ago when we 8 were looking at post the accident, NRC decided, 9 Commission decided they didn't need filtered vents 10 because we get substantial filtering in the pool.
11 There's no filtering here, right? This is just going 12 to put containment atmosphere straight outside.
13 MS. GRADY: I think the flow path is 14 through a filter to the stack.
15 MEMBER BLEY: Designed to handle fission?
16 This is not the normal stuff you'd be filtering in 17 normal operation.
18 MS. GRADY: No, it is not, but this 19 supposed to be our accident, this is --
20 MEMBER BLEY: And that, is the filter 21 supposedly designed for that?
22 MS. GRADY: I don't know.
23 MEMBER BLEY: I don't either. But I know 24 when we looked at fan coolers and PWR containments, it 25 was a real issue that probably they won't work because NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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141 1 they'll plug up and then they'll melt from the heat 2 source, from the fission products post-accident 3 because that's not the atmosphere they designed to 4 work in.
5 So either the filters might plug or they 6 might disappear. So it could be a, just a direct 7 release outside of the stuff that's in containment.
8 You didn't look at that.
9 MS. GRADY: I did not look at the filter, 10 no. But venting the containment is the action, the 11 mitigating --
12 MEMBER BLEY: In the GTGs.
13 MS. GRADY: That NuScale has identified as 14 the action to take, yes.
15 MEMBER BLEY: Okay, thank you.
16 MS. GRADY: Next one.
17 MS. PATTON: We have Boyce Travis 18 available to answer any questions, the earlier 19 question.
20 MEMBER BLEY: Okay.
21 MR. TRAVIS: So there were some questions 22 about mixing. I wasn't here for the discussion, so if 23 anyone could repeat the question, I could probably 24 answer it.
25 MS. GRADY: On the ANSI standard.
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142 1 MEMBER BLEY: There were two questions 2 there. We, I think we understand that you looked at 3 mixing, there would be mixing inside the containment 4 up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
5 MR. TRAVIS: Inside both the containment 6 and the RCS, yes.
7 MEMBER BLEY: Okay, we're focused on the 8 containment on this. And then NuScale told us that 9 they need to meet ANSI N13.1-2011, which requires 10 sampling the representative. And my question in that 11 area is are you, did you look at that, and are you 12 convinced that meeting that ANSI standard is adequate 13 -- will give adequate confirmation that we'd get 14 representative sampling through that system in a 15 reasonable time following an accident.
16 MR. TRAVIS: So I'm not familiar with the 17 specific ANSI standard. When I was looking at mixing, 18 I was looking at it more from an engineering 19 perspective in terms of the motivators behind mixing, 20 which is there's a temperature differential between 21 the containment at the pool and the RCS and the 22 geometry that doesn't lend itself well to having an 23 area that would concentrate hydrogen.
24 And so based on some experimental data 25 that had been performed and a look at some of the non-NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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143 1 dimensional numbers that were present in the 2 containment region, we came to a reasonable assurance 3 finding that a sufficient amount of mixing would exist 4 up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and some time beyond 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
5 MEMBER BLEY: In containment.
6 MR. TRAVIS: Within the containment, yes.
7 MEMBER BLEY: Okay, and I guess then as 8 far as we know, and as far as the staff who are here 9 know, nobody's really considered that. And I think 10 all we have to go on is engineering judgment from the 11 staff that when they design this, they'll make sure 12 they get adequate flow through the system and it will 13 be represented. But no reliance on the standard --
14 MR. TRAVIS: No, that's correct.
15 MEMBER BLEY: Okay, thank you.
16 MS. GRADY: Okay, I also believe that we 17 need post-accident hydrogen and oxygen monitoring to 18 inform the timing of operator action to avoid the 19 following. And that is risking an impulse pressure to 20 the inside of the containment vessel, which --
21 PARTICIPANT: We cannot hear.
22 MS. GRADY: I'm sorry. Okay, I also think 23 that we need the post-accident hydrogen and oxygen 24 monitoring to inform the timing of the operator action 25 to avoid risking an impulse pressure to the inside of NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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144 1 the containment vessel, which at 45 days would be 2 approximately double the impulse pressure at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
3 Now, at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> that impulse pressure was 4 deemed to be not threatening the containment after a 5 structural evaluation by NuScale. But they didn't go, 6 as Dr. Corradini has elicited, they didn't go beyond 7 that to see --
8 MEMBER BLEY: Because of the short 9 duration of the ---
10 (Simultaneous speaking.)
11 MS. GRADY: Exactly, okay. But at 45 12 days, the impulse pressure is now double what it was 13 at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The impulse pressure at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> was 14 evaluated structurally. The dynamic flow of this 15 converted into a static pressure. The static pressure 16 was then compared on the vessel itself and also on the 17 flange bolts of the larger bolted flanges.
18 And it was found that the vessel could 19 withstand at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and did not exceed the ASME 20 Service Level D limits, which is what DDT loads are 21 compared to. However, they did notice that the CRDM 22 access flange, which is the big one, 67 inches up on 23 the top of the reactor vessel top head, the flange 24 bolt load was about 85% of what was allowable at 72 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />, okay.
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145 1 So that's probably if it were going to 2 fail and if you kept increasing the pressure, that was 3 probably the location of a most likely failure point.
4 But at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, it wasn't exceeded. Now we get to 45 5 days and they doubled the impulse pressure. And Anne-6 Marie Grady, who is not a structural engineer, thinks 7 we're probably going to exceed the Service Level D 8 allowable loads on those flange bolts.
9 I take that -- I offer that as engineering 10 judgment, there is no calculation, but that's a point 11 of reference. And I think if we think that, and I 12 think it, then we ought to avoid it. And we ought to 13 avoid it by knowing what's going on in the 14 containment.
15 MEMBER RICCARDELLA: And those bolts are 16 on the reactor vessel flange or containment flange?
17 MS. GRADY: Oh, I only talk about the 18 containment, so on the containment vessel.
19 MEMBER RICCARDELLA: Okay.
20 MS. GRADY: This to get access to --
21 MEMBER RICCARDELLA: All right.
22 MS. GRADY: Yeah, that's correct. And if 23 we don't damage the containment and exceed the 24 allowable limits on the flange bolt or something else 25 almost as vulnerable, then we would not be risking an NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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146 1 uncontrolled release to the public.
2 Now, as for capability, this is why I 3 think that the system is going to work and is going to 4 be able to gain representative samples and gain useful 5 information in order to take mitigating actions.
6 First of all, it's a closed-loop monitoring flow path.
7 It's established when the containment pressure is 8 below 250 psig, which is the design pressure of the 9 CES, the post-accident -- the sampling system and the 10 containment flooding and drain system.
11 It requires un-isolating the CES and the 12 CFDS isolation valves. It creates a flow path through 13 the sample pump and the in-line gas monitors and 14 returns it to the containment vessel. The flow path 15 is non-safety related, as NuScale has said, as is 16 acceptable for equipment specifically used for 17 mitigating a severe accident, per SECY-90-016, under 18 the topic equipment survivability.
19 So except for the containment isolation 20 valves, everything else is non-safety related. And I 21 know everybody here is aware of that fact.
22 Okay, in the SER phase 4, Chapter 6, the 23 staff concluded the entirety of the containment, both 24 in the annular region and the dome, would be mixed at 25 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, as Boyce has said. And that was is review.
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147 1 NuScale asserts post-72 hours that convective mixing 2 is driven by decay heat, and that there are no 3 subcompartments to impede mixing. Both points of 4 which I agree.
5 If the non-condensables rise to the, meant 6 to be CNV dome, without mixing, conservative values of 7 oxygen and hydrogen readings would result, and we'd 8 just be taking earlier action.
9 DR. SCHULTZ: So Anne-Marie, you said that 10 NuScale has asserted this, and then you've just said 11 that staff agrees.
12 MS. GRADY: I've said staff agrees 13 convective mixing is driven by decay heat and there 14 are no subcompartments, yes.
15 DR. SCHULTZ: Thank you.
16 MS. GRADY: Oh, the last, I see your 17 point. The last sentence is my conclusion.
18 DR. CORRADINI: Right, but there is data 19 from other designs and other large scale experiments 20 that show an open system, you will pool non-21 condensables at the top due to condensation.
22 MS. GRADY: Yes.
23 DR. CORRADINI: So I'm not disagreeing 24 with what your conclusion is, but I'm only saying that 25 there's data that confirms that sort of behavior.
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148 1 MS. GRADY: Yes.
2 DR. CORRADINI: Okay.
3 MS. GRADY: Okay, in the A -- in your ACRS 4 accident source term letter, you had some comments or 5 questions about the rationale for longterm post-6 accident monitoring. Your letter states that, quote, 7 Weeks are available before monitoring information is 8 needed to inform mitigating actions. The staff 9 elaboration on that is the following. Combustible 10 mixtures, which means five percent oxygen, would occur 11 at 45 days. This in the FSAR, Chapter 19.
12 There's also at 30 days a minimum 13 concentration of four percent oxygen, which has been 14 shown experimentally to allow combustion. So maybe 15 it's not 45 days, maybe we could have combustion at 30 16 days.
17 Okay, now wondering what this would mean 18 in terms of identifying the time when the oxygen 19 concentration would not support combustion, I looked 20 at our confirmatory calculation, which was just a 21 production by -- of hydrogen and oxygen from 22 radiolysis, very similar to what NuScale did.
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149 1 really possible and you could still take action, I 2 would say you could wait up, it would occur at around 3 15 days. My staff recommendation is that if you start 4 monitoring as early as 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and no later than 15 5 days, you would avoid the combustion and the potential 6 DDT conditions that could follow combustion.
7 So, it doesn't, I was trying to point out 8 we don't have weeks, the timeframe is shorter.
9 MEMBER BLEY: I'm still thinking back 10 where I was on several slides ago. If we have a vent 11 path that's not going to be filtered, somebody at NRC 12 and somebody at the power plant are going to have to 13 be very brave to open that flow path. And those of us 14 who sit here and say, well, we might get into trouble 15 with a hydrogen burner explosion have to be, will be 16 weighed against well, how likely is that and how 17 likely is that to break anything.
18 And do I really want to open this thing up 19 and start dumping it to the atmosphere. And with, you 20 know, on a filtered vent I think that was a real 21 concern when we first -- on a vent for the boilers, 22 that was big concern initially. But once we thought 23 enough about how much filtering you get in the pool 24 and people were really trained on it, I think that 25 concern has abated.
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150 1 But on a plant that wouldn't have any 2 filtering, I'm not sure. I think that's going to be 3 pretty darn tough spot we're putting people in. But 4 let's go ahead, I'm just making that comment off the 5 top of my head.
6 MS. GRADY: Okay.
7 MEMBER MARCH-LEUBA: So, what is in the 8 containment? What's the chemical composition of the 9 containment on --
10 MS. GRADY: Other than hydrogen and oxygen 11 and some steam boiling off?
12 MEMBER MARCH-LEUBA: There won't be any 13 steam. Everything is condensed. This is steam to be 14 moisture.
15 MS. GRADY: Other than hydrogen and 16 oxygen, I don't know what else is in the containment.
17 Some residual nitrogen, but I don't think it's --
18 MEMBER MARCH-LEUBA: Iodine, strontium, 19 xenon?
20 MR. STUTZCAGE: All the radionuclides will 21 be there. Most of the iodines would be largely 22 decayed away, but there will be some still there.
23 MEMBER MARCH-LEUBA: But you said the 24 pressure was to be 250 psi?
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151 1 the capability of the flood and drain line.
2 MEMBER BLEY: It has to be less than that 3 before you open up the containment, is what they were 4 saying.
5 MS. GRADY: Yes, that's correct.
6 MEMBER MARCH-LEUBA: The question I'm 7 leading to, is there going to be sufficient pressure 8 in containment to be able to force a flow out of it?
9 I mean, is the pressure going to be 10 greater than atmospheric if all you have is a little 11 bit of hydrogen and oxygen in a big volume?
12 MS. GRADY: Well, they're producing 13 hydrogen and oxygen by radiolysis. We are increasing 14 the pressure all the time.
15 MEMBER MARCH-LEUBA: Is it sufficient to 16 create how much pressure?
17 MS. GRADY: Well, there's also going to be 18 a sample pump that's going to draw from the 19 containment as well as the back pressure in the 20 containment.
21 DR. CORRADINI: But if we could -- I'm 22 assuming NuScale is still on the line. Since they did 23 some conservative calculations, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, would they 24 be willing to say what the pressures are that they're 25 computing at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to answer --
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152 1 MEMBER MARCH-LEUBA: Yeah --
2 DR. CORRADINI: -- your question?
3 MEMBER MARCH-LEUBA: -- that would be 4 nice. At 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> I wouldn't expect any steam to be 5 left there other than humidity. I mean, we have steam 6 in this room.
7 MS. GRADY: I don't know what the total 8 pressure is at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
9 I do know that NuScale has looked at the 10 containment atmosphere just looking at the increase in 11 pressure to move to the production of hydrogen and 12 oxygen from radiolysis.
13 And at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, it's approximately 70 14 psi, but that's just -- well, yeah. It's just --
15 that's just through the -- from radiolysis.
16 If there was already pressure in there, it 17 would be more.
18 MR. TESFAYE: Perhaps we have some 19 information --
20 MEMBER MARCH-LEUBA: So, you're saying 70 21 psi of hydrogen and oxygen.
22 MS. GRADY: Plus whatever was there when 23 -- yes, I am saying that at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. And at 60 days 24 it's about 150 psi.
25 MEMBER MARCH-LEUBA: Boyce maybe -- okay.
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153 1 MR. TRAVIS: Yeah. So, this is Boyce 2 Travis again.
3 So, for some context, like, this is not a 4 simply analysis, per se, because it depends on the 5 degree of core damage and the amount of radiolysis 6 that's happening.
7 MS. GRADY: Uh-huh.
8 MR. TRAVIS: So, it could be a range of 9 pressures from on the order of, you know, 20 to 40 up 10 to -- like Henry (phonetic) said, up to 150 depending 11 on how long in the event you are, and what the degree 12 of core damage, and how much clad-coolant interaction 13 there's been, plus the radiolysis that's happened as 14 a result of the event. So --
15 MEMBER MARCH-LEUBA: So, roughly, it could 16 be up to 150 psi of --
17 MR. TRAVIS: At 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, I would guess 18 tens of psi. As the event transpires 15 days, 100 to 19 150 psi is probably a good estimate.
20 MEMBER MARCH-LEUBA: I don't just throw --
21 you know me, guys. I don't just throw wild things.
22 Why don't you monitor the pressure?
23 MS. GRADY: I beg your pardon?
24 MEMBER MARCH-LEUBA: Why don't you monitor 25 the pressure?
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154 1 If the main contributor to pressure in the 2 containment is hydrogen and oxygen, why do I need 3 mass spec or an infrared system? I measure the 4 pressure.
5 If the pressure goes above 100, you vent 6 it.
7 MR. TRAVIS: Yeah. And so, the reason --
8 part of the reason for that is you don't know the 9 constituents that are going into the containment.
10 So, if you had a severe core damage event, 11 it's going to be almost all hydrogen and the 12 radiolysis is producing hydrogen and oxygen 13 stoichiometrically.
14 If you had a core damage event that was 15 less severe that only had a -- let's -- you know, tens 16 of percent of clad-coolant interaction, you generated 17 less hydrogen initially, but your radiolysis is 18 generating stoichiometric hydrogen and oxygen until 19 you get to that combustible mixture that Henry has 20 discussed.
21 MEMBER MARCH-LEUBA: Let's assume you 22 release all the gases that are contained in the UO2 23 pellets, all of them. What would be the pressure that 24 you would be getting in containment? Not the 100 psi.
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155 1 the oxygen when you could just measure the pressure.
2 DR. CORRADINI: But I think it's -- I 3 thought what Boyce was saying was it's a non-unique 4 value.
5 You could have various combinations of 6 hydrogen and oxygen and steam concentration to get the 7 same pressure. That's what I thought the --
8 MR. TRAVIS: That's exactly right. The 9 pressure just tells you how much gas has been 10 generated.
11 It doesn't tell you what the constituents 12 are in the mixture of hydrogen/oxygen, which is the 13 concern at issue.
14 MEMBER MARCH-LEUBA: The oxygen is almost 15 a constant reaction by radiolysis. It comes from the 16 high-energy gamma rays and you have a pretty good 17 correlation for radiolysis.
18 I think it's extreme to an isolated 19 containment to do something you can bound simply by 20 other measures, but that is me. You know me. I'm 21 different. Especially when I keep asking, does the 22 system work? And you -- nobody can tell me the system 23 actually works.
24 CHAIR KIRCHNER: It hasn't been designed.
25 MS. GRADY: Yes, that's --
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156 1 MEMBER MARCH-LEUBA: It hasn't been 2 designed, but you don't have a spec that says it must 3 work at least this well.
4 If you tell me how well it needs to work, 5 I'll shut up and put you on your ACRS and say, okay, 6 whatever you do the sampling, you have to be able to 7 sample -- the representative sample on the containment 8 means you cannot have a delay longer than 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br />.
9 You make up your mind how many hours you 10 are willing to take a delay on, and that becomes a 11 spec that they have to meet and they'll design it.
12 But right now, you cannot tell me it 13 doesn't have a 1,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />.
14 MS. GRADY: As long as we can sample in 15 enough time to take mitigating action --
16 MEMBER MARCH-LEUBA: I can't hear you.
17 CHAIR KIRCHNER: You're just very quiet.
18 You're soft-spoken. You have to really speak out.
19 MS. GRADY: Okay. As long as we can 20 sample in time to take mitigating actions, I'm not 21 particularly concerned about --
22 MEMBER MARCH-LEUBA: I am.
23 MS. GRADY: Why? We want to protect to 24 containment integrity, we don't want to have it to 25 fail.
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157 1 As long as we can take action in time --
2 let's say 15 days is the answer. What do you care?
3 MEMBER MARCH-LEUBA: The problem is you 4 are protecting the containment integrity, containment 5 which is all under the water, by opening the 6 containment to this vent that Dennis was talking 7 about.
8 MS. GRADY: But if we open it up at a time 9 when there's not going to be any combustion events in 10 the containment, we're not risking anything.
11 It's going to be an intact flow path; 12 isn't it?
13 MEMBER MARCH-LEUBA: It's very 14 counterintuitive and it -- you should have a 15 specification that says, this sample system should 16 work as well as this.
17 MS. GRADY: Okay.
18 MEMBER MARCH-LEUBA: And then --
19 MS. GRADY: But this system is a severe 20 accident mitigating system and it hasn't been fully 21 designed yet.
22 MEMBER MARCH-LEUBA: Yeah. So, the --
23 when I'm designing the system -- because I'm going to 24 start working for them now.
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158 1 system, to what specification do I need to design it 2 for? I don't know. I don't understand.
3 I mean, you say, I want to have hydrogen 4 and oxygen, I need it, I need it, I need it. I agree.
5 But then you say, but it okay if it doesn't work.
6 MS. GRADY: No, I didn't say that.
7 MEMBER MARCH-LEUBA: Yeah, that's what you 8 said.
9 MS. GRADY: I don't care how long the 10 flush time is as long as we get a representative 11 sample and we get the information early enough so we 12 can take action and avoid the DDT, et cetera.
13 MEMBER MARCH-LEUBA: So, there has to be 14 a set of requirements or specifications or goals that 15 the design must satisfy.
16 MEMBER BLEY: If they had argued that the 17 standard gives you that, I'd be more content, but --
18 MEMBER MARCH-LEUBA: I'm trying to get it 19 here, but they want $70 for it.
20 (Discussion off the record.)
21 MS. GRADY: You can get it online, though, 22 from the NRC, Jose.
23 MEMBER MARCH-LEUBA: We will -- over lunch 24 we will find out.
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159 1 things that occurred during our interactions with you, 2 if my memory is correct, you postulated a leakage rate 3 for this system.
4 MS. GRADY: I did not.
5 CHAIR KIRCHNER: You didn't?
6 MS. GRADY: That wasn't my part of my 7 review.
8 CHAIR KIRCHNER: Somewhere we were 9 presented material --
10 MS. GRADY: We have.
11 CHAIR KIRCHNER: Yeah. Sorry, I didn't 12 mean to --
13 MS. GRADY: Okay.
14 CHAIR KIRCHNER: -- impugn you personally, 15 but the staff -- and I'm not impugning the staff, no.
16 I'm just recollecting that the staff presented us 17 material that suggested a leakage rate which would 18 lead to a dose.
19 And that also informed our thinking 20 because that was of concern. And it wasn't clear what 21 that dose was going to be, but I will say it was not 22 insignificant.
23 It wasn't consistent with ALARA. So, that 24 was part of the thinking. I've been going through the 25 viewgraphs and I don't see that anywhere, but there NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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160 1 was some analysis done.
2 Was that you, Ed?
3 MR. STUTZCAGE: Yeah. That was Michelle 4 Hart --
5 CHAIR KIRCHNER: Michelle Hart.
6 MR. STUTZCAGE: -- and she can speak to 7 it. She's here. But, yeah, that was based on maximum 8 acceptable leakage rate for a sampling system in the 9 ANSI standard --
10 CHAIR KIRCHNER: Right.
11 MR. STUTZCAGE: -- and the range of flow 12 rate.
13 CHAIR KIRCHNER: Right.
14 MR. STUTZCAGE: So, we don't have the 15 specific information, but it was based on those 16 values.
17 And I believe -- I mean, yeah, the values 18 could exceed the part 100 dose limits at the upper end 19 of those flow rates.
20 CHAIR KIRCHNER: And that was part of the 21 information we were presented. And that was one of 22 the things that kind of got us thinking it was another 23 trigger, if you will, to say, okay, what's the --
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161 1 dose for something that was of uncertain value.
2 And that informed our thinking as well, 3 and I don't see that in those viewgraphs.
4 MR. TESFAYE: That's the reason for the 5 rule carve-out that we'll be discussing.
6 CHAIR KIRCHNER: Okay.
7 MR. TESFAYE: We have not reached any 8 conclusion on that aspect of the design. So, we're 9 not making any decision --
10 CHAIR KIRCHNER: Okay.
11 MR. TESFAYE: -- on the leakage because we 12 don't have enough information.
13 CHAIR KIRCHNER: But I just want to point 14 out that that weighed in our thinking that, you know, 15 you raised the fact that there's the potential for 16 this exposure and release.
17 And then we're saying, well, how valuable 18 is this information when if we think what has happened 19 has happened and there are other ways to ascertain 20 that, let's go ahead and inert the containment and be 21 done with this.
22 That's one person's opinion, by the way.
23 I would go right to inerting the containment. I have 24 experience with inerted containments and I -- and then 25 we're done.
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162 1 MS. GRADY: Well, if we inert the 2 containment, let's say, at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> immediately --
3 CHAIR KIRCHNER: Right.
4 MS. GRADY: -- we still need to confirm 5 that it is inert, that we've added enough nitrogen.
6 So, we'd still need to --
7 CHAIR KIRCHNER: So, I would design it --
8 we're not in the design business --
9 MS. GRADY: I know.
10 CHAIR KIRCHNER: -- but there are better 11 ways to get that information without un-isolating 12 containment.
13 Anyway, go ahead. Go ahead go through.
14 MEMBER REMPE: Can I ask, why didn't you 15 vent earlier and sample as you vent? I mean, 16 basically it takes a while for a severe accident to 17 progress.
18 Did that get considered?
19 MEMBER MARCH-LEUBA: That's what they're 20 doing. They're venting to the CES.
21 MEMBER REMPE: Right. But if you do it --
22 MEMBER MARCH-LEUBA: They don't vent to 23 the environment.
24 MEMBER REMPE: Yeah. But if you would 25 vent earlier and monitor before 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, you could NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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163 1 see how -- and you know it's not combustible then.
2 But if you started doing it really early 3 -- it's the rules of the game and you can't do that?
4 I mean, maybe the game rules ought to be changed.
5 It's just --
6 MEMBER MARCH-LEUBA: Well, sorry. I'm going 7 to say what he said before, because the reason I'm 8 complaining about this was because what we have here 9 is that if I open the isolation valves, I render the 10 operator/the control room inoperable. You told us --
11 PARTICIPANT: Potentially.
12 MEMBER MARCH-LEUBA: Potentially.
13 PARTICIPANT: Not --
14 MEMBER MARCH-LEUBA: And I said, well, I'm 15 going to render my control room inoperable, 16 potentially, for what?
17 If we need oxygen monitoring, which I know 18 you do believe it and I think I want -- I want to have 19 it too, let's build it right. Let's build one that 20 works.
21 I have no confidence that this one works.
22 That's what I'm saying.
23 MEMBER DIMITRIJEVIC: I want to also make 24 sure that -- because I did already make the point and 25 I said, if they open this before 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> as currently NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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164 1 they have in PRA, they would not satisfy safety goal.
2 If this valve is opened before 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, 3 safety goal is not of the condition or containment 4 performance is burned because it will be one. It's 5 10.1, yes.
6 MEMBER RICCARDELLA: Wait. Wait. The 7 probability if they open that valve into the CES 8 system, the probability of that not -- of that leaking 9 or not containing is not one.
10 MEMBER DIMITRIJEVIC: Yeah, but they're 11 not taking credit for non-safety system. So, they 12 have to assume --
13 MEMBER RICCARDELLA: Wait.
14 PARTICIPANT: It's up to 19.
15 MEMBER DIMITRIJEVIC: Yeah. So, how model 16 is set --
17 MEMBER RICCARDELLA: So, after 19, we 18 don't --
19 MEMBER DIMITRIJEVIC: Yes.
20 MEMBER RICCARDELLA: -- take credit for 21 non-safety systems?
22 MEMBER DIMITRIJEVIC: No. In containment 23 isolation, no. So, the thing is -- for containment 24 isolation, for everything else --
25 (Laughter.)
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165 1 MEMBER DIMITRIJEVIC: -- non-safety system.
2 I just want to say that's probably not 3 true, I mean, that this -- I mean, probably they're 4 not going to have a large release in that time and 5 probably the system will not leak.
6 But how I would model the set currently, 7 that's what I say. How model is set currently, if 8 they open it before 72 hours, the condition of 9 containment probability is one.
10 MEMBER RICCARDELLA: But that's fixable.
11 MEMBER DIMITRIJEVIC: Well, they have to 12 fix the PRA. It's a different story.
13 MS. GRADY: But, as you know, it's not 14 modeled to be opened for this action before --
15 MEMBER DIMITRIJEVIC: No, I know.
16 MS. GRADY: -- 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
17 MEMBER DIMITRIJEVIC: I know. I know.
18 Yeah, but that's what I'm questioning. So, I want to 19 say if they commit that this is not -- I mean, if 20 there is a guarantee they're not going to open before 21 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the PRA is fine.
22 MS. GRADY: That's why they did the 23 structural analysis --
24 MEMBER DIMITRIJEVIC: Right.
25 MS. GRADY: -- for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> --
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166 1 MEMBER DIMITRIJEVIC: Right.
2 MS. GRADY: -- exactly.
3 MEMBER DIMITRIJEVIC: Right. Okay. I 4 just want to make sure that if they open before 72 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />, they have a different safety goal problem as 6 the model is set now.
7 MS. GRADY: I understand your point.
8 DR. CORRADINI: So, my interpretation --
9 I know you have a couple slides to go through, but I'm 10 just trying to understand the logic.
11 So, the logic is that the carve-out is 12 until there is a calculation based on the current 13 design to show that it's acceptable in terms of dose 14 aspects, the concept is acceptable once that is shown.
15 So, that means they can come back -- the 16 COL applicant can come back and say, we're going to 17 ask for a design change, we're going to ask for an 18 improvement in the pressure rating of the system, 19 we're going to ask for an exemption. That's totally 20 up to the COL applicant later.
21 So, everything is on the table given the 22 way this is done as you're proposing it.
23 MR. TESFAYE: Yeah. The exemption part I 24 don't think is going to be a solution, but design 25 change or calculation or leaking -- leakage NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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167 1 information --
2 DR. CORRADINI: Okay. All right.
3 MR. TESFAYE: -- yeah.
4 DR. CORRADINI: Okay. I just wanted to 5 make sure I understood the parameters of what the 6 carve-out meant.
7 MR. TESFAYE: Yeah.
8 DR. CORRADINI: Understood.
9 MS. GRADY: The carve-out only relates to 10 leakage from this --
11 DR. CORRADINI: Correct.
12 MS. GRADY: -- path.
13 DR. CORRADINI: Understood.
14 MS. GRADY: Not monitoring.
15 DR. CORRADINI: Understood.
16 MEMBER MARCH-LEUBA: Okay. So, we don't 17 know whether it works or not and we're not carving 18 that out?
19 MS. GRADY: Pardon?
20 MEMBER MARCH-LEUBA: Alright. I'm beating 21 a dead dog or a dead horse here, but the fact that the 22 monitoring system should actually perform the intended 23 function, which you have no confidence now that it 24 does -- you cannot tell me that -- I have no 25 confidence in this, that should be part of the carve-NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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168 1 out, too.
2 MS. GRADY: I've told you why I have 3 confidence it's going to work. Perhaps we could move 4 on.
5 MEMBER MARCH-LEUBA: But I have no --
6 CHAIR KIRCHNER: Yes.
7 MEMBER MARCH-LEUBA: -- basis to judge 8 that belief.
9 MS. GRADY: Okay.
10 MEMBER SUNSERI: Well, I mean, this won't 11 help you any, but I feel obligated to say it. I used 12 to do startup testing on power plants under 13 construction and, you know, I did the post-accident 14 sampling system and there would be a measurement of 15 the purge time required to get a representative 16 sample.
17 Because of the as-built configuration, 18 there would a leak test. There would be making sure 19 that you could get a representative sample. So, there 20 would be testing done to prove that the sampling 21 system worked as it intended.
22 I think your question is, is what's 23 intended here, right?
24 MEMBER MARCH-LEUBA: Yeah.
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169 1 between systems that you use for normal operation, as 2 you've just identified, and something that's only 3 there for severe accident mitigation. Okay.
4 MEMBER SUNSERI: Just to put an 5 exclamation point on my point, if there's going to be 6 a system design to do this, there will be criteria 7 associated with that design that will be tested as 8 part of the commissioning of the plant.
9 And they will ensure that it works before 10 they --
11 MEMBER MARCH-LEUBA: Who defines the 12 criteria. Why are they --
13 MEMBER SUNSERI: Yeah, I don't know.
14 MEMBER MARCH-LEUBA: Why can't nobody tell 15 me what the criteria -- that's what I'm saying. It 16 shouldn't be criteria I can test my system against.
17 You certified the design would work and 18 you cannot give me the criteria I have to test it 19 again.
20 MS. GRADY: I'm satisfied that the 21 applicant has considered the important aspects of the 22 design and they're committing to having it work.
23 That's what I'm satisfied with given that it's in the 24 severe accident management guidelines.
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170 1 have another item, Item D, and you make a statement 2 that there's outer pressure, temperature and radiation 3 sensors available to follow severe accident 4 progression.
5 And that is what they are for, but they're 6 not there for identifying potential combustion of 7 gases.
8 And in the -- my clarification here is 9 from the equipment survivability design. When you 10 look at the component of the variable, the wide-range 11 containment pressure is going to be qualified until 12 core damage. Not 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Certainly not 60 days.
13 The narrow range containment pressure is 14 going to be qualified up to an hour after the 15 transient.
16 The under-the-bioshield temperature 17 indication is going to be qualified for one hour after 18 the transient.
19 And the under-the-bioshield radiation 20 monitor is going to be qualified for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after 21 core damage.
22 So, this indication of temperature, 23 pressure, radiation sensors are, by qualification, not 24 going to even be available. And furthermore, they 25 don't tell you anything about the potential for NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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171 1 combustion.
2 That's just a clarification on your point 3 in the letter.
4 MEMBER PETTI: We allow non-safety 5 systems. I mean, these things will be used by the 6 operators.
7 They're not going to go, oh, no, that was 8 outside of qualification in the real --
9 MS. GRADY: No. I was just trying to give 10 you a point of data that they might not be --
11 MEMBER PETTI: They might not be, yeah.
12 MS. GRADY: -- there to use. They'll use 13 whatever works, I'm sure.
14 MEMBER PETTI: Right. Right.
15 CHAIR KIRCHNER: But they're really no 16 different than a lot of other systems where you don't 17 require non-safety -- where you don't require safety 18 grade for post-accident qualifications.
19 I mean, it works both ways. These aren't 20 just going to disappear.
21 MS. GRADY: Okay.
22 CHAIR KIRCHNER: Yeah.
23 MS. GRADY: And we probably all expect 24 that they would be functional, but bottom line is they 25 still don't tell you anything about hydrogen and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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172 1 oxygen.
2 They tell you what's going on in the 3 containment in other ways or outside the containment 4 under the bioshield.
5 CHAIR KIRCHNER: Uh-huh.
6 MS. GRADY: There were a lot of discussion 7 in an earlier ACRS session/meeting about alternatives 8 that did not require un-isolating the containment.
9 NuScale has not proposed any, we have not 10 thought of any. All of the accident -- all of the 11 ways of obtaining this information, that we know of, 12 require un-isolating the containment.
13 And the options for actions are, as we've 14 talked about before, inerting or venting.
15 MEMBER REMPE: Again, I know -- I guess I 16 fully don't appreciate the rules of the game, but it's 17 just like you're talking about injecting nitrogen if 18 the applicant were to say let's vent earlier and then 19 monitor what's going on, because usually you don't get 20 core damage early in an event.
21 That could alleviate things a lot easier 22 if --
23 MS. GRADY: Core damage basically takes 24 place and is finished long before the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is up.
25 MEMBER REMPE: Right.
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173 1 MS. GRADY: It's the radiolysis we're 2 concerned about.
3 MEMBER REMPE: So, it seems like you could 4 continue to monitor from the venting and understand 5 and anticipate before you get to combustible 6 configurations earlier.
7 MS. GRADY: Well, yes. The design is --
8 MEMBER REMPE: Yeah.
9 MS. GRADY: -- the design is meant to 10 continuously monitor.
11 MEMBER REMPE: Right now, your second 12 bullet was what I was trying to suggest, venting it 13 earlier and having it get directed, right?
14 MS. GRADY: No. Those are the two 15 mitigating --
16 MEMBER REMPE: Right.
17 MS. GRADY: -- actions that have been 18 recommended and the design supports.
19 MEMBER REMPE: And if they were to do 20 that, couldn't they vent and monitor through that 21 second bullet, is where I was trying to go.
22 MR. STUTZCAGE: Yeah. I think venting 23 here --
24 MEMBER REMPE: They're blowing out a 25 stack.
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174 1 MR. STUTZCAGE: Venting here is to the 2 atmosphere. I think you don't want to do that for the 3 radiological reasons unless you really have to.
4 MEMBER REMPE: Earlier is better than 5 later.
6 MS. GRADY: No.
7 MR. STUTZCAGE: No. No. The radiation 8 doses would be higher earlier.
9 MEMBER REMPE: Well, it depends on how 10 early you're talking about.
11 DR. CORRADINI: Well, I think we're back 12 to the assumptions. They're assuming a severe 13 accident. So, it --
14 MEMBER REMPE: We don't have the option 15 that people typically have in a severe accident. You 16 have to assume --
17 DR. CORRADINI: They're not mitigating the 18 accident. They're assuming there is one and now deal 19 with it.
20 MEMBER REMPE: Okay.
21 MS. GRADY: Okay. And my last real slide 22 was we were asked if we had done -- if one had been 23 done, a risk evaluation for monitoring versus non-24 monitoring. And I tried to put this in a little table 25 to make it -- to compare the different options.
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175 1 And if the operator takes an action, the 2 timing of the action, whether or not they could 3 prevent DDT, whether or not the monitoring path was 4 isolable and what the results were, and venting or 5 inerting if you do it between 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and 15 days, as 6 far as I'm concerned, there's plenty of time to do it.
7 The hydrogen and oxygen monitoring flow 8 path is isolable. Yes, it is. There are limited 9 numbers of reclosing of the containment isolation 10 valves after you've taken that action that NuScale has 11 taken credit for in their design. It's in the FSAR.
12 If you do take the -- either of those two 13 top actions, you prevent DDT from occurring and, 14 therefore, opening the containment isolation to take 15 those actions will not lead to a large release.
16 MEMBER BLEY: And why is that? You've had 17 a core melt and now you're venting either up the stack 18 or to the rad waste system.
19 MS. GRADY: It would be a release, but it 20 wouldn't be a large release because by that time a lot 21 of the aerosols have dissolved back into the --
22 MEMBER BLEY: Okay. Just the decay and --
23 MS. GRADY: Yes. Exactly.
24 MEMBER RICCARDELLA: Excuse me a moment.
25 What's DDT?
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176 1 MS. GRADY: That's the deflagration-to-2 detonation transition. It's the one that gives the 3 highest pressure class.
4 MEMBER RICCARDELLA: Okay. Thank you.
5 MS. GRADY: If you don't take action, 6 however, there's nothing for the operator to do. We 7 don't have to worry about reclosing the containment 8 isolation valves, but you have a potential failure.
9 And in my case, the example was the CRDM 10 access flange bolts failing after about -- after 15 11 days.
12 So, you risk an open containment and 13 that's the -- probably the likely location it would be 14 opened.
15 MEMBER MARCH-LEUBA: Okay. I wanted to 16 give you some -- why I'm so vocal about this. I have 17 experience with sampling systems.
18 When I was in R&L, we used to run a UF6 19 loop which was pipes about this small running in the 20 loop.
21 The volume is minimal, and we were 22 sampling that loop to know the partial pressure of UF6 23 through an infrared system like every ten minutes.
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177 1 sampling it and we were measuring the content of UF6, 2 and the partial pressure of UF6, and we didn't sample 3 this much volume at ten millimeters of mercury 4 absolute pressure.
5 Okay. If you use the system I was using 6 to measure that for the period infrared system, you 7 will never ever empty the CES four-inch pipe.
8 I mean, I tell you in a week, I never 9 empty this much volume -- I'm holding a coffee cup --
10 at 10 millimeters of mercury absolute pressure.
11 So, the criteria and the requirements for 12 that psi system, how much flow you go through there, 13 it's important that -- the system I was using, which 14 would work perfectly for your purposes, would not ever 15 get a representative sample for the containment, ever.
16 So, you need to establish some kind of 17 bypass flow around your sensor so that you actually 18 suck something from the containment so that the CES is 19 representative -- okay.
20 I'm telling you the system, I was using in 21 Oak Ridge to measure UF6, would not work for this.
22 MS. GRADY: I think what you're saying, 23 it's impossible to size a system that would work and 24 do this, and I think you're wrong and it hasn't been 25 sized yet.
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178 1 MEMBER MARCH-LEUBA: Okay. You can decide 2 this thing wrong.
3 MS. GRADY: Yes.
4 MEMBER MARCH-LEUBA: Right. So, there 5 should be some criteria set for how well it works. I 6 think by bringing it up, again, in the -- to give it 7 publicity on these meetings, the applicant will 8 probably design it right.
9 MS. GRADY: Committing to establish a 10 representative sample is a criteria.
11 MEMBER MARCH-LEUBA: Ma'am, a criterion 12 that has not been given much thought.
13 MS. GRADY: I agree on my part. I don't 14 know how much thought has been given by the applicant.
15 MEMBER MARCH-LEUBA: Nobody can tell me 16 what the flow rate is through the sampling system.
17 Nobody can tell me what the volume is.
18 I agree with you that an oxygen monitoring 19 the system is extremely valuable and should be there.
20 I'm insisting that if you are going to 21 open containment, at least ensure that the system 22 works, right?
23 And I don't get any confidence that 24 anybody has given any thought about how the system 25 works.
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179 1 MEMBER SUNSERI: Well, actually at least 2 my thinking, I'm starting to come around to the 3 staff's position on this a little bit. Let me 4 summarize maybe what I'm thinking -- what I'm hearing 5 that gives me more confidence.
6 First off, it's not a four-inch pipe that 7 we're taking a section of. It may be a four-inch 8 nozzle, but it's going to be reduced down to some 9 limited size tubing and isolated from the rest of the 10 CES system for this sampling part. That's one. And 11 that makes me feel more comfortable.
12 Two, there are criteria, I think, 13 representative -- having a system that is going to 14 provide a representative sample at a 72-hour period, 15 I think, is some bounding criteria that a designer 16 would use to design the system.
17 I think having a sampling pump that's 18 going to pull sample off and, you know, not have to 19 rely on a differential pressure system to operate, 20 which was not known to me, and now is, I think makes 21 sense.
22 So, it's starting to look more like a 23 traditional sampling system now than it did when I 24 originally heard the idea.
25 So, you know, I'm not -- I mean, on the --
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180 1 on a by-design sampling system you got to breach the 2 containment as well to get the sample, right, but you 3 have an isolation valve that you open and close.
4 So, that sounds like it's going to happen 5 in this case, too. So, I guess I'm -- I guess, Anne-6 Marie, you've done a good job of alleviating some of 7 my concerns about this system.
8 MS. GRADY: Thank you.
9 MEMBER REMPE: Thank you, Anne-Marie.
10 CHAIR KIRCHNER: With your indulgence, 11 we'll go further into the hour, if that's alright.
12 MR. STUTZCAGE: Yeah. I only have a 13 couple slides here to try to address some of the 14 radiological concerns.
15 So, one of the questions that the ACRS 16 asked about the dose to a worker going out to re-17 isolate the system -- and basically just this slide is 18 we just -- there's too many unknowns for us to come up 19 with the dose to the worker.
20 As we discussed, the dose values to the 21 offsite and the main control room were, you know, 22 based on varying parameters in the -- for flow rate in 23 an ANSI standard and a maximum leak rate.
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181 1 sizes, ventilation flow rates in the room, the volume 2 of the room, et cetera, to be able to come up with a 3 dose to an individual performing an action to re-4 isolate the system.
5 Next slide, please. So, as we discussed, 6 as Anne-Marie said, the staff believes that the 7 information obtained from monitoring is beneficial in 8 assisting operators in making decisions following an 9 accident.
10 Therefore, the staff believes that at this 11 stage of the licensing the best path forward is to 12 retain the rulemaking carve-out.
13 And as we discussed, the carve-out is on 14 the radiological pieces, the regulation for 15 considering leakage and the dose to offsite and 16 members of the public. And for potential operator 17 actions in the field, that regulation is also 18 included.
19 So, one of the -- another potential 20 solution, besides what was discussed earlier, was if 21 the applicant was able to demonstrate the system could 22 be re-isolated, that would, you know, relieve the 23 concern of potentially un -- you know -- controllable 24 release to the environment from opening the system.
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182 1 address.
2 Next slide, please. So, and here's some 3 of the benefits of the rulemaking carve-out. Carve-4 outs are about a licensing tool that are used when 5 appropriate.
6 The carve-out approach does not foreclose 7 any future regulatory decisions or design changes for 8 this issue, and it retains flexibility for staff and 9 NuScale to continue to evaluate this issue while still 10 providing finality on the large majority of the 11 design.
12 And that, I think, concludes our 13 presentation on hydrogen and oxygen monitoring.
14 DR. SCHULTZ: Ed, just to summarize, you 15 mentioned the three different areas that you have 16 concerns about.
17 You don't have enough information to be 18 able to address those concerns --
19 MR. STUTZCAGE: Right. And that's why 20 it's in the rulemaking carve-out for the co-op of the 21 community to try to provide that information and one 22 way or another address it.
23 DR. SCHULTZ: From an engineering sense, 24 you believe that, you know, there ought to be a 25 solution or at least you would be in a position to be NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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183 1 able to analyze whether there, in fact, is a problem.
2 MR. STUTZCAGE: Right.
3 DR. SCHULTZ: The concern is that you 4 haven't been able to address it.
5 MR. STUTZCAGE: Right. Right.
6 DR. SCHULTZ: Not that there is a concern 7 that is --
8 MR. STUTZCAGE: I think that accurately 9 describes it. Thank you.
10 MR. TESFAYE: Okay.
11 CHAIR KIRCHNER: Yes. Let's keep going 12 because I know at least one person has to leave in a 13 little bit. So, I'd prefer to continue.
14 MR. TESFAYE: Yeah. We should go faster.
15 Okay. The next few slides will be presented by Raul.
16 MR. HERNANDEZ: Hi. Good afternoon. My 17 name is Raul Hernandez. I was -- I was a reviewer for 18 the - plant assistant for the spent fuel pool area --
19 spent fuel pool design and spent fuel pool cooling.
20 And in the letter that you guys provided, 21 you mention that you wanted to talk about the 22 resolution of open item 9.1.2-1.
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184 1 sink, because there's just one combined pool, did not 2 include leakage channels behind the welds of the 3 walls. It did provide them on the floor of the pool.
4 The floor of the pool -- there's leakage 5 channels not behind the main panels. We are --
6 because the panels are -- we're not expecting the 7 panels to fail, but operational experience has shown 8 that welding of stainless steel, usually you have some 9 leakage through them. So, there is some leakage 10 channel behind the welds of the panels.
11 And the applicant design did include 12 leakage channels on the floor and the periphery of the 13 pools, but they did not include any behind the walls.
14 So, the staff issued several RAIs. This 15 was not an issue of only one branch. There were like 16 four different branches.
17 And we did an audit with the applicant.
18 And after discussing the result of the audit with the 19 applicant, the applicant decided to add those leakage 20 channels behind the walls of the pool.
21 The leakage detection system basically is 22 just the channels behind the welds and it gets routed 23 to the rad waste drain system.
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185 1 identify leakage, and that's where it gets identified 2 basically.
3 You were asked -- one of the questions 4 that you posed on the letter was about the 5 identification on the alarms and they are part of the 6 rad waste system.
7 MEMBER REMPE: So, is there anything 8 special about the levels they selected? In your SE 9 that you mentioned that they had alarms to go off at 10 predetermined levels, was it just something they --
11 MR. HERNANDEZ: The alarms are not 12 specifically for the leakage detection of the pool.
13 MEMBER REMPE: Uh-huh.
14 MR. HERNANDEZ: They are the alarms of the 15 sumps of the rad waste system.
16 MEMBER REMPE: Okay.
17 MR. HERNANDEZ: During normal operation 18 the rad waste systems isolate all the flow into it.
19 So, any unidentified leakage would come from the pool 20 leakage detection system.
21 MEMBER REMPE: Okay.
22 MR. HERNANDEZ: They have -- if the pumps 23 actuate because of a level alarm, it will inform in 24 the control room.
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186 1 level alarm, because the rate of flow is too high, 2 then it's alarmed locally in the control room and I 3 think it's a waste management control room, too.
4 MEMBER REMPE: Okay. I just wanted to 5 give a high level. I think some of these questions 6 could have been resolved just from an informal 7 communication.
8 And we might want to consider that in this 9 process in the future because it was just -- didn't 10 have enough information to do this on our own.
11 MR. TESFAYE: Yeah. We understand. I 12 sort of mentioned that at the beginning of this 13 presentation.
14 DR. SCHULTZ: Okay. These are monitors 15 that have set points that alarm. We're not getting 16 readings in each of these three locations, but we're 17 getting alarms.
18 MR. HERNANDEZ: The reading is that the 19 pumps were actuated, you know. The alarms for 20 actuation of the pump is basically the pump -- the 21 pumps were actuated.
22 But the flow when it gets transferred to 23 the rad waste system, we get sample, we get -- it's 24 treated through the -- like the normal rad waste.
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187 1 you.
2 MR. HERNANDEZ: Uh-huh. Okay. Now, the 3 next slides is talking about the differences between 4 the Phase 2 and Phase 4.
5 This is -- okay. None of them were 6 related to a design change on the spent fuel pool 7 cooler system. Those were mostly changes to the 8 wording on the SE.
9 In this case, this is a concurrent change.
10 As part of the Chapter 15 evaluation, one of the 11 assumptions for the peak containment pressure was what 12 is the initial temperature of the pool, because that 13 determines the temperature of the containment walls, 14 and the temperature was lowered from 140 to 110. So, 15 the cooling system's maximum temperature limit was 16 lowered from 140 to 110.
17 When the staff evaluated the design of the 18 system as described in the DCA, the system is capable 19 of maintaining the pool below a hundred degrees. So, 20 changing the limit did not change the operation of the 21 system at all.
22 Next. In this one, it's -- yeah, this 23 could have been clarified at informal setting. The 24 safety limit for the spent fuel pool has not been 25 changed. It is 55 feet.
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188 1 There is a discussion in Section 9.1.3 2 dealing with always maintaining -- well, not always.
3 Provisions to keep at least ten feet of water above 4 the stored fuel. And this is for radiation shielding 5 -- to provide adequate radiation shielding.
6 The discussion about the safety limit is 7 the amount of water needed to maintain the fuel cooler 8 for a longer period of time to provide cooling, and 9 the applicant identified this level as 55 feet.
10 The safety evaluation of the spent fuel is 11 discussed in Section 9.2.5, which is the ultimate heat 12 sink, because the spent fuel pool and the ultimate 13 heat sink is just one body of water.
14 So, when we did the thermal evaluation for 15 the system, there was no way to isolate one heat 16 source from the other. So, we just combined one 17 thermal evaluation in Section 9.2.5.
18 Next. This is -- in the Phase 2 we were 19 -- okay. The ultimate heat sink is designed to 20 maintain sufficient inventory of cooling water. So, 21 should -- no makeup is needed for 30 days, but Phase 22 2 stated that no makeup is needed for several weeks.
23 Once -- this change was due -- was 24 performed to maintain consistency between the two 25 sections. We already reach a conclusion that the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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189 1 design has sufficient water for at least 30 days.
2 So, it's better to be consistent through 3 all this, so we made the changes accordingly in this 4 section.
5 This change is reference items. In the 6 Phase 4 SE we made reference to the DSRS. In Phase 2 7 we made reference to the SRP.
8 During the final review process, the 9 applicant in Section 1 -- in Chapter 1 the applicant 10 made clear that they are in conformance with the DSRS.
11 So, the staff revised our SE to be consistent with 12 this.
13 There is no significant changes between 14 the requirements of the DSRS and the SRP. They are 15 basically equivalent.
16 The DSRS was modified to account for more 17 than one core. So, they changed the reference to 18 rated thermal power to account for all the cores, 19 which the SRP is only focusing on one.
20 MR. TESFAYE: Thank you.
21 MR. HERNANDEZ: That was my last slide.
22 MR. TESFAYE: The next slide will be 23 presented by Chang Li.
24 MR. LI: There is also -- the difference 25 that's in Phase 2 SER -- between the Phase 2 SER and NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
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190 1 the Phase 4 SER that shows some questions.
2 The chilled water systems provides the 3 cooling function for the heating and the ventilation 4 systems.
5 The SRP Section 9.2.7 provides guidance to 6 review the systems. So, in Phase 2 SER it's concluded 7 that this systems conforms to GDC 44.
8 GDC 44 is about cooling systems -- cooling 9 requirements that -- and later I think in a concurrent 10 process, the OGC pointed out actually in Chapter 3, 11 there is a section 3.1.4.15 discussing about the 12 conformance of all different GDCs.
13 And NuScale indicates that they do not 14 conform with GDC. Instead, they conform with their 15 design-specific PDC 44 for the cooling systems.
16 The PDC 44 systems, which I stated 17 earlier, I don't want to read it, is similar for 44 18 with the exception that they take care of the safety 19 related systems that the cooling is discharged to --
20 being removed from the ultimate heat sink instead of 21 GDC 44 says the cooling is removed by the other 22 cooling system such as service water systems.
23 So, in that case, the review of the 24 systems, the chilled water system is non-safety 25 systems. It's not important to safety systems.
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191 1 So, if -- when we read that PDC 44, 2 actually all those provisions talking about ultimate 3 heat sink, talking about this redundancy review, 4 interconnections to leak detections, isolation 5 capabilities and single failures, so forth, are not --
6 this provisions are not applicable for the chilled 7 water systems because they are non-safety.
8 So, the wording that's been revised to 9 state now says the chilled water systems are reviewed 10 against the PDC 44, and the provisions in that PDC 44 11 does not apply to the systems.
12 So, that's -- actually there is no change 13 in terms of the systems.
14 MR. TESFAYE: Okay. Thank you.
15 Okay. So, the last couple of slides 16 since, you know, at the beginning of this presentation 17 I mentioned that we didn't discuss open items, how we 18 close them, I want to make sure that we have addressed 19 all the open items for Chapter 9 in this presentation.
20 So, the remaining open items -- there were 21 a couple of open items Section 9.1.1. Both of them 22 related to information that we didn't have. They were 23 both addressed by COL items in this section. And the 24 staff has evaluated the COL items, and they found them 25 to be acceptable.
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192 1 The next one is -- in Section 9.3.2 there 2 were several open items specifically related to either 3 exemption request for process sampling system or the 4 AST topical report methodology.
5 Those were completed with our Phase 4.
6 So, all these items were closed. So, the issuance of 7 the SER for the AST and the approval of the exemption 8 request in Chapter 9.
9 And the last open item deals with lighting 10 system. There is a typo here. It says, this 11 exemption of course is tied -- it should have said, 12 this open item is tied to the completion of the 13 exemption request for GDC 17 and conformance to Reg 14 Guide 1.75.
15 Both those things have been addressed in 16 Section 8.3.1 of the SER. So, this open item is 17 closed.
18 So, all the open items have been closed.
19 And because of our new approach, this streamlined 20 approach, we don't discuss how we close these open 21 items in the ACR. We don't even discuss confirmatory 22 items in the SER.
23 We just leave them as bubbles in the Word 24 document so we can just -- once they are confirmed, we 25 can drop them and issue the final SER.
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193 1 So, this is a new way of doing business 2 now. So, we've learned something from this and we 3 will improve on the process for the next one.
4 MEMBER REMPE: Again, I didn't -- when we 5 brought this up and discussed it in full committee, I 6 mentioned I don't think any of these things are risk 7 significant, but I don't have the knowledge to say 8 let's not bother anymore.
9 So, an informal meeting -- and I think I 10 even had a caveat, is there anything risk significant?
11 And I think you said at the beginning of this 12 presentation there were on changes to the systems, et 13 cetera. There was a lot of just conforming with minor 14 corrections or whatever.
15 So, that helps, but maybe we could have 16 done this without having the whole committee listening 17 to it or the whole subcommittee listening to it.
18 MR. TESFAYE: Thank you.
19 CHAIR KIRCHNER: Thank you, Getachew.
20 Members, any further questions of the 21 staff? No?
22 This is an open meeting, so I'm going to 23 turn next to the public and see if there's anyone in 24 the audience who wishes to make a comment.
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194 1 identify yourself and make your comment.
2 (Pause.)
3 CHAIR KIRCHNER: Seeing no one, the next 4 -- we need to open -- the bridge line is open. Okay.
5 If there is anyone out on the public line who wishes 6 to make a comment, would you state your name and 7 please make your comment?
8 MS. FIELDS: Yes. This is Sarah Fields.
9 I'd like to go back to the discussion of 10 Thelma and Louise and certain considerations related 11 to that movie.
12 That movie was filmed in Moab, Utah, and 13 where you'd see in part of the movie them driving 14 around seemingly going someplace, but they're really 15 just driving around in Arches National Park.
16 In Moab, we have a very well-developed 17 emergency response program for people who go off 18 cliffs. And people go off cliffs.
19 So, emergency response to any accidents is 20 very well-developed in this community. And that, of 21 course, is relevant to your discussion today and to 22 the whole review particularly when the NRC and 23 industry would like to limit emergency response 24 programs for small modular and advanced reactors.
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195 1 and Louse is when they exited Arches National Park, 2 they went about going down -- turning left, going 3 downhill about a half a mile you have the Atlas 4 uranium mill tailings pile.
5 And that now is a $1 billion taxpayer-6 funded mill tailings removal project. And that 7 happened because of over 30 years of Nuclear 8 Regulatory Commission mismanagement of the mill 9 tailings.
10 There were egregious errors on the part of 11 the Nuclear Regulatory Commission, and that is why 12 taxpayers are paying for the removal of these tailings 13 that were produced by a commercial entity, and this 14 has affected our community.
15 So, wherever you have a nuclear 16 installation regulated by the NRC, whether it's a mill 17 tailings, a uranium mill or a new nuclear designed 18 operation such as NuScale SMR, it impacts the 19 community.
20 And when things go wrong, it's the 21 community, it's the workers, it's the taxpayers, it's 22 the rate payers who will be impacted, and I think that 23 both the NRC and the ACRS should put all this into a 24 larger context.
25 Particularly a context where, as with the NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433
196 1 Moab uranium mill tailing site, the NRC never went 2 back and produced a document that outlines all their 3 egregious errors from suppressing documents, from not 4 only having a fraction of the surety that was required 5 to remediate the tailings and site.
6 And that's why Congress took over and gave 7 it to the DOE for -- and eventually a decision was 8 made to take those tailings off the floodplain of the 9 Colorado River while the NRC wanted to just leave them 10 there.
11 So, you have community issues that should 12 be taken into consideration. And when things go 13 wrong, it's up to the NRC to assure that there will be 14 documentation of what went wrong.
15 So, as -- if and when a NuScale 12-module 16 reactor is constructed and operation commences, I 17 would expect the NRC will make sure that whatever 18 assumptions they originally made were the correct 19 assumptions.
20 Then if even small things go wrong or are 21 not in keeping with the original expectations, that 22 there will be a complete review of -- and a complete 23 public review of what exactly is happening and what 24 NRC decisions were correct or incorrect as this 25 facility moves forward. Thank you.
NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433
197 1 CHAIR KIRCHNER: Thank you, Ms. Fields.
2 Any other members of the public wishing to 3 make a comment, please do so.
4 (Pause.)
5 CHAIR KIRCHNER: Okay. Hearing none, at 6 this point I think we can adjourn our meeting. Thank 7 you all.
8 (Whereupon, at 12:35 p.m. the meeting was 9 adjourned.)
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 NEAL R. GROSS COURT REPORTERS AND TRANSCRIBERS 1323 RHODE ISLAND AVE., N.W.
(202) 234-4433 WASHINGTON, D.C. 20005-3701 (202) 234-4433
LO-0220-69059 February 28, 2020 Docket No.52-048 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738
SUBJECT:
NuScale Power, LLC Submittal of Presentation Materials Entitled ACRS Subcommittee Presentation: NuScale FSAR - Chapter 20, PM-0220-69058, Revision 0 The purpose of this submittal is to provide presentation materials to the NRC for use during the upcoming Advisory Committee on Reactor Safeguards (ACRS) NuScale Subcommittee Meeting on March 4, 2020. The materials support NuScales presentation of NuScale FSAR Chapter 20.
The enclosure to this letter is the nonproprietary presentation entitled ACRS Subcommittee Presentation: NuScale FSAR - Chapter 20, PM-0220-69058, Revision 0 This letter makes no regulatory commitments and no revisions to any existing regulatory commitments.
If you have any questions, please contact Jim Osborn at 541-360-0693 or at josborn@nuscalepower.com.
Sincerely, Zackary W. Rad Director, Regulatory Affairs NuScale Power, LLC Distribution: Robert Taylor, NRC, OWFN-8H12 Michael Snodderly, NRC, OWFN-8H12 Christopher Brown, NRC, OWFN-8H12 Gregory Cranston, NRC, OWFN-8H12 Michael Dudek, NRC, OWFN-8H12 Omid Tabatabai, NRC, OWFN-8H12
Enclosure:
ACRS Subcommittee Presentation: NuScale FSAR - Chapter 20, PM-0220-69058, Revision 0 NuScale Pow er, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360-0500 Fax 541.207.3928 www.nuscalepower.com
LO-0220-69059
Enclosure:
ACRS Subcommittee Presentation: NuScale FSAR - Chapter 20, PM-0220-69058, Revision 0 NuScale Pow er, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360-0500 Fax 541.207.3928 www.nuscalepower.com
NuScale Nonproprietary ACRS Subcommittee Presentation NuScale DCA FSAR Chapter 20 March 4, 2020 1
PM-0220-69058 Revision: Copyright 2020 by NuScale Power, LLC.
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Presenters Jim Osborn Licensing Engineer Chris Maxwell Senior Reactor Operator 2
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DCA Chapter 20 Changes
- The DCA text was revised in Section 20.1.3 to include pointers to Tables 20.1-1, 20.1-2 and 20.1-3
- Footnotes were added to Tables 20.1-1, 20.1-2 and 20.1-3 to clarify that monitoring is not relied upon for the mitigation strategies and guidelines
- Footnote states, Monitoring is not relied on for the mitigation strategies and guidelines, but installed instrumentation provides at least 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of module monitoring and at least 14 days of UHS monitoring as a supplementary capability.
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DCA Section 20.1.3 Changes 4
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DCA Table 20.1-1 Changes 5
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DCA Table 20.1-2 & -3 Changes 6
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Acronyms AC Alternating Current SFP Spent Fuel Pool UHS Ultimate Heat Sink 7
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Portland Office Richland Office 6650 SW Redwood Lane, 1933 Jadwin Ave., Suite 130 Suite 210 Richland, WA 99354 Portland, OR 97224 541.360.0500 971.371.1592 Charlotte Office Corvallis Office 2815 Coliseum Centre Drive, 1100 NE Circle Blvd., Suite 200 Suite 230 Corvallis, OR 97330 Charlotte, NC 28217 541.360.0500 980.349.4804 Rockville Office 11333 Woodglen Ave., Suite 205 Rockville, MD 20852 301.770.0472 http://www.nuscalepower.com Twitter: @NuScale_Power 8
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LO-0220-69072 March 3, 2020 Docket No.52-048 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738
SUBJECT:
NuScale Power, LLC Submittal of Presentation Materials Entitled ACRS Subcommittee Presentation: NuScale Topic - Hydrogen Monitoring, PM-0220-69071, Revision 0 The purpose of this submittal is to provide presentation materials to the NRC for use during the upcoming Advisory Committee on Reactor Safeguards (ACRS) NuScale Subcommittee Meeting on March 4, 2020. The materials support NuScales presentation of hydrogen monitoring.
The enclosure to this letter is the nonproprietary presentation ACRS Subcommittee Presentation: NuScale Topic - Hydrogen Monitoring, PM-0220-69071, Revision 0.
This letter makes no regulatory commitments and no revisions to any existing regulatory commitments.
If you have any questions, please contact Matthew Presson at 541-452-7531 or at mpresson@nuscalepower.com.
Sincerely, Zackary W. Rad Director, Regulatory Affairs NuScale Power, LLC Distribution: Robert Taylor, NRC, OWFN-8H12 Michael Snodderly, NRC, OWFN-8H12 Christopher Brown, NRC, OWFN-8H12 Gregory Cranston, NRC, OWFN-8H12 Michael Dudek, NRC, OWFN-8H12 Getachew Tesfaye, NRC, OEFN-8H12
Enclosure:
ACRS Subcommittee Presentation: NuScale FSAR Topic - Hydrogen Monitoring, PM-0220-69071, Revision 0 NuScale Pow er, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360-0500 Fax 541.207.3928 www.nuscalepower.com
LO-0220-69072
Enclosure:
ACRS Subcommittee Presentation: NuScale Topic - Hydrogen Monitoring, PM-0220-69071, Revision 0 NuScale Pow er, LLC 1100 NE Circle Blvd., Suite 200 Corvallis, Oregon 97330 Office 541.360-0500 Fax 541.207.3928 www.nuscalepower.com
NuScale Nonproprietary ACRS Subcommittee Presentation NuScale Topic Hydrogen Monitoring March 4, 2020 1
PM-0220-69071 Revision: 0 Copyright 2020 by NuScale Power, LLC.
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Presenters Matthew Presson Licensing Project Manager Jim Osborn Licensing Engineer 2
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Introduction
- Design Basis vs. Beyond Design Basis
- Timing of Detrimental Combustible Mixture
- Operational Decisions for Hydrogen (H2) Monitoring
- Radiation Protection Issue
- Equipment Capability to Withstand Combustion Events
- Containment Mixing and Sampling 3
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Design Basis vs. Beyond Design Basis
- The NuScale facility was designed using a framework of Design Basis and Beyond Design Basis categories for accident mitigation:
- Design Basis Accident (DBA)
- A postulated accident that a nuclear facility must be designed and built to withstand without loss to the systems, structures, and components (SSCs) necessary to ensure public health and safety.
- Beyond Design Basis Accident (BDBA)
- This term is used as a technical way to discuss accident sequences that are possible but were not fully considered in the design process because they were judged to be too unlikely. In that sense, they are considered beyond the scope of design-basis accidents that a nuclear facility must be designed and built to withstand.
- As the regulatory process strives to be as thorough as possible, beyond design-basis accident sequences are analyzed to fully understand the capability of a design.
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Design Basis vs. Beyond Design Basis
- Design Basis Accident (DBA)
- If an SSC is relied upon to remain functional (to meet regulatory criteria) during and following a DBA, then the SSC must be categorized as (as appropriate):
- Single Failure Proof
- Safety-Related
- Seismic Category 1
- 1E Power
- If an SSC is not categorized as such, it cannot be relied upon for accident mitigation
- Therefore, the safety analysis of an DBA can only credit SSCs that are appropriately categorized, as above
- SSCs that are categorized in a lesser category cannot be credited in accident analyses
- Example: Typical Chapter 15 accidents 5
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Design Basis vs. Beyond Design Basis
- Beyond Design Basis Accident (BDBA)
- Because BDBAs are considered more unlikely than DBAs, nonsafety-related SSCs can be credited for accident mitigation
- Example: ATWS (10CFR50.62) and SBO (10CFR50.63) allow the use of nonsafety-related equipment for accident mitigation
- Often include multiple failures beyond those considered for DBEs, and thus more realistic assumptions are allowed in the analyses
- This is also why 10 CFR 50.44 was revised by the NRC (in 2003) to allow the hydrogen monitoring system to be nonsafety-related, therefore not single failure proof, not seismic category 1, and no 1E power source
- Therefore, the NuScale hydrogen monitoring system is not safety-related, not single failure proof, not seismic category 1, and does not have 1E power, because it is used only for beyond design basis accidents 6
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Timing of Detrimental Mixture
- A detrimental mixture is a combustible mixture which can threaten containment integrity
- Analysis shows there is a minimum of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> before a detrimental mixture can be developed
- 100% core damage is not the most limiting scenario relative to time
- 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is NuScales design basis passive coping period
- after 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the applicant states that this represents a reasonable period of time to implement severe accident management guidelines to mitigate the accumulation of combustible gases. This time period aligns with that used in current regulatory precedent and is therefore acceptable. Chapter 6 SER, Section 6.2.5.4
- Exemption from 10CFR50.44(c)(4) is not recommended 7
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Operational Decisions for H2 Monitoring
- Analyses show there is at least 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> before a combustible mixture could threaten containment
- Therefore, the plant personnel have time to weigh options and inspect systems before use
- Reg Guide 1.7 provides a risk-informed decision process
- Appropriate priority with other activities
- Need for the information by decision-makers
- Insights from experience or evaluation
- Therefore, in the unlikely use of the H2 monitoring system, evaluations and inspections can occur 8
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Radiation Protection Issue
- The system is unlikely to leak because:
- Included in the Leakage Control Program
- Used during normal operations
- Operators have sufficient time to inspect system prior to use
- If the H2 monitoring system leaks during its use, operators could isolate and repair the leak
- The ERO to develop ad hoc, unplanned operator actions performed under 10 CFR 50.47(b)(11)
- NRC Staff states that the DCA scope of design does not provide enough information to perform this dose analysis
- Staff position is that this will be carved out of the rule to be resolved at a future time 9
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Equipment Capability to Withstand Combustion
- The containment can withstand any combustion event for the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />
- Per FSAR Table 3.2-1, the pressure boundary of monitoring path can withstand combustion events, like the containment
- NuScale and NRC Staff agree that this design capability is provided for the monitoring pathway 10 PM-0220-69071 Revision: 0 Copyright 2020 by NuScale Power, LLC.
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Containment Mixing and Sampling
- ANSI N13.1-2011 requires sampling be representative
- Regulations [10 CFR 50.44(c)(1)] require that containments ensure a mixed atmosphere during design basis and beyond design basis accidents
- Analysis shows that containment is well-mixed, even neglecting ECCS flow, with plant conditions stable
- NuScale and NRC Staff are in agreement regarding compliance with 10 CFR 50.44(c)(1).
- Given the large margin between the calculated Ra and conditions indicative of turbulence, the staff finds it reasonable to conclude that the entirety of containment will be mixed (even before considering the effect of additional flow stimulated by steam flow from the RVVs and condensation on the walls). -Chapter 6 SER, Section 6.2.5.4 11 PM-0220-69071 Revision: 0 Copyright 2020 by NuScale Power, LLC.
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Summary and Conclusions
- Core melt accident is a beyond design basis accident
- Consistent with industry practice, allows nonsafety-related SSCs
- The low frequency of a NuScale core melt accident makes it hard to see how it can be considered credible
- Bounding analyses shows there is a minimum of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> before containment can be threatened
- Decision to place system into service would follow RG 1.7 risk-informed process and appropriate precautions
- There is sufficient time to inspect and evaluate system condition
- If excessive leaks develop, can isolate and repair
- Monitoring path can withstand combustion events
- Containment is well-mixed and representative sampling is required 12 PM-0220-69071 Revision: 0 Copyright 2020 by NuScale Power, LLC.
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Acronyms ATWS Anticipated Transient Without SCRAM BDBA Beyond Design Basis Accident CES Containment Evacuation System CNV Containment Vessel DBA Design Basis Accident FCI Fuel-Coolant Interaction FR Federal Register GDC General Design Criteria Mcyr module critical year ms milli-second SBO Station Blackout SER Safety Evaluation Report SRM Staff Requirements Memo SSC Structure, System, or Component TMI Three Mile Island 13 PM-0220-69071 Revision: 0 Copyright 2020 by NuScale Power, LLC.
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Portland Office Richland Office 6650 SW Redwood Lane, 1933 Jadwin Ave., Suite 130 Suite 210 Richland, WA 99354 Portland, OR 97224 541.360.0500 971.371.1592 Charlotte Office Corvallis Office 2815 Coliseum Centre Drive, 1100 NE Circle Blvd., Suite 200 Suite 230 Corvallis, OR 97330 Charlotte, NC 28217 541.360.0500 980.349.4804 Rockville Office 11333 Woodglen Ave., Suite 205 Rockville, MD 20852 301.770.0472 http://www.nuscalepower.com Twitter: @NuScale_Power 14 PM-0220-69071 Revision: 0 Copyright 2020 by NuScale Power, LLC.
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Containment Isolation Failure
- Chapter 19 documents an assessment of whether a severe core damage event, with a steam explosion that results in containment failure (e.g., CES containment isolation failure) could lead to a large release (NUREG-0396)
- The conclusion is that at the earliest possible time of fuel-coolant interaction (FCI), the airborne fraction of volatile fission product aerosols is less than the calculated threshold for a large release.
- 6.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> is the earliest possible time of FCI for intact containment accidents 16 PM-0220-69071 Revision: 0 Copyright 2020 by NuScale Power, LLC.
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Containment Isolation Failure
- If containment is unisolated for the purpose of combustible gas monitoring resulting in a leak, this would be a similar situation, except that it would be expected to occur at a later time, potentially as late as 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />
- This would result in additional containment aerosol deposition
- The release would not be directly to the atmosphere
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Presentation to the ACRS Subcommittee NuScale Power, LLC (NuScale)
Design Certification Application Review Safety Evaluation with No Open Items:
Chapter 9, Auxiliary Systems And Related Topics March 4, 2020
Technical Reviewers:
Anne-Marie Grady, NRR/DRA/APLC Angelo Stubbs - NRR/DSS/SCPB Michelle Hart, NRR/DANU/UART Bob Vettori - NRR/DRA/APLAB Edward Stutzcage - NRR/DRA/ARCB Tony Nakanishi, NRR/DRA/APLA Tony Gardner - NRR/DNRL/NCSG Alexandra Siwy - NRR/DSS/SNRB Alexander Chereskin - NRR/DNRL/NCSG Alissa Neuhausen - NRR/DRA/APLC Fanta Sacko - NRR/DEX/EENB Ryan Nolan - NRR/DSS/SNRB Andrew Yeshnik - NRR/DANU/UART Raul Hernandez - NRR/DSS/SCPB Nan Chien - NRR/DSS/SCPB Dawnmathews Kalathiveettil - NRR/DEX/EICA Hanry Wagage - NRR/DSS/SCPB Chang Li - NRR/DSS/SCPB Project Managers:
Greg Cranston - Lead Project Manager Getachew Tesfaye - Chapter Project Manager March 4, 2020 2
Contents Phase 3 Open Items Requiring Further ACRS Review H2 and O2 Post-Accident Monitoring and Process Sampling System Pool Leakage Detection System (PLDS)
Pool Bulk Temperature UHS Minimum Safe Water Level and Makeup Water DSRS Section 9.1.3.III.3.D vs SRP Section 9.1.3.III.1.D Chilled Water System (CHWS) and GDC 44 /PDC 44 Requirements Other Phase 3 Open items 3
Status of H2 and O2 Post-accident Monitoring in Containment H2 and O2 post-accident monitoring is used to measure the gas concentrations in the CNV to identify flammable conditions early enough to prevent a deflagration to detonation transition (DDT) event.
The NuScale CNV integrity post severe accident following a DDT event has been analyzed to be maintained for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Radiolysis which produces both H2 and O2 continues for weeks after a severe accident and could lead to a potential DDT threat at or about 45 days.
Exemption Request #2 staff finding credits H2 and O2 post-accident monitoring for mitigation actions.
Exemption Request #16, (PASS) staff finding credits the capability to monitor H2 and O2 concentrations as required by 10 CFR 50.44(c)(4) 4
Focus Area - ACRS AST letter Need for long-term post-accident H2 and O2 monitoring.
To inform the timing of the following actions:
Inert the containment atmosphere with nitrogen via CVCS and DNS or Vent the containment during accident conditions (i.e., routing the gas either to the plant exhaust stack (RBVS) or to the gaseous radwaste system (GRWS).
and Confirm success of above mitigating actions Inform the actions in the EOP and the severe accident management guidelines (SAMG) 5
ACRS AST letter and related topics Need for long-term post-accident H2 and O2 monitoring.
By informing the timing of operator action, avoiding:
Risking an impulse pressure to the inside of the CNV, which, at 45 days:
would be approximately double the impulse pressure at 72 hrs, and could lead to CRDM access flange (CNV25) bolt load exceeding the ASME Service Level D strain limits Risking an uncontrolled release to the public.
6
Focus Area - ACRS AST letter Capability of the design for accurate long-term post-accident H2 and O2 monitoring.
The H2 and O2 monitoring closed loop flowpath is established by:
Confirming CNV pressure is < 250 psig (design pressure of CES, PSS, and CFDS)
Unisolating the CES and the CFDS CIVs Creating a flow path from the CNV via CES through the PSS sample pump and in-line gas monitors, and returning to the CNV via CFDS.
This flowpath, except for the CIVs, is non-safety related, as is acceptable for equipment specifically used for mitigating a severe accident, per SECY-90-016, Equipment survivability.
7
Focus Area - ACRS AST letter Capability of the design for accurate long-term post-accident H2 and O2 monitoring.
In SER P4, chapter 6, staff concludes that the entirety of containment, both in the annular region and dome, would be mixed at 72 hrs post-accident.
NuScale asserts that post 72 hrs:
convective mixing is driven by decay heat, and there are no sub-compartments to impede mixing If non-condensables rise to CNMV dome without mixing, conservative O2 and H2 concentration readings would result.
8
Focus Area - ACRS AST letter ACRS comments about the rationale for long-term post-accident H2 and O2 monitoring.
In the December 20, 2019, ACRS letter (Item b):
Weeks are available before monitoring information is needed to inform mitigating actions.
Staff elaboration:
Combustible mixtures (5% O2) would occur by 45 days post-accident The minimum concentration (4% O2) would occur by 30 days Prior to reaching combustible mixtures (O2 > 3%) would occur in 15 days Staff conclusion:
Start monitoring as early as 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and no later than 15 days.
9
Focus Area - ACRS AST letter ACRS comments about the rationale for long-term post-accident H2 and O2 monitoring.
In the December 20, 2019, ACRS letter (Item d):
other pressure, temperature and radiation sensors available to follow severe accident progression Staff clarification per the NuScale equipment survivability design:
Component/variable Duration of qualification Wide Range Containment Pressure Until core damage Narrow Range Containment Pressure 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> after transient Under the Bioshield Temperature 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> after transient Under the Bioshield Radiation Monitor 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after core damage None of these components indicate potential for combustion of gases.
10
Focus Area - ACRS AST letter ACRS comments about alternatives to long-term post-accident H2 and O2 monitoring that dont unisolate the containment The options for actions which prevent combustible/detonable conditions in containment all include reopening isolation valves:
Inerting by injecting N2 into the containment via the CVCS or Venting the containment by using the CES system and directing the gas to the RBVS stack or the GRWS No alternatives have been provided or identified by NuScale which would provide the concentration in containment of the combustibles, H2 and O2 without unisolating the CNV.
11
Focus Area Topics PSS post-accident monitoring of O2 and H2 risk evaluation Operator action to Time for operator H2O2 monitoring Prevent DDT prevent H2 Result action path isolable? pressure pulse combustion DDT Opening CNV will vent CNV via 3days< t <15 days yes yes not lead to large CES+RBVS release Opening CNV will inert CNV via 3days< t <15 days yes yes not lead to large CVCS+DNS release potential failure of CRDM access take no action N/A N/A no flange bolts after 15 days 12
Focus Area - ACRS AST letter Dose to an Individual Re-Isolating the Combustible Gas Monitoring System:
The staff does not currently have enough information from NuScale such as system flow rate, system leakage rate, ventilation flow rate, room volumes, the specifics of the piping and equipment, etc., to be able to estimate the dose to an individual performing actions to re-isolate the systems.
13
Focus Area - ACRS AST letter Rulemaking Carveout for Leakage Associated with H2/O2 Monitoring:
The staff believes that the information obtained from monitoring is beneficial in assisting operators in making decisions following an accident.
Therefore, the staff believes that at this stage of licensing the best path forward is to retain the rulemaking carveout.
14
Focus Area - ACRS AST letter Rulemaking Carveout for Leakage Associated with H2/O2 Monitoring:
Benefits:
Carveouts are a valid licensing tool that are used when appropriate, The carveout approach does not foreclose any future regulatory decisions or design changes for this issue, and Retains flexibility for staff and NuScale to continue to evaluate this issue while still providing finality on the large majority of the design.
15
Pool Leakage Detection System (PLDS)
Open Item 9.1.2-1 Concern : The staff identified that the PLDS did not include leakage channels behind the pool walls, the staff requested the applicant to modify the design of the PLDS accordingly, or to justify how the proposed design meets its intended function.
Resolution: After several RAI responses and a Staff audit, the applicant modified the PLDS to include leakage channels behind the UHS pool wall liner.
The PLDS functions in conjunction with the RWDS equipment drain subsystem. The PLDS directs liner leakage into the RWDS sumps. These sumps are monitored for sump levels, temperatures and radiation. Alarms are monitored locally, in the main control room, and the waste management control room.
16
Pool Bulk Temperature Phase 4 SER Section 9.1.3.4.4 states that the pool cooling systems are designed to maintain the pool bulk temperature below 110ºF.
The Phase 2 SER had a temperature of 140ºF.
As a result of the revision of the containment peak pressure analysis discussed in Chapter 15, the applicant reduced the maximum initial reactor pool temperature from 140ºF to 110ºF.
Revision 3 of the NuScale DCA revised the temperature limit for the pool cooling systems in Section 9.1.3.
The change in operational limits is bounded by the thermal analysis performed at 140ºF and evaluated in Section 9.2.5.
17
UHS Minimum Safe Water Level and Makeup Water Section 9.1.3.4.4 of the Phase 4 SER indicates that the minimum safe water level for the UHS (with respect to ECCS operation) is 55 ft from the floor of the pool. The Phase 2 SER stated that this minimum height was 3 meters above the top of fuel.
This does not represent a change in the system design.
The minimum safety water level (assumed in the thermal calculations) remains unchanged at 55 feet from the bottom of the pool. Section 9.1.3.4.1 of the Phase 2 SER indicated this.
The minimum coverage of 10 ft (3 m) is to ensure adequate radiation shielding for the operator on the pool deck.
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UHS Minimum Safe Water Level and Makeup Water Section 9.1.3.4.4 states that the UHS is designed to maintain sufficient inventory of cooling water, such that no makeup water is needed for at least 30 days. The Phase 2 SER states ..such that no makeup water is needed for several weeks.
Section 9.2.5 of this SE concluded that UHS maintains sufficient inventory such that no makeup water is needed to fulfill its intended functions for at least 30 days.
This change maintains consistency between the two SE Sections.
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DSRS Section 9.1.3.III.3.D vs SRP Section 9.1.3.III.1.D The Phase 4 SER stated that the DSRS Section 9.1.3.III.3.D recommends that the cooling system should retain at least half of its full heat removal capacity assuming a single active failure. The Phase 2 SER stated that the SRP Section 9.1.3.III.1.D recommends that the minimum heat removal capacity of the forced-circulation cooling system be greater than 0.3 percent of the reactor rated thermal power.
This does not represent a change in the system design, DCA Chapter 1 indicates that the applicant is in compliance with DSRS, the SE was revised to more accurately reflect the regulatory basis.
Section 9.1.3.4.4 (page 32) addresses the systems capability to handle 0.3 percent of the total plant thermal output.
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Chilled Water System (CHWS) and GDC 44 /PDC 44 Requirements The discussion about the ability of CHWS to meet GDC 44 /PDC 44 differs significantly in the Phase 4 and Phase 2 SERs.
The CHWS provides cooling for the heating and ventilation systems. SRP Section 9.2.7 provides guidance for the CHWS for the conformance of GDC 44 on the cooling water function. In Phase 2 SER, the staff concluded that the CHWS complied with the requirements of the GDC 44.
NuScale cooling water system is committed to conforming to PDC 44, instead of GDC 44.
NuScale PDC 44:
A system to transfer heat from structures, systems, and components important to safety, to an ultimate heat sink shall be provided. The system safety function shall be to transfer the combined heat load of these structures, systems, and components under normal operating and accident conditions. Suitable redundancy in components and features, and suitable interconnections, leak detection, and isolation capabilities shall be provided to assure that the system safety function can be accomplished, assuming a single failure.
In the NuScale passive design, the CHWS does not support any safety-related SSCs under normal and accident conditions. Therefore, in Phase 4 SER, the staff determined the provisions of PDC 44 do not apply to this system.
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Other Phase 3 Open items 9.1.1 - Criticality Safety of New and Spent Fuel Storage Open Item 9.1.1-1: Because the applicant did not specify a neutron absorbing material, the staff requested additional details on manufacturing and materials qualification
- The applicant added COL Item 9.1-9, which will demonstrate that the selected material and the as-manufactured neutron absorber products meet the acceptance criteria in the criticality and materials analyses Open Item 9.1.1-2: The applicant indicated its intent to make the structural analysis of the spent fuel racks a COL item
- The applicant added COL Item 9.1-8, which will provide a structural evaluation and confirm that thermal-hydraulic, criticality, and material analysis aspects remain valid The staff reviewed the COL items and finds them acceptable.
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Other Phase 3 Open items 9.3.2 Process and Post-accident Sampling Systems Open Items 9.3.2-1, 2, 3, 4, 5, 6, and 8.
These seven open items were tied to the completion of the exemption request for post-accident sampling requirement and the accident source term (AST) topical report.
These open items were addressed with the exemption request approval in Section 9.3.2 of the staffs SER and the SER for the AST topical report.
9.5.3 Lighting Systems Open Item 9.5.3-1 This exemption request is tied to the completion of the exemption request for GDC 17 and conformance to RG 1.75. The applicant stated that the guidance in RG 1.75 regarding physical separation between lighting circuits that are not safety-related and safety-related circuits is not applicable because all onsite AC power systems are not safety-related and non-Class 1E.
This open item is addressed by exemption from GDC 17 and evaluation of RG 1.75 in Section 8.3.1 of the SER.
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Abbreviations AST accident source term HVAC heating ventilation and air conditioning CDE core damage event PSS process sampling system CDST core damage source term PWR pressurized water reactor CES containment evacuation system RBVS reactor building ventilation system CFDS containment flooding and drain system REA rod ejection accident CNV containment vessel rem Roentgen equivalent man COL combined operating license RG regulatory guide CRHS control room habitability system RRV reactor recirculation valve CRVS normal control room HVAC system RVV reactor vent valve CVCS chemical and volume control system SA severe accident EOP emergency operating procedures SAMG severe accident management guidelines DBST design basis source term SECY Commission paper DCA design certification application SGTF steam generator tube failure DF decontamination factor SMR small modular reactor EQ environmental qualification SSCs structures, systems and components ES equipment survivability TEDE total effective dose equivalent FHA fuel handing accident TR topical report DRAFT 24