ML20207E258
| ML20207E258 | |
| Person / Time | |
|---|---|
| Issue date: | 05/27/1999 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| ACRS-T-3074, NUDOCS 9906040210 | |
| Download: ML20207E258 (235) | |
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ORIGINAL FFICIAL-TRANSCRIPT OF PROCEEDINGS 0: j NUCLEAR REGULATORY COMMISSION <
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 1
Title:
ACRS MEETING ON SEVERE ACCIDENT MANAGEMENT '
TRO4 i AC'RS ;
RE ~RN OR:G NE i TC BNti:TE d g i M/S T-2E264 415-713; i Docket No.: 7;wers: * -
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Work Order No.: ASB-300-799 O
I LOCATION: Rockville,MD i
DATE: Thursday, May 27,1999 PAGES:1 - 168 9906040210 990527 FDR ACRS T-3074 PDR
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I DISCLAIMER UNITED STATES NUCLEAR REGULATORY COMMISSION'S ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 1
MAY 27, 1999 The contents of this transcript of the proceeding of the United States Nuclear Regulatory Commission Advisory I Committee on Reactor Safeguards, taken on May 27, 1999, as reported herein, is a record of the discussions recorded at the meeting held on the above date.
This transcript had not been reviewed, corrected and edited and it may contain inaccuracies.
1 1 UNITED STATES OF AMERICA
() 2 3
NUCLEAR REGULATORY COMMISSION j
l 4 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 5 ***
6 ACRS MEETING ON SEVERE ACCIDENT MANAGEMENT 7
8 9 U.S. Nuclear Regulatory Commission 10 Room T2-B3 11 Two White Flint North l-12 Rockville, Maryland 13 14 Thursday, May 27, 1999
( 15 16 The subcommittee met, pursuant to notice, at 8:30 17 'a.m.
l l 18 1
19 PRESENT:
20 THOMAS S. KRESS, Chairman, ACRS 21 ROBERT L. SEALE, Member, ACRS l 22 GRAHAM B. WALLIS, Member, ACRS 1
l 23 MARIO V. BONACA, Member, ACRS ,
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2 l' ' PARTICIPANTS:
2 PAUL BOEENERT, Cognizant ACRS Staff Engineer 3 A'. EDWARD SCHERER, Southern California Edison 4 THOMAS G. HOOK, Southern California Edison 5 MIKE SNODDERLY, NRR .!.
6' ROBERT CHRISTIE, Performance Technology 7 OWEN THOMPSON, Nuclear Fuels Analysis Group 8 GARY HOLAHAN, NRR 9 MR. MALLIAKOS 10 MR. RAINSBERRY 11 MR. PARVIZ MOIENI 12 13-14
() 15 16 17 :
l 18 19 1
20 !
l 21 22 23 l 24 25 O ANN RILEY & ASSOCIATES, LTD.
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Il 3
1 PROCEEDINGS
/ \ 2
{8:30 a.m.)
b 3 DR. KRESS: Will the meeting please come to order.
4 This is a meeting of the ACRS Subcommittee on 5 Severe Accident Management. I'm Dr. Thomas Kress, Chairman 6 of the Subcommittee. ACRS Members in attendance are Drs.
7 Mario Bonaca, Robert Seale, and Graham Wallis.
8 The purpose of this meeting is to review the 9 application of the Southern California Edison Company for an 10 exemption to the hydrogen control requirements for the San 11 Onofre Nuclear Generating Station. The Subcommittee will 12 gather information, analyze relevant issues and facts, and 13 formally propose positions and actions as appropriate for 14 deliberation by the full Committee.
( 15 Mr Paul Boehnert is the cognizant ACRS staff 16 engineer.for this meeting.
17- The rules for participation in today's meeting 18 have been announced as part of the notice of this meeting 19 previously published in the Federal Register on May 3, 1999.
20 A transcript of this meeting is being kept and 21 will be made available as stated in the Federal Register 22 notice. It is requested that speakers use the microphone 23 and before they start please identify themselves with name 24 and affiliation so that we can get it on the record.
25 We have received a written request from Mr. Robert
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4 1 Christie'of Performance Technology for time to make an oral l
() 2 3
statemen't to'the' Subcommittee, and he is scheduled to speak
'following the conclusion of the NRC staff presentation.
4 I don't have any additional comments to make. Do 5 any of the Members of the Subcommittee wish to say anything )
6 before we start?
7 Seeing none, I say we just get into it, so I'll 8 call upon Mr. Ed Scherer of Southern California Edison to 9 get us started.
10 You may go up to the front. It would be much 11 better for us. We_get a stiff neck looking over this way.
12' MR. SCHERER: My name is Ed Scherer. I'm manager 13 of nuclear regulatory affairs at Southern California Edison, 14 and I was just going to be making a very brief set of
() 15 remarks, and the basic presentation will be given by Mr.
16 Hook. So if we could'just start with some of the overheads.
17 Basically the outline of our request is to 18 eliminate the existing hydrogen control system from the 19 design basis of San Onofre 2 and 3 based on a risk-informed 20 submittal we made recently to the staff. By removal we mean l 21 to-remove them from the technical specifications and from 22 referencing in the USFAR. We would remove them from our 23 emergency operating instructions. And while we might not 24 physically remove the equipment, we would reduce the 25 maintenance resources on the system that is found to be not i
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1- risk-significant.
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2 DR. KRESS: Now when you talk about the hydrogen 3 control system, that includes more than just the 4 recombiners, doesn't it?
5 MR, SCHERER: That's correct. And we will talk 6 specifically about the four components of the system.
7 DR. KRESS: Okay 8 MR. SCHERER: One part is part of the containment
'9 design that obviously is a physical part of the containment, l
10 and it won't be affected. But we will talk about the four 11 parts of the system that are affected.
12 DR. KRESS: I had in mind specifically the purge
! 13- and vent. Was that considered part of the hydrogen -- l
~14 MR. SCHERER: Yes.
() 15 DR. KRESS: Yes. Okay.
16 MR. SCHERER: The purge is considered part of the i i
17 system. The four parts of the system would be the 18 recombiners, the purge, the monitoring, and of course the 19 ability of the containment to mix.
20 DR. KRESS: Are you going to say what you would do i l
21 with the purge and vent system?
22 MR. SCHERER: Yes. I I
-23 This effort was originally conceived as part of an 24 NEI whole-plant study. This was considered Task 0, which !
25 was a three-part application. We'll go into that in some ,
1 l
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6 1 detail. The first was an application from Arkansas Nuclear
(~} 2 1 asking for relief on the time required to put the hydrogen I
\s s 3 monitoring into service. The second was our application, 4 and there was a third application considered behind ours as 5 a Task 0 effort for this whole-plant study.
6 It has now been subsumed into the NRC program for 7 modifying Part 50 to be risk-informed, and is part of their 8 tasking memorandum.
9 And again, our application is consistent with 10 risk-informing the maintenance rule, i.e., we found that the 11 hydrogen control system as it currently exists is not and 12 would not be under a revised maintenance rule a 13 risk-significant system.
14 DR. KRESS: Is that -- you have then run some sort
() 15 of a risk analysis --
16 MR. SCHERER: Yes.
17 DR. KRESS: To make that determination?
18 MR. SCHERER: Yes. And basically if you go to the 19 next slide, the reason we're making this application, and 20 that was the purpose of my introduction, is to get to this 21 point, is that we found the reason that we're requesting 22 elimination of the requirement for the hydrogen control 23 system is that it is not needed for accidents based on 24 realistic assumptions. If you utilize realistic 25 assumptions, the hydrogen control system is not needed. If 1
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7 1- you take a' severe accident, a hypothetical severe accident,
(} 2 then the hydrogen control system does not meaningfully
-3 contribute to the management of the hydrogen that could be 4 -generated. It's not sized such that it can meaningfully 5 ' reduce risk. i 6 DR. KRESS: That's a rate issue, I take it. The 7 recombiners don't really have a capacity to -- do they
.8 saturate, or --
)
9 MR. SCHERER: You can only really use a recombiner 10 system between about 1 percent hydrogen, and at about 3-1/2 11 you terminate the use of the recombiner.
12 -DR. KRESS: Yes, that's for other reasons, though, 13 but you could use -- you know, if'you were between those 14 ' ranges --
() 15 MR. SCHERER: Right.
16 DR. KRESS: You could use it for a long, long, 17 long time. You wouldn't saturate it. It's just the rate --
i 18 MR. SCHERER: Rate.
19 DR. KRESS: Rate function. It doesn't take 20 hydrogen out fast enough that it just -- it gets overwhelmed 21 by the severe. accident --
'22 MR. SCHERER: Exactly, i
i i
23 DR. KRESS: It would just go through that range so 24 fast.
25 MR. SCHERER: In a realistic, it's not needed. In O, ANN RILEY & ASSOCIATES, LTD.
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1 a severe accident, it's overwhelmed. There is a narrow band 1
() '2 3-in'the middle,La design basis accident. In that theoretical design basis accident ~it would keep up with and could 4 mitigate it..
5J .DR. KRESS: Okay.
6 MR. SCHERER: But that's in a very narrow band --
7 DR.'KRESS: And you're going to tell us why that's I 1
8 not a useful --
9 MR. SCHERER: That's part of our presentation. i l
10 DR. KRESS: Okay. 'i 11 DR. WALLIS: So it was designed based on the 12 design basis accident.
I 13 MR. SCHERER: Exactly.
14 DR. KRESS: The design basis accident didn't get
() 15 into these runaway hydrogen productions in severe accidents.
16 It's mostly water reaction with the clad, and, you know, 17 radiolysis, so it's very low rates of generation.
18 MR. SCHERER: Radiolysis. And again it's a 11 9 - post-TMI requirement that looked like it was a good idea at 20 the time.
21 DR. KRESS: It sounded like a good idea after all 22 that --
23 MR, SCHERER: Exactly.
24 DR. KRESS: Hydrogen debate at TMI.
25 MR. SCHERER: Yes.
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9 1 Finally the backup, the hydrogen purge system,
() 2 3
would not be needed in that we have a large dry containment and we could on a theoretical basis withstand the burn, and
- 4. of course if you go into a hydrogen purge, you always stand 5 'the risk of not being able to isolate the containment after 6 the purge, and there is a measurable risk of -- ..
7 DR. KRESS: Let me ask you about that. The purge j 8 system is a vent filter systemi right?
9 MR. SCHERER: The hydrogen purge is part of the-10 system; yes.
11 DR. KRESS: It's filtered, though.
12 MR. SCHERER: Hepa filters; right.
13' DR. KRESS: So even if the valve stuck open, 14 you're going through a filtered system, and what are you
() 15 releasing, the noble gases?
16 MR. SCHERER: Yes.
1 17 DR. KRESS: And wouldn't they get released anyway?
18 Because you have sufficient leakage --
)
19 MR. SCHERER: I'm talking about once you purge, l 20 the risk of not being able to close the valves after you 21 . intended to complete your purge.
22 DR. KRESS: I know, but you'd still have to go 23 through the filter system.
24 MR. SCHERER.: Yes, you would still go through the 25 hepa filters.
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!' 10 l 1 DR. KRESS: Yes. So it's not --
2 MR. SCHERER: But you're also challenging those 3 filters as well.
4 DR. KRESS: Oh, I see.
5 DR. SEALE: You roll them out.
6 DR. KRESS: You may have a problem there. So the 7 risk could be going up just from that.
8' MR. SCHERER: Yes.
9 DR. KRESS: Okay.
10 DR. WALLIS: You spoke of a hydrogen burn.
11 MR. SCHERER: Um-hum.
12 DR. WALLIS: How about detonations?
13 MR. SCHERER: We've looked at that.
14 DR. WALLIS: Difference in the loads. You're
() 15 going to talk about detonations, too?
16 MR. SCHERER: Are we going to --
17 MR. HOOK: Yes.
18 DR. WALLIS: Okay.
19 DR. BONACA: Just one question. Talking about the 20 - purge. Is the reason why you cannot close the purge or you 21 may fail it open? I notice it's tied to just the loss of 22 one train will cause the valve to fail open? I was reading 23 here in the application, page 5, and it says that when the 24 hydrogen purge unit is operated following a LOCA, then loss 25 of train B power would prevent closing the containment O ANN RILEY & ASSOCIATES, LTD.
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, 11 1 isolation valve.
.2. Does it'mean that it'is vulnerable to just one 3 failure, one single failure?
4 MR. SCHERER: Yes. Tom?
5 MR. HOOK: Yes.
6 DR. BONACA: And that was part of the original 7 design? Or is it supposed to be safety grade?
8- MR. SCHERER: I don't think the requirement was 9 that it be single failure proof.
10 DR. BONACA: Okay.
11 MR. SCHERER: This is a post-TMI addition to the 12 plant.
13 DR. BONACA: Okay. Thank you.
14 MR. SCHERER: Finally, we believe that eliminating
() 15 the hydrogen control systems and the activities associated 16 with the hydrogen control systems simplifies the emergency 17 operating instruction, streamlines it and simplifies it at a 18 time when people are.trying to make difficult and complex
- 19. decisions. So we consider that simplification.a positive --
- 20. a risk-positive benefit.
21 So those are the basic reasons we made this 22; application for a change and for the elimination of the 23 system. I state those as conclusions. To derive those 24 conclusions we put together a presentation which will be 25 given by Mr Tom Hook, who is our manager of the Nuclear
()
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12 1 Safety Groupland'is responsible for the PRA analysis that
.2' supports this application.
[}
3- If there are no further questions.
4 MR. HOOK: Good morning. My name is Tom Hook.
-5 I am with Southern California Edison Company. The 6 NEI Whole Plant Study.was the initiator for this activity as 7 Ed indicated. And we started work on this in 1997, and I 8 made I think a number of presentations to the staff on this,.
9 the elements of this application since that time.
.10 This activity that we selected for our license 11 change was one which had been submitted previously by 12 Waterford Nuclear Station, and similar to the Arkansas 13 nuclear request, that had been submitted previously as well 14- and rejected.
() 15 This has been a multi-year effort. We made our 16 . submittal on September of last year after-about a year of 17 presentations and analysis. The purpose of the NEI Whole y 18 Plant Study was to examine the impact of regulations on l
19 plant safety cost using PRA insights. There were three 20 pilot plants in the NEI Whole Plant Study, of which we were 21 one. The Task Zero elements were elements to test the
'22 ability of the staff and the licensee to develop 23 applications that would support revision of the regulation 24 through exemptions.
25 The Whole Plant Study has evolved into the NRC L
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13 1 project entitled, " Modify Part 50 to be Risk-Informed," and
~
('a') 2 the tasking memorandum and the description of that activity 3 is in the SECY-98-300, Option 2 and Option 3, relating to 4 phased rulemaking to revise the scope of structure systems 5 and components subject to regulation.
6 The next slide, I have already discussed this and, 7 broadly, the Arkansas nuclear exemption request was to l 8 extend the hydrogen sampling time from 30 to 90 minutes. As ,
9 I indicated, that had been previously submitted and l j
l 10 rejected, and it was granted by the NRC in the last year.
11 We made a submitte.1 based upon our Waterford 12 submittal a number of years earlier to eliminate hydrogen 13 control requirements from the design basis and then a third 14 plant has been contemplating submitting an exemption from n
(
v
) 15 the 10 second diesel start time and loss of off-site power 16 concurrent with a loss of coolant accident, and that has not 17 been submitted.
18 To move on to the hydrogen control system, the 19 current licensing basis for the hydrogen control system is 20 to limit the containment hydrogen concentration post-LOCA to 21 below the flammability limit, which is approximately 4 22 percent for hydrogen in a containment atmosphere post-LOCA.
23 And the regulations that describe the requirements for the 24 design of the hydrogen control system are 10 CFR 50.44, 25 standards for combustible gas control and lightwater l
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14 l' reactors, 10 CFR'50, Appendix A, the'GDC 41' containment
() 2~ atmosphere cleanup,l10 CFR 50, . Appendix C, Section 6, i 3 emergency response data system for the hydrogen inputs to 4 that system.
5 DR. KRESS: Let me ask you-a question about the 6 regulatory' process. I was wondering whether the recombiners
]
7 play any role in severe accident management guidelines that 8 you have, which are not requirements, but are I think 9 . voluntary. Are they in there anywhere?
10 MR.. HOOK: Yes,-the hydrogen recombiners are in 11l the severe accident management guidelines and there is-12 direction on use of the hydrogen recombiners in a severe !
13 accident. And I can describe that if you are interested.
14 DR. KRESS: Well, I was wondering what would
() 15 happen to those. Would that be removed.from'the guidelines 16' if this --
-17 MR. SCHERER: Let me speak to that. Our intent, 18 if this is approved, is we would probably leave the
'19 recombiners in place, and our severe accident management 20 guidelines would continue to refer to the recombiners if 21 available. We would not eliminate any reference to the 22' recombiners, we would simply predicate it on as they are 23 available. )
24 DR. KRESS: Okay. Thank you.
I
- 25. MR. SCHERER
- Which is essentinlly the way we l
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1 15 1 refer to them now.
2 DR. SEALE: Could you just refresh our memories?
[%.)T 3 Here you have mentioned that the flammability limit is 4
{
4 percent. I seem to recall there is something called a 5 deflagration limit and a ignition or an explosive limit.
6 Could you remind us as to what those percentages are so we 7 get an idea of what the margins are?
8 MR. HOOK: Owen or Parvis, do you have any 9 information?
10 MR. MOIENI: This is Parviz Moieni from SONGS 11 also. The detonation is much, much higher. I think I have 12 seen like 13 -- more than 13, 13 to 16 percent. And this is 13 just the burn, which is 4 to 6 percent.
i 14 DR. SEALE: That is what I understand.
r'
(%) 15 DR. KRESS: You can get detonations as low as 10 16 percent. I 17 MR. MALLIAKOS: My name Asimios Malliakos. I am 18 working in the hydrogen area. We have --
19 DR. SEALE: With whom?
l 20 MR. MALLIAKOS: NRC.
21 DR. SEALE: I'm sorry.
22 MR. MALLIAKOS: Yes, we do have the flammability 23 limits, which flammability limits and the other ones, the 24 explosion limits that you are.saying, probably you are 25 talking about the detonability limits. Now, flammability
(}
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16 1 limits, we have three different limits, is the upper limit
() 2 3
which is 4 percent, when you have the flame basically can go upwards. We have the 6 percent if we can propagate in a 4 horizontal way. And we have the downward limit which is S-5 somewhere in the area between 7 and 8 percent.
6 Detonability limits, of course all of these things 7 can change with the amount of steam that we have.
8 Detonability limits, the lowest we have is like 12-1/2 9 percent.
10 DR. SEALE: Okay. That jibes with my 11 recollections.
12 MR. HOOK: And consistent with the individual 13 plant examination evaluation that-we perform of the 14 containment, we did not assume that there was any potential-() 15 for detonation, even in a severe accident, based upon the 16 hydrogen concentrations we would see in a severe accident 17 with the worst case assumptions.
18 And the last reference is Regulatory Guide 1.7, 19 which describes in more detail --
20 DR. KRESS: I want to return to that last 21 statement, because I think it is important. If you use the 22 you said worst case limits, if you go through the severe 23 accidents and calculate the range of hydrogen generation 24 over the full sequences, you are saying that the 25 concentration never gets up to this 12.5 percent because of ANN RILEY & ASSOCIATES, LTD.
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1 17 1 your volume of your containment?
2 MR. HOOK: That's correct.
)
3 DR, KRESS: That's important because even without 4 -- even having no recombiners in there at all, you would 5 never get above the detonation limits.
6 MR. HOOK: That's correct.
7 MR. BONACA: That's because also you rely on your 8 car fans for ventilation, for circulation and containment?
9 DR. KRESS: For mixing, yeah.
10 MR. BONACA: Mixing.
11 DR. KRESS: You could get pockets in 12 stratification. Yeah, you have got to always consider that.
13 MR. BONACA: No , I was -- my question was, how 14 much do you rely on active components to not having large
() 15 pockets of hydrogen concentration above 12-1/2 percent?
16 DR. KRESS: Yeah, that is -- you had becter rely 17 on mixing.
18 MR. BONACA: Okay. You have to rely on those.
19 DR. KRESS: You are not going to take out the 20 mixing systems, are you?
21 MR. HOOK: No.
'22 DR. KRESS: I mean they are still going to be in 23 there. But this the virtue of having a large dry 24 containment.
25 MR. HOOK: Exactly. The next slide, this
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p 18 1 describes the subsystems of the hydrogen control system, and
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)
- 2. I am going to describe in more detail the elements of each 3 of these-subsystems. The first subsystem is the monitoring 4 subsystem, and this is a post-accident monitoring subsystem 5 that is it provides a direct read-out of the hydrogen. It 6 has monitors located inside the containment.
7 The next subsystem is the recombiner subsystem and 8 the purge subsystem and the mixing subsystem.
9 DR. SEALE: You say hydrogen, you have detectors 10 or hydrogen monitors, several in the containment?
11 MR. HOOK: We have two trains of hydrogen monitors 12 and they are located in the containment. And.I think the 13 next slide describes that in more detail. Okay.
14 DR. SEALE: Okay. You are going to tell me how 15
(( ) many and so on?
16 MR. HOOK: Yes. Yes. In slide 10, to describe 17 the hydrogen monitoring subsystem, we have two redundant 18 safety-related monitors that are designed to measure 19 hydrogen concentration inside the containment and alert the 20 operators to initiate the hydrogen recombiners or the 21 hydrogen purge system. The detectors are located inside the 22 containment.
23 The monitors themselves are located -- the 24 detectors are located above the operating deck inside 25 containment. Their operating range is 0 to 10 percent ANN RILEY & ASSOCIATES, LTD.
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19 1 hydrogen. .The monitoring is manually initiated by the
)
2- operators following direction from the emergency operating
'3 instructions.
'4 DR. KRESS: These are continuous online readings, 5 they are not grab samples?
6 MR. HOOK: That is correct, they are continuous 7 online.
8 MR. BOEHNERT: Could you move that slide up a 9 _little bit, please, so people can see it?
10 MR. HOOK: Yes.
11' MR. BOEHNERT: Thank you.
12 MR. ~ HOOK: The emergency operating instructions 13: caution the operators to calibrate the hydrogen monitors 14 prior to their use, since they are not temperature f%
() '15 compensated automatically, and there is a limit to the
- 16. number of times they can be recalibrated during an event 17 based upon their design, which is approximately 40 -- 40 18 times. And the calibration is performed remotely outside 19 the containment by instrumentation and control personnel.
-20 So they cannot be relied upon until they are calibrated, and 21 as'the temperature in the containment changes during the 22- accident, they have to be recalibrated at every point that 23 -they.take them where the temperature has deviated.
24 DR. KRESS: Can you take the reading and correct 25- it without recalibrating the instrument? Correct it for
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20 1 temperature if you knew what the temperature was?
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2 MR. HOOK: I don't believe that is part of our 3 process. I don't'think that is --
4- DR. KRESS: What'is the operating physics of the 5 monitor, is it a probe to measure -- a thermal conductivity 6 probe?
7 MR. HOOK: I don't know. Parviz, Owen, do you 8 have any information on that?
9 MR. MOIENI: I don't have any details, but I know 10 that basically there are -- a calibration is done. They 11 have nitrogen _and hydrogen bottles which are located inside 12 the containment, but the calibration basically is done 13 remotely from outside the control room. But how the physics 14 works, I don't know.
-( ) 15 DR. KRESS: It depends on what kind of_ probe it 16 is. You may be able to correct it analytically.
17 DR. SEALE: It sounds like --
18 DR. KRESS: It may be a conductivity probe.
19 MR. SNODDERLY: Dr. Kress, this is Mike Snodderly 20 from the staff. What San Onofre, of course, is speaking of, 21 is their specific application. Other plants are capable of 22 recalibrating or adjusting based on bias curves from the 23 manufacturer, so, in other words, you get containment 24 temperature and then you come up with a bias.
25 Other plants do it by using the grab sampling
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21 1 capability. Measure a grab sample in a gas chromatograph
(} 2 and then recalibrate based on that to compensate. So there 3 is other things that one can do besides going down and 4 performing a total recalibration.
5 I would -- there was a study done in 1981 by 6 Sandia that looked at, you know, what is the best way to 7 monitor hydrogen and how do you do this, and they also took 8 a survey of industry. And, basica.' ly , 90 percent of the 9 plants out there use thermal conductivity detectors.
10 And there is two big differences in how they use 11 them. One I would classify as a wet measurement.
12 Basically, they pull it through a heat traced sample line, 13 measure the thermal conductivity of t11e mixture. Then they 14 put it into a chamber where it is saturated with oxygen, and O
( j 15 the hydrogen is burned off. Then they measure the thermal 16 conductivity again and the difference is the hydrogen 17 concentration.
18 DR. SEALE: Yes.
19 MR. SNODDERLY: Now, that is rare. Alost utilities 20 don't do that. Most utilities just take what we would call 21 a dry sample, so it is not in a heat trace line, the steam 22 condenses out and they compare the thermal conductivity with 23 hydrogen just compared to air. And that is -- that is how 24 they measure the hydrogen.
25 DR. KRESS: Now, this particular is specific for ANN RILEY & ASSOCIATES, LTD.
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1 22 1 the SONGS 2 and 3 units. So --
[ 2 MR. SNODDERLY: I think it specific in sense of 3 how they deal with the bias due to temperature for the 4 thermal conductivity detector. Their thermal conductivity 5 detector i's typical of most people in the industry.
6 DR. KRESS: What I was -- the purpose of that 7 comment was, if your guys grant this exemption, does that 8 have hidden implications or ramifications for other. plants 9 that'you talk about? Does it set a precedent or something 10 that you have to keep following?
11 MR. SNODDERLY: Yes. I believe'we could speak to 12- that, I guess when --
13, DR. KRESS: Okay. We will wait-for your guys.
14 MR. SNODDERLY: Yes, that may be more appropriate.
() .15 DR. WALLIS: I am wondering why you mentioned 16 these last items.
17 MR. HOOK: These are limitations in using the 18 monitors, that is the reason why we identify --
19 IMt. WALLIS: You want to do away with them? I 20 mean one argument could be these are lousy monitors, you 21 need better ones.
22 MR. HOOK: Well, we haven't proposed to do away-23 with the monitors, we have proposed to remove them from the 24 design basis. ,
25 DR. WALLIS: Yeah, but to say that they are ANN RILEY & ASSOCIATES, LTD.
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23 1: ~ awkward-to use is no reason for-doing away with them if they 2 could'be useful. One could say that we need a better
[
3 technology for monitoring hydrogen.
4 DR. KRESS: That leads to another question. What 5 are you going to do with-this information? What do you do 6 with the information on hydrogen once you get it?
7 DR. SEALE: You just need a-bigger tank.
8 DR. KRESS: Is that part of your emergency 9 operating procedures and plans for emergency response?
10 MR. HOOK: Yes, I am going to get-into that, but 11 that is --
12 DR. KRESS: Oh, you are going --
13 MR. HOOK: Yes. I will describe how we use the 14 monitors in terms of operating equipment and identifying the
()- 15 severity of the core damage.
16 DR. SEALE: Is it true that the ability to 17 recalibrate or the number of times you can recalibrate is 18; tied to the capacity of the storage tanks you have available
'19 for providing a hydrogen, a known hydrogen concentration 20 sample?
21 MR. HOOK: That's correce 22 DR. SEALE: So it is nt- he monitors are lousy, 23 -it is just they had a limited size reservoir of hydrogen for 24- that standard samples.
25 DR. WALLIS: They are lousy if someone has to take ANN RILEY & ASSOCIATES, LTD.
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24 1 a lot of time to recalibrate during a period when they ought gf 'T 2- to be doing something else.
3 MR. SCHERER: And that is the reason we brought up
- 4' those points. During a time where this would be
- 5. necessarily, we are adding complexity to a process'and it is 6 not feeding a decision that is necessary to be made. And 7 that_is the balance of our presentation, that we are asking J 8 the' operators and the people making the decision s to gather 9 a lot of information on'the use of the system, where we 10 would put it into operation at 1 percent and would not 11 operate it over 3-1/2 percent. We need to gather data to 12 make a determination whether to use that system during a 13 very difficult time.
,_ 14- And the point is we shouldn't be diverting I
() 15 16 people's attention to making that decision, that we could eliminate that decision process because it doesn't 17 meaningfully add to risk reduction.
18 DR. WALLIS: Well, it seems that having a measure 19 of hydrogen concentration would be useful. It doesn't have 20 to be a distraction unless one makes it a distraction in ;
1 21 their procedures. l I
22 MR. SCHERER: There is a lot of useful information 23 that we would like to have during an accident but what we 24 are trying to do is keep the operators focused on decisions
.25 that are necessary to protect the health and safety of the l ANN RILEY & ASSOCIATES, LTD.
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25 1 public and reduce risk.
/ .2 DR. BONACA: I think, however, that the question 3 is that would you want to be in a degraded core condition 4 without the ability of measuring hydrogen concentration?
5 Certainly the answer is no. What means do you have. I 6 think you have an application you mentioned also, the PASS 7 system.
8 MR. SCHERER: Right.
9 DR. BONACA: I think some people are telling us 10 the PASS system is so slow and so it seems that the same 11 argument is being made about the monitoring system and the 12 PASS system and I would like to know how we are going to 13 determine then hydrogen concentration if we are in the 14 condition of the core?
() 15 MR. SCHERER: And that is an excellent question.
16 This application was submitted before we made a decision 17 whether we were going to submit an application. separately to 18 modify or eliminate our PASS system, so if'in fact we do and
}-
19 we are currently planning on submitting an application on 20 the PASS system, we probably will decide to leave in a i
2 11 hydrogen monitoring system or leave in the capability to get
- 22. a grab sample, so'there will have to be an ability to get 23 .the hydrogen sample and determine the lweel of hydrogen in 24 the containment.
25 One option is to leave this system in place. The O ANN RILEY & ASSOCIATES, LTD.
Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
26 1 other is to go for a grab sample, so very frankly, if we
() 2-3 are'-- u".ch we' intend to do but had not done prior to this meeting
- harmonize an application here with an
- 4. application, a future application to eliminate the PASS 5 system, we would have to address that issue. It probably 6- would end up leaving the hydrogen monitors there.
7 DR. KRESS: I think so, because this looks like 8 superior --
9 DR. SEALE: -- technology.
10 DR. KRESS: -- technology to the PASS system.
11- MR. HOOK: Moving on to the next slide, 11, a 12 description of the hydrogen recombiner system is provided.
13 There are two redundant safety-related recombiners in the 14 containment designed to maintain the hydrogen concentration
() 15 below the flammability limit of 4 percent following a design 16 basis loss of coolant accident.
17 The hydrogen recombiners are located on the 18 operating deck inside the containment. They are basically 19 large heaters, electric heaters that heat the air flow up to 20 1150 degrees F. at a rate of 100 cubic feet per minute for 21 each recombiner, causing the hydrogen and oxygen to react 22 -and create water. They are manually initiated by the 23 operators when the hydrogen concentration'is between 1 and 24 3.5 percent, as directed by the EOIs and as measured by the 25 hydrogen monitoring system.
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27
.1. -DR. WALLIS: They initiate presumably at 1
/*\s r 2 percent. I think they don't initiate somewhere between 1
%J.
3- .and 3.5 percent.
4 MR. HOOK: By the time you take the reading from 5- the hydrogen monitor system, it may be above 1 percent.
6 That is the-reason why it. indicates 1 and 3.5 so whenever --
l 7 DR. WALLIS: By the time you take the reading it 8 could be 4. {
l j 9 MR. HOOK: Depending on the severity of'the 10 accident,'it could be 4. That is correct. In a severe l u '11 ' accident,-you could be above the 3.5 percent before you take l '
12 the reading.
L - .
13 DR. WALLIS: This 100 cubic feet a minute seems ,
14 very low.
) 15 DR. KRESS: It's driven by natural convection, 16 aren't they?
17 MR. HOOK: That's correct. There's no fans --
18 .it's a natural --
19 DR. KRESS: There are heating elements?
20 MR. HOOK: Yes. .It is just a large electric j ~21 heater that has a --
22 DR. KRESS: That's why the capacity. This is 23 useful information but I looked through the documents that I
' 24 have and what I was looking for was the rate at which it 25 . removed hydrogen from the containment, in cubic feet of h
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28 1 hydrogen per minute.
2
'( } I couldn't get that out of the reading. Do you 3 have a good feel for'what that number is? You know, I would 4 like to compare the rate at which it removes it to the rates 5 at which it is being produced under various circumstances.
6 I didn't find that in the stuff I had available.
7 Do you know what that number is?
8 MR. HOOK: We have also looked in the literature 9 for that number and we could not locate that number in the 10 literature or in the calculational aids for this reaction 11 and management guidelines. '
12 DR. WALLIS: Well, what is the volume of the 13 containment?
14 DR. KRESS: This is large --
() 15 DR. WALLIS: It's huge, isn't it, in cubic feet?
16 We are in cubic feet so it is --
17 MR. MOIENI: It is over 2 million cubic feet.
18 DR. KRESS: Two million.
19 DR. WALLIS: So it is 20,000 seconds -- 20,000 20 minutes to put that through the~recombiner? Very small.
21 DR. KRESS: Yes.
22 MR. HOOK: It was specifically designed for the 23 hydrogen generation rate assumed for the design basis 24 accident per the Reg Guides.
25 MR. SCHERER: I think you are coming to the 1
I
[}
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29
'1' conclusion we did, that it is too -- it not sized to keep up
~2 with a severe accident generation rate.
(
3 DR. KRESS: Let me ask you about that.
4 MR. SNODDERLY: Sorry, Tom -- in our presentation 5- as part of what we tried to establish the value of the 6 recombiners, we did some calculations with a code, the COGAP 7 code and I think we will be able to give you an idea of the 8 removal rates.and production rates.
9 I think the problem you have is -- to do what ycu
'10 wanted to do is to say -- because it depends on the 11 concentration of hydrogen in containment and that changes.
12 DR. KRESS: Okay. It's a mass transfer problem.
13 MR. SNODDERLY: But this may help. At least it 14 did with me, the sense that you are talking about a 2
() 15 million cubic foot containment, two recombiners that turn 16' over about a 100 standard cubic feet per hour, and so you
~ 17 are talking about seven and a half, eight days to turn over 18 containment.
19' DR. KRESS: Yes, so you can get a percent there.
20 MR. SNODDERLY: So I think the thing to remember 21 is'that the recombiners are very efficient at recombining 22 the hydrogen in the mixture they see. The problem is to get 23 the mixture there takes prohibitively long.
24_ But my suggestion would be to see if we can answer 25 that based on some of the analysis.
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30 1 DR. KRESS: Well, the other question had is we
(
}
2~ keep talking about these things were designed for design 3 basis accident space and not severe accident space and that 4 severe accident space the hydrogen generation overwhelms 5 it -- you know -- it's just not very useful there, but a lot 6 of the sequences you go through a period it looks like 7 design. basis before you get to severe accidents. You are 8 generating that hydrogen that you would get in a design 9 basis prior to reaching the runaway hydrogen generation.
-10 Now the question I would have is is the rate fast 11 enough to remove enough hydrogen during that pre-period that 12 it lowers the concentration to some significant level that 13 would be useful to you.
14 MR. SNODDERLY: I think the way I would answer
() 15 that, Tom, is that the design basis accident that we are 16 -trying to address would be associated with about 5 percent 17 metal-water reaction, and we would say that the threat of 18 containment failure from that amount of hydrogen is not of 19 concern and I think what San Onofre's going to try and show
- 20. you is -- and what we are also going to discuss -- is the 21 bounding case of, say, 75 percent metal-water reaction, and 22 the resulting hydrogen and the resulting loads on 23 containment and from that bounding argument saying that that 24 .s not a threat to containment, to say that you have covered i
25 this -- the cases that you are talking about.
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- i. .. .
31 1- DR. KRESS: What I was wondering about is there 2 some limit that you might be above or below with and without j
(}
l 3 the recombiners, and that_ limit might be this downward 1
4 propagation --
5 MR. SNODDERLY: I would argue no because you are 6 sending it out into such a large two million cubic volume 7 source and it gets diluted so that is really what is making 8 the recombiners ineffective, because it doesn't matter if
.9 you are putting an amount of hydrogen that they could handle 10 or it would not exceed 4 percent where there would be a I
11 benefit, you have still diluted that through or we are 1
12 assuming that it is diluted through the volume, and in order 13 for the recombiner to see it, you are going to have to wait 14 until it. turns over the complete containment -- or not the 15 complete containment but a lot of it.
16 DR. KRESS: It is still a rate question. That is 17' why I was interested in it.
18 Okay. Well,-these arguments you are making all 19 are good arguments for large dry containments. It sure is 20 nice that we are dealing with the large dry containment
\
21 here. I I
22- MR. SNODDERLY: Right, and I think that's -- at 23- the end of my slides I am going to discuss further i
24 implications and how the revision to this rule make affect 1
other designs.
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32 l :1 DR. KRESS: That is what I was getting at.
2 MR, SNODDERLY: I think what you are going to find 3
is that for the ice' condensers and the Mark 3 containments I 4 think you could argue that because the igniters are there 5 that you don't need the recombiners.
6 DR. KRESS: Absolutely.
)
7 MR. SNODDERLY: And then I think the argument that 8 has been made by GE for the Mark is and 2s which are inert, 9 and they are worried about controlling oxygen and that is 10 why they need the recombiners but they have made an 11 interesting submittal. What you find is that if you have 12 about two atmospheres of hydrogen in the containment 13 atmosphere, which you would for most of the -- for most 14 accidents of concern, it suppresses the radiolysis rate, and 15 they have made a topical report submittal which I think the 16 only thing that is missing is that the one thing you worry 17 about is the radiolytic rate is suppressed by the hydrogen 18 overpressure but it is also created by poisons such as 19 iodine -- the iodine ions in the sump. So the only iodine 20 they considered was from a TID type source term, which we 21 have switched from gaseous to particulates, so now I think 22 they would have to go back and reconsider the effect of all 23 that particulate iodine in the sump. I think it is still 24 going to show that you are not going to get enough oxygen.
25 So to answer your question, I think you can make a ANN RILEY & ASSOCIATES, LTD.
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33
- 1. pretty good argument that you don't need recombiners for the
() 2-3 Mark is and 2s and so that would cover all the containment designs.
4 DR. KRESS: I. appreciate that. That was very 5 useful. Sorry for the interruption.
6 MR. HOOK: And just a comment on your question
- 7. about' the potential for the generation of hydrogen at the 8 rate assumed in the design basis. From my perspective in 9 evaluating severe accidents, that would be an event where we 10 have core damage starting, but it's terminated very quickly, 11 similar-to TMI, where there was a starving of injection 12 flow.
13 I think based upon the changes that have been 14 made to the EOIs -- emergency operating instructions --
) 15 since Three Mile Island that the likelihood of that event 16 where we have initial injection and then a' starving of it is 17 very unlikely now.
So I think it's unlikely to have the E18 - design basis event for-which they were designed..
19 And lastly, the emergency operating instructions 20- caution the operators not to use the recombiners at any time
'21 the hydrogen concentration is greater than 3-1/2 percent, 22 which is assumed to be the lowest level where flammability 23 could occur to preclude a hydrogen burn. And the accident 24 management guidelines also provide this direction, that they 25 will not.be used when the hydrogen concentration ~is above l.
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34 1 3-1/2 percent.
2 DR. WALLIS: Well, that sounds like a good way to 3 keep hydrogen concentration below 6 percent is to ignite it.
4 DR. KRESS: Use these as igniters.
5 DR. WALLIS: Yes, use them as igniters.
6 MR. HOOK: That --
7 DR. WALLIS: Just leave them on.
8 MR. HOOK: That was never contemplated in the 9 accident management guidelines that were developed by 10 Western Engineering.
i 11 DR. WALLIS: Now once these instruments are being 12 calibrated, they are reading continuously, so this chap who 13 has decided to switch them on at 2 percent and sees the 14 concentration rising rapidly has plenty of time to switch 15 them off before it reaches 3.5 percent?-
16- MR.' HOOK: Unless the temperature in the 17 containment has changed significantly during that time where 18 he's --
19 DR. WALLIS: Then he has to recalibrate it again?
20 MR. HOOK: He has to recalibrate.
21 DR. SEALE: I don't know if you're prepared to 22 talk about it, but I'd be interested in knowing why one bang 23 .is better than three burns.
24 DR. WALLIS: I think three burns are better than l l
25 one bang.
l l
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1 F
l 35 1 DR. SEALE: I do too.
() 2 3
MR. HOOK:
DR. KRESS:
These are all burns.
It's all a rate problem, how much --
l 4 it's how much energy you're putting in the containment, and 5 what you're taking out.
l 6 DR. SEALE: Sure, but if you rise --
7 DR. KRESS: Three burns is better than one big '
! 8 one. '
l 1 9 DR. SEALE: I agree. I' agree.
10 DR. KRESS: It spreads it out.
11 DR. SEALE: That's why I say I don't know why you 12 want to turn it off. So it turns into an igniter.
13- MR. SNODDERLY: This is Mike Snodderly again. We 14 would agree that based on the PRA model in the NUREG-1150, i
15 there is -- not high reliance, but one of the big 16 contributors'to this is reliance on spurious ignition-17 sources.
18 DR. SEALE: Yes.
J 19 MR. SNODDERLY: I mean, we consider this an 20 excellent spurious ignition source, so we would not agree 21 with their current guidelines that would say to turn off the i
22 internal. Now that's clear for an internal recombiner. It 23- may not be as clear for an external recombiner, where you l 24 could possibly be pulling a rich hydrogen mix through a 25 small tube outside containment, recombining where it may i
i l
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36 1 ignite, and then you have an unisolated leak outside I
V) 2 containment. So it's not as clear for that case. But 3 clearly our recommendation would be for the San Onofre 4 accident management guidelines to keep internal recombiners 5 on.
6 MR. HOOK: Okay. Moving on to the next slide, 12, 7 hydrogen purge subsystem. The hydrogen purge subsystem is a 8 safety-related single-train purge designed to maintain 9 hydrogen concentration below the flammability limit of 4 l 10 percent following a design basis loss-of-coolant accident by i
11 a controlled containment vent.
12 The vent is through a hepa filter. It has a fan I i
13 as well which provides a capacity of 50 cubic feet per )
14 minute, which is similar to the rate at which the hydrogen
() 15 recombiner by itself a single train could remove the 16 hydrogen. It's manually initiated by the operators when the l
17 hydrogen concentration is greater than 3-1/2 percent and 18 rising as directed by the emergency operating instructions.
19 It's basically a backup to the recombiners.
20 The EOIs caution the operators to obtain a release 21 permit from the chemistry department prior to initiating a 22 hydrogen purge, which would imply an administrative activity ;
23 that has to occur, and you have to have personnel available 24 to make those decisions and issue the permit. And the 25 possibility exists for long-term loss of containment
(}
(_/
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37 1 integrity if hydrogen purging is initiated based upon the
() 2 failure modes of the valves, the fact that the purging 3 system's not designed for beyond 60 psi venting process, and 4 the hepa filters are not designed for a greater-than 60 psi
!5 differential pressure.
6 The inside valve is a motor-operated valve. The 7 outside valve is an air-operated valve. If it lost power, 8 the inside valve would be unable to close, which is one of 9 the more likely events that would lead to a core damage 10 event where you have a long-term or a continuing loss of 11 offsite power.
12 DR. KRESS: Could you close the outside valve?
13 MR. HOOK: I The outside valve is an air-operated '
14 valve, and that could be closed with d.c. power to actuate
() 15 the solenoids, to deenergize the air.
16 There's also a -- before the hydrogen purge can be 17 initiated, there are manual valves, or at least one manual 18 valve that has to be opened on the hepa filter to allow that 19 path to be open, and that valve would -- it would be highly 20' likely that valve would not be accessible to reclose that 21 manual valve in the event the other two containment 22 isolation valves failed to close.
l 23 DR. KRESS: Are you required to test the integrity 24 of this system occasionally, the hepa filters and
-25 everything, to see if the valves open up and you get the
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38 L
. 1. right flow and things like that?
2 MR. HOOK: Yes, we test the containment isolation l
l 3 valves for their ability to clcse and open per their design i
4 requirements, and I'm sure there are tests on the hepa 5 filters to make sure they have the --
6 DR. KRESS: Efficiency?
7 MR. HOOK: Efficiency to remove the design basis 3
{
8 radionuclides.
]
- 9. MR. SCHERER: Please don't take our point that we 10 don't have confidence in these valves, but anytime you open 11 a valve and initiate a purge, our point is you always -- j
- 12. DR. KRESS: There is always a probability; yes.
13 MR. SCHERER: There is always a finite possibility '
14 that we can't reclose the valves.
15 DR. KRESS: Sure. It's a real probability.
16 DR. BONACA: I would like.to hear more about the 17 fact that you don't need it, rather than the fact that it is 18 'not good-enough. It means that is not single failure proof, 19 has limitations of all kinds, while it could be improved,'or 20 could have been made better. I would like to hear about why 21 you don't need.it, rather than, you know, concerns you have 22 .-about it sticking open.
'23 MR. HOOK: We're going to discuss that later.
24- The next slide is a' description of the hydrogen
- j. 25 ~ mixing system, which we are not proposing to remove from the
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, 39 1 design basis. The hydrogen mixing system is basically the 1 i
[_g) 2 internal design of the containment structure which at San u I
l \,,/
3 Onofre provides generous vent paths from all the lower 4 compartments in the containment, and there were extensive 5 Jealkdowns as a part of the individual plant examination to 6 look at the containment and its ability to provide large 7 vent paths for hydrogen. There's also the containment spray 8 system, which reduces temperature and the likelihood of a --
9 and radionuclides from the' inventory.
10 DR. KRESS: What activation turns that on? What 11 signal? I l
l 12 MR. HOOK: Containment pressure and --
1 13 DR. KRESS: Most.of them operate off of -
14 containment pressure. ]
15 MR. HOOK: Containment pressure is the one I 16 recall.
17 DR. KRESS: Yes.
18 MR. HOOK: And basically the containment cooling l 19 actuation signal, which feeds off the containment pressure.
20 DR. KRESS: So suppose if you had a design basis 21 LOCA the pressure would set this off just to get rid of the 22 steam.
23 MR. HOOK: That's correct.
24 MR. SCHERER: Most of the hydrogen mixing 25 capability was originally designed in for the steam.
l l
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r 40 1 MR. HOOK: I want to clarify the question relating
{ .2 to a design basis LOCA. Based upon the evaluation that 3 we've performed looking at the design basis hydrogen 4 generation, the' design basis hydrogen generation is 5 significantly greater --
6 DR. KRESS: My point for asking that question i 7 about the sprays was my impression was that during design 8 basis space you get the hydrogen out before you turn those 9 sprays on. But I'm not sure of that. Maybe you guys can 10 tell me.
11 MR. SCHERER: I'm sorry, Tom, could you --
12 DR. KRESS: My question was whether the 13 containment sprays are a good way to mix -- I know they'll 14 really mix up the containment. The question is whether
() 15 you've already got the hydrogen out there before you turn 16 them on or not.
17 MR. SCHERER: No , the hydrogen would not be out.
18 DR. KRESS: Under design basis space?
19 MR. SCHERER: Design basis the sprays would be on 20 before the hydrogen is generated. Right?
21 DR. KRESS: That was my question.
22 MR. HOOK: Okay. And also the rate of hydrogen j 23 generation in a design-basis LOCA is significantly less than j 1
24 the rate at which'the design basis assumes is required for i 25 hydrogen generation based upon the rule and the l .
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41 1 conservatisms that were added as a result of Three Mile I -2 Island, and we'll describe those.
3 And the containment emergency fan coolers are also 4 available in a single -- based upon the individual plant 5 examination evaluation of the emergency fan cooler cooling
- 6. capacity. A single' fan cooler, of which there are four fan 7 coolers in the containment, a single fan cooler by itself j 8 without containment spray has the' ability in the design
_9 basis event to prevent the containment pressure from i j
10 exceeding the design basis for a design basis LOCA.
- 11. And lastly, the containment air circulators, which 12 are large circulators in the containment which move l 13 significant amounts of air from the lower and upper parts of 14 the containment, are available for hydrogen mixing.
15 And.as I indicated, no exemptions were requested 16 for the mixing functions.
17 Slide 14 is just an overview of the three aspects 18 of the risk-informed evaluation process based upon ]
19 Regulatory Guide 1.174. I'm going to describe how the 20 exemption'affects defense in depth at the plant, the safety l 21 margins, and the risk impact of --
22 DR. WALLIS: You were talking about H2 mixing i 23 before. Sorry.
24 MR. HOOK: Yes.
25 DR. WALLIS: And we established that the O
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42 l
1 recombiners don't keep up with things at all. These mixing
[v')
2 processes are rapid enough to keep things mixed, and you 3 didn't get a quantitative assessment of how rapidly things 4 are mixed.
5 MR. HOOK: That's in my slide 22.
6 DR. WALLIS: Oh, you're going to come to it.
7 Okay.
8 MR. HOOK: Yes.
9 DR. WALLIS: Okay. :
l 10 MR. HOOK: Slide 22 specifically addresses that 11 DR. WALLIS: Okay. Thank you.
12 MR. HOOK: In defense in depth the hydrogen 13 control system is not needed for accidents based upon 14 realistic assumptions, and we'll show you a graph that
()
,s 15 supports that. The hydrogen control system is not sized to 16 mitigate severe accidents. We've already discussed why that l
17 occurs. The hydrogen control system is only valuable for 18 unlikely design basis accidents. And there's a table there 19 that shows without the hydrogen control system, the hydrogen 20 that's generated is less than 4 percent for the realistic.
21 It's less than 4 percent for the design basis. Assuming 22 that they do operate. And for the beyond design basis, the l 23 l hydrogen generation is much greater than 4 percent. j 24 If we do not have the hydrogen control system, the 25 recombiners and the purge, which is the second row, the
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1 43 3 1 realistic; indicates less than4 percent, the design basis
~
~
f 2- Lgreater than 4 percent.
13- DR. WALLIS: This 4 1 percent you mean is the 4 percent concentration in the containment?
S' MR. HOOK: In the containment.
6- DR. . WALLIS: You talked about' generation rate.
- '7 MR.-HOOK: I'm sorry. LThe containment --
8- DR. WALLIS: There's no title on this chart.
9 MR. HOOK: And then for the individual systems and 10' their usefulness, the hydrogen monitor is not useful for the ill realistic in terms of there not being sufficient hydrogen 12 : generated for there to be value in having'the parameter 13 available. 'For a. design basis it is;useful because it's 14 tused to determine when,the hydrogen recombiners and purge
() 15 are used. And beyond design basis it's not useful because-
' 16 ' .the concentration'of hydrogen in the containment is beyond-11 7 - that which the systems that are available, the recombiner 18 and the purge, could be used.
19.. There are other methods available, such as PASS 20 and-radiation levels'to determine the level, the amount of J21 hydrogen that -is generated and'the Severe Accident and
~22; Management Guidelines provide specific direction on how to 23 ' utilize or how to determine the amount of hydrogen in the 24! containment if the hydrogen monitors are not available.
25 DR.I KRESS: I think that is the'one item on the
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44 1 paper we might debate usefulness under, you know, in design t 2- basis space. -It is information.
3 MR. HOOK: I.would agree it is information, yes.
4 'MR. SCHERER: And as I indicated, we will.probably 5 will revisit that issue even if you were to agree that it 6 does not add.value to the question of hydrogen control we 7 probably as part of our PASS application would revisit that 8 issue.
9 DR. WALLIS: .I understand the slide. I don't 10 understand the title.
11 DR. KRESS: Which part don't you understand?
12 DR. WALLIS: The defense-in-depth. I don't quite 13 understand why defense-in-depth is --
14 DR. KRESS: The question is, does it compromise
) 15 your containment as a defense-in-depth provision?
16 DR. WALLIS: I was going to ask them what they 17 meant by defense-in-depth.
18 DR. KRESS: Yes, why don't you ask about that. I 19 would like to know.
20 MR. HOOK: That's a good question. The Reg Guide 21 is hard to figure that out, what is meant by 22 defense-in-depth and in fact there's the implication in the 23 Reg Guide that risk analysis plays a role in determining the 24 adequacy of defense-in-depth.
25 For the containment here, the defense in depth 1004 RILEY & ASSOCIATES, LTD.
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- v. ..
45
- g. -1 would be its ability to withstand a burn and the likelihood h
i-m 2 of a burn occurring.
(}
3 DR. WALLIS: The slide really talks about the 4 usefulness of the H-2 control system so I just wondered why 5 you invoke this defense-in-depth title. .Does that make it 6 somehow more important or.something?
7 DR. KRESS: The issue is if you are using 1.174 8 thinking , you have to say you do not depart from the 9 defense-in-depth philosophy and I think what they are saying 10 here is this is their 1.174 contribution on that 11 defense-in-depth requirement.
12 DR. WALLIS: Oh, there's actually a line item they 13 have to respond to?
14 DR. KRESS: Yes -- which is a little strange, I'll 15 have.to admit.
16 DR. WALLIS: Well, until we have a 17 defense-in-depth meter, we won't quite know.
18 DR. KRESS: The defense-in-depth issue here is I 19 think you need.-- there's two of them in my mind. You need 20 information on hydrogen to assess the accident and to make 21 emergency response decisions. It is an information 22 defense-in-depth. You certainly can consider the 23 containment as a. defense-in-depth barrier, so you want to be 24 able to do both of those You want to preserve the
.25 ' containment integrity and have this information.
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46 1 I can't think of other defense-in-depth issues --
O 2 there might be.some, but I can't --
i d {
i
'3 DR. BONACA: Except in the original intent, I l l 4 guess, for' design' basis events, both recombiner and purge 5 were intended to prevent concentrations from getting to the 6' flammability limit, so it was a preventive characteristic 7 that --
8 DR. KRESS: Which is a defense-in-depth --
9 DR.-'BONACA: A defense-in-depth --
10 DR. WALLIS: There is a sequence of events --
11 DR, BONACA: That's right, so --
12 DR. HALLIS: -- and you put in something at each i i
13 stage and you are proposing to remove something from the l 14 sequence.
15 -MR. SCHERER: The phrase " defense-in-depth" as 16 indice.ted earlier is taken right out of the Reg Guide. That 17 was how we picked the phrase. But I agree-with the comment
.18 that basically when you typically think of defense-in-depth 19 you are beyond the question of cladding integrity, you are 20 beyond the question of reactor coolant system integrity if I i
21 you are debating an issue of hydrogen generation inside the l 22 containment, so your remaining defense-in-depth is the ;
23 integrity of the containment and your emergency actions that 24 you would take offsite.
25 This application would not degrade in our opinion 1
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e 47 1 those remaining barriers as part of the defense-in-depth.
2 DR. WALLIS: It would help in a way if we had a
, 3 diagram. You have the fuel in the reactor coolant system 4 and then you have the containment and then you have at each 5 stage you have a barrier or an action and this is part of 6 the defense-in-depth sequence, trying to keep the 7 hydrogen -- and they are removing it so what is the effect 8 of-it could perhaps be determined in some way analytically.
9 DR. BONACA: Just one point. Containment clearly 10 is defense-in-depth and you are telling us that a burn will 11 not challenge it, even without these systems.
12 These systems were in place to prevent the burn so 13 that yo' have defense-in-depth. You also prevent the 14 challenge to the containment. Other things which are put in 15 place were conservatisms in the calculation of hydrogen rate 16 and you are proposing to not consider those, so I would like 17 to hear about that, because I mean I view also those kind of 18 analytical assumptions made, the computer code has 19 ' defense-in-depth, so, you know, it is important that we hear 20 about that, because that is the central point to the design 21 basis. You know, we are supposed to exceed 4 percent and 22 now you are saying you will never get there. l 23 MR. HOOK: That's correct, and there's following 24 slides that describe the realistic assumptions in 25 calculation. 1 o
j g '
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48 i 1 DR. KRESS: Did you guys want to say something? I 4 5
2 saw some movement over there.
3 MR. HOLAHAN: This is Gary Holahan of the Staff.
4 I think-when we think about defense-in-depth and 5 when you read 1.174 it is sort at a little more 6 philosophical level than greater than 4 percent, less than 4 7 percent. I think the intent of that section was to make 8 sure that when you are changing something, a license 9 amendment or exemptions, that you are maintaining the 10 philosophy that fuel is a barrier, that prevention is 11 important, that containment is an important barrier, so if I 12 wanted to know if there were defense-in-depth philosophy 13 being maintained through this process I would ask whether I 14 was significantly challenging or changing any of the
() 15 16 functional or physical barriers, okay?
So I think you could take this information and 17 construct an argument about what it says about how you are 18 challenging containment or not challenging containment. I 19 think that is the relationship to the concept.
20 DR. BONACA: Exactly.
21 DR. WALLIS: This is at sort of a qualitative 22 level but eventually one should be able to compute what is 23 the effect on probability of release or something like that.
24 Do you actually have some prediction or is this all 25 qualitative type arguments that you don't need it, it O ANN RILEY & ASSOCIATES, LTD.
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49 1- 'doesn't really help, and therefore we can do away with it, 2
) or is there some assessment of what is the net'effect of 3 doing away with it'on public safety?
4 MR. HOOK: I will describe that but basically as a 5 result of the ultimate containment pressure and the 6 uncertainty in the ultimate containment pressure and leak 7 capability, we don't believe the containment integrity is 8 affected at all by the potential for hydrogen burn in a 9 severe accident.
10 DR. WALLIS: So there is zero effect?
11 MR. HOOK: That's correct.
12 'MR. SCHERER: Zero is a tough number.
13 DR. KRESS: Yes. There's bound to be something 14 there, but it is negligible.
() 15 MR. SCHERER: And we agree with Gary Holahan's 16 discussion on the philosophical approach to 17 defense-in-depth. If we believed, for example, that this 18 was a meaningful protection, a risk-significant protection 19 of the containment integrity, then we wouldn't be here with 20 this application.
21 The fact that we believe there's a very narrow 22 aren 2nd only a very narrow area where this would provide 23 meaningful protection to the containment that we're in with l
24 .this application, so remember, this was a post-TMI fix to 25' protect against another TMI event at the time.
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50 o If we were designing this system from scratch and 2 we believed-this was a significant issue, then we would 3 design different systems with different capabilities to 4 protect against what we perceived, if that was the case, to 5 be a significant threat, That is not the way this system 6 was designed or implemented 20 years ago when these 7 requirements were established.
8 DR. KRESS: Let me ask a question, and I don't 9 know if this is the right place, but it seems to be, and 10 this is maybe for the Staff also.
11 Risk space is when we are talking about prompt 12 fatalities and late fatalities and things like that is 13 dominated by the severe accidents that go so far that they 14 fail-containment and it is hard to fail one of these kind of
() 15 containments but you can do it when you invoke all of the 16 severe accident phenomena and get deep into a severe 17 accident, and with the very low probably accidents they 18 still dominate the risk.
19 In design basis space, you have these design basis 20 accidents that you design the containment to and show that 21 it doesn't fail and that your leak rate and the pressures 22 you reach during those are such that you don't exceed doses.
23 The dotis are the criteria.
24 Of course you will have to redo your design basis 25 accidents to show that those doses aren't exceeded.
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51 1 Now my question is that there are a number of
'l 2 severe accidents that don't fail containment so they don't l 3 enter into risk space but you could get a lot of dose out l
l 4 during those that exceed certain. dose limits you have in 5 design basis space but you haven't considered those because 6 they.are too low of probability, but my question is if there 7 were a criterion on frequency of release of a given l 8 magnitude, this would -- not having recombiners in there 1~
l 9 might increase that over some range of frequencies that -- I
, 10 may be getting way off --
1 L -11 DR. WALLIS: Let me ask you, Tom, if you talk 12 about failed containment suppose we have this hydrogen vent 13 system or purge system. Suppose it partly fails. That is l
14 not a failed: containment but it is still a leak to the
() 15 outside world?
16 DR'. KRESS: It is debatable whether that is a 17 failed containment or not. If your through filters and 18 everything hold together and are still --
19 DR. WALLIS: Suppose part of the filter blows 20 out --
21 DR. KRESS: Then that is a failed containment.
22 DR. WALLIS: Even a small leak?
23 DR. KRESS: Even a small one because it will 24 bypass 25 DR. WALLIS: So when you talk about major i -
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1 52 l'
accidents which don't fail containment you are excluding
/T 2- those small leaks from that. sort of source?
O 3 DR. KRESS: Yes, but a vent filter system I don't 4 think in my mind if it held together would not be failed 5 containment because the risk you get out of that is -- most 6 of the; risk is due to the iodines and cesiums, and those get 7 filtered out and noble gases go right through it but they 8 don't -- you know, you can -- in my mind that doesn't 9 constitute a failed containment. j I
10 DR WALLIS: All right.
11 DR. KRESS: Oka; . I guess I'm a little off base 12 on that frequency increase of --
-13 MR. HOOK: Well, we focus on the potential for z 14 large early release consistent with the Reg Guide, which
() 15 would have the potential for a fatality at the site boundary f 16 and there would have to be a multiple inch opening in the 17 containment at high pressure and a severe accident for there !
18 to be the likelihood that that wonid ever occur, and that is 19 beyond the leakage that we would assume could occur even 20 with the pressurized containment with all the containment 21 boundaries closed, so it may exceed Part 100 but it would be 22 less than that which could create the possibility for a l
. l 23 large or early release.
24 MR. HOLAHAN: Dr. Kress, could I try it also?
25 DR. KRESS: Yes, please.
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53 1 MR. HOLARAN: When we talk about design basis. We
[T 2 are normally talking about preventing accidents but from a i V
3 source term point of view the design basis source term looks )
I 4 like a severe accident. It is pretty close. The TID source 5 term and a realistic core melt source term are not really '
6 that different, so if you are talking about dose to the 7 public, the only thing that really seems to matter between 8 design basis and severe accident is whether the containment 9 fails, so if you have a design basis with containment 10 leakage or you have a severe accident with no containment 11 failure but with some leakage, those are not really very 12 different, and if you want to know the value of all of these 13 sort of systems, their real value to whatever curve you draw 14 of doses has to do with whether you are significantly r'%j i 15 affecting the probability of containment failure.
16 If you convince yourself that you are not doing 17 that, then the dose numbers don't come out very different.
18 DR. KRESS: The problem I have though, I have had 19 a beef with the design basis accident containment that has 20 to do with the pressure you get is -- diffuses the blowdown 21 steam and I am not so sure we shouldn't have included a l 22 little hydrogen burning on that pressure because the 23 probability -- you know, design basis space is supposed to 24 be , well, you have a cut-off on probability on account of i
25 you are dealing with a higher frequency range and less l
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54 1 severe accidents take care of themselves by low probability.
1
(Y :2 Well, I think a probability of a hydrogen burn in design-
- \,,)
3 basis space is pretty high and that is why I am saying I 4 think our' design basis space may be wrong to put things in 5 -there to control hydrogen may be a defense-in-depth concept 6 in design basis space if indeed it reduces the doses you get ;
7 and you would get more dose because you've got a higher 8 pressure.
1 i
9 You know, it's a concept that I am not '
10 articulating very well. It's not well formed.
11 MR. SNODDERLY: No , I think you did, Dr. Kress, 12 but don't forget 50.44 you also have this 75 percent l
13 metal-water reaction that you have to address and ensure l i
14 that will not exceed the 13 percent.
-( 15 DR. KRESS: That is part of the design _ basis. '
16 MR. SNODDERLY: That is part of the design basis 17 and that is considering hydrogen and that resulted in 18 igniters in BWR Mark 3s and in ice condensers but not in ;
i 19 sub-atmospherics or large drys, so I think a significant -- l 20 DR. KRESS: That may express the concern --
21 MR. SNODDERLY: The hydrogen source term is l 22 considered in the design basis and I think when I speak part !
23 of what we looked at is the results from 1150, because what 24 it comes down to, I think, is either you are comfortable --
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g-V=
55 1- because recombiners aren't going to help you with'the
~
j _2 hydrogen source terms you are talking about now in the i 3 threat to containment.
l 4 As Gary said, either -- if containment doesn't 5 ' fail, you are okay, so right now 1150 says it is not a 6 containment threat, and we'll give you the results and then 7 give you the places that you can go to say, hey, I am l
. comfortable with my model decision or I am not, but right 3
8 1 l 9- now 1150 would say it is not a contributor.
l 10 DR. SEALE: I think your disquiet or unease, if 11 you will, with the design basis accident is very nicely 1
12- summarized in the third bullet up there.
13 DR. WALLIS: Do you mean the word "unlikely"?
14 DR. SEALE: Yes, yes. I mean we really danced out j
() 15 on the point of a needle here.
16 DR. KRESS: Tom?
l 17 MR. HOOK: The last point, hydrogen purge is not i
! 18- useful in a realistic event because it would not be needed.
1 I 19 It is presumed to be detrimental in design basis l
l 20 and beyond design basis because there would in reality be no 21 need to operate purge to protect the containment integrity 22 but if it sticks open when it is used, it could provide a 23 release path to the environment which potentially could not
- 24. be reclosed.
25 And it would have dose implications regardless of whether ANN RILEY & ASSOCIATES, LTD.
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(
l 56 1 1 .it's design basis or beyond design basis.
( ) 2 In the next slide, 16, this describes a parametric 3 study that we performed. We looked at a number of cases.
4 The base case is the design basis using the FSAR-5 assumptions, which come from Reg Guide 1.7 and the Standard 6 Review Plan 6.2.5 guidelines.
7 Case 1 is a sensitivity that we performed where we l 8 I look at the' metal-water reaction, which is what MWR stands i 9 for. We removed the conservatism in the metal-water 10 reaction assumption, which Reg Guide 1.7 indicates that the
{
11 licensee should use a factor of 5 conservatism based upon 12 actual experimental data and analysis for the metal-water 13 reaction. And, second, we looked at the 20 percent 14 radiolysis conservatism that's identified in~the standard f
15 review plan and also removed that from the calculation of 16 the amount of hydrogen generated. And I'm going to show you 17 on the table and a following figure what the impact of this 18 case 1 is.
19 Case 2 was similar to the case 1 except-we revised t
20 the sump radiolysis yield from .5 molecules of hydrogen per 21 100 ev per the reg guide to .4, which is a midpoint between f
22 the reg guide and a paper analysis by WestinghouEO and also 23 Oak Ridge National Lab. And that reflects a more realistic !
24 assumption about the radiolysis, which is the slow, 25 'long-term buildup for which hydrogen recombiners were i
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r 57 1 originally designed to mitigate.
2 Case 3 is the same as case 1, except the sump
(
3 radiolysis yield was changed to .5 -- from .5 to .3 4 consistent with the Westinghouse, Oak Ridge National Lab 5 data. So that's even a more realistic or one might 6 characterize optimistic assumption about the amount of 7 hydrogen generated from radiolysis.
8 And if you look at the next slide, slide 17, it 9 looks at the hydrogen concentration in the containment 10 following 20 days, 25 days, and 30 days for each of these 11- cases, the design basis and the sensitivity cases utilizing 12 more realistic assumptions or removing the conservatisms 13 that are explicitly identified in the reg guide and standard 14 review plan. And we see that for the design basis.we exceed
() 15 the flammability limit, which is presumed to be between 4 16 and 6 percent in the reg guide, before 20 days, and in fact 17 it's in the range of 15 days, 14 days that we actually 18- exceed the 4 percent in the design basis.
19 For case 1 we see that we only reach the 20 flammability limit at 30 days. In cases 2.and 3, where 21 there are more conservatisms removed, we see we don't reach 22 the flammability limit up to 30 days. And based upon this 23 table and then the following graph and slide --
24 DR. WALLIS: What's the virtue of reaching it at a )
25 later time? j 1
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58 1 1
1 MR. HOOK: It's presumed that at the point of 30 J
1
(} 2 . days there'would have'been sufficient time passed and 3 availability of engineering and emergency response personnel 4 to provide engineered means to remove the hydrogen at that 5 point through external recombiners, through a vent process, 6 a filtered vent'--
7 DR. WhLLIS: Do these things exist?
8 MR. HOOK: They are not design features at the 9 plant right now. They would have to be engineerod and 10 installed --
11 DR. WALLIS: So there may be really no virtue in 12 putting off the 4 percent for a few days. You're assuming 13 someone knows what to do in those intervening days. It's an 14 assumption of some sort. I
() 15 MR.' HOOK: Specific to which case?
i 16- DR. WALLIS: Well, you're assuming that in these 17 intervening weeks someone has hitched up some system which 18 is removing hydrogen.
19 MR. HOOK: Or you have depressurized the 20 containment through containment cooling. By restoration of 21 power you've restored containment cooling, you've brought 22 the pressure down to the atmospheric, and you cleaned up the 23 containment considerably, so you could even purge at that 24 point.
25 DR. WALLIS: So you're relying on something which ;
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59 1 is so far not specified.
2 MR. HOOK: That's. correct.
}
3 And we just selected 30 days as a point where we 4 believe there would have been sufficient time available to 5 bring in or design some engineered capability to respond to l
6 the hydrogen at that point, before it got up to the point i 7 where it would burn, or above 4 percent.
8 MR. SCHERER: You are correct, that the virtue of 9 time is that it gives -- and if you look at the next slide 10 you'll see that it builds up rather slowly, and there's time )
11 for us to make decisions before you reach a flammability 12 limit.
'13 DR. WALLIS: This is also time to make mistakes.
14 MR. SCHERER: True.
() 15 MR. HOOK: In slide 18 we see the actual 16 generation rate based upon our calculations, and you see --
17 this is a case where there's no hydrogen recombiners or --
18 DR. WALLIS: This is concentration; this isn't 19 generation rate.
20 MR. HOOK: Oh , I'm sorry, hydrogen concentration. )
i 21 And you see at approximately ten days we're about 3-1/2 22 percent in the design basis where we would terminate use of 23 the recombiners, and the other cases you see the 24 sensitivities, case 1, 2, and 3, in the red. And blue, in 25 lighter blue, or green, the actual concentrations are very i l
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1
! 60 1 similar and are below 4 percent and rise slowly,
[~]
v 2 primarily --
3 DR. WALLIS: Excuse me. There concentrations here 4 are without recombiners?
5 MR. HOOK: That's correct.
6 DR. WALLIS: If you had recombiners in there with 1
7 the black curve, what would it look like? I
\
8 MR. HOOK: They would initiate the hydrogen l 9 recombiners at 1 percent.
l 10 DR. WALLIS: And then it would go up and curve 11 over?
1
! 12 MR. HOOK: It would go up and curve over. And l 1
1 1
13 that's --
l 14 DR. WALLIS: So it would actually have 30 days i rx i I
\m /
15 below the three cases shown.
16 MR. HOOK: That's correct.
l 17 DR. WALLIS: So it would look better.
18 l MR. HOOK: Yes. This is a case -- !
' l 19- DR. WALLIS: If we added a dashed curve with 20 recombiners, that would complete the picture here? Could l
21 you show that on the --
22 MR. THOMPSON: Excuse me. My name's Owen 23 Thompson, Southern California Edison. I'm the manager of 24 the nuclear fuels analysis group.
25 The FSAR shows a black line, and if you initiated
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61
- 1. afsingle recombiner at 3-1/2. volume percent, it would then-
.2 be a single recombiner vent exceeding 4 percent at'any time 3 in the future.
4 DR. WALLIS: It would flatten off --
5 MR. THOMPSON: Flatten off. If you have --
6 DR. WALLIS: One recombiner.
7 MR. THOMPSON: Right. If yor. had two of them 8- going, it would turn it around, or if you had one recombiner 9 'and the purge system, it would turn it around.
10 , DR. BONACA: And that's starting at 3-1/2 percent?
11 MR. THOMPSON: Yes. In effect the recombiners are 12 sized to handle the radiolysis in corrosion terms.
13 DR. KRESS: The-shape of these curves suggests 14 that you have a' rapid rate early and a slower rate later.
() 15 MR. THOMPSON: That's correct. The way the model 16 is done is we actually model a puff release initiated by the 17 corrosion of the' zinc-based paint, thin aluminum, 18 Zircaloy-water reaction from the cladding, and the hydrogen 19, coming out of solution that's in solution in the~RCS So 20 you have this initial burst, and also you have the 21 temperatures in containment rapidly rising, so you have an 22 accelerated corrosion of the remaining zinc and aluminum.
23 And then as the temperature falls off, you basically end up 24 being dominated by radiolysis and some corrosion.
25 DR. KRESS: So you have the temperature transient
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l 62 1 of'the containment built into this-curve.
,2 MR -THOMPSON: Yes.
3
~
DR. KRESS:. As well as the-leakage out of the
~4 containment?
l 5- MR. THOMPSON: ~No. -We assume that the -- for this 6 the containment is tight..
7 DR. WALLIS: So it is true, this picture, if you
]
., 8 : put it in recombiners, it looks as if they are being useful, 9 ;even in your cases 1,-2, 3. I 10 MR; THOMPSON: For design basis; correct.
11 DR. KRESS: That's what they were designed for.
12 MR. THOMPSON: Exactly.
13 DR. KRESS: To keep you below 4 percent in the-14 design basis. What you're saying is is -- 1
() 15 DR. WALLIS: The reality --
16 DR. KRESS: You don't really need~it.
- 17. DR. WALLIS: They think there's a conservatism and 18 they're going to have 30 days.
11 9 DR. KRESS: Yes.
20 EDR . WALLIS: Instead of ten days to do something, 21- such as switch on the recombiners.
22 MR. HOOK: Moving on to slide 19, this describes 23 the safety margin evaluation. The SONGS 2&3 is a large, dry l 24 containment for each unit with a design pressure of 60 psig.
25 Large, dry containments are the least susceptible to damage
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l 63 1 from hydrogen burn based upon the TMI 2 accident where there l i
n.
G ')
2 was an 8.1-percent containment hydrogen concentration, which 3 is approximately a 45-percent metal-water reaction that 4 resulted in a peak containment pressure of 28 psig, and the 5 design pressure of the TMI 2 containment was 60 psig.
6 DR. KRESS: Where did you get this 8.1 percent in 7 TMI from? 4
{
8 MR. MOIENI: We got it from an EPRI report, 9 NSAC -- I don't remember the number, but this was from an 10 EPRI -- NSAC-61 I think.
11 DR. KRESS: That's quite a precision anyway, 8.1 l
12 percent, for TMI. That's probably plus or minus 5 percent 13 or something. !
14 DR. WALLIS: It was probably 45 percent plus or
('%
(ss ) 15 minus 5 percent, metal-water reaction, and then this is what 16 happens if you use 45 percent.
17 MR. MOIENI: Tom, I've seen different numbers, but 18 we picked this one because we could basically relate it to a ,
19 reference.
20 DR. KRESS: Your point here is just that your 21 containment's pretty good, and even a high percent of 22 hydrogen probably doesn't even get you close to the design 23 pressure, much less the failure pressure.
24 MR. HOOK: Right. And there's significant 25 conservatism in the design basis calculations, since they
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t
.1 64 1 don't consider the heat removed from the containment
() 2 3
structures and other -- and heat transfer to them and such, so.that in a real hydrogen burn, we would expect the actual 4 pressure to be-significantly less than what we calculate 5 using the codes we used for design basis.
6 DR. KRESS: Yes, I wouldn't.
7 DR. WALLIS: How long does the burn take? It's 8 over in~a second or a millisecond or in a minute or what?
9 DR. KRESS: The heat transfer doesn't have time 10 to --
11 DR. WALLIS: How long does it take? Is it a big 12 flame that --
13 MR. HOOK: I honestly don't know.
14 DR. WALLIS: Is it fractions of a second?
() '15 DR. KRESS: It's. seconds.
16 DR. SEALE: Yes.
17 DR. KRESS: Depends on whether it's upward 18 transferring or downward transferring or whatever, but it's 19 seconds.
20 DR. SEALE: Well, the pressure certainly suggests 21 it was pretty quick.
22 MR. MALLIAKOS: This is Asimios Malliakos from the 23 staff.
24 A hydrogen burn of what, like 8.1 percent, we're 25 talking about a speed -- whatever I recall from my mind from
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1
)
00 l b 1 previous experience -- we're talking about a few feet a 2 second. We're not talking about something like a detonation
)
3 that will take -- l 4 DR. WALLIS: So it takes a minute or so.
5 DR. KRESS: It may take a minute.
6 MR. MALLIAKOS: We're talking a few minutes, let's 7 say, to go through.
8 DR. KRESS: But the heat transfer is not going to 9 happen.
10 DR. SEALE: It's a whoosh rather than a bang.
11 MR. MALLIAKOS: That's right.
12 DR. WALLIS: So it compresses the mixture in the 13 other side of the building? As the hydrogen burns here it 14 expands does it compress the remaining hydrogen mixture?
() 15 DR. KRESS: Oh, yes, the pressure --
16 DR. WALLIS: So it is more readily burnable 17 somewhere else?
18 MR. MALLIAKOS: Again, this is Asimios Malliakos ,
l 19 from the staff. J 20 The speed of this deflagration is so slow that I 21 will say it compresses at the same time the entire 22 containment. The case that you are talking about is that j 23 you compress the unburned mixture is -- it can be in the i 24 case of a detonation. ;
1 25 DR. WALLIS: Thank you. I l
1
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66 1 MR. HOOK.: Industry and NRC evaluations, the NRC
[
2 evaluation documented in NUREG CR 5662 show that large, dry 3 containments can withstand large hydrogen burns, up to 75 4 percent metal-water reaction. And there was a detailed 5 containment integrity analysis performed as a part of the 6 individual plant examination at San Onofre performed by EQE 7 structural engineers from earthquake engineering where they i
8 looked at all -- individually all the containment 9 penetrations and performed detailed calculations on the leak 10 as well as failure likelihood of those penetrations at 11 various pressures. And we developed a pressure curve for a l
- 12. rupture and leak for the containment to determine the median 13 leak pressure is approximately 157 psig.
14 And the median of the rupture pressure is 175 psig.
() 15 16 DR. WALLIS:
distribution like?
These are medians. What's the 17 MR. HOOK: The 95-percent leak pressure for the 18 SONGS containment is about 99 psi.
19 DR. WALLIS: So it's quite a long way away from 20 that.
21 MR. HOOK: Yes. And that's why if you look at the l
L 22 SONGS accident management guidelines, they direct that j 23 purging be considered when the containment pressure reaches 24 99 psig and continues to rise. So at that point we know l
25 there is leakage occurring at 99 psig which could be ANN RILEY & ASSOCIATES, LTD.
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67 1 significant.
] } 2 That leakage -- the weakest penetration that 3' causes leakage at that pressure is the fuel transfer canal 4 valves, which;would then leak into the fuel handling 5 building where the fuel pool is located at 99 psig. They 6 would.not be penetrations that start leaking to the outside 7 environment directly. And the rupture pressure is basically 8' the failure of the containment tendons or a gross failure of 9 the. containment. And the 95-percent-confident rupture 10 pressure is about 139 psig. So that's the distribution. So
'11 that'was a combination probabilistic deterministic analysis 12 by EQE of our containment.
13 In the next slide relating to severe accidents, 14 the SONGS from the SONGS 2&3 individual plant examination, 15 .we concluded in running the MAAP code and in the evaluations 16 that were performed for us by FAI that the hydrogen control 17 systems are ineffective or detrimental in mitigating 18 hydrogen during severe accidents. ;
19 NUREG/CR-5567 supports this conclusion, and the j 20: NRC's post-TMI evaluations concluded that large, dry 21 ~ containments could withstand hydrogen burns following severe 22 accidents. !
1 23 DR. WALLIS: When were these recombiners put into <
24 the system? What was the date of installation?
25' MR. RAINSBERRY: Early eighties.
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68 1 DR. WALLIS: Early eighties?
() 2 3
MR. HOOK: I'm not sure if they were there at the initial commercial operation. I would guess they were.
4 MR. SCHERER: I believe they were at the initial 5 operation. This is a post-TMI plant.
6 DR. WALLIS: Right.
7 MR. SCHERER: It was originally licensed in '82, 8 and I believe they were 'here..
t i 9 MR. SNODDERLY: The rule existed prior to TMI, 10- There were recombiners at TMI. As a result of TMI, the rule 11 changed, and for recombiners it resulted in that you needed 12 a dedicated penetration instead of allowing it to come off 13 an existing penetration. That was --
14 DR. WALLIS: I'm just thinking of trying to
()
j 15 explain this to some public group that here's something 16 which is being required and has been installed for almost 20 17 years or something and now it's been determined it wasn't 18 necessary all that time, therefore we'll take it out. You 19 have to do a little more explanation than that probably.
20 MR. HOOK: Moving on to slide 21, additional l 21 information from the SONGS 2&3 individual plant examination.
l 22 The containment can withstand the impact of a worst-case 1
23 hydrogen burn at 11-1/2 percent. That accounted for both i
1 24 in-vessel and ex-vessel hydrogen production.
25 DR. KRESS: Did you use the MAPP code for that?
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1 69 1 MR. HOOK': This was actually a hand calculation by
() 2 3
FAI, by Bob Henry and FAI.
DR. KRESS: Yes, I know about it.
4 MR.'MOIENI: This_ specific one is not really a
.5 MAPP calculation. But the series of analyses we performed 6 you see the impact of hydrogen burning on containment, and 7 those were performed by MAPP. But this' specific one, no.
8 That's not a MAPP. This is a very, very conservative
- 9. calculation, worst-case calculation.
10 DR. KRESS: Okay.
11 MR. HOOK: And these are the assumptions in the 12 calculation that indicate their conservatism. We suppressed {
13 all hydrogen burning up to a single point, so there was no I 14 preburn or partial burns, and it accumulates all at once.
() 15 We assumed an adiabatic isochoric, complete combustion, 16 which is a - means no confined volume with no leakage and
-17 no temperature or heat input or output'to the containment 18 structures. And that bounds the containment pressurization 19 from the burning.
20 The scenario is a loss of secondary heat sink with 21 limited injection from three charging pumps to maximize the 22 metal-water reaction. And this is an extremely unlikely 23 event. This assumes that our normal high-pressure safety 24 injection large-capacity injection system is not 25 functioning. The low-pressure safety injection system is
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70 1 not-functioning. But somehow we have three charging pumps 2 functioning,.which=provides the exact amount of water that
)
'3 maximizes the metal-water reaction. So this is an extremely
- 4. unlikely severe accident, but it's the worst case in terms 5 of providing just the right amount of water to maximize the 6 metal-water reaction, j 7 DR. WALLIS: This 142 psig is above your 95 8 percentile.
9 MR. HOOK: That's correct. I 10 DR. WALLIS: So there's a 5-percent chance that 11- this will fail the containment.
12 MR. HOOK: That's correct.
13 And the amount of hydrogen generated is 14 approximately 2,400 pounds based upon the calculation. And
(). 15 the postburn. peak containment pressure is 142 psi. The
- 16. actual. realistic assumption is that the burn would be i
17 significantly less in terms of its pressure than calculated !
.18 here based upon the TMI event.
19 DR. WALLIS: Could I ask you here, we're on :
20 this -- if you had recombiners operating, they wouldn't 21 change this 11.5 percent, or would it be perhaps 10.5 22- percent or something.
23 MR. HOOK: They would not affect --
24 DR. WALLIS: Wouldn't really it, because --
25 MR. HOOK: It wouldn't affect it. We would turn 1
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o o
y 71 i
1 it off at 3-1/2, and even if they were operating, they would
, I~
V) 2' overwhelm -- they would cause a preburn if they were 3- operating probably before we got anywhere near --
4 DR. WALLIS: That would be better. It would be much better to have them act as igniters early on.
~
j 5 Then you i
6- would avoid this few-percent chance or a bit more maybe 7 because --
8, DR. KRESS: Yes, I think that was the nature of my l 9 question earlier.
10- DR. WALLIS: So there is some significance. There 11 is a change.
]
l 12 MR. SCHERER: But you are adding realism to
! 13 something that we intentionally took it out of to create the I
14 worst case. I think that's the miscommunication here. Tom
() 15 was trying to point out that we had intentionally tried to !
l 16 create the circumstance, no high-pressure safety injection, 17 no low-pressure safety injection --
l 18 DR. WALLIS: So you're saying the probability of I 19 this is --
20 MR. HOOK: Yes.
l 21 MR. SCHERER: Yes, In fact, it is almost -- you j l
22 would'have to multiply your 95-percent probability times the l
l 23 probability of exactly this sequence of events occurring.
l 24 DR. WALLIS: That's right, but whatever that is, l 25 there is an impact at that level.
l l
O i ,/
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72 1 MR. SCHERER: Right.
) 2 -DR. WALLIS: You're multiplying 10 to the minus 8 3 by 10 to the minus 2 instead of 10 to the minus 3 or 4 something has happened, but you're saying it's a very small 5 number.
6 DR. SEALE: But basically everything is -- you're 7 still chemically. reacting the hydrogen.
8 DR. WALLIS: Right.
9 DR. SEALE: So the energy is there. And so you 10 haven't done anything that really --
11 DR. WALLIS: If we'd preburned it --
12 DR..SEALE: Yes. It's still in there, and the way 13 you calculated it, you don't have any heat sinks or anything 14 else. So it's --
() 15 DR. KRESS: It wouldn't help with this 16 calculation.
17 DR. SEALE: It's six of one and a half a dozen of 18 the other.
19 MR. HOOK: Right. And there are containment 20 failure modes obviously in the individual plant examination 21 where we overpressurize or -- and overheat the containment, 22 and so -- the point is the hydrogen recombiners don't play 23 in the current way we operate them per the EOIs and the 24 accident management guidelines. They'll play a role in 25 mitigating that event.
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73 1 Slide 22, this addresses hydrogen pocketing, and
() 2 3
this was the question raised earlier about the benefit of mixing. Hydrogen pocketing is not an issue for SONGS 2&3 4' based upon the event paths and the mixing from the 5 containment fan coolers, the containment spray, and 6 containment dome circulators. And the question was, what is 7 the capability of both systems in terms of processing and 8 moving the air around, and that was evaluated in 9 NUREG/CR-5662 for several large, dry containments. And 10 depending upon the containment volume and capacity, the time 11 required to process one containment volu:.ne by fans alone is 12 approximately 10 to 30 minutes. And that's consistent with 13 the SONGS design.
14 DR. KRESS: It's not the metric used, but have you 15 ever exercised a multidimensional transport code to find out 16 the distribution.of hydrogen in your containment with all 17 these fans going and things, to see if there are pockets 18 anywhere -- or most of these are good design features that 19 eliminate pockets, I agree, and these are good rules of 20 thumb but the final proof of the pudding is to have a 21 calculation of hydrogen distribution. Maybe the flow 22 patterns are such that you get it all concentrated in the 23- middle or somewhere. I don't know what the flow patterns 24 are but -- has that ever been done?
25 MR. HOOK: No. Owen is shaking his head no, and O ANN RILEY & ASSOCIATES, LTD.
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I 74 1 he would be the person who would do that.
() 2 Also, just to note the hydrogen recombiners are-3 located up in'the area.of the containment which is the open 4 atmosphere area do not provide any benefit in terms of 5 pocket burning.
6 DR. KRESSi It wouldn't have anything to do with 7 -hydrogen recombiners. I am just asking the question in 8 general because I don't see that this has anything to do 9 with hydrogen combiners.
10 DR. WALLIS: Fan coolers are low down in 11 containment, aren't they? They are low -- there's a ring of 12 service water or something that goes to the containment, and 13 then there is a big --
14 MR. HOOK: Actually, ours are up high in the
'15 containment.
16 DR. WALLIS: They are high? Not too high, because 17 you are worried about getting, what do you call it? --
18 getting column separate or something.
19 MR. HOOK: Yes, we are.
20 DR. WALLIS: So you can't be too high or you'd get 21 gas pockets in there or voids and then you get -- so they 22 are not too high and there is piece of containment above 23 them, but what I am concerned about would be if some 24? hydrogen went up there and stayed up there.
25 DR. KRESS: That is where they have the dome.
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l 75 l 1 DR. WALLIS: That is why you have something at the l
'( 2 dome.
3 MR. HOOK: 'Right. The dome circulators are at the 4 top.
I 5 DR. WALLIS: It would be useful~if you could have l
6 some kind of a prediction of mixing which is more 7 sophisticated than this.
8 MR. HOOK: Okay. Let me go on to Slide 23.
9 The hydrogen monitoring system has limited 10 usefulness for severe accidents. It is only designed for a 11- maximum of 10 percent and we could potentially see hydrogen 12 concentrations above 10 percent.
13 It needs compensation for temperature. This is 14 reiterating the comments made earlier. The hydrogen
,(O,) 15 recombiners are not useful for severe accidents because of l 16 their limited operating range. We turn them on at 1 percent 17 and turn them off at 3.5 percent per the EOIs and the 18 Accident Management Guidelines.
19 We turn them off at 3.5 to preclude a burn and the 20 hydrogen generation rate in severe accident for all the core 21 damage events that we evaluated in the IPE far exceeds the 22 recombiner. capacity.
23 The hydrogen purge is not useful and is 24 detrimental for severe accidents because it creates the 25 potential for a large fission product release due to a I ANN RILEY & ASSOCIATES, LTD.
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76
'l ' failed open purse value with a-high likelihood that the HEPA
() 2 3
filters will not_ survive a large differential pressure on the order of 99 psi, which is the point at which we would 4 use them in a severe accident per Accident Management ;
I 5 Guidelines.
6 The hydrogen generation rate would far exceed the 7 ' capacity of the hydrogen purge system. ,
8 Slide 24 in' terms of the emergency operating 9 instruction of removing from the design basis and EOIs the 10 hydrogen control requirements, the current emergency 11 operating instruction control steps and activities could 12 potentially distract the operators during extremely busy 13 periods following the accident, and this is consistent with 14 the arguments that were provided by~ Arkansas for their
() 15 request that the hydrogen sampling be delayed from 30 16 minutes to 90 minutes.
17 The current hydrogen control activities have no
)
18 meaningful benefit in terms of mitigating accidents as a.
19 result of their being sufficient defense-in-depth for the 20 containment'and the opportunity to mitigate long-term 21 radiolysis buildup at the 30 day point for a realistic 22 hydrogen generation rate from a LOCA.
23 Elimination of hydrogen control steps and 24 simplification of the EOIs will have a positive impact on 25 calculated plant risk by reducing operator error, having the i
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I (202) 842-0034 i
77 1 . operator that could be -~- avoid having to provide the review j
) 2 of'the hydrogen monitor, hydrogen concentration we believe l 3 would have an impact in reducing core damage on the order of 4 approximately 20 to 50 percent by providing a person that 5 could focus on the other critical safety functions -- heat 6 ' removal'and core inventory, reactor coolant system inventory l
7 makeup.
8 DR. SEALE: By god, we finally got human action l
l 9 into a risk assessment. I 10 DR. KRESS: But it's qualitative.
11 DR. SEALE: No.
12 [ Laughter.]
13 DR. WALLIS: It's like the argument you used 14 before --
l
() 15 DR. SEALE: Sure.
[ 16 DR. WALLIS: If you had a better system which l 17 didn't require so much operator action, then that would also 18 reduce the operator error.
19 MR. HOOK: That's correct.
l 20 DR. WALLIS: It could be a technical fix rather 21 than just removing it completely, if it were useful.
I 22 MR. HOOK: If it were meaningful.
l l
23 DR. WALLIS: Right.
24 MR. HOOK: Lastly, we believe that the removal of ;
i 25 the steps from the emergency operating instructions for a j
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)
78 1 design basis but not a severe' accident would have a positive
(} 2 impact on the calculated plant risk by reducing the 3 probability of a failed open containment purge valve if the 4 event later went to a severe accident.
5 The next slide, 25, is a discussion of the Severe 1
6 Accident Management Guidelines and how the hydrogen control 7 system interacts with them, and I think I have discussed 8 most of this but this is a case where we looked at what will 9 we do in the Accident Management Guidelines if the hydrogen 10 control system is unavailable and the direction in the AMGs 11 is to prevent fission product release by bottling up the 12 containment and all the penetrations to maintain as 13 leak-tight as possible the containment, to reduce 14 containment temperature, using the fan coolers or
() 15 containment spray, and minimize.the long-term hydrogen 16 buildup from the metal-water reaction or corrosion, since 17 that is a temperature-dependent process, remove fission 18 products by operating the containment fan coolers and the 19 spray so that they are not available, so they are condensed 20 or not available to be released --
21 DR. WALLIS: What do you mean,. precipitate or 22 something? What do you mean remove?
23 MR. HOOK: Remove them from potential release 24 through the leakage --
25 DR. WALLIS: You mean put them on the floor I ANN RILEY & ASSOCIATES, LTD. l
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l L !
l 79 l
1 instead -- ;
2 DR. SEALE: Yes, knock them down --
[G )
3 MR. HOOK: You know, water versus being in the 4 atmosphere where they could leak out of the containment.
5 Monitor or estimate the hydrogen concentration --
6 there are engineering --
7 DR. KRESS: Do the Severe Accident Management 8 GuidelineF actually say operate the containment spray "or" l 9 the fan coolers or does it say "and" --
10 MR. HOOK: It says "and" -- either of them is 11 effective in removing sufficient heat to get below the 12 design basis.
13 DR. KRESS: I was talking about removing fission 14 products. I am not so sure how good the fan coolers help
(~x
() 15 you there. That bullet is preceded by " remove fission 16 product" --
17 MR. HOOK: Right. Well, the fan coolers obviously 18 don't remove as much of the fission products as the 19 containment spray but they do condense noncondensible --
20 DR. WALLIS: They drip. There is all the material 21 that runs off them, presumably.
22 MR. HOOK: Right.
23 DR. SEALE: And they homogenize the atmosphere so 24 that you get more contact with the -- I 25 MR. SCHERER: And the core is played out.
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80 1 DR. KRESS: You know, it's a matter of rates, how es
( ) 2 much you are going through those fan coolers.
/
3 DR. SEALE: Sure.
4 DR. KRESS: But the containment sprays get the 5 whole atmosphere.
6 MR. HOOK: That's correct.
7 DR. KRESS: They are much more effective.
8 MR. HOOK: They are much more effective in terms 9 of fission product --
10 DR. KRESS: That is why I said I wouldn't have had 4
11 an "or" in there. I would say operate the containment 12 sprays and the fan coolers is the way I would have said it.
13 DR. WALLIS: That makes sense.
14 MR. HOOK: Right, and there are calculational aids 15 associated with the Severe Accident Management Guidelines 16 that allow you to estimate the hydrogen concentration if you 17 don't have the hydrogen monitors or a PASS sample 18 capability. ;
19 This is based upon the radiation levels, heat 20 containment or even outside the containment from portable 21 radiation monitoring instruments.
22 DR. WALLIS: You are asking the operator to do )
23 this, so you really should make a comparison between before ;
24 and after how much distraction to the operator is it going 25 to be using these engineering analyses as opposed to the old
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I 81
-1 method of relying on the --
]) 2 DR. KRESS: These are already in there.
3 MR. HOOK: Yes, the operators would probably not
~
4 be doing this. This would be done as a result of direction 5 from the technical support center to health physics 6 personnel.
7 DR. WALLIS: So it is somebody else who is doing 8 that?
9 DR. KRESS: Yes, right. These are already in the 1 10 guidelines. This is another subject they are adding.
11 MR. HOOK: Yes, these are already in the 12 guidelines. There are already activities that are performed 13 and also --
l 14 DR. WALLIS: But you are asking them to monitor H2
) 15 concentration and if you have the meter which you are 16 proposing to take out, it would be a lot easier, so there is 17 an effect on this.
18 MR. HOOK: Right. Well, we are not proposing to 19 take out the meter. We are proposing to remove it from the 20 -design basis and I mean that is a critical point. We 21 . haven't said anywhere that we are taking --
l 22 DR. WALLIS: You are not asking people to 23 recalibrate it now, are you? Do they still have to 24 recalibrate it during an accident -- going to use it?
25 MR. HOOK: Yes. In terms of long-term cleanup, h
\/
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E 82 1 after. extensive ~ scrubbing of the containment atmosphere the
[t )T 2 AMGs provide the: opportunity or direction that the hydrogen 3 vented be -- hydrogen can be vented via the mini-purge or 4 other temporary filtration systems.
5 DR. KRESS: What is a mini-purge?
6 MR. HOOK: We have as part of our design at the 7 plant an' ability to remove containment atmosphere through a 8 controlled vent' path as a part of normal operation and this 9 vent path is used frequently and it doesn't have a HEPA 10 filter in it so there is no potential for blowing out a HEPA 11 filter but it is a moderate capacity system greater than the 12 capacity of the hydrogen purge, and the AMGs indicate that 13 that would be a potential vent path if the hydrogen purge 14 path was unavailable.
(m,,) 15 DR. SEALE: I am just curious about how familiar 16 you are with this hydrogen monitoring instrument, which you 17 are going to take out of your guidelines but you are still 18 going to have available and all. What if you just turned it i 19 on and you got a reading. Now you know it hadn't been 20 calibrated. Is the reading, is the difference between a 21 calibrated and'uncalibrated number 20 percent error or a )
I 22 factor of two? Do you know?
l 23 MR. MOIENI: The difference between the actual and 24 the-basically error reading is about half a percent, .5 25 percent.
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E l 83 l 1 DR. WALLIS: Is this something that creeps up on (m; 2 your over the years or is it something which --
3 MR. SCHERER: It has temperature changes.
4 DR. KRESS: It has temperature changes.
5 MR. SCHERER: The issue is one of in a severe 6 accident you are going to use what information you have, 7 compensated or uncompensated, and you are going to make your l 8 best judgment.
9 The point that we were trying to make with all of 10 this point on adjusting the readings is if you are trying to 31 control within a 1 percent to 3.5 percent and if you impose i
12 )
upon yourself a limit of 3.5 percent, you want to know with !
I 13 some degree of accuracy when you approach that limit before 14 turning it off, and you want to know how accurate it is
/~N
() 15 before turning it on.
16 Those are unnecessary complications but certainly I
17 in a severe accident you are going to take what you can get j 18 at the time you are going to make it and you are going to 19 make the best decision you can. That is the basis on which i
20 the Severe Accident Management Guidelines are written. i 21 DR. SEALE: That was the basis of my question, and 22 the other thing is that if you make the apparently 23 unthinkable decision of deciding to let these things acts as 24 a burner -- pardon me, an igniter, once you get above 3.5 j 25 percent and you put a calibration curve in which tells you
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84 1 how~much you offset the stuff the reading by as a function
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}
2 of temperature, then you' don't have to worry about 3 recalibrating it.
4 DR. KRESS: That sounds like a reasonable approach
'5 to me.
6 DR. SEALE: And you really simplify things then, 7 don't you?
8 'DR. WALLIS: Just leave it on.
9 .MR. HOOK: And we propose to. remove the hydrogen 10 monitoring steps from the emergency operating instructions, 11- but now from the Accident Management Guidelines.
12 DR. SEALE: Yes.
13 MR. HOOK: And turning to Slide'26, it is a 14' summary of everything we have discussed in our presentation.
() 15 The proposed change does not affect the SONGS-2, 16 -3 defense-in-depth containment design based upon the 17 ultimate containment capability and the challenge that a
.18 design basis event would provide. Large dry containments 19 'like San Onofre 2 and 3 have the capability to withstand
- 20. worst-case hydrogen burns with a 75 percent metal-water 21 reaction and not fail with relatively high certainty. )
22 The hydrogen control system is not needed for 23 accidents based upon realistic assumptions, utilizing the 24 Westinghouse and Oak Ridge National Lab assumptions.about 25 the amount of radiolysis and the amount'of cladding O ANN RILEY & ASSOCIATES, LTD.
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- 1. interaction.
2 The hydrogen control system is not sized for
(
3 severe accidents and it could potentially detrimental in the 4- case of the hydrogen purge.
5 Creating a vent path that potentially could not be closed.
6- The elimination of the hydrogen control steps and activities
- 7. from the emergency operating instructions will result in a 8 risk-positive change in our opinion based upon the reduction 9 of complexity of the emergency operating instructions and in 10 the removal of the likelihood of a stuck-open purge path.
11 The reduction in burn to maintain the hydrogen 12 control equipment and the impact of the hydrogen purge doses 13 on equipment qualification in control room habitability 14 requirements are significant, especially for the equipment
-A
( ) 15 qualification requirements. In removing the prospect of 16 utilizing hydrogen purge in a design basis event, we could 17 then replace failed equipment that currently has stringent
- 18. radiation equipment qualification requirements with 19 equipment that does not need so strict requirements on the 20' radiation doses.
l 21 We believe that would be a significant burden 22 reduction. And granting this exemption supports the 23' risk-informing 10 CFR 50 regulations, by providing an 24 opportunity for us to identify a low-safety-significant 25 system and set of components that we believe would not be l
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86 1 subject to any of t he risk-informed sections of Part 50, and 2 that this would'be an example of identifying a j 3 low-safety-significant system as a part of the Task 0 that 4 would provide.an example for how we would then proceed on 5 risk-informing Part 50 and redefining the scope of
.6 structures, systems, and components for which the 7 maintenance rule.and 50.59 and Appendix B and other sections 8 of 10 CFR 50 would apply.
9 DR.-KRESS: You mentioned this would be a 10 significant burden reduction or else you wouldn't be here, 11 right?
{
12 MR. HOOK: That's correct. l j
13 DR. KRESS: Just out of curiosity, how much money 14 is it going to save you?
15 MR. SCHERER: The money savings are not that 16 significant, since we have already installed the equipment.
17 It was picked as a Task 0 because we believed that it was a j 18 clearly risk -- not a risk-significant system. We could 19 make a case that it did not meaningfully contribute to the 20 risk reduction at the plant.
21 DR. KRESS: So it's a step in implementing 22 risk-informed regulations and by the way I get some burden 1 23 reduction. !
l 24 MR. SCHERER: We do get some burden reduction, and 25 maybe this is as appropriate a place as any to say what we i
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- 1 would do if the exemption were granted. We believe we've i 2 made a case that based on a risk-informed submittal -- 1 3 DR. KRESS
- Well, let me ask you another question l
4 about that. What is the SONGS 2&3 value for CDF and LERF?
5 I haven't seen it mentioned anywhere. It's probably in your 6 IPEs maybe.
7 MR. HOOK: The combined internal and external j 4
,8 initiating event core damage frequency for San Onofre 2 and 9' 3 with all the post-IPE and IPEEE modifications implemented 10 is approximately 8 times 10 to the minus 5 for core damage,
! {
l 11 and for large early release -- 70 -7, okay. l 12 DR. KRESS: 7 times 10 to the minus 7.
13 MR. HOOK: Right. And as you may know, we are in 14 the final stages of implementing the diesel generator 15 unit.to-unit cross-tie capability which was one of the fI 16 recommendations that came out of the individual. plant l 17 examination of external events. And that should be 18 completed within a couple months. And that will result in 19 the numbers that I quoted.
20 DR. KRESS: Thank you.
21 DR. WALLIS: So the explanation to the public is 22 that in the enthusiasm for regulation following TMI these ;
23 things were put in, and after however many years of l 24 experience, 15 years --
25 DR. KRESS: And increased knowledge.
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1 DR. WALLIS: And increased wisdom in the meantime,
(~'E 2 it'has been discovered that they really aren't necessary, d
j 3. and therefore you. propose to remove them. So this implies 4 that there was an overreaction to TMI perhaps at some time 5 in installing equipment which really was not useful.
6 MR. SCHERER: And we would maintain some benefit 7 from the existence of the equipment. That's what I was 8 going to be discussing next is what would we do in the event i
9 that our exemption request would be. approved. First, taking I
10 it in reverse order or slide 9, hydrogen mixing inside 11 containment would remain unchanged. It's part of our 12 containment and it's part of our design, and that would 1
13 remain the same as it is today.
14 As Tom pointed out, we have three systems
() 15 . currently in effect with the ability to purge the 16 containment --
our main purge, our minipurge, and the i 17 hydrogen control capability that we talk about here. It 18 would be our intent that we would remove the requirement for 19 that system from the FSAR and from the technical' 20 specifications. We would reclassify the existing equipment 21 as nonsafety related, but we would not physically remove it 22 from the plant.
23 The same would be true in the hydrogen recombiner.
24 We would remove any reference to it from the FSAR in the 25 technical specification. We reclassified the components as i
i l '
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t 89
$ non-safety-related. But we would maintain them in the plant 2 . without any commitment to heroic efforts to keep them in 4 l 3 effect. And in the case of certainly the purge and the 4 hydrogen recombiners, we would continue to refer to them in 5 our severe accident management guidelines as we do today 6
that we would take credit for them and we would utilize them 7 as they are available.
8 DR. SEALE: This somewhat puts me in mind of how 9 . we dealt with what we call the regulatory treatment of i 10 nonsafety systems for AP600. They were there, but they --
11 and would be useful, but they kind of get exempt from all 12 the quality one things and the safety-related --
13 MR. SCHERER: Actually by doing that we actually 14 increase the availability because by being able to treat
() 15 them as nonsafety-related components becomes more-16 cost-effective to maintain them as a piece of equipment in 17 the plant, and certainly having spent the money to install 18 them in the first place, even recognizing the very narrow 19 window we believe that they provide value, they provide 20 value. So we would maintain them to the extent we could.
21 I'm not committing to in the future spend heroic 22 efforts to keep them on line, but we would not do anything
-23 to compromise them or remove them or spend money to l 24 physically rip them out of the plant. We would maintain 25 them, and we would take credit for them in our severe !
f N.
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90 1 accident management guidelines should they prove of use.
2 DR. SEALE: These changes in essence are the --
3 constitute a reallocation, I guess you'd say, of certain 4 resources'from a license basis requirement to a voluntary 5 action.
6 MR. SCHERER: Yes. j i
7 DR. SEALE: And it's my understanding from the 8 staff that we don't give credit for voluntary actions. Now 9 what you've suggested here is that these things don't amount 10 to a hill of beans or whatever you want to characterize it 11 as, in the CDF and LERF assessment for the plant anyway, and I 12 your assessment is -- perhaps nonquantitative but generally 13 -- is that the net effect actually is a positive effect 14 because it removes certain distractions and allows a
() 15 reallocation of available manpower to more significant 16 concerns in the event of an accident.
17 Is that a fair summary?
18 MR. SCHERER: I think that is a fair assessment 19 that in an unlikely event what we would do, and I think Tom 20 had a slide which talked about -- I'm trying to find the 1
21 number of it -- in a severe accident we would button up the !
22 containment. We would cool the containment. And we would 23 try to the extent we could to clean up the atmosphere in the 24 containment.
25 DR. SEALE: Gary wants to say something.
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91 1 MR. SCHERER: And the elimination of short-term i 2 ' requirements to make decisions on hydrogen recombiners would 3- probably be a' positive in attempting to do exactly that.
4 MR. HOLAHAN: I just wanted to clarify a point 5 about the staff and the Commission's views on voluntary I 6 actions. In the context of severe accident management 7 guidelines and many other commitments that licensees make, 8 the. staff does recognize those as a valid approach to deal 9 with some issues. In fact, the Commission has told us to, 10 you know, monitor voluntary actions in the shutdown area, 11 for example.
12 I think what you were referring to is -- what the 13 Commission has told the staff is when you're considering 14 ~ whether..a rule should be required or not on a given issue --
() 15 DR. KRESS: The backfit --
17 DR. SEALE: Yes. Right. Right.
18 MR. HOLAHAN: The backfi. tests.
19 DR. SEALE: Yes.
20 MR.~HOLAHAN: You should be' cautious about how you 21 give credit for voluntary actions, particularly those that
, ~22 can be changed. Okay? So things like equipment that's in p
l 23 place I would say is less likely to be changed unless 24 there's some, you know, monetary advantage. The market for 25 used or old, previously owned recombiners isn't all that
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'l great. Hopefully not.used, just previously owned
() 2 3
DR. SEALE: Well, we have an interesting case here, because these guys have a risk meter.
j 4 MR. HOLAHAN: Um-hum.
5 DR. SEALE: Will the status of these components 6 change on your risk meter once you make the change?
7 DR. KRESS: It won't even show up, I don't think.
8 DR. SEALE: I don't think it'll show up, but if at 9 some point down the road you decided to take them out, would 10 that change your risk meter?
11 MR. HOOK: The answer is no.
12 DR. KRESS: The risk meter is not sensitive --
l 13 MR. HOOK: They are not risk-significant in the 14 maintenance rule --
() 15 DR. SEALE: That's got it. I think that's true.
l 16 I just --
l 17 MR. HOOK: Our expert panel evaluation as well as l 18 the quantitative PRA concluded they were not 1
19 risk-significant.
20 DR. SEALE: But that may be a very interesting 21 question to ask in other cases where you have voluntary and 22 then suddenly no longer are honoring those voluntary actions 23 down the road with other people perhaps or other plants. It l 24 might be an interesting question to ask.
25 DR. KRESS: Yes. The question is what is -- is i
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93 1 there any regulatory control over voluntary things or --
2 DR. SEALE:
- ( Oh, just recognition. '
3 DR. KRESS: Not control but do you monitor and 4 recognize.
5 MR. HOLAHAN: I think the answer is not much. I 6 think, you know, the industry has come out, NEI and I 7 presume that San Onofre is participating in a commitment l 8 management system that, you know, NEI proposed. It has a 9 process for testing whether, you know, things that they've 10 committed to that don't have underlying regulatory 11 requirements, whether those should continue to be done or 12 whether they.should be changed, what the change process is, 13 or whether the Commission should be informed of some of 14 those changes.
() 15 You know, on this particular issue we haven't 16 quiet settled on, you know, what's a commitment and what's a 17 requirement, what's nobody cares. But I think there is some 18 middle ground in which -- and I think there ought to be some 19 middle ground.
20 DR. SEALE: Yes.
21 MR. HOLAHAN: Because in fact the technical 22 analysis says some things are very important, some things 23 are not important --
24 DR. SEALE: Yes.
25 MR. HOLAHAN: And there is a real technical middle I-i ANN RILEY & ASSOCIATES, LTD.
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94 1 ground. So part of this. pilot activity is sorting out how
'2- do you deal with what you might call marginally important
}
3 equipment. Is it appropriate to deal with it through a 4 commitment process --
5 DR. SEALE: Yes.
6 MR. HOLAHAN: Which has, you know, is respected in 7 some way by both sides, even though it's not a regulatory 8 requirement like a tech spec or a design basis.
9 You know, I think if we were to agree to such an 10 arrangement, we'd really like to know if those recombiners 11 left someday, so that we could reconsider the wisdom of the 12 deal 13 DR. SEALE: Yes. Yes.
14
~
MR. HOLAHAN: I think that's one of the things (O j 15 we're going to learn in this pilot activity is how do you 16 come to closure on those issues that are -- that don't pass 17 all your risk-significant tests but for some events or for 18- preventing some= undesirable situations do have some value.
19 How do you deal with those.
20 DR. SEALE: Yes. Yes, well, clearly we've been 21 scratching our heads a little bit about this problem, too.
22 DR. WALLIS: Gary, you could answer my question.
23 This is supposed to be an example of the beginning of 24 risk-informed regulation, I take it, and sort of the thin 25 end of the wedge, let's say.
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} 95 1 MR. HOLAHAN: It's one example.
2 DR.'WALLIS: So one should say what do we learn
- 3. about the principles which are to be used in this sort of 4 regulation. And what I've learned is that there are some 5 risk increases by not having the requirements there. I
- 6. mean, there is ---some hydrogen is not removed. Therefore, 7 there has got to be some increase in risk. But there's some j 8 risk decrease because the operators aren't distracted. No I 9 one has a measure of any of these risks, but the general l - 10 feeling is it doesn't matter anyway because it's small. So I I 11 we haven't really tested any criteria or principles yet.
12 MR. HOLAHAN: Well, I think we're testing some 13 principles. I don't think we're testing the guidelines or 14 the criteria. I 15 DR. WALLIS: The principle is that arguments can 16 be made, and you're receptive to them. But we haven't sort 17 of said you're going to measure it this way or the tradeoff 18 is' going to be balanced this way or -- there's nothing sort .
1 i l
19 of hard that's been established yet.
20 MR. HOLAHAN: I think in this example you're 21 l right. We have other examples in which, you know, there are i 22 core damage frequency and large early release and we're 23 comparing them to the guidelines in the report. But this 24 'is -- this was put up as an example I think for a different 25 purpose. It wasn't to test the guidelines or the criteria, ANN RILEY & ASSOCIATES, LTD.
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96 1 it was to test the willingness of the staff to give
/~'i 2 exemptions to things that maybe didn't look so important.
C/
3 It was more a test of wills.
4 DR. WALLIS: The speed with which they could 5- respond --
6 MR. HOLAHAN: And the speed -- j 7 DR. SEALE: k Yes.
)
8 MR. HOLAHAN: And efficiency with which they could 9 respond.
10 DR. WALLIS: Yes, and also to test whether the 11 ACRS would tolerate --
- 12 MR. HOLAHAN
- Yes, and how the Commission would 13 respond. Yes, test of the whole process.
14 DR. KRESS: Okay. Well, with that I am going to I
() 15 16
.think -- do you have some more comments?
MR. SCHERER: I have one comment on the discussion
- 17. that I am very concerned about a grey area in between, and I 18 want to make it clear as the applicant we have asked for it !
19 to be removed from the FSAR and the tech spec, to put it in j 20 some grey area in between.
21- We have said and we clearly will put it -- we 22 would be happy to put on the record our intention not to 23- physically remove the equipment and to how we would utilize 24 it. -But to leave it -- put it in some grey area in between 25 would-leave us on the real horns of a dilemma in today's ANN RILEY & ASSOCIATES, LTD.
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97 1 regulatory environment, and that is what is the allowed L{} 2 3
outage time, how much money do I have to spend to repair it if a hydrogen.recombiner failed and it was a heroic effort 4 to replace it, am I committed to do that?
5 Clearly we want to maintain as much capability as 6 we could,-but part of the reason for this application is to l
l 7 test the principle of as stated by the Commission if it is 8 'in fact a low-risk item, it is risk-insignificant, is there l 9 an ability on the part of the staff and the ACRS and the 10 Commission to let go of an issue if we can in fact 11 demonstrate it is risk-insignificant. But there's never a 12 zero, no zero standard here or 50.59 or anywhere else, but 13 if we_ demonstrate down in the risk-insignificant realm, can 14 we set it aside and move on to more risk-significant issues?
( )- 15 DR. WALLIS: So you won't remove it, but if it 16 stops working,.you won't fix it? I'm not quite clear about 17 your remarks there.
18 MR. SCHERER: _Well, we would maintain it, we would i
19 fix it, but we would not be committed to doing anything 20 heroic to keep it online. I mean, it depends -- I'll give 21 you an example, extreme example. If it costs us $1,000 to 22 put it back in operation, we'll put it back in operation.
23 If'it costs us $1 million to put it back in operation, we 24 probably would not be putting it back into operation.
25 DR. SEALE: And if it failed in-the middle of a O ANN RILEY & ASSOCIATES, LTD.
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98 1- run, you wouldn't shut the plant down to fix it.
)
( 2 MR. SCHERER: .That's correct.
3 DR. WALLIS: If you were faced with spending $1 4 million, would you feel you could just make that decision, 5- or would you feel you had to check with the staff?
6 MR. SCHERER: If our exemption is granted, we.
7 would feel that we could.in fact.make that decision.
8 DR. WALLIS: So you could allow it to deteriorate I 9 and eventually become dysfunctional or whatever the word is, t.
10 MR. SCHERER: It comes back to.that issue of is 11 the staff, the ACRS, and the Commission prepared to let go 12 of this issue.
13 DR. KRESS: That's a good point, good question.
14 DR. SEALE: Thank you very much for making the
\
(_) 15 . question very, very clear.
16 DR. KRESS: With that, I am going to declare a 17 recess-for 15 minutes, so we would like to be back about 18 five minutes until eleven.
I 19 [ Recess.]
20 DR. KRESS: At this time we will turn to the NRC l l
21 Staff presently and Mike Snodderly, you're on, buddy.
22 -MR. SNODDERLY: Thank you, Dr. Kress.
23 Dr. Kress, I wanted to clarify one thing. When l 24 you spoke of the AP600 RTNS and what we had done in RTNS --
25 DR. KRESS: Yes.
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i 99 1 MR. SNODDERLY: I would consider this one step
( 2' below that level or the RTNS program, because remember in 3 RTNS the controls were essentially if something is out for
! 4 .three months.then you notify the department head, if it is 5 out for six months, you notify the department manager, and
- 6. if it is out for more than a year you notify the Vice 7 President of Nuclear.
8 DR. KRESS: That was part of the RTNS.
9 MR. SNODDERLY: I Right, and so that -- I just 10 wanted to make clear that what was being proposed or 11 discussed and what has been discussed would not rise to that 12 level.
13 DR. KRESS: Thank you.
14 MR. SNODDERLY: I guess where -- I'm sorry, Paul, r~s
() 15 does everybody have a copy of the slides ready-to go?
16 DR. KRESS: Yes.
17 MR. SNODDERLY: Let's start with Slide 2 because 18 when we meet with the full committee I will use these full 19 -set of slides but since most of this material we have 20 already gone over to try and speed things up a little bit.
21 The main point I wanted to make with this slide 22 was I think Dr. Bonaca made a good point. What we are 23 -saying here is that in the past the intent was to show that l l
24 you could either withstand the consequences of:an ]
25' uncontrolled burn, but we had the recombiner system
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E 100
'l installed to prevent that.
2 Now what we are really saying is that uncontrolled
)
3 burning is accaptable and is not a risk to public health and 4 safety as shown through the San Onofre IPE and the Staff's 5 NUREG-1150. What I am going to do in this presentation is 6 take you through those results and try to establish that, 7 but that is really the -- I guess the change in 8 defense-in-depth or where we were and where we are going..
9 MR. HOLAHAN: Mike, would you summarize where we 10 are in the review process with these requests?
11 MR. SNODDERLY: Sure.
12 DR. KRESS.: Well, before you do that, I would 13 interpret that to say we are accepting some reduction in 14 defense-in-depth on the basis of using risk information.
() 15 MR. SNODDERLY: Why don't we come back to that at 16 the end of the presentation and then, yes, I think we will 17 be able to -- hopefully we will be able to not quantify the 18 change in defense-in-depth but I think we will have a much 19 better feel for what was intended here.
20 DR. WALLIS: Are you afraid of quantifying 21 defense-in-depth?
22 MR. SNODDERLY: No , sir, but I think at the end of 23 this presentation, I'll be able to give it my best shot --
24 or what I think is or what is at least on the docket or 25 available to us as tools today.
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101 1 MR.'HOLAHAN: I am not sure that defense-in-depth 2 is a quantity to be quantified. It might be a principle to
(}
.3 be respected.
4 DR. WALLIS: It's not ephemeral.
5 MR. HOLAHAN: Well, it gets pretty close to it.
6 MR. SNODDERLY: To respond to Gary's request, the 7 status of the review is that, as was mentioned by Southern 8 California Edison, we received a request for exemption in 9 September. We currently have a commitment on the Chairman's 10 tracking list to complete this effort by June 30th.
11- As you have heard today, it looks as though we may 12 need a letter from Southern California Edison to help 13 clarify some intentions for the recombiners and the purge 14 system, and it appears that they are going to change their
() 15 direction as far as hydrogen monitoring with a supplemental 16 PASS submittal in the future, so I think we are going to 17 come close to meeting the June 30th date.
18 DR.'KRESS: And you need a letter from us --
19 MR HOLAHAN: No.
20 MR. SNODDERLY: No.
21 MR. BOERNERT: No?
22 DR. KRESS: That's the question.
-23 MR. HOLAHAN: Do we need a letter from you?
24 DR. KRESS: Or would you like one or do you need 25- one?. I was assuming that we would probably have a letter at ANN RILEY & ASSOCIATES, LTD.
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102 1 the June meetings.
_2 MR. BOERNERT: That's what we were working on.
3 MR. HOLAHAN: Certainly you can write a letter.
l 4 The question is do we need a letter.
5 DR. KRESS: Yes. 1 6 MR. HOLAHAN: If you do not write us a letter we '
i 7 will proceed with a license amendment and the exemption. I 8 understand that the committee has an interest in all of our 9 . implementation activities for risk-informed regulation. I t
10 don't know that we need a letter on each one.
11 DR. KRESS: Yes, that's right.
12 MR. HOLAHAN: A sort of progress report on do you I
13 think we are doing the right sorts of things, but I don't 14 'see that as a necessary decision element for San Onofre.
DR. KRESS:
( 15 So unless we had severe heartache or 16 heartburn with it --
17 MR. HOLAHAN: Oh, we don't mind if you write nice 18 letters.
19 [ Laughter. ]
20 MR. HOLAHAN: But I don't think it is essential.
21' Earlier on, we were developing policy issues and stuff like 22 that and I think it was essential to have the committee's 23 views and the Commission acting at that level, okay? Now we 24 are basically in the implementation stage, even though these 25 are obviously early examples and everyone is a little more 1
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103 l- 1 interested.
t
(} 2 DR. KRESS: No, I was assuming that this would go, 3 if you guys make a recommendation, go to the Commissioners.
- 4 You may not be interested in what our views of it was.
1 5 MR. HOLAHAN: We will inform the Commission 6 because it happens to'be on the Chairman's tracking list of 7 things we have committed to do, but we don't consider it a l 8 policy issue so we are not going to ask --
9 DR. KRESS: Or something they have to sign off l 11 0 on --
l l 11 MR. HOLAHAN: No.
l 12 DR. KRESS: And they may or may not be interested 13 in what the ACRS thinks of this then.
14 MR. HOLAHAN: I don't think -- because I don't see
() 15 that the Commission has an action, okay? --
the Commission 16- probably is interested in the status.
17 DR. KRESS: They won't be reviewing anything --
18 MR. HOLAHAN: I don't expect the Commission to be 19 reviewing it.
20 DR. KRESS: -- so they won't be saying what did 21 the ACRS say about this?
22 MR. HOLAHAN: That's right. ;
23 MR. LOEHNERT.: Is this being handled at the office j 24 level? j l
25 MR. HOLAHAN: This is an exemption and in fact it j l
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.1 is being handled at a lower. level. I
() .2 DR.-KRESS: Well, that's helpful. We may or may 3 not have a letter. Thank you, Gary.
4 ;MR. SNODDERLY: If we could, I would like to go to 5-- a Slide 5.
6 What I am going to try to do here is try to give 7 everybody some idea of what it is -- the intention of the l 8 rule originally, what we think, the amount of hydrogen we 9 think you would get from a design basis' accident, TID 14844, 10 the amount of hydrogen associated with it, and then 11 NUREG-1565, early in-vessel and late in-vessel.
l 11 2 The first' thing I would like to do is add is for 13 these cases, which would be severe accident cases, you would 14' be overwhelmed. The recombiners would be overwhelmed.
l 15 The rule says you need to address hydrogen from
~16 zirc metal-water reaction, radiolysis, and corrosion, so
'17 that is represented here in these three rows.
18 For a true design basis LOCA, double-ended 19 guillotine break, 50.46(b) limits you from not exceeding one l
20 percent zirc metal-water reaction. The amount of solids 21 that would be released would be much less than .1 percent 22 and the corrosion rate is defined by Reg Guide 1.7. It is 23 conservative, very conservative.
24 Now 50.44 said for this source term you would not i 25 exceed the 4 percent flammability limit for probably 60 ANN RILEY & ASSOCIATES, LTD.
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l
c 1
105 1 days, a very, very long time, so I doubt recombiners would f) 2 have been required if this'was the hydrogen source term you 3 were concerned about or trying to address.
4 50.44 - .what is in the rule is represented by ,
5 this column. It.says you need to deal with 5 percent zirc 1
6 metal-water reaction. You need to be able to handle 1 7 percent of the solid fission products mixed with the
(
8 coolant.
l 9 You can see here the reason I put this column :bi 10 was TID 14,844. That accident would be associated with 11 about 40 percent metal-water reaction, 1 percent solid 12 fission products, so.you can see that this right here -- no 13 longer are we in design basis space. We are beyond design
)
14 basis space but not quite severe accident space. We are in (Oj 15 this in-between, so I wanted to try to do that to give you .
16 guys some idea.
17 This is what the utilities were told to design for 1 18 and you would need recombiners to keep this amount of I
l 19 hydrogen below the 4 percent flammability limit.
20 DR. KRESS: Where did you get that 40 percent for l
21 TID 14,844?
22 MR. SNODDERLY: I just estimated it, Tom. I am 23 just trying to give you guys an idea --
24 DR. KRESS: Was there a consistency argument with l
l 25 the source term?
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106 1- MR. SNODDERLY: The only point I am trying to make
( 2 hereiis it is less than~100 percent but greater than 5 and 3- doing a scaling that I:just estimated it to be somewhere 4 around 40, but I don't have any reference or exact number.
5 DR. KRESS: It doesn't show up in 14,844. It is 6 just_a number that you have come up with?
7 MR. SNODDERLY: Right. I am just saying for this 8 ~ amount of solid fission products --
9 DR. KRESS: Consistency calculation.
10 MR. SNODDERLY: --
I would say that would be 11 associated with about a 40 percent metal-water reaction.
12 -DR. SEALE: If you are going to get that much 13 fission product release, you are going to have about that 14 much metal-water reaction.
() 15 DR. KRESS: I wasn't arguing with the number. I 16 was just wondering where you got it, because I had never 17 seen it.
18 MR. SNODDERLY: That's me.
19 DR. KRESS: Okay.
20 MR. SNODDERLY: And so now I updated things for 21 NUREG-1465 and again I estimate that is about 40 percent.
22 It would be about 1.75 percent of the solid fission products 23 released and when you include the late in-vessel or in the 24 ex-vessel source terms you go up to about 8 percent of the 25 solid fission products released and you are between 40 and ANN RILEY & ASSOCIATES, LTD.
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107 l 1 100 percent metal-water' reaction I 'T 2 So recombiners are not going to do you any good V
3 for these --
4 DR. WALLIS: Well, the recombiners as presently l 5 designed and installed.
6 MR. SNODDERLY: -- as presently designed and 7 installed, yes.
8 DR. WALLIS: Not just the number of zirc-water L
l 9 reaction, it is also the rate at which it happens, isn't it, l 10 that leads to overwhelming? It happens quicker in these l 11 severe accidents.
l L
12 MR. SNODDERLY: Yes. All this is going to happen.
l 13 DR. WALLIS: I mean you could say, which probably 14 is not practical at all, I mean obviously a conclusion could
( .15 be that if they are overwhelmed we need bigger ones.
16 MR. SNODDERLY: Right.
17 DR. WALLIS: That could be.
18 MR. SNODDERLY: But the intent of the rule as 19 originally intended was to address this severe accident, 20 which I am trying to do. The point I was just trying'to 21 make was --
22 DR. WALLIS: Oh,'yes, that was their rule but if 23 you now learn they have been overwhelmed, one regulatory 24 action, if you are a diehard believer in recombining 25 hydrogen, could be, well, we need a bigger one.
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i 108
'l MR. SNODDERLY: 'Well, I would argue not that you
( 2- believe in recombiners, that you need a system to. control
'3 hydrogen, and a more appropriate system would be igniters, 4 for.these types of hydrogen source terms.
5 DR. WALLIS: One alternative is still to say --
6- MR. SNODDERLY: Not bigger recombiners.
7 DR. WALLIS: -- we will rely on the recombiners.
8 You can't dismiss it out of hand. You just have to say 9 there is a better alternative.
10 MR, SNODDERLY: Typically we don't say you need to
- 11. supply System X or System Y or type of system, just you need 12 to provide a system that could handle "x" --
13 DR. WALLIS: But for some reason in the past the 14 recombiners were the design which was favored and now
() 15' another design alternative is decided to be better, so you 16 'really need to consider all possible designs, one of which 17 might be to have bigger recombiners.
18 MR. HOLAHAN: If you think about it in the limit 19 as the recombiner got bigger and bigger and as the 20 recombiner approached two million cubic feet, it becomes an 21 igniter.
22 DR. WALLIS: Well, that's right. As I say, don't '
23 just sort of ignore it. At least give some rational
- 24 arguments for how big it needs to be.
25 DR. SEALE: But the volume doubles. That's the i t-O ANN RILEY & ASSOCIATES, LTD.
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I 109 1 problem with recombiners.
() 2 3
DR KRESS: You know, part of the argument is if you had to put in a recombiner system that could handle that l
4 part of the thing, it would never pass the backfit rule, I 5 don't think.
L l 6 MR. SNODDERLY: And that leads us into my next '
7 point. What about the source term and what is the threat 8 from that, and so where we are going to go now is I want to 9 take you into the results of NUREG-1150, because 1150 looked l
10 at the risk from this type of a hydrogen source term. It 11 did not look at the risk from these types of source terms 12 because it was bounded by this, so this is what is of 13- concern.
14 What you would do if you were really concerned
() 15 about this or you thought it was a major threat to 16 containment, you would install igniters.
17 And that was done for the ice condensers and for 18 Mark 3s but not for large dries and subatmospherics, so l 19 let's go look at the results of NUREG-1150 and see what that 20 tells us.
21 DR. KRESS: When you -- on that last table you 22 had?
23 MR. SNODDERLY: Yeah. .
1 24 DR.. KRESS: Up in the corner you had for NUREG-11 l 25 -- 14.65 made in-vessel and ex-vessel corresponding l
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110 1 'according to 100 percent of. metal-water reaction.
() 2 MR. SNODDERLY: Right Right.
3 ,
DR. KRESS: Most of that, a lot of that stuff 4 comes from the core-concrete, most of it.
5 MR. SNODDERLY: I would say from 75-percent -- i 6 DR. KRESS: And the metal, the metal that is in 7 there is a lot of the steel and not zirc, it produces that 8 hydrogen there.
9 MR. SNODDERLY: That's right.
10 DR. KRESS: I was wondering where -- I mean is 11 that 100 percent of the zirc you have there, because there 12 is a lot of steel in that core-concrete?
l 13 MR. SNODDERLY: Right. The 100 percent of that 14 zirc metal-water was to compensate for core-concrete
( 15 interaction. I would have put 75 percent there if it was l
l 16 _just late in-vessel When you go ex-vessel, that is why I 17 took it -- I wrote 100 instead of 75, to account for. And 18 that is typically what has been -- the way we ha're handled 19 it in the past.
20 Like 54.34. The reason the utilities argued, or i 21 industry argued, why do I have to handle 100 percent I
22 metal-water reaction, clearly, 75 percent is all I need to 23 address, or that is all that would happen in a severe l 24 accident? We said we wanted you to address 100 percent to l
l 1
25 account for hydrogen from zirc -- I'm sorry, from CCI, ANN RILEY & ASSOCIATES, LTD.
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l 111 1
1 core-concrete interaction.
/m Okay.
V) 2 Basically, NUREG-1150 looked at -- breaks 3 it down into four -- looks at containment failure from four 4 bins, early containment failure, late containment failure, 5 bypass and no containment failure. Okay.
6 For a large dry plant, they modeled Zion, which 1
7 would be what you would compare with San Onofre. 73 percent 8 of the time, no containment failure. 1.4 percent is early 9 containment failure. 24 percent is late containment 10 failure, and .7 percent was bypass. So hydrogen combustion 11 was looked at in the first two bins, early containment 12 failure and late containment failure.
13 Now, for early containment failure, which was 1.4 14 percent of all containment, in other words, you look at all e
.( 15 containment failure, 1.4 percent of it was from early. And 16 for early containment failure, it was just composed of 17 in-vessel steam explosions, over-pressurization and.
{
18 containment isolation failure.
19 Draft revisions of the accident progression event 20 trees did look at hydrogen, but it found that it was such a i
l 21 negligible contributor that it was eliminated from the final l l
l 22 review. So it is not even considered for early containment 23 failure which would be prior to vessel breach. Okay.
24 And now the reason they came up with that l
25 conclusion is there was an expert elicitation panel and ,
1 O
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1 1
112 l
1- their, I guess you would call them deliberations, or their I p
i 2- logic-is outlined in NUREG-1150, Volume 2, Appendix C-4 and
\ss) - !
3 NUREG/CR-4551, Volume 2, Part 2. '
4 And the reason I give that you is we are not going 5 to have time today to really go into the details of how they 6 came up with the results, but just the results today. And l 7 if you are -- and I would recommend that there is a good 8 summary in there, and you would like us in the future to 9 come back and discuss the details more. But, really, that 10 is -- that is where the crux is. And if you believe the l 11 1150 modeling, then hydrogen is just not a containment 12 threat for large dries. I 1
13 Now, what they looked at is the amount of hydrogen 14 r"N created, the probability of spurious ignition and then the )
(,) 15 possibility for detonation. And the key there is you find
~
16 out for-the spurious, there is a lot of spurious ignition 17 sources. The control rod drive mechanisms, the control rod 18 drive fans, all the pumps, valves. There is a high 19 likelihood that you are going to get a spurious ignition and 20 so that plays a lot -- that results in a lot of it being, 21 you know, a low risk contributor.
22 But the bottom line is the decision -- and the 23 decision was made -- and also containment strength, that is 24 the biggie. And, barically, for 75 percent metal-water 25 reaction for San Onofre, you are going to end up like 11.5 ANN RILEY & ASSOCIATES, LTD.
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113 1; ' percent hydrogen. And although that is going to be a test 2
.( ) for containment strength, it is not going to result in 3 containment failure, that has been the overall conclusion.
4 So that is why it doesn't show up as a major contributor for 5 early containment failure.
6 Late containment failure. Late containment 7 failure, which was 24 percent of the containment failure i
8 percentage --
9 DR. KRESS: That early containment failure, does 10 that encompass then all of the LERF?
l
)
11 MR. SNODDERLY: All of it. All of it. So all of 12 it, in other words -- well, what it is says is the only way 13 -- LERF is based, is from containment failure, as Gary 14 pointed out earlier. And the only time you are going to get
( ) 15 containment failure early is because of one of those three 16 phenomena.
17 DR. KRESS: You are saying hydrogen doesn't affect 18 it?
19 MR. SNODDERLY: Hydrogen didn't even rise to that 20 level to be modeled -- well, modeled but them removed.
E 21 Okay. Late containment failure, 99.5 percent of 22 that 24 percent is from basemat meltthrough, CCI, .5 percent 23 was from hydrogen. Okay. So, again, it is just not a big j i
24 contributor.
25 And so what falls out of that was a lot of the
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l t
114
- 1. basis _for NUREG/CR-5662, which San Onofre talked about,
( ) 2 which is the value impact analysis - _can you justify 3 putting igniters into large dries based on the risk? And i
4' what basically it worked out to is that the amount, when you 5 look at -- well,.I am over-simplifying, but, basically, they 6- just said, since hydrogen didn't even -- it showed up as .5 7 percent of the 24 percent, they conservatively said, let's 8 just look at 10 percent of the large early release 9 frequency, which ends up being about 1,860 person rem. The 10 cost of the igniters was determined to be 2.6 million, so it 11 works out to $1400 per person rem, which is greater than the 12 thousand dollar per person vem, and igniters were determined 13 to be not cost justified.
14 DR. KRESS: I though the number was $2,000.
E[ 15 A thousand.
- d. MR. SNODDERLY:
16 DR. KRESS: It is two in the reg.
17 MR. SNODDERLY: Well, it was a thousand at the 18 time the decision'was.made.
19 DR. KRESS: At the time of the decision, it was a 20 thousand. So this says --
21 MR. HOLAHAN: But those were more expensive l 22 dollars in those days.
1 23 DR. KRESS: That's true, you are right.
l l
24- MR. SNODDERLY: That's true. !
.25 DR. KRESS: It says, this comment that we heard i
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1
115 1 from the committee, that it would be nice to have those
() 2 3
recombiners left on just to be ignition sources is probably not even worth it either. In the first place, they are not 4 located in the right place to be igniters. In the second 5 place,'they are not very -- there's two of them and the 6 igniters don't even show up in here hardly anyway. And 7 igniters'aren't worthwhile for large dry containments 8 anyway.
9 MR. ~ SNODDERLY: I would argue that if you look at 10 the spurious ignition models and the amount of credit that 11 is given, and this -- there is some uncertainty in there, i 12 and the more spurious ignition sources you can add, and 13 especially ones such as this, I would argue --
14 DR. KRESS: It is some help.
() 15 MR. SNODDERLY: The insight from the PRA would be 16 that it is an additional spurious ignition source, it is I
17 . going to help you, just leave it on.
l 18 DR. KRESS: Yes. I 19 DR. WALLIS: Now, I have got a question for you, i
20 You said that -- I guess it is the next slide, too, that the I 21 worst case scenario is a hydrogen concentration of 11.5 22 percent, which I guess is below the detonation value.
23 DR. SEALE: Just below.
24 MR SNODDERLY: Just below.
25 DR. WALLIS: This is for 75 percent metal-water l
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116 1 reaction. .But if someone said, oh, it should be 85 percent V) l 2 metal-water reaction, then you would step over the explosion
, .3 limit, wouldn't you?
4 MR '. SNODDERLY: Okay. Graham, what I-would like 5' Eto point out, okay, early containment failure is prior to 6 vessel breach. Prior to vessel breach means you are 7 in-vessel, and in that case we would argue that 75 percent 8 metal-water reaction is bounding or covers -- that is about 9 the amount of zirc metal-water reaction you would expect.
10 DR. WALLIS: Bounding or is it an estimate? I 11 mean there is a probability it might be 80 percent.
12 MR, SNODDERLY: Very, very, very, very small. On 13 the tail end. I think what we are going -- I am going to 14 get to your point, is that where you would consider greater
() 15 than 75 percent metal-water reaction, those -- that series 16 of accidents occurs for -- beyond vessel breach. Okay.
17 When you go ex-vessel.
18 So now you have got to consider more than 75 19 metal-water reaction. But the problem in -- not the 20- problem, but what works out is you release all that molten !
l l
21 core and it is dispersed throughout -- that is a great I 22 ignition source. And so that -- no, I mean the PRA model 23 chows that --
that you are going to burn then, and not 24 continue to build up at these greater hydrogen levels.
l l 25 DR. KRESS: If you look at all the severe accident l l i ANN RILEY & ASSOCIATES, LTD.
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l
117 1 codes that we have,.you know, like MAPP and MELCORE and
() 2 stuff, it is -- you know, you can do all sorts of dialing in 3 the parts to try to maximize your hydrogen production in 4 part. And you just can't hardly get it up to 75 percent.
5 You know, no matter you do, it is hard to get 75 percent 6 hydrogen until you get it out inside and add the extra core
- 7. concrete. It is -- that is a pretty good bounding number.
8 DR. WALLIS: I guess it all irrelevant for this-9 discussion anyway, because the recombiners, as presently-10 configured, won't do you any good at all in any of these 11 situations.
12 MR. SNODDERLY: Exactly, Graham. I am just trying 13 to bound -- I am trying to say -- a complaint of the 14 committee, or a comment has been, you guys haven't 15 quantified the risk significance of'the recombiners. And 16 what I am trying to say is the risk from hydrogen is this 17 case, and this is what has been modeled and quantified and 18 it clearly bounds'the recombiners.
19 DR. KRESS: Yeah, let me put in a little bit of 20 qualification of that comment, because it does come from me.
21 If we look at risk-informed regulation 1.174, our risk 22 metrics are LERF and CDF. But if you look at all the )
23 regulations, we are really concerned about other regulatory 24 objectives. We are concerned about doses. We are concerned l 25 about frequency of releases of fission productions through i
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118 J
1 non-failed containments. And the comment was meant to say,
( 2 Well, they probably -- you probably can quantify the effects 3 oon LERF and CDF. Well, LERF -- CDF is not part of it. But 4s we really ought to have other risk objectives in a 5: risk-informed regulatory system. We don't want to throw
'6 away all the things we are worried about in the regulations 7 and just go to LERF.
8 MR. SNODDERLY: Right.
9 DR. KRESS: And it has concerned me that all we 10 are thinking of is LERF here. We ought to be thinking of 11 otherl things. And that is -- the quantifying of those risks 12 that I was thinking of.
13 MR. SNODDERLY: Yes.
14 DR. KRESS: But, you know, we are getting there ye 15 because you are talking about what effects it has on an 16 unfailed containment as well as failed? And does it 17 actually increase the doses and the release rates and how j 18 much, and is it significant? And so you are hitting on 19 that. It hasn't been really quantified, but qualitatively, 20' it looks like it doesn't have much effect on that either, j
)
21 MR. SNODDERLY: That helps.
22 DR. KRESS: That was the comment.
23 MR. SNODDERLY: Now, what I was trying to get 24 across here with this slide is that hydrogen -- the risk 25 from hydrogen has been quantified by the staff in NUREG-1150 i
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119 1 and here are the results. '
() 2 3
DR. KRESS:
MR. SNODDERLY:
But that is all LERF.
~
And that is all LERF. And that is 4 all LERF.
5 DR. KRESS: And I agree with that, it has been 6 pretty well quantified.
7 MR. SNODDERLY: Now, I think -- well, I will leave 8 it at that. I will leave it at that.
9 Okay. So now that we have determined that 10 recombiners really won't help with containment failure, what
- 11 is -- I guess what I was struggling with was, well, is there 12 any value to the hydrogen recombiners? Before we cross the 13 bridge to say you don't need them, let go of all the 14 regulatory controls, what value would they have? So let's
() 15 go to slide 8.
16 And, basically, what I -- to do that, it turns out 17 that the recombiners are of value in preventing a subsequent 18 burn. In other words, they can't help you with that zirc 19 metal-water reaction burn that comes out quickly. Dr. l 20 Wallis, in TMI, the zirc metal-water reaction occurred '
I 21 between one-and-a-half and three-and-a-half hours in the ;
22 accident, so that is the timeframe you are talking about for
{
23 zirc metal-water and that would clearly overwhelm the 24 recombiners. '
25 DR. WALLIS: It was one-and-a-half hours.
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l 120 l 1 MR. SNODDERLY: I'm sorry, after --
2 DR. WALLIS:
) I didn't-begin to overheat until two l 3 hours.
l 4 MR. SNODDERLY: From the Ragahovan report, they 5- estimate that the hydrogen was created between l 6- one-and-a-half hours and three-and-a-half hours.
7 DR. WALLIS: Tht is a broad -- okay.
8 MR. SNODDERLY: But it was over that time period.
9 To answer your question, well, what is the release rate and l 10 could the recombiners have any effect? So the release time i
l 11 is going to be somewhere in the hours and, clearly, it is L
12 going to overwhelm the recombiners.
13 So you have that burn. And we have all come to
'14 the conclusion that burn won't fail containment. We have
() 15 looked at in Generic Safety Issue 121, we looked at the 16 effects of equipment survivability. In other words, do we 17 think that there is going to be a big risk? Yeah. you are j l
18 not going to fail containment, but are you going to fail the l 19 instrumentation?
l 20 And there has been a lot of work that has been 21 done at Sandia. And, basically, the conclusion was that for 22 -- you could survive a single burn associated with a 75 23 percent metal-water reaction. There was some concern for 24 multiple burns in a source compartment. In other words, you 25 get a burn, it heats up the compartment, and then before it l l
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i-121 1
can return back to the normal containment -- or not normal
.( 2 containment temperature, but the lower. containment 3 temperature, you have a subsequent burn. And they did see 4 some potential for failure there.
5' But the bottom line is it was determined it was l 6 not -- or it was more likely that the equipment that the 7 equipment would survive and that wasn't a concern, or there 8 wasn't any need for further qualification of the equipment.
l 9 But now you have got this large radiolytic source l
10 term in the sump, and you are creating -- due to radiolysis, l 11 you are creating hydrogen again. Now, what is the risk from l
12 that hydrogen? So what I did was, we have a code called l 13 COGAP and Asimios Malliakos from the Office of Research, 14 together we went in and we tried to modify the code to make
() 15 it -- take it from a design basis code to look at it more 16 from a severe accident aspect.
17 So what we did was we zerced out the zirc 18 metal-water reaction, the contribution from that. We zerced 19 that out. And for radiolysis, what we did was we reduced 20 the G value to take out some of the conservatism there, but 21 we increased the source term from that 1 percent solid 22 fission products to 8 percent. Remember, at the beginning 23 back there, that we would expect for a late in-vessel, 24 ex-vessel. So we took that amount of decay energy, put that 25 in the sump to see how much hydrogen we would get.
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E' 9 122
~1: DR. KRESS: Did you put any iodine and cesium?
I
/~
2 MR. SNODDERLY: Seventy-five percent of the 3- iodine.
4 DR. KRESS: Well, the iodine -- the cesium was 5 probably.where you get --
6 MR. SNODDERLY: Well, 95 percent of it is cesium 7 iodine. So of that 75 percent of the iodine in the core, we 8 put.it'in the sump.
9 And, basically, what we found was that at 30 days, i
10 you are somewhere between 5 and 7 percent hydrogen. So that 11 is -- how would I portray that? You know, that is something
.12 that -- it is not a risk to containment. It is a burn that 13 you could definitely handle, but is it something that you 14 would want to cycle the containment through? I guess what
) 15 we are coming to is --
116- DR. KRESS: It seems like a good place to have a l 17 purge vent, because the fission products are already settled y 18- out and the noble gases are gone. So you could -- that 19 looks like it would be a good place to have a purge vent 20- control.
21 MR. HOLAHAN: Well, if I had a recombiner, I would 22 rather use the recombiner than do a vent.
23 DR., KRESS: Yeah, I guess having a containment I
24 is --
25 DR. SEALE: They are going to hold.
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123 1 DR. KRESS: Yeah, I think you are right.
() 2 MR. SNODDERLY: So, anyway, what I trying to get 3 acrcss is that you won't exceed the lower flammability limit 4 for 11 days, you won't exceed -- you will be at 5 to 7 5 percent at 30 days, which we would not consider a threat.
6 There is no way it would be a threat to containment. But we 7 will have a lot of time to think about how -- whether we are 8 going to -- what we are going to do. It will be something 9 --
it looks -- it would justify taking it out of the 10 regulatory space, taking it out of the tech specs but it 11 does appear that --
- 12 DR. WALLIS
- Meanwhile, all the newspaper 13 reporters are saying hydrogen is building up in the 14 containment and no one knows yet what to do with it.
15 MR. SNODDERLY: Right. Well, and let's face it, 16 the other reason that this has been difficult to apply the 17 Reg. Guide 1.174 to this particular piece of equipment is l 18 that the real basis for this equipment as stated in the 19 Statement of Considerations is that, due to the adverse 20 public reaction to the possibility of venting. And as Dr.
21 Kress said, the way you would deal with this is to purge and 22 vent.
l l
23 Now, even though we all agree here that that is 24 not risk significant and it is acceptable from a public 25 health and safety standpoint, it was determined that -- no.
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1 I
l l
124 1 So whenever we try'to now apply risk arguments to an
() 2 3-emotional kind of_ argument like that, well, that is how we got to'where we are today.
4 DR, WALLIS: Hydrogen gets emotional, too, or it 5 was.during TMI. There was a big deal made of hydrogen.
.6 DR. KRESS: Yeah. ;
1 7
MR. HOLAHAN: But part of that~ big deal was the 8 perception that a containment burn would fail,-contactor i j 9 vessel, and the containment. And I think if you understand 10 that that is not the case, or extremely unlikely to'be the 11 case, you have to recognize that, you have to deal with l l
12' that. '
l 13 DR. WALLIS: You have to somehow make the public 14 aware that it is not likely to be the case. l
/"'y i V. 15 MR. HOLAHAN: Yes.
16 DR.'WALLIS: So that when hydrogen builds up after l
l 17 an accident, if it ever occurs, and the news comes out, and 18 this sort of -- they follow the build up, that they don't 19 reach the wrong conclusion.
20 MR. HOLAHAN: Yes.
21 MR. SNODDERLY: And I think that has been done in 22 NUREG-1150, NUREG/CR-5662, you know, to say we don't need 23 igniters for large dries and in utility IPEs.
24 MR. HOLAHAN: It seems to be in the long run, that l
'25 is one of the reasons why probably an exemption on one 1
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125 1 ' plant, but leaving the regulations in place is not a good a
[ } 2 way of sending messages to, you know, have people understand 3 what we really think are the safety issues.
4 DR. KRESS: Is changing the regulations part of 5 this package here~, you are going to change the regulation?
6 MR. HOLAHAN: My perception of how we would do 7 this is in the near term, this would be an example -- it 8 would be done by exemption, it would be an example. If 9 other : licensees wanted to come in in the near term, I think 10- we would deal with it as additional exemptions.
11 Then to the extent that these insights are 12' generic, and they certainly are generic for, in my mind, for 13 large dry containments.
14 DR. KRESS: For large dries, for sure.
) 15 MR. HOLAHAN: We would initiate rulemaking. Now, 16 we are on the verge of starting a lot of rulemaking in 17 risk-informed Part 50. Okay. So I think this one would go 18 in line with all those others. I am not convinced it is the 19 most important thing we could change in the regulation, so l
20- it probably wouldn't --
21 DR. KRESS: Yeah, because it is not that much of a 22 burden reduction.
23 MR. HOLAHAN: It is not that much of a burden.
24 Probably it would be, you know, it would be acknowledged 25 that this is an area that we are interested in changing, but jl l
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126 1 I think we probably would want to do a bunch of other things 2 first.
_[y ). 4 3 DR. KRESS: You are not likely to get a lot of 4 exemption requests here, you think?
I 5 MR. HOLAHAN: I doubt it.
6 DR. KRESS: That is what I would have thought.
1 7 Okay.
8 DR. SEALE: Well, the large dries in town, may l 9 come in.
10 MR. SNODDERLY: I guess, so now I hope we all i 11 agree that -- it appears that from this perspective, it is 4
12 difficult -- you can't justify keeping the recombiners in 13 the tech specs and within the design basis, that they are 14 strictly for severe accidents. And then, so now you would
() 15 say, well, okay, do they fall out into'the maintenance rule?
16 Well, you can see by the way they have been modeled by the 17 staff and by San Onofre, they would fall out of the 18 maintenance rule, they wouldn't rise to that level of safety 19 significance.
20 So now we are the point, well, they are currently 21 in the severe accident management guidelines. So now let's 22 look at the commitment that San Onofre has made to the ,
i 23 severe accident management guidelines, not only San Onofre, l l 24 but industry in general. And I guess by December -- by last 25 December plants were asked to -- most-of the commitments
- (~')
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127 1_ that had-been made by plants is that we have implemented
[v) 2 severe accident management guidelines in accordance with NEI 3 91-04, which was'the severe accident closure program, and 4 that they have completed training of the personnel on those 5 guidelines.
6
~
Now, ninety -- so that, so really NEI 91-04 is the 7 governing document for severe accident management 8 guidelines. That, and within that it says, you know, you 9 should use the generic severe accident management guidelines 10 that.were developed by your vendor as a starting point, or 11 as a point of departure.
12 So, and another thing NEI 91-04 recommends is use 13 of existing plant capabilities and that is key, because 14 right now there would be no -- if the exemption is granted,
( -
15 there would be nothing that would prevent San Onofre from 16 removing the recombiners from the plant, therefore, they are 17 not longer existing, therefore, they could be removed from I 18' the severe accident management guidelines. So I think that 19 is where we are -- .
1 20 DR. KRESS: That is where you are at.
21 MR. SNODDERLY: That is where we are at right now. ;
22 And if we had some type of a commitment from San Onofre 23 saying that they would not rip them out, o-r that they would 24 just be left in place, then they would, in my mind, be 25 existing and then they would remain, continue to remain
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128 1 within the severe accident management guidelines.
ll 2 DR. KRESS: Do you have a vehicle for that kind of 3 commitment?
4 MR. SNODDERLY: You have -- everything we have 5 talked about, I think that been pretty well discussed. You 6 know what -- I think you are well aware of the current 7 status.
8 DR. KRESS: Yes.
9 MR. SNODDERLY: I mean that is what we are 10 wrestling with. San Onofre has made some suggestions or 11 proposals, but that is where we are at.
12 DR. KRESS: Okay.
13 MR. SNODDERLY: What else did I want to say here 14 on this slide? I don't think there is any --
h 15 DR. KRESS: Well, that last bullet is how you are 16 doing.
17 MR. SNODDERLY: Yeah. Just quickly, the way I 18 would write the -- the basis for the exemption would be 19 under 50.12 (a) (2) (ii) , which application of the regulation 20 in the particular circumstances would not serve the 21 underlying purpose of the rule where it is not necessary to 22 achieve the underlying purpose of the rule.
23 DR. KRESS: You know, in the document, the request 24 for the document, it spelled out what the underlying purpose 25 of the rule is. Do you have -- do you agree with --
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129 1 MR. SNODDERLY: No. Their -- my take was a little
() 2 3
bit different. Their take was that the underlying purpose of the rule was to prevent containment failure.
4- DR. KRESS: Right.
5 MR. SNODDERLY: My underlying purpose of the rule 6 was the first slide, slide 2, to show that uncontrolled hydrogen burn would not -- sorry 8 DR. WALLIS: Why is it that you have to speculate 9 about the. underlying purpose of a rule?
10 DR. KRESS: Well, because it was made a long time 11 ago and --
12 DR. WALLIS: Well, rules state right up front what 13 its underlying purpose is.
14 MR. HOLAHAN: And when the Commission issues
() 15 rules, it issues what is called a Statement of 16 Consideration, which is legally considered a statement of 17 the intent of the rule.
18 DR. WALLIS: That is the problem I had with the R19 last one we looked at. It was always -- it didn't seem to 20 have.a really clear statement of what it was trying to do.
21 MR.-SNODDERLY: Well, let me take a shot at this i
22 one and see. Well, I believe that the underlying purpose of 23- the rule was to show that either show that you could l l 24 withstand the consequences of an uncontrolled hydrogen L 25 oxygen recombination without loss of safety function, or i l ANN RILEY & ASSOCIATES., LTD.
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l 130 l
1 provide a system that would prevent that from happening.
[' 2 And I think what we have shown is that the plant can
(
3 withstand an uncontrolled hydrogen oxygen recombination or 4 burn, not only for the pseudo source term defined in the 5 regulation, but beyond that. And so that is -- it is a 6 slight difference from the licensee's. I think only that --
7 I think the licensee's just look at containment integrity, 8 where I think you also have to consider equipment 9 survivability and the impact of that burn on the equipment 10 inside. That is all.
11 So that is -- I just want to let the committee 12 know the approach that I am going to take, or that the staff 13 would. I think that is the basis we are going to use for 14 granting the exemption.
(O,j 15 DR. WALLIS: So the implication is that you have 16 to decided to grant this request?
17 MR. SNODDERLY: I think the current status is that 18 we agree that it can be removed from the design basis. It 19 can be removed from tech specs. And, yes, the exemption can 20 be granted. But -- but now --
21 DR. WALLIS: And will be.
22 MR. SNODDERLY: Yeah, will be. Yes, right now I 23 think I have -- let me put it this way, Dr. Wallis, I think 24 I have outlined an approach that would justify granting the 25 exemption and removing it from the design basis. What I am l
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131 1
1- concerned about is that I think I still see a place for this
/ 2 system within the severe accident management guidelines, but
}
3: I don't have a mechanism to assure myself that it will 1
4 remain within those guidelines, except -- unless the 5 licensee agrees not to rip the system out. That is where I 6 believe the staff is.
7 DR. KRESS: So when a request for an exemption 8 comes in like this, basically, to take out the-hydrogen 9 control system?
10 MR. SNODDERLY: Right.
11 DR. KRESS: And you say, well, that is good, but 12 we would like for you to leave the monitors in. Is there --
13 I mean you have got a request that says the request is for 14 everything. If you grant the exemption, it says, okay, you
() 15 can take everything out.
16 MR. SNODDERLY: Let's talk about hydrogen 17 monitoring.
l 18 MR. HOLAHAN: We didn't talk about monitoring yet.
19 DR. KRESS: Okay.
20 MR. SNODDERLY: That is a good lead-in, let's talk L 21 about monitoring. I don't think we can support the l :
22 exemption request. I think that hydrogen, continuous j 23 hydrogen monitoring is the preferred hydrogen monitoring --
24 it is preferred over PASS, as you have been briefed on, and 25 that it is accepted as an alternative to PASS for the zero l l
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132 l 1 -to 10 percent range. Now, where the continuous' monitors are
() 2 3
weak is that they can only got up to 10 percent hydrogen.
Now, what I would like to show you is -- now, the l
l 4 current CE severe accident management guidelines, the ones 1
5 that we have reviewed and that we have -- anyway, they 6 changed their -- talking to the CE folks, they have changed l 7 their severe accident management guidelines for hydrogen and 8 so what I am going to show you right now is the Westinghouse 9 guidelines and my understanding is that the CE guidelines l
l 10 are now consistent with this. Now, again, this isn'c what 11 San Onofre would have to do, because the guidelines, the 12 generic guidelines are that. Remember, I said a point of 13 departure. So my understanding is that San Onofre does 14 something slight different than this, but maybe that is why
() 15 we are at this point where we disagree about the need for 16 hydrogen monitoring.
17 And, basically, the main thing -- okay, the reason 18 there is a wet and a dry hydrogen measurement is most --
19 they are most thermal conductivity meters, but remember I 20 told you earlier that some of them keep the steam within, 21 and so that is wet, and if you condense the steam out, you 22 .are dry. So that is why there is two curves.
I 23 The main thing you have to see here, though, is --
l 24 sorry. Basically, here is where we are having a problem.
25 Between 10 and 12 percent, you would not have a hydrogen
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1 i
133 l 1 severe challenge, your containment can handle it. So, do 2 you want to vent?
V( g l 3 And if you are at 10 percent on your monitor, 4 well, you may say -- you know, do you want it just because 5 your monitor says it is 10 percent and you think you could j 6 be possibly greater than that? You may have to make the l
7 decision to vent here instead of here. And so I think what I 8 the staff -- the staff's position is that you need something 9 to handle within here.
10 Now, what I heard from San Onofre earlier today is 11 they can do by using containment high range rad monitors to 12 correlate to the amount of hydrogen -- or the amount of core 13 damage and then back that out and figure how much hydrogen 14 is.
) 15 DR. KRESS: How do you feel about that? Do you 16 think --
l 17 MR. SNODDERLY: How do I feel about that? ;
l 18 DR. KRESS: Yes.
19 MR. SNODDERLY: I think it is possible, but I l 20 think it is more of a last resort kind of thing. I think 21 right now you have a system installed in this plant right 22 now that allows you to do a grab sample, which I have a lot 23 more confidence in than --
24 DR. KRESS: The calculation.
l 25 MR. ~ SNODDERLY: Than a correlation to containment
(~'
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134 l
l 1 high range rad. I think that-is'a good backup strategy but l
() 2 3
I think would justify again -- right now you have NUREG-0737 requirement for PASS grab sampling. I don't think you 4 'should have to have timing requirements, because I think the 5 only time you are going to need it is to confirm your L6 continuous monitors, but to help you supplement in this 7 area. And so I don't think you should have timing 8 requirements associated with it. I don't think it should be l 9 in your tech specs. But I think it should be part of your 10 EOPs. I think that would then put it into your maintenance l 111 rule and then you determine, and then maintain it as a 12 non-safety related system.
l 13 DR. KRESS: I agree with you.
14 MR. SNODDERLY: So that is my position.
() 15 DR. KRESS: I agree with that, too. I wouldn't 16 dismiss out of hand, though, the possibility that you could j j 17 make a usable correlation between hydrogen and the fission 18 products.
I 19 MR. SNODDERLY: Oh, the correlation has been 20 developed by the staff, because that is something we use in l
21 .the Ops Center and that the licensees use it in the TSC. My 22 point is that you have got a capability, an existing 23 capability to do grab samples, and do we really want to let 24 that go and rely on --
1 25 DR. KRESS: Especially if you can get around the ANN RILEY & ASSOCIATES, LTD.
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I 135 1 time requirements and spread it out.
() 2
.3 MR. SNODDERLY: So I think a significant relief is due in this area. I think the three hour requirement for 4 hydrogen grab sampling is way over restrictive. I think 5 allowed outage times and tech specs with these things is 6 overly restrictive. But I think there is a place for these 7 things, it .:'s u in the severe accident management guidelines, 8 but because you don't have a regulatory control, I think the 9 maintenance rule may be appropriate for the hydrogen grab 10 sampling. Now, --
11 DR. KRESS: I don't recall out letter on that 12 PASS, but it sounds like that is pretty much in agreement 13 with'what we said. !
14 MR. SNODDERLY: We did review that letter and this
) 15 philosophy would be consistent with that, that you maintain l
l 16 the capability for long-term grab sampling. And so we would 17 agree with the committee, but that would not be consistent 18 with the exemption request that is being requested by San 19 Onofre.
20 So I think what is going to happen with San i
21 Onofre, what I thought I heard, maybe they can help us, is I b
22 that they also have reassessed their hydrogen monitoring :
1 23 strategy and they are going to come in for PASS relief as 24 well, so we would be all -- it would be consistent. And I 25 would~ hope that their submittal would be consistent with the i
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136
( 1 'ACRS letter:and with the position that I outlined. If it is
() 2 3
not,.then we will have to reconsider this again or,-you know. <
4 DR. KRESS: But if.you have already granted the
-5 . exemption, you can't --
6 MR. SNODDERLY: Well, we have -- that'is with-the 7 . Westinghouse - =we are still in the process of reviewing the 8 Westinghouse core damage assessment methodology and their 9 PASS request, that hasn't gone out the door yet. j 10 DR. KRESS: That one hasn't.
11- MR. SNODDERLY: But what was -- what you were 12 briefed and what you wrote the letter on, and we all agree 13 is that hydrogen grab sampling can be -- you can grant;an 14 exemption from the timing requirements and from removing --
15 from the regulation, but that you still maintain the 16 capability.
17 DR. KRESS: I agree with you.
18 MR. SNODDERLY: Okay. Now how you are going to 19 assure you, that is still a gray area, I think, within the 20 PASS, with the PASS people, too. But I think what'I would i
21 suggest is that you keep it in the EOPs, but out of the tech 22 specs, and then it falls into your maintenance rule to be 23 maintained. So that is where I think we are with hydrogen i 24L monitoring. ;
25 'The last thing we need to talk about is vent and
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137 1 purge. I think the exemption request can be granted because
() 2 3
basically it is -- the reason for the 50.44 purge requirements, it was a backup to the hydrogen recombiners.
4 And so once you make the decision that you don't need 5 recombiners, well, then you don't need the purge.
6 Then I think the -- so for the same reasons 7 outlined previously, we would grant the exemption.
8 Now, the other thing, I just want to quickly talk 9 about venting and the severe accident management guidelines.
10 Right now, as was stated previously, the licensee currently 11 meets this requirement with a filtered eight inch vent line 12 and we like the fact that it is filtered, but the fact that 13 it is only rated for 10 psid, we would agree with the 14 licensee that it doesn't make sense to vent the containment
() 15 at such low pressures, and that we would agree that you 16 should -- that venting should be more of a last resort type 17' of an action, that because of the high strength of 18 containment, you are going to do that at much high 19 pressures, as they have suggested, 99 pounds. So you are 20 going to blow out that duct work, you are going to bypass 21 the filter anyway, so we would not see that as a preferred 22 path, and we don't see this system as being that valuable.
23 But, again, we would expect it to -- because of some 24 sequences that we had not considered, I guess we would -- we 25 agree with the licensee's approach to not maintain it, to ANN RILEY & ASSOCIATES, LTD.
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138 1 keep it in the plant, not to rip it out, and then to keep it 2 as part of the severe accident management guidelines.
3 DR. KRESS: Besides, out to be some rewards for 4 having a large dry containment.
5 MR. SNODDERLY: There ought to be. It is --
6 DR. WALLIS: Did I just hear --
- 7. MR. SCHERER: Can I just make a quick comment?
8 MR. SNODDERLY: Sure.
]
9 MR. SCHERER: We don't disagree with the point you 10 'made on purging in the third bullet there. But just for 11 preciseness, our current severe accident management
~12 guidelines actually recommend using the low pressured 13 system, but cautions that as pressures go up, you need to 14 reconsider that decision. So it is absolutely consistent
() 15 with the point you are trying to make, but in precise 16 wording, the severe accident management guidelines, the 17 preferred path is the filtered purge, but it recognizes that 18 that has to be reconsidered as pressure goes up and 1
19 certainly as you get to 99 pounds, that would be the j 20 decision.
21 MR. SNODDERLY: Thank you for clarifying that.
22 And that is why I wrote verbally here because this was in a !
23 meeting we had back in March, was when this came up and I l 24 wasn't sure. But, again, I think we are all -- the approach 25 is consistent and we are in support of --
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139 1 MR. SCHERER: We certainly agree with the 2 conclusion you are reaching with that.
3 DR. WALLIS: Did I mishear, when SONGS was 4 presenting, I thought the HEPA filter line had a 60 psi 5 design pressure, did I mishear something then?
6 MR. SNODDERLY: I would like to defer that --
7 MR. SCHERER: We did not say, we did not mean to 8 indicate it had a 60.
9 DR. WALLIS: Then maybe I misheard you. Now you i 10 are telling us there is a 10 psi.
11 MR. SNODDERLY: Oh, I think I know -- where Graham 12 was saying, when guys calculated the flow release, flow rate 13 was 50 cubic feet per -- 50 standard cubic feet, isn't that i
14 based on a pressure of 60 pounds? Was that --
() 15 MR. SCHERER: I have the severe accident i
16 guidelines in front of me and it reads, HEPA filter housing '
17 is designed for 1 psig air inlet temperature of 200 degrees 18 F and 100 percent relative humidity. I 19 DR. WALLIS: 1 psig.
20 MR. HOOK: That is the filter housing versus the 21 piping from the containment.
22 DR. WALLIS: . Yeah, that is right. So he is right i 23 that you would blow out the duct work.
24 DR. SEALE: You blow out the filter.
25 DR. WALLIS: Well, there is a difference between O ANN RILEY & ASSOCIATES, LTD.
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140 1 blowing out the filter and the duct work. You may have a
( ) L2 valve -- I thought.there wa's a valve downstream that you 3 could float.
4 MR. SCHERER: At 99 pounds, you are not going to 5 have the HEPA filter anymore. That is the issue.
6 DR. SEALE: That is the bottom line.
7 MR. HOOK: But we would expect the valves to still 8 close.
9 MR. SCHERER: Right.
10 MR. SNODDERLY: What about the duct work leading 11 -- yeah, and the duct work leading to the filter would be --
12 I guess you were told at the meeting, whatever, 10 pounds, 13 so that is still the case differential.
14 MR. SCHERER: Basically, at 99 pounds, we would (O,j 15 prefer to use the mini-purge.
16 MR. SNODDERLY: Okay. I think that is all I had
.17 for today,'and that is what I would plan to present on, I 18 guess next -- June 2nd to the full committee.
19- DR. KRESS: That sounds good. At this time I 20' would like to turn the floor over to Bob Christie who has l l 21 agreed to make a few comments to us. Now, Bob this is going 22 to be a little broader than just this application?
23' MR. CHRISTIE: Yes, I would like to put this is in 24 a little bit of perspective for the other plants. And you 25 have my handouts -- oh, my name is Bob Christie, Performance 1
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141 l' Technology in Knoxville, Tennessee, and my mean time to
_()' 2 recurrence appearing before the ACRS seems to be about --
3 you people haven't been able to get rid of me yet, so, you 4' know, every six months or so the operation appears in front 5- of you and tells you what it wants.
]
6 Yeah, it is a little broader. I would like to put
-7 in the context of the pilot programs.
8 DR. KRESS: It hasn't been a problem, Bob.
9 MR. CHRISTIE: It is always a problem, Tom.
10 [ Laughter.]
]
11 MR. CHRISTIE: And I won't take my slides in 12 order, so -- but I would like to talk about, number one, 13 just the objectives and --
14 DR. WALLIS: Your objective or is this quote from
) 15 someone else?
16 MR. CHRISTIE: No , this is the objective. We have 1
i 17 a program entitled " Risk-Informed, Performance-Based !
18 Regulation Whole Plant Study."
19 DR. WALLIS: .This is a quotation from an NRC ]
20 document?
21 MR. CHRISTIE: This started back in 1977. There !
22 are documents back and forth, and this is in that document l 23 in our program plant.
1 24 DR. WALLIS: 'So these are not your words, these 25 ~ are NRC words?
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142 1 MR. CHRISTIE: No, this is.from the industry.
[ 2 DR. KRESS: You didn't mean '77? l 3 MR. CHRISTIEi Excuse me?
l 4 DR. KRESS: You said 1977.
5 'MR. CHRISTIE: I meant '97 -- '77, boy, we would 6 have really been humping. We should have maybe done it in 7 '77, but part of life.
8 So, anyway, these are the objectives of the 9 program that we-have. As Tom explained, we theoretically l
- 10 have three pilot programs, given that everything works. And j i
11 what the objective -- we just feel that there has to be a 12 way to demonstrate a more objective and efficient way to 13 maintain adequate protection of public health and safety, 14 and then the other thing is to promote the common defense,
() 15 security and protect the environment from the present.
16 DR. WALLIS: So that what we have just heard is an 17 example of all this?
18 MR. CHRISTIE: Hopefully, yes.
19- DR. WALLIS: You said nothing about more objective 20 and efficient, you said nothing about defense and security.
21 MR. CHRISTIE: Well, that is --
l 22 DR. WALLIS: Anything about --
23 MR. CHRISTIE: I want to talk to you about that.
24 Okay.
1 25 DR. KRESS: Bob, Graham'wasn't -- he wasn't when i
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143 1 we reviewed'this before
('~) 2 MR. CHRISTIE: I know. He hasn't been -- right, tj 3 he hasn't been involved in too many of it.
1 4 DR. KRESS: Yes. I i
5 MR. CHRISTIE: We do have a program plan, I will 6 get you a copy of it, Graham. And it was started because 7 two years ago we thought was a good opportunity to make some 8 . changes to the regulations, and to do it in a broad scope 9 approach taking the whole plant, trying to integrate the 10 whole plant, all the processes in the plant, the cost of the
.11 plant, the generation that the plant produces, and the risk l 12 that the plant presents to the public, all in one package, 13 to the best of our ability, and we were going to do this 14 through the use or probabilistic risk assessments at the
,o t
) 15 three plants, again, the three plants being Arkansas Nuclear 16 1, San Onofre and South Texas. I 17 The thing that we have been talking about today, 18 as Tom says, is Task Zero, as Dr. Holahan said, it was just 19 ~-- we picked because Arkansas Nuclear 1, San Onofre and 20 South Texas have been heavily involved from about 1994 on in 21 all kinds of regulatory matters, the inservice inspection, 22 inservice testing, graded QA, et cetera, and not seeing a 23 heck of a lot of results, we came up with the Task Zero, 24 which was to be some sample examples to be used, basically, 25 to test the will and the ability of the NRC staff to process i
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144 l
l 1; changes.through regulation. Well, not so much to the
-O 2 regulations, but'to the requirements.
. O L
i 3 And we started out.with a requirement NUREG-0737, l 4 which was the Arkansas Nuclear 1 Task Zero, to just change 5 the monitoring time from 30 minutes to 90 minutes. And that 6 'was submitted in March 1998 and approved.in September 1998.
7 Then we escalated from there to Task Zero at San Onofre, 8 which we have been talking today, which isfreally to change l
9 the regulations. Now, we are go'ing into 50.44, the GDC and 10 some other-pieces of the regulations. And, so, you know, 11 the first one was supposed to be easy, the second one was 12 supposed to be moderate and the-third which-theoretically 13 would have been South Texas on the 10 second diesel would 14 have been hard, but we' haven't got past moderate yet. . So,
() 15 and things have changed a lot since then.
l .16 And listening to what we did today, I just --
you l 17 know, when we picked these as examples two years ago, we l
i 18 picked examples that basically people said, you are right, 19 this is not risk significant, we have the requirements 20 either via NUREGs or regulations, so we should change.
l 21 Okay. I have yet to hear anyone say that the existing 22- present hydrogen control system at San Onofre or Arkansas 23 Nuclear 1 or South' Texas is a risk significant system.
24 DR. KRESS: You know, I said it depends on your 25! risk metrics.
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p 145 1 MR. CHRISTIE: Well, I am just saying adequate
() 2 3
. protection of public health!and safety, as we presently
. define things and that. And I have yet to hear anyone that 4 says that these existing hydrogen systems have an impact on.
5 adequate protection of public health and safety..
6 DR. KRESS: Well,.I don't know that adequate 7- protection of public health and safety has ever been 8 defined, that is the problem'.
9 MR. CHRISTIE: That's correct, too. That's 10 correct, too.
11 DR. KRESS: Yes.
12 MR. CHRISTIE: And that, as you know, is one of
-13 the problems we have had and one of the objectives that we 14 had in the pilot program, to see if we could go in and get a
() 15 more objective affair.
16 MR. BONACA: And there is a lot of --.a whole lot 17 they don't understand still about severe accidents and we
-18 don't. There is a lot of uncertainty that makes me cautious 19 about, you know, about taking out things.
20 MR. CHRISTIE: Okay.
21 MR. BONACA: You know, just the issue of we don't 22 know.a whole lot about what may happen in those kind of 23 severe accidents.
24 DR. KRESS: What he is saying is the uncertainties 25 are large and they need to be dealt with some way, and the !
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l 146 J
.1 way to. deal with uncertainties is defense-in-depth, which is f ill-defined, and hard to quantify and things of that nature.
2 1 3 MR. CHRISTIE: Okay. And, again, you know, we can 4 spend a lot of time on adequate protection, we can spend of f
5 time on defense-in-depth. I don't want to do it. I just 6 - want to say there is a basic agreement I think between the 7 staff and'the industry that the existing hydrogen control
! 8 systems are not risk significant. Okay.
DR. KRESS:
9 I think that is a safe thing to say.
l 10 MR. CHRISTIE: Okay. As far as I am concerned, l
l 11 that has been pretty much in agreement. And'in the latest 12 tasking memorandum, there is a statement to the fact, by the 13 staff, that it isn't, but, you know, all other things being 14 equal, they still want some things. Okay.
15 My point of it is, if it is not risk significant, 16 why haven't we received the approval? And we can talk about 17 this forever, but I think in a lot of ways, there is a lot 18 of reasons, and it is not because that the senior management 19 in the Nuclear Regulatory Commission doesn't want to make
~20 the changes, I think they do, it is they want to make them
)
21 in a manner in which everybody is happy. You know, all !
22 particulars are covered. And in some ways I won't say it 23 goes to, as we talked about in some of the stakeholders
- 24. meetings,'this concept of perfection versus good enough, but 25 certainly there is part of that in there. Okay. And l ANN RILEY & ASSOCIATES, LTD.
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147 1 Chairman Jackson is pretty clear in her instructions to the
() 2 3
staff, that once we. determine -- once the utility or the licensee comes to the staff and makes the argument it is not 4 risk significant, and they are not able to refute the 5 . argument, then sooner or later, you have to let it go.
6 Okay.
7 And that is something I think we are messing. I 8 mean it is not easy for a utility to come to the staff of 9 the Nuclear Regulatory Commission to make such a request, 10 and it is not easy for the staff of the Nuclear Regulatory 11- Commission to approve it. But when we reach the point at 12 which we have decided that, yes, indeed, this is not a risk 13 significant system, then we ought to be able to figure out a 14 way to let it go. Okay.
(}j l
15 So that is, you know, the main thing that I say.
16 I don't know how to give the assurance to everyone that 17 everything is going to be perfect. Okay.
18 DR. KRESS: Perfection is the enemy of good 19' enough?
20 MR. CHRISTIE: Well, you know, that has been used 21 before, too. Right. It is not going to be that way. But 22- the exemption request was done in a good faith effort. I 23 think in a lot of ways I-myself was personally unclear as to 24 whether.50.12'would work to' provide the framework for doing
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148 1 framework. I don't think the words are quite exactly right, 2 but they are close enough for what you wanted to have. And 3 writing the exemption across the board, as defined in the 4 San Onofre, I think is justified under 50.12. The existing, 5 present hydrogen control system at San Onofre and we will 6 get to Arkansas and South Texas, et cetera for the large 7 drives, is not risk significant and should be removed from 8 the safety space and from regulatory concern.
9 DR. KRESS: This is the rule that spells out the 10 underlying basis for which you can grant exemptions.
11 MR. CHRISTIE: Right. It basically says -- it is 12 two parts. The first part you have to say is, you can't, by
.13 making the change, move into the region and they use the old 14 words " undue risk." Okay. So making the change, you can't
() 15 move the plant into a region called undue risk, that is the 16 first one. And as pointed out by Dr. Seale, this move or 17 this granting of this exemption is not moving us into undue 18 risk, as a matter of fact, when you take it as an entity, 19 and the entire thing is a risk positive move. It moves us 20 in a risk positive direction. So the first part is met.
21 Then you -- also in order to make changes in the 22 regulations, you have to have what is known as special 23 circumntances, and this is where you get in, as Mike 24 Snodderly was talking about, you know, does it meet the
-25 original intent. There is also -- that is, when the ANN RILEY & ASSOCIATES, LTD-.
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149 1 submittal was submitted, the primary reason for 50.12 2 special circumstances, but there is two others and that has
~( )
3 to do with initial information that is available to us 4' today, that we didn't have back, you know, prior to Three 5 Mile Island, and also that you are indeed making a risk 6 positive move in this thing.
7 So I think we met all the requirements of the 8 50.12, and did so in a good faith manner and really put a 9 lot of work. It cost the utility quite a bit of money to do 10 that work.
11 DR. KRESS: Yes, the point that bothers me about 12 that a little bit, Bob, is not that I don't think what you 13 said is true, I think it is, you very well could. But that 14 seems like that is the old system. You are coming right in
() 15 and you say this is the rule, we can get an exemption based 16 on this. It is not risk-informed at all.
17 MR. CHRISTIE: Oh, yes it is. Absolutely.
18 DR. KRESS: Well, it is, I'm sorry. But you could 19 have done this with risk-informing it.
20 MR. CHRISTIE: Oh, no, you could not have done 21 with without Three Mile Island and all the studies that have 22 been done since Three Mile Island. There is no way you 23 wculd have come in with this argument without Three Mile 24 Island and all the risk studies. You have got all the --
25 DR. KRESS: I guess what I am saying is this, the l
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150 1 requirements for an exemption do not say in'there if your
()
\J 2- risk status is low enough and you come in with a request for l
1 3 an exemption to the rule because it doesn't increase your 4 risk beyond something acceptable, then that is a good reason 5 for an exemption. It doesn't say that in this.
6 MR. CHRISTIE: Right. I am not saying that.
7 DR. KRESS: That is what I am saying risk-informed 8 regulation is, that as well as --
9 MR. CHRISTIE: Oh, that is where we want to get 10 to.
11 DR. KRESS: Yes.
12 MR. CHRISTIE: That is where we want to get to. I 13 have no problem with that.
14 DR. KRESS: So this falls short of testing.the
() 15 16 risk-informed process because you are coming in under the old regulations.
17 MR. CHRISTIE: No, we are using the existing {
18 regulations to test the will and the ability of the Nuclear 19 Regulatory Commission to use risk arguments to change the 20 regulations.
21 DR. KRESS: Yes, but they have always --
-22 DR. WALLIS: Those are human factors, though.
23 MR. CHRISTIE: Excuse me?
24 DR. WALLIS: Those are human factors. That is not 25 risk-informed. Those are human factors.
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151 1 MR. CHRISTIE: But if you didn't have the risk
/~'\ 2~ analysis, you couldn't make the argument.
.Q 3 DR. SEALE: Bob, I have a slightly different 4 problem with this.
5 MR. CHRISTIE: Okay.
6 DR. SEALE: This system was designed to put a 7 certain capability in place that was perceived at the time 8 and it is primary a post-TMI requirement, really.
9 MR. CHRISTIE: No, the --
10 DR. SEALE: Well, the hydrogen monitoring I think 11 became important at that point. Right, Gary?
12 MR. HOLAHAN: Yeah, I think the hydrogen 13 . monitoring is a post-TMI item.
14 DR. SEALE: Right. And it was a part of the (f 15 regulation. It included some components like the monitoring 16 system that told us what the hydrogen concentration would 17 be. It also included some rather breathtaking ideas like a 18 filtered event, albeit it in this case, in this particular 19 design, albeit it a rather modest one and so on. And they 20 were all embedded in the regulation.
21 Now, we have done our regulatory risk assessments 22 and so on, and we say, you know, these things are all really 23 over in -- don't really have any effect on risk, and the 24 only time it really.might be important to be able to ignite 25 the hydrogen is in the case of those things that almost ANN RILEY & ASSOCIATES, LTD.
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i 152 1 never really. enter into regulatory risk assessments, namely, I I 2 severe accidents. So, let's get rid of it.
3 And I think at this point nobody really has an 4 argument. The problem you have is that in the inventiveness 5 of the human spirit in the reactor operator, and they are 6 human, we have found other uses for some of these things. l 7 We have been able to see that having the capability to do 8 these things, hydrogen monitoring and so on, has some value I 9 in those areas where our risk assessments fear to tread, and I 10 in any event don't give us numbers that are very helpful and 11 so on, anyway, and taking a pure, rigid interpretation of l 12 what regulatory requirements would be, says that I don't i 13 care what these things are for, if they don't help with l 14 risk, I am going to throw them out. Throw the baggage out, rh N ,) 15 not going to worry about it. And the fact that there are 16 other benefits that these things might have, that can be 17 useful in the event of a severe accident and so on is beside 18 the point. And I think that is a pretty darn narrow, rigid )
19 view.
20 MR. CHRISTIE: Okay, and let's explore it, because 21 I think you are misinterpreting what we intend to try and do 22 in the pilot programs. And I think it is appropriate at 23 this time, I will put my basis slide, which you have all --
24 well, maybe Dr. Wallis hasn't seen and Dr. Bonaca hasn't 25 seen, but the others have seen. Okay. And it says the l
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153 1 primary responsibility for the safety of the plant lies with
.[y): 2 the people who run the plant, and they don't shy away from 3 that all, not any more.
l 4 DR. SEALE: I am not going to argue with that.
5 MR. CHRISTIE: Right. And the regulatory arena l 6 should be such that it assures adequate protection. And, 7 again, we have all got the problem of what adequate 8 protection is and all the rest of that. But it is a lesser.
9 responsibility for the Nuclear Regulatory Commission than it 10 is for the utilities, and the utilities make decisions 11 constantly about the risk to the plant, removed from the 12 regulatory arena, that adequately guarantee those plants are 13 safe. In the last 20 years since Three Mile Island, the 14 utilities have made tremendous strides in improving the
() 15 performance of that plant, forgetting about all regulatory 16 requirements. Our initiating events, as far as automatic 17 scrams, have dropped down from probably 7 to 10 down to less 18 than 1. Our ability of the systems to respond to scrams 19 when they do happen has gotten better. Accident sequence 20 precursors -- et cetera, et cetera. That is their 21 responsibility.
22 DR. KRESS: Do you think all of that would have 23 come'about if we had not had a Nuclear Regulatory 24 Commission?
l l 25 MR. CHRISTIE: Absolutely.
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l 154 1 DR. KRESS: It would have happened anyway? j 2 MR. CHRISTIE: Absolutely. Had to.
[J') When you look 3 at the thought that you could lose a $2 billion affair, not l 4 only lose the capability to generate revenue, but you also 5 had to pay for all the cleanup and everything else that
{
6 happened, absolutely.
7 DR. KRESS: So why do we have a Nuclear Regulatory ,
l 8 Commission?
9 MR. CHRISTIE: Ah, there is the question that I 10 have asked you people before. Why do we have a Nuclear 11 Regulatory Commission and not a Coal Regulatory Commission 12 or a Natural Gas Regulatory Commission, et cetera? And we 13 all know the answer, the answer is fear of nuclear. And it 14 is nothing wrong with that. I mean a lot of people have an s~ {
l
(%) 15 emotional fear of the nuclear, and we need a regulatory 16 commission.
17 DR. KRESS: I think nuclear is a hazard of a 18 different type.
19 MR. BOERNERT: Yes.
20 MR. CHRISTIE: It is. And the utilities are not 21 in any way, shape or form recommending that we get rid of 22 the Nuclear Regulatory Commission. We would just like it to 23 be more efficient and effective.
24 And this example, Dr. Seale, as far as I know, the 25 hydrogen monitoring, knowing what the percentage of hydrogen
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155 1 is in the containment, is used for nothing by the majority
(} 2 of1 the~ plants that have large dry containments, except to 3 turn on the recombiners and the purge system. And we know 4 in the severe accident space, the recombiners and the purge 5 systems-are ineffective. They have benefits possibly in an 6 operational sense, and no one denies that there are. There 7- arefmaybe operational events that have nothing to do with 4
8 accidents where recombiners might be, but that lies in the 9 purview of the utility, not in,the regulatory sense.
10 And so this is where we are today, and this is 11 about as clean a cut case _as I have ever seen. We have 12 agreement that here is an existing hydrogen control system l 13 for which 20 years ago, we set out a set out requirements 14 that don't have applicability today. We have lived with
() 15 them for 20 years. Now we want to get rid of them. We have 16 followed the process that was set down in the regulations 17 for trying to get rid of them, and we are very close to 18 getting rid of them.
19 DR. WALLIS: I think, Bob, for post-accident 20 : analysis,:both during the 30 days we heard about where 21 ' people are trying to figure out what to do, and also'in the 22 next-year or two, if there is an event like this, where 23 people are trying to figure out what happened, it would be
- 24. very useful- to have a trace of the hydrogen concentration in 25 that containment.
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l 156 j 1 MR. CHRISTIE: We do not have in any shape or 2 form, to the best of my ability, in a lot of the plants I 3 have been -- I know this pretty much for Arkansas, because I 4 have been working with them pretty heavy -- they do not use 5 it. They do not use it to set up the emergency action k 6 levels that they have. They don't use it to set up any of 7 the things, cue operators will not turn anything on. The 8 technical support center would not use it to dictate, you 9 know, who is evacuated and who is not evacuated, et cetera.
10 One of the things we learned since Three Mile 11 Island, and this is why I say you can't make this argument i
12 if you hadn't done all your homework following the Three 13 Mile Island event, and we learned a lot between '79 and '99.
14 Okay. We use all the other things that are in there, core
() 15 exit thermocouples, radiation monitors, et cetera, et 16 cetera. Those are the things that are written in our EOPs, 17 EOIs, our severe accident management guidelines, et cetera.
18 As far as I know, the hydrogen monitoring is just 19 a confirmatory action, not even in accidents, it just a 20 confirmatory thing that people would have to back up the 21 actions that are already spelled out in all the procedures.
22 DR. KRESS: I think Graham would say that just 23 because you don't use them, doesn't mean they are not 24 useful.
25 MR. CHRISTIE: Well, I think a decision has been
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l 157 1 made.
( 2 DR. SEALE: Well, if you haven't generated any 3 hydrogen lately to detect, it is pretty clear that you don't 4 need them. But if you generate some hydrogen, you might 5, . well need them.
6 MR. CHRISTIE: And, again, I am not saying that as 7 an operational tool they are not useful. And I am not 8 saying that the utilities won't make up their own mind as to 9 what to do with them. I am saying that for them to be in 10 regulatory space and safety-related, with all the 11 requirements that are on them, is not effective and 12 efficient.
13 DR. KRESS: That I think we might agree with 14 there.
() 15 DR. SEALE: Ah, I agree with that. But my problem 16 is there is no middle ground that says that this instrument 17 should have some status so that it -- we can be sure that it 18 remains available. That is the prob 3em.
19 MR. CHRISTIE: Why don't you believe that the 20 utilities will make that decision in the correct manner?
21 DR. SEALE: Because you just told me a while ago 22 there are some of them that do good things and some of them 23 that don't do some good things that the goo'd ones do. There 24_ .are advanced utilities and there are troglodytes out there.
25 MR. CHRISTIE: You know, again, I would be the p-
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158 1 last to say that.every utility in the United States is 100
() 2 percent perfect in every decision that they make. Okay.
3 But I believe that the utilities in the United States have 4 the experience, the people at the plants are responsible 5 people, they are trained people, they really care about it, 6 and of all the people in the.world that are concerned-about 7 the safety of the plant, it is the people at the plant.
8 DR. SEALE: I don't argue with that at all. I 9 just don't think --
10 MR. CHRISTIE: And to expect that the Nuclear 11 Regulatory Commission is going to be able to monitor the 12 plant in such a way, to such a degree that things such as 13 the existing hydrogen control system is part of the 14 regulatory space, I think is incorrect. That is why we went 15 that far.
16 DR, KRESS: I think that is a better argument 17 there. The Nuclear Regulatory Commission does have 18 responsibility to assure the safety and public health.
19 MR. CHRISTIE: Right.
20 DR. KRESS: But they can't monitor everything.
21 MR. CHRISTIE: That is correct.
22 DR. KRESS: And to try to diminishes their ability 23 to monitor things that are important. And this may be one 24 of those things.that just doesn't rise up to enough of a j 25 level that they should be putting much resources in. l l
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159 1 MR. CHRISTIE: That is-exactly --
(r) 2 DR. KRESS: That is a reasonable argument for it.
3 MR. CHRISTIE: That is exactly the argument we 4 have been making.
5 DR. KRESS: Yes.
6 MR.' CHRISTIE: We made that argument. And we made 7 it in the submittal. We have made it in all the 8 presentations.
- 9 We do not in any shape or form intend -- I can't 10 - tell you -- when you concentrate on the things that are 11 really important, you get better at them, okay, and that is 12 what we intend to do. In the pilot programs, we believe 13 that if we identify the important things, pay attention to 14 _ them, we get better, and that is where we are going to get
) 15 more' effective and efficient. And the things that don't 16 - rise to the level of importance to. adequate protection of j
.17 public health risk and we are going to have to figure out 18 how to do that in a better fashion than we have in the past.
19 We are going to do it. ;
20 MR. BONACA: Well, I haven't been with the '
21 Commission more than three months, but I can say that, first l 22 of all, there is a clear role in safety for the Regulatory ;
l l 23 . Commission. Let me just say that once you have an accident l l
24 at one plant, the Regulatory Commission is the only thing j i
25 that protects all the investment of the other power plants, !
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5
160
'l because the public is looking for that-Commission to answer 2 questions, to provide some convincing statements. I want to 3 just -- you know, we can talk about that forever, there is a 4 role for it. And because of it, there is an expectation to 5 prudency.
6 I see a lot of positive aspects in this 7 application, but certainly I am not going to simply say, 8 just because you are asking for it, I am going to give it.to 9 you. I mean I want to be convinced. And that is what I !
10 believe all of us on this committee think.
11 DR. SEALE: Yeah.
12 MR. BONACA: That is all I want to say about that.
13 And I think some things are convincing and some are a little 14 bit less convincing. For example, one thing I would like to 15 see in general is not a piecemeal application of a number of 16 elements but comprehensively. I would have liked to see the 17 PASS system discussed in this presentation too, because I 18 think that to some degree I could be convinced about doing 19 without the hydrogen monitoring system if somebody told me 20 the PASS system was great.
21 Now, I know from experience, because I have been l
22 with power plants, the PASS system is not good. It takes a l 23 long time to get a sample and that kind of stuff. So that 24 reinforces somewhat my concern with this position of 25 delivering or not supporting the hydrogen monitoring system.
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161 1 So, but, again, I think in general I don't see that I have 2 any resistance to what you are saying.
D) 3 MR. CHRISTIE: Okay. I guess it would be a good 4 time to put up, you know, what I think is the summary, which 5 .you have seen before.
)
I mean this is truthfully a good 6 time. I mean right now, with the things.that are going on 7 in the Commission and the things that are going in 8 utilities, and the preparation for the economic deregulation 9- of the electric power industry, it is a good time for 10 change. I think we are ready.
11 I cannot -- you know, when we put Task Zero in, I 12 didn't realize the importance it would get. But it is 13 important, it has become a very critical issue because if 14 the utilities are going to make the commitment to really
) 15 making a major effort to change the 10 CFR, they have to
- 16. know that when we come to the end of it, there is going to 17 be real change, there is just not going to be talk, there 4
18 has got to be action.
1 19 DR. KRESS: You have some good bullets up there.
20 I don't see a bullet that says what the ACRS role ought to 21 be.
22 DR. SEALE: We don't have any resources, that is 23 for sure.
1 24- DR. KRESS: Never mind answering that.
1 25 MR. CHRISTIE: But, again, it is a good time. I i
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I
P 162 y 'l think we are preparing. The utilities are prepared, I think
'( ) 2 the staff is prepared and we can move on. And I -- you 3 know, as I stated to this'-- well, not this committee, but 4 to the' full ACRS, when the Arkansas Nuclear 1 was approved, 5 -hey, it takes an active change and an active faith in the 6~ staff of the NRC to make that change. And when they do it, 7 they should be applauded for it. But if they don't do it, 8 then I am not sure that you can expect the utilities to move l 9 as well as they could.
10 DR. KRESS: We certainly thank you, Bob, for your 11 comments, and you'are welcome to come back.
12 MR. CHRISTIE: Every six months.
13 DR. KRESS: Well, whatever, whenever you feel we 14 need.
() 15 MR. CHRISTIE: Oh, now that is dangerous to ask me 16 about that.
- 17. DR. KRESS: I also want to thank the Southern i
18 California Edison people and the staff.
19 At this point we need to make a little bit -- give 20 a little thought to next week. We do have this as an agenda 21 item on next week's full ACRS committee. The subcommittees 22 only develop trial positions to put forth as strawmen to the 23 full committee, and the full committee needs to hear some 24 condensed version of what we have heard today. And we have
~ 25 90 minutes total allocated for the full committee meeting to 1
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7 _.
163 1 cover what we have been at here for -- what, four. hours.
[J~h :2 MR. BOEHNERT:
DR. KRESS:
Yes, roughly four hours.
3 So we need to think about what we are 4' going to say. I pretty much like the slides that we got 5 from the staff, pretty much in the form that they are, so I 6 wouldn't condense those much, Mike. They are pretty good, I 7 think. And so you might to basically repeat that part of 8 it.
9 The presentations from Southern California Edison 10 need to be condensed, but I think you might count on maybe, 11 at least 40-50 minutes' worth of presentation time.
12 MR. BOEHNERT: No , no, no, total time.
13 DR. KRESS: Total time, which includes answering 14 questions and stuff. But their part of this 90 minutes
( 15 should be about 50 minutes of it, I think.
16 MR. BOEHNERT: Yes, yes.
17 DR. KRESS: So you may give some thought as to 18 what you think your message is that you want the full 19 committee to hear. And some of the things I would suggest, 20 you want to say this is actually what we are requesting.
21 And maybe get into the four parts of the control system and 22 what you would -- what the request would mean. And the 23 discussion you had about what would happen to these things 24 if the exemption is granted would be useful, your 25 perspective on that. And your risk arguments are kind of O ANN RILEY & ASSOCIATES, LTD.
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164 l 1- necessary, too. You will need to condense them some way, I 2 think, but you need to get those risk arguments in there.
3 And you might also want to think about including the l 4 defense-in-depth comments that you made. Other than that, I 5 don't have any good advice on how to condense it down. You 6 know, I think you might go a little lighter on some of the 7 regulatory objectives, regulatory bases, because I think we 1
8 get that anyway. So that might be a place where you can go 9 a little lighter. And other than that, I look forward to --
l 10 does the rest of the subcommittee have any comments on what 11 we might need to hear, what the full committee might need to 12 hear other than that?
13 DR. SEALE: Well, I think we want to be sure that 14 we delineate what the concern is regarding exactly the 15 status of the residual parts of the system would be once the 16 exemption is --
17 DR. KRESS: Yeah, and the' combination of them 18- saying what their perspective is and what Mike was saying.
19 DR. SEALE: And it should do it, but I think you 20 will need to keep in mind that that is the dichotomy that we 21 need to have drawn pretty clearly here, because I think we 22 are all interested in what the rest of the committee has to 23 say on this issue. I certainly am.
24 DR. KRESS: You know, I know the committee is very 25 interested in this and will use it as part of their basis l i
i h'
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165 1 'when they review other risk-informed initiatives. At this
() 2 13L point-ILam not sure whether we will have a letter or not,
- because'as Gary said that is an issue --
4 HMR . BOEHNERT: Yeah, that is an issue we have to 5 wrestle with.
6 DR.-KRESS: I think whether we have a letter or 7 not, we will, number one, be dependent strongly on my 8 recommendation as to.whether we have a letter or not, and I 9 haven't made up my mind yet about it. I am leaning towards 10 actually'not having a letter, but I think if the letter is 11_ going to be -- if the letter were to be negative, we might 12 want one, but if it is going to be highly positive, then it 13 is sort of a choice. Right now I think -- I can't speak for 14 the full subcommittee or even much'less for the full 15 committee,- but it is likely to.be supportive ofLthis with 16 the possible exception of needing hydrogen monitoring in 17 some way to assure _that that is either in there for severe 18 accident management with the thing.
19 So, but I don't know whether we will have a letter l 20 or not. i 21 DR. WALLIS: Yeah, I' don't feel we need a letter. i l 22 I think that this is useful to observe this process.
l
-23 DR. KRESS: Yeah, it helps. It helps.
24 DR. WALLIS: Observe the staff doing this. I 251 think both groups of presentations were good. And if the l
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166 1 issue is simply to-demonstrate the willingness of the staff
/\
U 2 to give us something, then that has been achieved and maybe 3 that is what has happened. But I am not sure that I would t
4 draw many useful messages about risk-informed regulation 5 from this example. It doesn't really'come up against the 6- major issues yet.
7 DR. KRESS: Yes, it doesn't arrive -- I agree with 8- you. It is a start.
9 DR. WALLIS: So I think when we get one like that.
10 Unless we can draw some conclusion that helps us deal with 11 the next issue from this one, then we probably don't need to
' 1:2 write a letter. And if we have learned something from this 13 that says this is what we need to bear in mind when we do 14 risk-informed regulation, then we would probabi9 gerhaps
() 15 tune in to that.
16 DR. KRESS: The thing I wanted you to try get a 17 little.better grasp on is, are our risk metrics complete?
18 DR. WALLIS: Oh, that concerns me. But in this 19 case we have not really talked much about risk --
20 DR. KRESS: Yeah, this one didn't rise to the 21 level of actually testing that. So that, you know, if it 22 had, then that would be an important lesson. But I don't 23 think it rose to that level, so that is --
24 DR. SEALE: We might want to consider, though, .the 25 idea of expressing to the Commission the concern that you i
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167 1 bundle too many things into the argument of no risk and
(\/
Ns-2 perhaps throw out parts of systems that you would prefer to l
3 retain.
4 DR. KRESS: I think that is an argument we need to 5 make when we talk about risk-informing Part 50. I don't j 6 think it has -- I don't think --
7 DR. SEALE: Because we have been told this is part 8 of that.
9 DR. KRESS: Well, it is not -- maybe it is, but --
10 I don't know, I don't think this is -- this is an exemption 11 request. And I don't think this is the place to raise that 12 kind of issue. I think when we get around to --
13 DR. SEALE: Yeah, but somebody is going to claim 14 it is precedent when we get to talking about 50.
A
() 15 DR. KRESS: Well, we will just say precedents are 16 precedents.
17 DR. SEALE: And they count a lot. i 18 DR. KRESS: Anyway, I don't think it is the right 19 place to raise that issue,.even though I think --
ll 20 DR. SEALE: Maybe you ought to have additional 21 comments to a letter that doesn't exist.
)
22 DR. KRESS: To that letter. Okay. But, anyway, '
23 with that, I want to thank everybody. I think the 24 presentations were well done, and you talked about the 25 issues frankly and we appreciate that. And with that, I am I
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l 168 1
1 1- going to -- unless there are any comments anybody else would
'/
}
2 like to make, Bob Christie or anybody else in the audience? 1 3 [No response.]
4 DR. KRESS: Seeing none, well, in that' case, I am 5 going to adjourn'this meeting.
6 [Whereupon, at'12:32 p.m, the meeting was i 7 ~ concluded.)
8 l 9 10 J 11
-1 12 13 14
() 15 1C 17 18 19 20 l
21 22 23 24 l 25 l
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REPORTER'S CERTIFICATE This is to certify that the attached proceedings f( ) before the United States Nuclear Regulatory Commission in the matter of:
NAME OF PROCEEDING: ACRS MEETING ON SEVERE ACCIDENT MANAGEMENT CASE NUMBER:
PLACE OF PROCEEDING: Rockville, MD were held as herein appears, and that this is the original O
( ,/ transcript thereof for the file of the United States Nuclear Regulatory Commission taken by me and thereafter reduced to typewriting by me or under the direction of the court reporting company, and that the transcript is a true and accurate record of the foregoing proceedings.
bbb k Mark Mahoney d Official Reporter Ann Riley & Associates, Ltd.
O, V
W ADVISORY COMMITTEE ON REACTOR SAFEGUARDS THERMAL-HYDRAULIC PHENOMENA SUBCOMMITTEE O REVIEW OF NRC REGULATORY ACTIONS / STATUS OF RETRAN-3D REVIEW MAY 26,1999 ROCKVILLE, MARYLAND I
Contact:
P. Boehnert- 301/415-8065 PROPOSED AGENDA topic SPEAKER IlME
- 1. Introduction G. Wallis, 8:30 a.m.
Chairman
- 11. Proposed Revision to J. Donoghue, NRR 8:40 - 10:00 a.m.
Appendix K- 10 CFR Part 50
-Introduction & Background
- Proposed Rule Revision
- Risk Considerations
] - Conclusions Ill. Subcommittee Caucus 10:00 - 10:15 a.m.
- Follow-on Actions for This item
- Decision to Bring to ACRS for Review BREAK 10.15 - 10:30 a.m.
IV. Status of NRC RETRAN-3D R. Caruso, NRR, 10:30 - 12:30 p.m.
Code Review / Development . N. Lauben, RES, of Code Review Guidelines Et al. l A. RETRAN Code Review
- Key Review issues !
- Problems /Concems 4
- Resolution Approach B. Code Review Guidelines
- Development of Review Standards / Acceptance Criteria
- Status of SRP Development
- Status of Reg. Guide Development 1
m.,
W Presentation Schedule: Page 2
- 5/2p W Sub. Mtg.
O L> LUNCH 12:30 - 1:30 p.m.
VI. Subcommittee Discussion of G. Wallis, et al. 1:30 - 3:30 p.m.
Proposed ACRS Structured Discussion on Development of Guidelines for ACRS Code Reviews (Open Executive Session)
Vll. Subcommittee Caucus 3:30 - 4:00 p.m.
- Code Review Guidelines
- Follow-on Actions for this item .
Vill. Adjoum 4:00 p.m.
I l
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RETRAN - 3D REVIEW STATUS !
l ACRS THERMAL / HYDRAULIC PHENOMENA SUBCOMMITTEE O RALPH R. LANDRY REACTOR SYSTEMS BRANCH DSSA,NRR MAY 26,1999 l
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O RETRAN - 3D REVIEW STATUS e REQUESTS FOR ADDITIONAL INFORMATION SENT TO O APPLICANT April 27,1999 e ADDITIONAL RAls BEING DEVELOPED TO INCLUDE CONCERNS OF ACRS AND REVIEW SUPPORT FROM RESEARCH l
O
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RETRAN - 3D REVIEW STATUS e NEUTRONICS REVIEW:
- 3-D TRANSPORT vs 3-D DIFFUSION COMPARISONS BEING O DONE FOR ewR ROD eaECTiON
- CALCULATIONS BEING DONE USING SPERT DATA i
- APPLICANT HAS BEEN ASKED TO PERFORM SPERT CALCULATIONS l i
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RETRAN - 3D REVIEW STATUS e 5 - EQUATION FLOW FIELD MODEL IS NOT ADEQUATE e QUESTIONS RAISED IN REVIEW BROUGHT RESPONSE THAT MODEL IS BEING REPLACED e PAPER PRESENTED BY CODE DEVELOPER AT NINTH INTERNATIONAL RETRAN CONFERENCE (JUNE 1998)
DISCUSSED PROBLEMS WITH MODEL e REVIEW IS PARTIALLY SUSPENDED WAITING FOR REVISED CODE DUE THIS SUMMER I
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O RETRAN - 3D REVIEW STATUS e APPROVAL PROCEDURE:
- SINGLE SER FOR CODE APPROVAL
- MAY ADDRESS RETRAN-3D EQUIVALENCE TO RETRAN-02 WHEN RUN IN RETRAN-02 MODE
- RETRAN-02 LIMITATIONS ADDRESSED BY RETRAN-3D WILL BE DISCUSSED i
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1 RETRAN - 3D REVIEW STATUS e SCHEDULE HAS NOT BEEN CHANGED AT THIS TIME:
- DRAFT SER IN SEPTEMBER 1999
- FINAL SER IN OCTOBER 1999 e IMPACT OF CODE REVISION HAS NOT BEEN ADDRESSED: I WAITING FOR REVISED DOCUMENTS TO DETERMINE MAGNITUDE OF WORK REMAINING O
~. . _ .
O APPENDIX K RULEMAKING Revising the 102% Power Level Requirement Briefing to the Advisory Committee on Reactor Safeguards Thermal-Hydraulic Phenomena Subcommittee May 26,1999 Joe Donoghue. BRXB (301) 415-1131 1
Appendix K Revision objecthe e Permit a reduction in conservatism of the reactor power level assumed for LOCA analysis
( e Remove an unnecessary regulatory burden i e Allow small, cost-beneficial power uprates or other beneficial changes e Avoid a large number of exemption requests 2
Appendix K Revision
Background
e initiated by use ofimproved feedwater flow measurement to reduce power measurement ;
uncertainty l
'e Caldon,Inc. Leading Edge Flowmeter (LEFM/) l e Earlylicenseeinterest l e Comanche Peak exemption request !
1
- ABB-CE Crossflow system l
3 I
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. Caldon LEFlW System O Time-of-Flight Measurement l
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P% d ;
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L'":::: ' ~
%*'a __
s_ .-
4 l
l l
ABB CrossflowSystem l
' Cross-Correlation" Technique O
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Appendix K Revision j Background (continued) l
- SECY 99-014 Rulemaking Plan
! e Staff Requirements Memo, February 19,1999
- CRGR Briefed during March 1999 l
l 6
7 Appendix K Revision Appendoc K Basis
- $ 50.46 requires ECCS evaluations based on "Best-Estimate" analysis or conformance to Appendix K e 102-percent of licensed power requirement is one of several conservative LOCA analysis criteria in Appendix K e Other regulations do not specify power level e Some Regulatory Guides and SRP Sections reference App. K or specify a power level 7
Appendix K Revision Appendoc KHistory e ECCS Hearings: Dio not give detailed basis for the powerlevel requirement O e ECCS Rule (39 FR 1002, Janusry 4,1974):
Acknowledged that conservative assumptions could be reduced with sufficient data e SECY-83-472,' Emergency Core Cooling System Analysis Methods for Light-Water Nuclear Powered Reactors": Presented rationale for 'best-estimate
- ECCS evaluation 8
Appendix K Revision l 1
Proposed Rule Revision Revise first Paragraph of Appendix K to read as follows:
eFor the heat sources listed in paragraphs 1 to 4 below it shall l
be assumed that the reactor has been operating continuously at a power level at least 1.02 thies the licensed power level (to allow for such uncertainties as instrtrnentation error the maxhlum peaking factor allowed by the technical ), with specifications. Anassumed Asef Aowerthan Wist n
V E"lll2'Of!* non=3'.""a"m""
wicertaln#es dJe m inainsnantadon omr.
9
Appendix K Revision h hiplications e Ucensees may save $4 million annually per plant in averted replacement energy costs with an approved one-percent power uprate e Ucensee benefits may be realized without increases in licensed power (e.g., change peaking factors or ECCS system requirements) _
e Licensees may adopt new instrumentation and change LOCA analysis without license amendment e Vendor / licensee ongoing power uprate programs 10 Appendix K Revision RiskConsderatens
- No significant risk issues raised ir evaluation of extended power uprates.
e Therefore, marginal power uprates (1%) do not require a risk evaluation (EDO letter to ACRS O- Sep.14,1998) e Deterministic requirements apply to power uprate or other technical specification changes.
e Proposed rule is not a risk-informed revision of
.10 CFR Part 50 as proposed by SECY 98-300 11 Appendix K Revision Baciditconsideratens e NONE, since this will be a voluntary measure e However, licensees seeking a power uprate or other technical specification change will be expected to provide sufficient justification with a submittal to the NRC O
12
Appendix K Revision Propowd Rule Schedule e Obtain office concurrences on proposed rule by July 1999 e Proposed Rule submitted to Commission by August 16,1999 e Publish Proposed Rule for Public Comment by October 1999 l
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PRESENTATION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS SUBCOMMITTEE ON SEVERE ACCIDENT MANAGEMENT l
" Risk-Informed Performance-Based Regulation, Whole Plant Study" l
Bob Christie Performance Technology l
May 27,1999 i
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BASIS I The primary responsibiliy for the "public health and safe y" of a nuclear unit lies wi::h the peop:.e a~
the site who are running the nuclear O unit.
The regulatory process :hai: oversees ne nuclear unit mus': ensure
" adequate pro:ection 0:?public hea:::h and safe:7."
l
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I O
TASK ZERO l i
l Tes : :he will and the ability of1:he staff of the Nuclear Regulatory Commission to l O make changes 1:o :he exis:ing requirement:s l based on quan:i':a:ive public heal:h risk evaluations.
O lY
I O
Status I
1 Arkansas Nuclear One submitted request for change on March 2,1998.
1 -
Arkansas Nuclear One submitted adc.itiona:. information on September 9, ;
O 1998-NRC staff approved request for change on September 28,1998. Issued orc.er granting c aange from 30 minutes to 90 minutes.
L -
Order is intendec. to be a " template" for L generic c:1ange. Ot:1er nue:. ear units can .
L submit request for change using ANO l materia: as guide.
O 1
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10CFR50.12 Specific Exemptions (a) The Commission may, upon application by any interested person or upon its own initiative, grant exemptions from the requirements of the regulations of this part, which are---
(1) Authorized by law, will not present an undue risk O to the public health and safety, and are consistent with the common defense and security. ;
(2) The Conunission will not consider granting an exemption unless special circumstances are present.
i O
6 tv ,
c ,
O 10CFR50.12 Specific Exemptions The special circumstance most relevant to Southern California Edison's request is:
I (ii) Application of the regulation in the particular circumstances would not serve the underlying purpose of the rule or is not necessary to achieve the l underlying purpose of the rule.
Special circumstances may also be present with O respect to:
(iv) The exemption would result in benefit to the public health and safety that compensates for any decrease in safety that may result from the grant of ;
the exemption. !
(vi) There is present any other material circumstances not considered when the regulation was adopted for which it would be in the public interest to grant an exemption.
O yIy
O The existing hycrogen control system is no: a rist signi:ican1: system.
Gran:ing ::1e recuestec. exemp : ion wil:.
improve :he safely focus a :.1e nuclear elec:ric power uni:s anc.
represen: a more e:5fec,:ive and O e:55cien: me:: 1od for main,:aining adec ua :e pro :ec:: ion 0:? pui.ic heal::1 ;
anc. safe'y.
O 8 tv
O Tasking Memorancum Upc. ate May 11,1999 "The staff held a public meeting with San Onofre on March 17,1999. The staff believes that although the recombiners and hydrogen purge is not a risk significant system, they are needed to support the severe accident management guidelines but do not rise to the level of a maintenance rule risk significant O system. The licensee is expected to develop an appropriate reliability and availability control which will provide justification for no longer including these systems in technical specifications."
1 O
9fIv
9 O
Chairman S:airley Ann Jac1 son NRC Senior Management Retrea1:
October 14,1998 i
"At the same time, we must be ready to let go of that which is not risk significant. When a licensee comes to us in licensing space, or during the inspection j process, or in enforcement proceedings, and contends that a given activity or issue is oflow risk O significance, and we cannot refute the contention, we must be prepared to let go. Our programs must require a rigorous challenge to licensee contentions, but when a risk-informed review indicates that no significant risk is presented, we should not resort to subjective judgment, management sensitivity, or personal preference to resuscitate a dead issue."
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Speedy approval of::he San Onofre !
submin::a10:? Sep :em 3er 10,1998, will be in <:he bes : in:eres :s 0:? the public, ;
the NRC, and the nuclear uni:s.
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needec. for success.
.SRC Commissioners and senior NRC managemen: mus: provic.e leac.ership anc. resources.
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