ML20206F372
| ML20206F372 | |
| Person / Time | |
|---|---|
| Issue date: | 04/30/1999 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | |
| References | |
| ACRS-T-3074, NUDOCS 9905060100 | |
| Download: ML20206F372 (168) | |
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ec GilIE.'!L PCBST.-307y OFFICIAL TRANSCRIPT-OF PROCEEDINGS dr-NUCLEAR REGULATORY COMMISSION l
%DVISORY COMMITTEE ON REACTOR SAFEGUARDS l
Title:
f' MEETING: SEVERE ACCIDENT MANAGEMENT I
l TRO4 (ACRS! l RETURN ORIGINAL ;
TO B XdITE M/S T-2E26 ,
415-7130 THANKS!
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' Docket No.: -
- Work Order No.: ASB-300-763 LOCATION: Rockville,MD
. DATE: Friday, April 30,1999 PAGES:1 - 119 9905060100 990430 T- 307 d PDR
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DISCLAIMER UNITED STATES NUCLEAR REGULATORY COMMISSION'S ADVISORY COMMITTEE ON REACTOR SAFEGUARDS APRIL 30, 1999 The contents of this transcript of the proceeding of the United States Nuclear Regulatory Commission Advisory
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t j Committee on Reactor Safeguards, taken on April 30, 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.
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1 1 UNITED STATES OF AMERICA 2 NUCLEAR. REGULATORY COMMISSION 3 ***
4 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 5 ***
6 MEETING: SEVERE ACCIDFNT MANAGEMENT l 7
8 9 U.S. Nuclear Regulatory Commission l
10 11545 Rockville Pike 11 Room T-2B3 12 Rockville, Maryland 13 14 Friday, April 30, 1999 15 16 The Subcommittee met, pursuant to notice, at 8:30 17 a.m.
18 '
19 MEMBERS PRESENT:
20 THOMAS S. KRESS, Chairman, ACRS j 21 MARIO H. FONTANA, Member, ACRS 12 2 ROBERT L. SEALE, Member, ACRS 23 MARIO V. BONACA, Member, ACRS 24 25 O ANN RILEY & ASSOCIATES, LTD.
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2 1 PROCEEDINGS 2
(8:30 a.m.]
3 DR. KRESS: Can we come to order, please.
4~ This is.a meeting of the ACRS Subcommittee on 5 -Severe AccidentLManagement. I am Thomas Kress,-Chairman of 6 the subcommittee.
7 The ACRS members'in attendance are Bob Seale, j 8 Mario Fontana, and Mario Bonaca.
9 The purpose of this meeting is for the
.10 subcommittee to discuss the' Westinghouse Owners Group 11 proposed revisions to the core damage assessment guidelines 12 and post-accident sampling system requirements for 13 Westinghouse Electric Company-nuclear power plants. The 14 . subcommittee will gather information, analyze relevant 15 issues'and facts and formulate proposed positions and 16 actions, as appropriate, for deliberation by the full 17 committee.
18 Paul Boehnert is the Cognizant ACRS Staff Engineer
.19 for this meeting.
t 20 Portions of this meeting may be closed to the 21 public to discuss Westinghouse Electric Company proprietary 22 information.
23 The rules-for participation in today's meeting 24 have-been announced as a part of the notice of this meeting 25 previously published in the Federal Register on April 2nd, ANN RILEY & ASSOCIATES, LTD.
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rm 2
(a) A transcript of the meeting is being kept, so it 3 is requested that the speakers please identify 4 themselves --tell the microphone who you are and who you are 5 with -- and then speak with sufficient clarity so people can 6 here you and basically that means use a microphone.
7 We have received no written comments or requests 8 for time to make oral statements from members of the public.
9 The comments I have on this meeting, before we 10 start, is for benefit of the subcommittee members, this 11 guidance on the core damage assessment was developed as a 12 TMI requirement and it's purpose was primarily to make 13 decisions on emergency response actions, but it is also 14 useful for recovery actions in case there is an accident. l O
N ,/ 15 The core damage assessment part of this was based 16 primarily on grab samples from the RCS and the containment 17 and these grab samples then would be taken to the laboratory 18 for analysis, and the problem with that you can readily 19 envision is the timeliness for making decisions on emergency 20 response.
21 The Westinghouse Owners Group has proposed some 22 revisions to the core damage assessment guidelines and the 23 post-accident sampling system and I think. Wolf Creek is the 24' lead plant for this, so today we want to develop our 25 subcommittee information for presentation to the full
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4 1 committee and we do expect to have a letter on this. I (vI :2l . guess that's in the May meeting we'll do that.
3- MR. BOEHNERT: Yes, it is.
4 DR. KRESS: So, with that, I guess the first j i
5 people on the Agenda are the Westinghouse Owners Group.
6 I'll call on Mr. Liberatori -- did I pronounce that right?- l l
7 MR. LIBERATORI: Pretty good. j i
8 MR- BOEHNERT:
. Did the slides get here, Lou?' )
9 MR. LIBERATORI: I have my slides.
10 MR. BOERNERT: No, we're looking for copies for 11' us yes, handouts.
1 12 MR, BRYAN: They are coming.
13 MR. BOEHNERT: Okay.
14 MR. BARTON: .Here they are. .
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( ,p 15 MR. LIBERATORI: Good morning, Mr. Chairman,
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members of the subcommittee.
l 16 My name is Louis Liberatori.
17 I am employed by Consolidated Edison Company of New York, !
18 Incorporated. I am the current Chairman of the Westinghouse 19 Owners Group and we are here today to present revisions that 20 we have been proposing to the Staff regarding how we access 1
21 core damage'and the appropriateness of post-accident 22 sampling to support that.
.23- We have structured the agenda as such. My intent 'I
-24 here is to make a few brief introductory comments and then !
25 turn it over to two of'our subcommittee chairmen who are I
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1 here today. Bob Bryan, who heads up our Analysis j f 2 ' Subcommittee will provide the technical presentation on core 3 damage assessment methodology changes, and Wayne Harrison, 4 who heads up our Licensing Subcommittee, will make the 5 presentation regarding post-accident sampling capabilities.
6 What we hope to do today is demonstrate to you two 7 basic outcomes of our work here. One is to show that the.
1 proposals we have made are properly focased on protecting 8
9 the health.and safety of the public and also that the 10 proposed changes fulfill post-accident needs based on our 11 current knowledge as to severe accident behavior, which as 12 you know has changed significantly in the 20 years since the 13 Three Mile Island accident.
14 For background purposes, the intended use of core A
(,j/ 15 _ damage assessment and post-accident sampling, as you 16 mentioned, was to support decision-making in a number of 17 areas in terms of emergency action level declarations, 1
18 offsite dose projections, protective action recommendations 19 or PARS, and also assuring that the plant has been placed in 20 a stable condition for the long term following an accident.
21 The underpinnings for these requirements in two 22 basic places. There are rules in place -- 50.47 and 23 GBC-64 -- that establish requirements for emergency planning 24 and capability for monitoring, and there are guidance 25 documents in' place, namely NUREG-0737 or Reg Guide 1.97, ANN RILEY & ASSOCIATES, LTD.
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1 which provide a lot of.the prescriptive type of requirements
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k 2 that utilities have had to comply with as a result of 3 . post-TMI actions.
4 I should note at this point that based on our 5 proposal we don't see any need for rulemaking or exemptions 6 with respect to the exicting regulations. However, what we 7 are proposing does change some of the prescriptive 8 requirements that are contained in the guidance documents on 9 this slide.
10' What our proposed changes to the core damage 11 assessment and PASS do is basically revise it to what our 12 . current understanding of severe accidents is. We have had a 13 tremendous amount of analytical and experimental research 14 work done. Much of what the industry is doing today has O)
(, 15 evolved with that. We have made changes to the emergency 16 operating procedures in terms of diagnostics. We now have 17 the severe accident management guidelines or the SAMGs. We 18 are moving forward on source term changes based on what we 19 think the fission product behavior is today -- and all these 20 things have moved forward, but the core damage assessment 21 and the post-accident sampling requirements have basically 22 stayed stagnant for the last 20 years, so we are at a point 23 where they were out of synch with where we have moved on
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24 virtually everything else on how we operate our plants. !
25 So the Westinghouse Owners Group took it on itself l
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- 1. to initiate an effort to propose changes to these which I\ 2- would bring it up to date basically with virtually G
'3- 'everything else.
4 One of the problems was effectiveness and 5 timeliness. As was mentioned earlier, from a practical 6- _ point of view in emergency preparedness exercises the timing 7 of the samples,'the accuracy of the samples and where they 8 came into play in terms of performing the exercise but 9 really weren't timely and weren't being used as part of the 10 emergency action level declarations or protective action 11 requirements.
12 We basically got there through many of the other 13 diagnostics and plant conditions before the sampling results 14 were ever available to us, so the procedures and equipment f"%
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15 are there because we are required to have them, but from a 16 practical point of view where everything else has moved they 17 are really not using that data anymore in a real-time 18 fashion.
19 Another objective was to be cost effective. A lot 20 of these systems are aging. They are 20 years old or so.
21 Many utilities are expending a considerable amount of 22 maintenance resources to keep these things running. A 23' number of plants have Y2K compliance problems with the 24 equipment in place and they are really faced with a decision
'25 ffor expending significant resources to replace these and
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1 when we looked at where we had gone in severe accident 4
2 knowledge we feel that we are spending money on systems for
.3 which there really isn't a corequisite safety benefit.
4 So we factored all of that into what we thought 5 the core damage assessment should be given today's knowledge 6 and primarily, as we go through our technical presentation, 7' you will see that it is based on fixed plant instrumentation 8 and' procedures and diagnostics, not really reliant on the 9 need to take samples and analyze them in order to support 10_ emergency accident decision-making, so really the bottom 11 bullet summarizes where we think we are, i
12 What we propose we believe better supports 13; accident management needs in a real-time basis, at the same 14 time providing-better protection of the health and safety to j 15- the.public.
16 We have been actively engaged with the NRC on our 17 two topical submittals, We have had a number of meetings 18 and we are responding to inquiries. There are still a few 19 items that we need to come to closure on with the Staff but iMF our expectation is we will come to closure on those and we 21 expect an SER some time in the near future.
22 DR, KRESS: Will we hear about those today?
23 MR. PALLA: Yes.
24 MR. LIBERATORI: So if there are no overview type 25 questions, I would propose we move to our first technical ANN RILEY & ASSOCIATES, LTD.
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1 ' presentation, which will be on the core damage assessment t
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j .2 methodology. l 3 MR. BOEHNERT: Bob, I don't think that thing is 1
4 turned on. Would you check and see? Should be a little red 5 : light on there.
6 MR. BRYAN: Sure will. l l
7 MR. BOEHNERT: There you go.
-8 MR. BRYAN: Good morning. My name is Bob Bryan 9 and I am the WOG Analysis Subcommittee Chairman, and I will 10 be talking about our core damage assessment methodology.
11' Justuas a matter of brief overview, what the core 12 damage assessment methodology is is a way for utilities when 13 we are in an event that has caused activation of our 14 emergency center to provide a quantitative assessment of r
3s ,) 15- where we think the state of the plant and the state.of the 16 < core is. It is very broadly looked at, and we basically 17 : focus on three fuel states, and that is where our clad is 18 intact so we have the principal fission product barrier 19 intact; we have a rupture where we have a release of noble 20 ' gases and some of the volatiles; and then at the point when 21- we get into significant fuel overheating where we will 22 essentially have a release of the remaining volatiles and 23 the nonvolatiles.
24 It is used as an aid in understanding where we are
-25 in an accident, where we are likely to go in an accident,
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10 1 and help us make projections in terms of emergency planning
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(v) 2 both in terms of system and offsite and where we may want to 3 go.
4 Up-front there was a question as I understood it '
5 about what is the risk impact of this. In terms of PRAs, it 6 is risk-neutral. It is not specifically modelled in our 7 PRAs. I think in terms of overall protection of the public !
8 you could say as we have a better understanding of what we 9 believe is going on and the phenomena, it provides a little 10 higher level of protection to have a more accurate 11 reflection of the plant.
12 DR. KRESS: Let me ask you a little more about 13 that statement, i 14 PRAs do mode) emergency response, of course, and O( ,j 15 the input into that emergency response is when do you start j 16 an action, a time on it, would this not -- it seems to me I 17 like what you are saying is you have already -- would base i 1
18 the decision on the information you have and that what you l 19 are asking to change doesn't change that decision any, so it 1
20 wouldn't have any impact on risk, is that -- l 21 MR. BRYAN: Not appracichle impact. In terms of 22 the way we do the operator actions and things like that, we 23 look at the steps in our emergency procedures, our abnormal 24 procedures. This is sort of an off-line process. It is not 25 one carried out specifically by the operators. It is a feed (9
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11 1 of information into our technical support centers so that 2 they can make recommendations to the operators to keep them 3 looking ahead so I think it enhances the process but in 4 terms of being something that is at a letter that it would 5 be modelled in any PRA, it isn't at this point.
6 DR. KRESS: You wouldn't base your judgment on 7 when to start the emergency response in a PRA --
8 MR. BRYAN: Oh, no.
9 DR. KRESS: -- based on this.
10 MR. BRYAN: No, sir.
11 DR. KRESS: Okay.
12 MR. BRYAN: As was mentioned before, basically the 13 existing core damage assessment was our first brush after 14 TMI. It was based on taking samples fairly early in the l, ,, 15 accident and it was set up to comply oxplicitly with the law 16 plus the recommendations in 0737 and Reg Guide 1.97.
l 17 We have done, as Lou mentioned, a lot of work,
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18 both the utilities and the NRC, in terms of understanding 19 progressions of accidents, our PRAs, and the tools that go i
20 with them have advanced considerably, and so we have updated 21- the methodology to reflect those new understandings, and we 22 will talk about these in a little more detail later in the l 1
23 presentation. ,
l 24 But to focus on the specifics, we looked at how 25 and when fission products are released from the core, how
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1 they are held up, where they.might be, and mechanisms for i I'T 2 ' removal from the containment atmosphere to help us
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3 understand and improve the accuracy of our projections.
4 We think the proposal-that we are doing supports f 5 our decision-making in terms of emergency action levels, 6 'which are unusual event, alert, site -- site emergency, and 7 general emergency, in making offsite dose projections as we 8 feed information to that, and then into our protective 9 action recommendations -
i.e., when we tell people to 10 shelter or evacuate.
11 DR. KRESS: Before you leave that slide, those 12 first three sub-bullets --
'13 MR. BRYAN: Yes, sir.
14 DR. KRESS: You are basing the quantification of O
s 15 the new knowledge on the MAAP code, I understand?
s_ f -
16 MR. BRYAN: Yes. I mean we have used MAAP to do 17 sensitivity studies of the releases and fission product 18 tracking, yes.
l 19 DR. KRESS: And basically then you would -- well, 20 I don't want to jump ahead but you take your signals, which l
21 ' consist of things like core thermocouples and core power and ;
l 22 stuff, and use the MAAP code, in a sense pre-use it, to say j 23 this means fuel has failed or not failed and --
24 MR. BRYAN: That is correct. What we have done is l
25 basically in the methodology we have set up a template that l
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_ i
e 13 1 Innus you, takes you -- it says, okay, here is a set of f)
.%)
2 instruments; if these are your responses, here are potential l 3 paths, here's other instruments, and you go through the same 4 gates, you get comparisons, and based on that you will make l 5 a projection of where you are and assign some degree of 6 confidence to what the answer is.
7 I thought it might be beneficial to just run you I 8 through how we do emergency planning right now, and the list 9 that I have up here reflects our current procedures. These 1
10 would be modified slightly if the WCAPs are approved, but 11 basically when you get -- there are many ways to get into 12 your emergency procedure, but as you progress through the 13 emergency action levels and you get up to the site emergency 14 and the general emergency level, basically you come back to
.p 15
( ,J . what's the status of your prime fission product barriers.
16 And so you go to the matrix there, and you're concerned 17 about the 1.)ss or potentia't loss of those, j 18 As an adjunct, you look at your plant radiation 19 levels, both in plant and on the site, and you can determine l
20 these things from your system conditions, you know, what 21 systems may be operating or not. You've got entries into 22 this from your emergency procedures that help you judge the 23 status of your systems. You have plant instrumentation, 24 thermocouples, hydrogen monitors, radiation monitors.
25 Currently we have a thing, if you have an RCS (O
s_) '
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I 14 j 1 liquid sample, if you're above a certain level, that's an l j
f'\
( ) 2 on-off switch for severe core damage. And then of course !
3 the emergency director can say I want to move to this level 4 at this point based on my judgment.
5 DR. KRESS: Your abnormal plant radiation 6 measurements --
7 MR. BRYAN: Yes, sir.
8 DR. KRESS: Are those primarily in the ;
i 9 containment? j 10 MR. BRYAN: The ones that we're using in this 11 methodology are high -- yes, are the in-containment i i
12 high-radiation monitors that were put in specifically for 13 postaccident monitoring over the range from release of 14 normal coolant activity up to, you know, basically complete
() 15 release of the core. And they'll be, at least -- I won't 16 speak for everybody, but in our plant I think in most ;
3 17 they're redundant safety-grade monitors. !
18 DR. KRESS: Are your hydrogen measurements 4
19 continuous measurement based on -- !
20 MR. BRYAN: Yes, they are.
21 DR. KRESS: They're not grab samples?
22 MR. BRYAN: No.
23 DR. KRESS: Okay. ;
24 MR. BRYAN: In making offsite dose projections, 25 which is one of the feeds into determining your protective A ANN RILEY & ASSOCIATES, LTD.
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u 15 1 . action levels, we have'a hierarchy, and this is'a typical
() 2 3
.one. We of course would base it on real-time releases.
_These~are thingsLthat our health physics people would 14 '
l measure off of the; field measurements that our field 5 monitoring teams are taking at the site boundary or off in 6 the environment around the plant. They can be projected 7 from the core damage assessment, at least for our utility
-8 and I think for a' number of others.
9 We have feeds between our core damage assessment
[2 0: team'and our dose assessment team that they. feed information 11 back and forth to make projections on what may be happening 12 ~ and this helps you with your'look ahead, and if all else i'
- 13 fails, you can revert back to the kinds of dosage that you 141 . expected to'see' based on your FSAR. accident analysis.
D V 15 DR. KRESS: If you knew which one of the accidents 16' you were in.
.17 MR. BRYAN: That's right.
18 Protection action recommendations, one thing to 19 understand is once you declare a general emergency, that by 20 definition requires entry into a protective action level.
'21 You have gotten to- a general emergency through one of these 122 three. processes,.at any rate, you've either lost your 23 fission product barriers or you're measuring something that 24 gives you reason to believe that you have a release in 25 progress or it is soon to come. So you enter that
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w 16 I
l' immediately.
J
.2 You then progress based on how the plant is going I 3- .and what you're measuring, either -- or projecting into ,
I
- 4' higher and higher levels of. protective action. But, you
]
know, the core damage assessment helps you feed your
~
5
{
6 projections, but these_.are done largely independently of the
'7 core' damage assessment methodology.
8 As we went to upgrade our' methodology, one of the 9- things'.that we wanted to do was to make sure that what we 10 did would be~ timely, get the information to the people that 11 needed it in~a time frame-that it would do them some good, 12 and as you've' pointed out, samples don't do that. In-plant !
13 instrumentation fills the bill much better, particularly j
~
14 when conditions are changing in the plant _ fairly rapidly.
- 15. You'd have to take a lot of samples if you had much of a 16 Ltransient going on to stay current. You can do that much
-17 better with the in-plant instrumentation.
18 We believe it should be accurate. When you get 19 into scenarios like this, you have to recognize that there 20' are fairly wide error bands whether you do it by samples or 21 by' instrumentation. Each one has liabilities on it. The 22- advantage of course of the in-plant instrumentation is you 23 have availability of on-time data that you can 24 cross-correlate to help you do that, and the other thing is
=~25 we feel the information is good enough to give us the
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i 17 1 accuracy we need.to.make the kinds of decisions we want to j ) 2 'make. You don't have to know precisely how much fuel damage ;
'3' you have or how much of the core is melted to make 4 reasonable decisions. You just need to know you've crossed 5 thresholds.
6 The last thing is availability of the information,
- 7. and in-this I think we're looking-at two things. As you go l
8 through plant states, we feel like the in-plant 9 instrumentation is as likely or more likely to be available 10 for a wider. range of scenarios than we would for in-plant 11 sampling. Most of the instrumentation _is DC backed. While l 1
12 you may be able to pull a sample using DC valves, you need l 13 AC sources-to analyze a sample or you have to ship it 14' offsite, which delays its availability.
(/ 15 'Probably more importantly is the impact on your 16 manpower. You have to send people out into a very bad 17- environment potentially to take these_ samples, and that's 18 not'a good thing to do. And in most of our current j 19_ processes, we have the capability to sample, b' ut it's sort 20 of the mechanism of last resort. If we have other 21- information available, we far prefer to do that than send 22 - people out into a high-radiation environment.
-23 DR. KRESS: I think that's a key item there. If I 24'
- .were to say -- if someone wanted to ask you a question why 25' Enot use both your in-plant instrumentation and the sampling, l
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18 1 I think that's your answer there. l
[~ 2 MR. BRYAN: Absolutely, s
l' 3 DR. KRESS: You'd just as soon not, because in the i
4 first place, it's not very useful to you, and in the second 1 5 place, it's a waste of manpower and dose --
6 MR. BRYAN: And those people are far better to be i 7 used in recovery actions that may be critical than having 8 them absorb dose taking a sample for you.
1 9 DR. KRESS: One of my questions when I first 10 started reading this is why not use both, you know, even 11 though it's not very useful to you, it's more information, 12 and I think that's the answer.
13 MR. BRYAN: Yes, absolutely, i 14 I'll tell a little bit of the specifics. In terms (n) 15 of assessing the core damage, we have three main instruments 16 that we're using. This is the core exit thermocouples --
1 17 DR. KRESS: Let me ask you about those. Are those !
18 in the coolant stream, or are they attached to the fuel 19 element? )
20 MR. BRYAN: They're in the coolant stream.
21 They're above the top of the core, and I'll talk about them 22 in a little more detail, but there are about 50 of them i
23 located around the -- covering the top of the core. l 24 We have our high-radiation monitors that help us 25 know when we've lost fuel cladding, and if we have a hole in l
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19 1 1 the RCS, have containment hydrogen, and these are the three
() 2 3
that we use in the methodology to quantify where we are.
.have potentially additional instrumentation, reactor vessel We 4 level, _the neutron monitors and the hot-leg RTDs that we can 5 use to help validate our numerical estimates. I
)
6 DR. KRESS: Do you also have cold-leg RTDs? l 7 MR.-BRYAN: Yes.
8 DR. KRESS: And flow measurement?
4 9 ~MR. BRYAN: Yes, although for most of these we 10 don't'think we're going to be having much flow. If we have ;
11 much flow we probably. don't have much problem.
12 DR. KRESS: That sure would be a leading 13 indicator, though. j i
14 MR. BRYAN: Yes. J
( 15 Our core exit thermocouples have a useful range of 16 about 2,000 degrees. As we note, the core exit 17- thermocouples are not going to be -- directly read clad 18 temperature. They lag by some amount, depending of course 19 on how much steam flow's coming out of the core at the time.
20- But basically _we've set these switches in the thing.
21 If we have no core -- we'll assume no core damage 22 if the core exit thermocouples are reading below 750 23 degrees. If we're between the range of 1,200 degrees for 24- large breaks'and 1,400 degrees for small breaks, and 2,000 25- degrees, we're in a situation where we think the cladding O
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m 20 1 has ruptured, and so we've released the noble gases and a I 2 G) lot of the volatile fission products to the RCS.
3 DR. KRESS: The difference between those 4 temperatures is the pressure of the RCS system?
5 MR. BRYAN: Yes. At the higher pressures, the 6 clad's not going to rupture quite as early, and that's the 7 basis for the dual criteria.
8 DR. KRESS: And these values like core exit j 9 thermocouple is at 750 based on MAAP calculations of when 10 some fraction of the core is actually at -- is all below the i 11 point at which you expect clad damage.
12 MR. BRYAN: Well, I think these -- I think these 13 temperatures are more taken from not so much MAAP 14 calculations as our knowledge of more of our regular fuel
() 15 evaluations. We know that if the clad's below 1,000 16 degrees, we're not likely to have any clad failures. I l
17 DR. KRESS: Wall, what I was trying to get to here 18 was, you know, if those are actually core exit 19 thermocouples. I don't know. Do you have a lot of flow or 20 have you lost flow, and are these based on some calculations 21 of full flow heat transfer coefficents, or are they based on
- 22. accident conditions where you actually went through a set of 23 scenarios where your flow is reduced? You may even have the 24 steam and hydrogen there. And that was --
'25 MR. BRYAN: We have looked at a wide range of 4
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l l
21 l i
l' scenarios, both large and small LOCA and transient events 1 I
l h
( )
2 that -- for non-LOCA events. And so these are consistent 3 with those results. Yes. {
4 And then if the core exit thermocouples are 5 reading 2,000 degrees or greater than 2,000 degrees, we're 6 pretty confident we're having a fair amount of fuel damage.
7 DR. KRESS: That's a pretty good sign there.
8 MR. BRYAN: Yes.
9 The methodology tries to make accounts for 10 understanding of where as we get readings from our 11 high-radiation monitors try to account for where the fission 12 products might be in the system, and so there's switches f 13 based on whether you have indications you have a large hole 14 in the RCS, whether you have a small hole in the RCS, i n
() 15 whether you have a transient ongoing, and so it helps walk 16 you through what the readings you're getting might mean in 17 - terms of what we believe we understand the processes to be 18 today. And so the-methodology accounts for the amount 19 released, what we have retained, and also in terms of 20 washout of the containment atmosphere by the spray system.
21 So we've tried to take that into account.
22 DR. KRESS: I presume these are gamma monitors.
23 MR. BRYAN: Yes.
24 DR. KRESS: The amount released and the amount
- 2 5. 'obtained in the RCS are of course sequence-dependent. It h'
%/
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C>
e 22
, 1, ' depends on what kind of accident you're in. So-you base
([~T -2. 'your-judgment about what that is based on.other things like d
3 core pressure and-'-- >
4 MR. BRYAN: ' Absolutely.
-5" 'D:R. KRESS: Level and things like that.
6 MR. BRYAN: Yes, sir.
7 DR. KRESS: 'And you decide'at least the basic kind 8 of accident you're in.
9 MR. BRYAN: That's correct. You do.
10 DR. KRESS: And then you can make those judgments.
11 MR. BRYAN: That's right.
l12 And, you know, when~you get into sort of I 13 independent of'this, and I'll speak again_for our utility, 14 the people that we have doing our core damage assessment are
() 15
~
our fuels people,-so we have very detailed information on 16 what the actual.burnup in the. core is and things like that, 17 and what the actual decay heats would be, to help aid in 18 this process. So, you know, this isn't done just in a 19 vacuum in terms of what has really gone on in terms of the 20' history of the plant to that point.
21 DR. KRESS: It almost implies sort of an online 22; calculation as you're --
'23 MR. BRYAN: ~That's the way we do it; yes, sir.
24 DR. KRESS: Okay.
25 MR. BRYAN: We also take into account that -- and ANN RILEY & ASSOCIATES, LTD.
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23 1 note to people that there are events that may be giving you
() 2 releases.outside containment and to give more credit back to 3 core exit thermocouples or other indication to help you in l 4 your event diagndsis and where the core may be.
5 DR. KRESS: Are there radiation monitors near 6 those steam generators?
7 MR. BRYAN: No, not necessarily. In terms of 8 ours,.I have an ice condenser plant, and so we have a fair 9 amount of concrete shielding from the high-radiation !
10 monitors we have in our upper compartment, we have another 11, set in the lower compartment, and so they see RCS, but we 12 have other monitors that are -- for instance, for steam line 13 events we have monitors on the steam line that aid with 14 diagnostic of tube ruptures. l
() 15 DR. KRESS: Is your plant Sequoyah?
16 MR. BRYAN: Yes, Sequoyah and Watts Bar.
17 DR. KRESS: I presume these guidelines we're l 18 developing and proposing are for all the Westinghouse 19- plants.
20 MR. BRYAN: That's correct. They do make some 21 notice -- for instance, we'll get into hydrogen in just a l
22 minute. There are some special' guidelines for the ice
'23 condenser, since we tend to --
24 DR. KRESS: You anticipated where I was going. l 25 MR. BRYAN: Yes.
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n 24 I
1 Similarly, hydrogen levels can give you'an l #'T 2 indication of how much fuel damage you have due to clad l
\~).
L3 oxidation. The methodology looks at the amount of hydrogen n
4- that's likely to be generated for large events that -- where 5 you boil the core off rapidly. You'll probably have less 6 hydrogen generated than you would for events that are 7- smaller where boildown takes longer. We look at hydrogen q 8 'that may be retained in the RCS, and we also try to account 9 for hydrogen that may be generated as you add water back 10 into an overheated core.
11 So -- and specifically the methodology notes for 12 the ice condensers that your hydrogen level may get up to a 13 certain level, and then I think based on what we've done l'4 probably in about the 5-percent range, and it would hold p)
( 15 . pretty constant, because the igniters are going to tend to 16 burn it off as it's produced. So you wouldn't see'the same 17 kind of rise that you might in a dry containment.
18 DR. KRESS: Do you have thermocouples inside your 19 containment vessel?
20 MR. BRYAN: We do. They are not safety grade and 21 they're not part of the safety-related instrumentation, but 22 yes, we have I-think it's about 24 or 28 thermocouples that 23 are located all around the containment that we use for 24 normal containment temperature monitoring.
25 ' Sort of in summary, basically our primary i
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r 25 1 assessments are made based on the core exit thermocouples
(~')s 2 and what we see in containment radiation monitors. You can G
3- use containment hydrogen to help validate this and provide 4 further quantification when you get into significant fuel 5 overheating, and then as we mentioned before, there were 6 some other instrumentation that help you understand the 7 progression of the accident such as vessel level and also 8 quantifying these. And we believe that what 've done is 9 consistent with what the state of knowledge today is.
10 In conclusion, we believe that the proposed 11 methodology is more accurate and more timely than the 12 existing methodology and that we recognize that there are 13 pretty significant arror bands on this, but this is true 14 both for the sampling system too, but within the bounds of (Oj 15 the kinds of decisions that you're trying to make here, and 16 the large stakes, that you don't need to be tremendously 17 accurate in that.
18 We believe, as I said, this is consistent with the 19 way that we do our emergency planning, and we try to be 20 conservative in terms of making recommendations. Most 21 importantly, we believe that the effectiveness of our 22 emergency planning is enhanced by doing this. Our )
i 23 information is more timely, better allocation of our 24 resources in tenns of dealing with an accident to use the )
25 in-plant instrumentation as opposed to a sampling system.
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l 26 l
l 1 DR. FONTANA: You said you do the assessment on {
()
e'-
l 2 line. Is that an algorithm that you plug into or some kind 3 of a chart, certain regions here in certain areas, or how do l 4 you do that? I 5 MR. BRYAN: Well, right now what we have is we 6 have a computer code set up that we can plug data into, and 7 then it'll crank out an assessment for us. We also have i
8 flow charts out there if the computer wasn't available or 9 something like that so that we can hand work through the 10 flow chart. We have basically a procedure that we can set 11 up that we work through for doing core damage assessment.
12 DR. FONTANA: Presumably the results that you get 13 by this -- I presume it's a simplified compared to a MAAP --
M MR. BRYAN: Oh, yes. Absolutely.
(~
( ,\) 15 DR. FONTANA: Or something like that. But you 16 take -- when you tested this you I take it compared against 17 the more detailed calculation to see if it's in the same 18 ballpark.
19 MR. BRYAN: Basically what we've done is we've 20 done sets of MAAP calculations of a wide range of scenarios 21 both to help -- one is to help us set up our drills to make 22 sure thac they have some element of realism in them in terms 23 of how thing progress, and also we can use that to backcheck 24 against the core methodology that we're using, and we've 25 done that.
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l l
27 1 DR. FONTANA: Yes. It looks pretty good.
-~T 2 MR. BRYAN: Within the bounds that we -- within l
(O 3 the range we need for this --
4 DR. FONTANA: Yes. Okay.
5 DR. BONACA: Could you go back to slide No. 14 and 6 just for the purpose of comparison, could you tell me -- no, 7 14 -- '
8 MR. BRYAN: Oh, I'm sorry. j 9 DR. BONACA: Yes. I was just curious to see, 10 currently, before this proposed change, where does PASS come 11 in in some of the determinations? I'm trying to understand, 12 you know, where -- what measured functions that you perform 13 today with PASS are going to be replaced directly with -- j 14 MR. BRYAN: Okay. What the methodology had in it i
(m,) 15 was, you would take an RCS sample to give you -- or a 16 containment sump sample or a containment atmospheric sample 17 and you would look at what, for instance, the radionuclide 18 compositions were, and then you could base -- based on what 19 the activities were you could make an assessment of what 20 kind of fuel failures you had. Also, you might have, you 21 know, a gas chromatograph or something like that so you 22 could look at a wider range of fission products that were 23 out there.
24 And so from those things you could make 25 assessments of what had actually been released. And so lT
(, /
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28 l 1 those would help you make determinations of what state the e~s
(
\_-)
2 fuel was in. And so that's the way the methodology was set I l
3 up in terms of -- and I'll speak once again just for our 4 utility, while our core damage assessment methodology, when 5 you go in the procedure, had that information in there, and i
6 so if you had that information available, you had a l 7 mechanism for evaluating it, it was certainly not our !
8 preferred method of doing it. We had other things already ;
1 9 built in -- already built into our standards that looked at I 10 the instrumentation. Those are our preferable sources.
11 Now, you know, what we'll da with this is we'll go 12 back and look at the way we have our setup and make sure 13 it's reflective of what's in this latest WCAP.
14 DR. KRESS: Where were your sample lines located I
/~T i
v) 15 for the RCS? i 16 MR. BRYAN: Well, we had a PASS facility that's i
17 located in our auxiliary building. It's reasonably close to 18 the containment, but it was down by our railroad bay so that 19 that was basically to facilitate getting the heavily 20 shielded casks out of the building.
I 21 DR. KRESS: Yes, that was part of my question. !
22 The other part was where do you actually tap into the RCS.
23 MR. BRYAN: I don't know where the actual sample I 24 points on the RCS were.
25 DR. KRESS: Now, this is my other question, are !
I i
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l 1 there more than one sample point, and where were they, l
O* 2 and --
lD l 3 MR. BRYAN: I'm sorry, I don't know the answer to 1
4 that.
- 5. DR. KRESS: Same thing with the containment in 6 atmosphere. .I know you sample out of the sump, but do you 7 also sample --
8 MR- BRYAN:
We have -- on the containment sample 9 we had a couple of -- we had at least two, one for the upper 10 compartment, one for the lower compartment. But I don't 11 believe we had more than two. But I don't --
12- DR. KRESS: So even with those, there's questions 13 of representativeness of the samples you have?
14 MR. BRYAN: Certainly. And when you go into the
() 15 methodologies, there are -- there were error bands assigned 16 to the samples to try to account for representativeness, 17 potential for plateout in the lines, things like that.
18 DR. KRESS: Lines are -- the distance to the 19 sample station is pretty long, so you actually have a pretty 20 long sample line?
21 MR. BRYAN: Yes, sir.
22 DR. KRESS: Anybody ever look at the potential for 23 plugging those up with aerosols and stuff like that?
24 MR. BRYAN: Well --
25 -DR. KRESS: Aerosols will plug up lines.
L
[3 N_)
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l ..
30 1 'MR.. BRYAN: Yes, they.will.
[v] 2 3
DR. KRESS: Do you know what size those sample lines are at all?
l 4 .MR. BRYAN: Go ahead, Bob.
5 MR. 'LUTZ: This is Bob Lutz from Westinghouse. We 6 did look at that, and outside of the times where you have 7 core concrete interaction going on where you have a lot of 8 very, very dense aerosols, in those times yes, there is a 9 very definite potential for plugging those lines. j 10 DR. KRESS: But by then you already 11 know everything you need to know.
1
.12 MR. LUTZ: For other times -- excuse me?
13 DR. KRESS: But, you know, there is a real 14 uncertainty into how much actual solid aerosols you're
( 15 getting. You're in the early part of the accident, too.
16 MR. LUTZ: Yes. We looked at that, and we don't j
- 17. think that there's sufficient aerosol material at times 18 without core concrete interaction to actually plug those 19 lines. We've looked at the total amount.of aerosol and the l 20 lengths of the lines, l
21 DR. .KRESS: What will you do with those lines and 22 that system if this change is made? Will they still be
- 23 - there?
24 MR. LUTZ: Yes, sir.
25 DR. KRESS: Available in case you need them type ANN RILEY'& ASSOCIATES, LTD.
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1 31 j 1 things --
() 2 MR. LUTZ: Yes, and I think you'll hear some of
~3 this in Wayne's presentation, but more than likely, we're 4 certainly not going to take them out, and they would 5 probably be our preferable source for taking samples -- {
6 because it's a shielded facility and we have both the 7 shielding for our flasks and we have dilution available 8 there.
9 DR. KRESS: I was thinking in terms of potential 10 need for recovery action.
11 MR. BRYAN: Yes. ..nd I believe Wayne Harrison '
12 will talk about that.
13 Last point, to the best of our understanding at 14 .this point we have no open issues with the staff on our I) 15 methodology. If it's acceptable to the subcommittee, I 16 believe the NRC would like to talk about the core damage 17 assessment methodology at 1.his point, and then --
18 DR..KRESS: Let's see. Yes, I think'that would be 19 appropriate right now. So we'll turn it over to you, Bob.
1 20 MR. BRYAN: Thank you very much.
-21 DR. KRESS: Thank you. You live in Tennessee?
l 22 MR. BRYAN: Yes, sir; I do.
23 DR. KRESS: Where's your orange T-shirt?
24 MR. BRYAN: Oh, it's underneath here.
25 .[ Laughter.]
i
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32
'l Also my underwear -- but I hate to show that.
2 [ Laughter.)
3 MR. PALLA: Good morning. My name is Bob Palla 4 and I am with the Probabilistic Safety Assessment Branch in 5 NRR. I am going to speak about the Staff's review of the 6 core damage assessment methodology 7 I will.try to be brief. I think you have got a 1
'8 pretty good background about how decisions are made at 9 plants and in fact they are made largely without the t 10 information from the post-accident sampling system, but thin 11 methodology that we have before us could improve the 12 decision-making process by making the available 13 information -- making it available sooner.
l 14 A little bit of background about the regulatory
() 13 basis for the core damage assessment methodology. Licensees 16- were essentially required to provide a core damage. j 17 assessment procedure to support the use of the PASS system.
18 In essence, if you have a. system to take samples you have to-19 in some way convert that into a core damage assessment and 20 the. methodology was thought to be a piece of the TMI l
21 requirement, TMI Item 2.B.3, Criterion 2, which on the face 22 of it doesn't look like you are requiring a methodology or a 23 procedure be developed, but that in fact is the way it was 24 interpreted and this was made a licensing condition on a 25 'numberLof plants in-the early '80s -- the fact that they-did C\
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l 33 1 not have a procedure for converting the PASS readings into
. /*
( 2 some estimates of core damage.
3 DR. KRESS: This was based on a proposal by NUMARC 4 at that time, the procedure?
5 MR. PALLA: Which -- what do you mean?
6 DR. KRESS: The actual PASS system and the core 7- damage assessment guidelines were --
8 MR. PALLA: Back in the early '80s?
9 DR. KRESS: In the early '80s? I thought I 10 understood that to be the case but wasn't sure.
11 MR. PALLA: Well, the actual -- I am unclear on 12 whether -- well, there wasn't any NUMARC but I am not clear 13 on the evolution of the system requirements.
3 14 DR. KRESS: It doesn't matter. It was just I
) 15 thought this was developed'by industry in the first place 16 and based on the knowledge they had back then, and now they 17 are --
18 MR. PALLA: The existing methodology very much so, 19 and I will speak in a few moments about the methodology that 20 is currently in place and when it was developed and 21 approved.
22 With regard to -- so we required that a procedure 23 be developed but in fact if y.; say what does it need to do, 24 where is the regulatory guidance on what the procedure needs 25 to do, the only real source of any guidance on the core
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l I
l 34 !
1 damage assessment procedure was found in a document prepared ;
(n)
~/
2 by the Staff in the early 1980s, and this document was l
3 distributed to licensees as part of our review of their PASS 1
4 systems.
j 5 Apparently, in going back through the record it l
6 looked like it was a trial and error process, trying to l 1
7 arrive at a procedure that the Staff thought accomplished i
8 what we thought needed to be done in interpreting the PASS j 9 results.
10 That post-accident sampling guide discusses I
11 various factors that should be considered when estimating j 12 core damage. For example, you would look for certain types 13 of fission products being available as well as looking to 14 see that certain fission products are not available in order
() 15 to ascertain the extent of core damage. You would expect, 16 if the damage was limited you would see the more volatile 17 species but you wouldn't see less volatile species that 18 might be associated with core-concrete interactions, for 19 example.
20 The guideline provides some discussion about some 21 categories of fuel damage and it tried to actually -- it had 22 four major criteria or categories -- no damage, cladding 23 damage, fuel overheating, and fuel melting -- and then it 24 tried to even further divide that into various degrees of 25 fuel damage and melting and the result was like 10 different ANN RILEY & ASSOCIATES, LTD.
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%- Court Reporters 1025 Connecticut Avenue, NW, Suite 1014 Washington, D.C. 20036 (202) 842-0034
35 1 subdivisions that we had envisioned at that time trying to 2 disposition the status of the core into.
-( )
-3 DR. KRESS: -Let me ask you something. The 4 original concept, grab samples to determine these. things, it 5 struck me as a little odd in the first place. Was this
- 6. because the focus at that time may have been on iodine and 7 you almost have to take samples to find out how much iodine 8 is around? Is that --
9 MR. PALLA: I am not certain about that. I 10 suspect it's had a strong flavor from TMI and just trying 11 to -- it would seem on the surface to be the most direct way 12 to assess something, but I am not clear at what exactly was 13 -the rationale behind it.
14 DR. KRESS: Well, the basis for that question is 1
.(3j 15 focused gamma monitors to look for cesium, for example, 16 ~ instead of iodine would be extremely simple, easy way to 17 look for a-key radioisotope and if your attention wasn't 18- focused on iodine you could focus it on cesium instead and 19 get information on-line, quick, timely, accurate -- you 20 know, that's one of the things about radioactivity. Its 21 accuracy and timeliness is really -- you know, one of the 22 problems we have with this is it's too easy to measure.
23 So my question really is focus on why was the 24 . initial choice to be a grab sample and not just a gamma 25 monitor?
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n 36 l 1-- MR. PALLA: I don't know if maybe someone -- Jim 2' O'Brien has any ideas about that.
'3- MR. LOIS: Lambros Lois, Reactor Systems Branch.
To begin with, the requirements that Bob has in quotation marks were developed from 077, which was a I 6- response to TMI and the departments became from commitments 7 of the individual-licensees to implement what the Staff i
8 asked. -There was no rule in the rulemaking a procedure, )
9 number 1.
10 Number 2, the gram sample concept developed from 11 the fact that once you have isolation the normal sampling 3 1
12 procedure is no longer available, therefore you have to have I
{
13 another system which will allow you under the severe
)
1 14 accident conditions to do the sampling, and then of course
]
() 15 all the other concepts developed -- namely, that you can 16 have^-- you'can plug those lines and so forth. l 17- 0737 also provided that these lines should be able ,
18 to be purged and so forth and so on, but eventually all 19 these' concepts and their implementation, number one, was 20 spotty, and number two, kind of fell apart.
21 Eventually what we wound up with, 10 or 15 years 22 'later, was some utilities did have something, some others
~
23 had different samples and different installations, and there 24- -was no uniform implementation of those " requirements" --
1 25 . quote / unquote, which came, as I said, from the individual l
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37 1 commitments that the individual licensees made.
() 2 3
DR. KRESS: That does make them though part of the licensing basis for the individual plants?
4 MR. LOIS: For the individual plants, that's 5 right. The requirements, the commitments that they made is 6 what became the requirement, the licensing requirement for 7 those,.but it is not uniform and it was not from end to end.
8' DR. KRESS: Thank you very much.
9 MR. PALLA: I guess another point is that sampling 10 is done for a wide range of parameters, radionuclides just 11 being one of them so you will hear more about boron and '
12 chlorides and dissolved gases, et cetera, so perhaps that is 13 thc real reason why the focus on PASS. While you are taking 14 the PASS sample you can get the radionuclide information.
(f 15 DR. KRESS: I could see, you know, if you are 16 looking.for other things like that, I could see that.
17 MR. PALLA: Okay, just real quickly, to wrap up on 18 this post-accident sampling guide, it laid out an example of 19 a process by which you might estimate core damage from 20- radionuclide information. It had-a brief discussion about 21 sample locations and where one should try-to draw samples 22 and then there was some discussion about auxiliary 23 indicators or secondary means of confirming the information 24 that you would get from the post-accident sample system.
25 With regard to the Standard Review Plan, there ANN RILEY & ASSOCIATES, LTD.
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38 1 really isn't any -- there is mention of the core damage
-(
v
)- 2 assessment procedure, but there is no guidance there.
3 DR. SEALE: Could I ask u question?
4 MR. PALLA: Yes.
5 DR. SEALE: Aren't there certain actions you would 6 like to -- want to take before you achieve isolation?
7 MR. PALLA: Containment isolation '.n general?.
8 DR. SEALE: Oh, no, before you get the system in a 9 non-circulating environment.
10 MR. PALLA: For example?
11 DR. SEALE: Well, you made the comment that one of 12 the reasons for the grab samples was that you didn't have-13 anything -- that there were certain things that were no )
14 available anymore once you achieved -- what was the
~N 15 terminology he used?
16 MR. LOIS: Isolation.
17 DR. SEALE: Isolation, I think -- but some of the
.18 numbers, some of the data you want you would like to have 19 before you get isolation. In fact, it is part of the 20 decision to isolate. Isn't that true?
21 So you are kind of foredoomed, aren't you?
22 MR. LOIS: Dr. Seale, the isolation signal will in 23- all cases that we perceive will be, will come in because of 24 conditions during the evolution of the transient, way before 25 you need that. You don't isolate becauce you are way into
(*
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39
.1 that state of the accident. -You isolate because much, much
[
'\ s l' 2 earlier than that you had the initiation of the accident 3 time-wise----time-wise earlier. i l
4' DR. SEALE: Some of the information that you would I 5: like to have you can get before you isolate.
6- DR. KRESS: Well, you certainly could use l 7 thermocouples, pressure --
1 8 DR. SEALE: Well, or the kinds of things that you 9 get because you have a-penetration of a steam generator tube 10 or something like that, and so those data are -- you are 11- never going to get those out of a sampling system because 12 the sampling system is not even available to you really i a
13 until after that has happened, so you have got a system that l 14 is kind of tied, your hands are kind of tied behind your l D 13
( ,/ back when you start.
16 DR. BONACA: I-think PASS, if I remember, I.mean
.17- really the need for PASS was tied to after the accident --
18 DR. SEALE: Yes.
- 19. DR. BONACA: -- the ability of taking a sample
'20- from the sump versus the ability of taking a sample from'the 21 RSC --
22 DR. SEALE: Yes.
23 DR. BONACA: -- comparing -- that was really the-24 need,'okay, and then what happened is that by inference it 25 was.then brought into the assessment that you have during'an 1
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40 1 ~ event, which really the PASS system is not going to help 2 you --
3 DR. SEALE: That's right. !
4 l DR '. BONACA: -- because simply, first of all, it 5 is a lagging indicator. 1 6 DR. SEALE: _Yes, exactly.
7 DR. BONACA: It doesn't do really what the intent
-8 was. I think PASS came out more from the frustration of l 9 being able to really sample independently sumps and RCS-and l 10- make comparisons and understand how -- after the accidents.
11 I mean you are talking about days and weeks after the' 12 accident.
{
l
_13 DR. SEALE: Okay.
14 DR' BONACA:
. That is really where the issue came I 15'. and later on of course there was an inference that then it 16 _ will be used for monitoring actually the. emergency and for 17- it, it just wouldn' t do the' job anyway.
18 MR. PALLA: Okay. Let me just pick up here with-19 regard to the methodology that is currently in place.
20 At Westinghouse plants it is largely based on the 21' Westinghouse Owners Group post-accident core damage i
22 assessment methodology -- acronym being PACDAM.
It was 23 approved in 1984 based on a review which confirmed that it 24 met the general requirements of the TMI action item. The 25 -PACDAM methodology relies'primarily on radionuclide analysis h
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41 1 but then the results would be confirmed by auxiliary '
2 indicators such as hydrogen concentration, ccre exit 3 thermocouples, reactor vessel. level instrumentation, and 1
.4 ' containment radiation monitors, but because of the primary 5 reliance on the sample, the timeliness is compromised
.6 because essentially the core damage assessment estimate is 7 noc available until you have got that radionuclide sample-8 and analyzed it.
9 The methodology does not account for hydrogen and ;
'10 fission product holdup in the RCS as well as fission product f- 11 deposition in the RCS and deposition in the sample lines, 12 which could be substantial.
1 13 As a result, as you heard from an earlier l 14 presenter --
f% i
.d-15 DR. KRESS: Let me ask you about that comment.
f '16 .Normally you guys in the regulatory business like to make 17 the most conservative decisions when it'comes to something 18 like emergency response. It sounds to me like when you.are 19 talking about holdup and RCS of hydrogen and fission
.' 2 0 products you are trying to make an assessment of what kind 21 _of accident'you're in and project real' numbers as opposed to 22 saying, hey, this could be this bnd.if it were the worst 23 accident and we'll make our decisions based on that.
24 Is that -- am I misinterpreting that?
25 MR. PALLA: We are trying to make a best guess at ANN RILEY & ASSOCIATES, LTD.
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F1 , l i
42 j 1- what the situation is, and I think the way that this, the l
.2 revised methodology tries to do it is with an 3 . acknowledgement that in reality what you are. measuring.is t j
i 4 only a, piece of what has been produced. l 5 There may be 50 percent of the inventory-that 4 l
isn't'even available to the monitor because it's held up in
~6.. !
7 the vessel.
8' DR. KRESS: There are several parts to the-9 . elephant. 4 10 MR. PALLA: So it is trying to basically in a very I 11 approximate manner reflect the reality that in a high 12 pressurc sequence you could have -- you know, not only 13I deposited but held up a lot of the constituents that you are
- 04' looking at, and you have to take that into account when you O
qj 15' do a reading.
16 DR. KRESS: So with realistic information you lL7 think you can make better decisions?
e
.18 MR. PALLA: Yes. I think to ignore those -- the 19 holdup issue, for example, would tend to bias.you and lead H2 0. you to potentially misleading information, so the best thing 21 to do'is to try to keep it as best estimate as you can.
22- DR KRESS: How far would you go into delineating
-23 the differences? Would you just talk about high pressure L '24 accidents'and: low pressure accidents and bypass accidents? i 25 You wouldn't actually get into much more detail
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)
-)
43 1 than that, would you?
m
( } 2 MR. PALLA: That's about it. There's high and low 3 and the criteria are and the setpoints are -- we looked at 4 that. I will talk about that very briefly.
5 DR. KRESS: Thank you.
6 MR. PALLA: Well, okay, basically the delays in 7 obtaining the core damage assessment estimates have resulted 8 in a lack of real integration of this information into the 9 emergency plan and into the decision-making process and to 10 answer the risk question, if you say, well what is the risk 11 impact of this methodology change, there really isn't a 12 direct relationship because you are not really waiting on 13 this information for a decision.
14 Now as the information is available, hours into rx (v) 15 the event, you would consider that along with anything else 16 that you have learned as the event progresses and you might 17 make adjustmentc, but this is really a second order effect 18 at best and I don't think it would be arguable that it would 19 be a risk-significant thing.
20 By improving the timeliness of the data, however, 21 you would create the opportunity to enhance the 22 decision-making process, so you could have a positive impact 23 on risk just by the timeliness change.
24 I just want to speak briefly about the scope of 25 our review of the methodology. We looked at the rationale
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- l. i _ _ _ _ _ _
L 44 1 for why this original methodology should be revisited and
(~si
,f 2 revised, and the rationale behind eliminating the use of the
-3 postaccident sampling system as the key parameter, or any 4 parameter, for that matter. Looked at the appropriateness 5 of the various indications that were being proposed as the 6 means of determining core damage such as the radiation 7- monitors,: core exit temperatures, looked at the approach, 8 the general scheme by which the status of the core was, you 9 know,' classified and the types of assessments that-are done 10 for the situation where you think you have cladding damage
{
11 and the situation where you think you've got something more 12 severe, some degree of overtemperature damage. And then we 13 looked at the setpoint values that are used-in the method 14 and the bases for that, the consistency of these set points
[N
( ,) 15 'with our understanding of severe accidents, which considers 16 MAAP but we considered other calculations as well.
- 17. DR. KRESS: Are you writing an SER?
18 MR. PALLA: We're writing an SER. It'll track 19 largely what I'm going-to say on the next few slides.
20 Okay. Going.into this of course you have to 21 realize _that we're reviewing this with a recognition of 22 what's the role of this process, of this methodology in the 23 overall decision making process and how accurate does it 24 really need to be to impact decisions. And we would agree
-25 with the statements that you heard earlier that we don't b
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45 1 think you have a need for a high, you know, very precise n
i V
1 2 estimate, nor do we think you could even have a precise l
3 estimate of these kinds of events. So we don't think you !
4 need the precision. You'd need to have something that's 5 approximate and that would be beneficial to be more timely j 6 than it currently is.
\
7 Okay. Some of the major arguments against the !
l 8 current methodology are essentially that there are fiss]on j 9 product retention mechanisms, there's holdup in the RCS, I i
10 spray effects are important, and if you didn't take that l 11 into account, the use of the PASS system as it's used in the 12 current methodology could lead you to quite simply just 13 misleading results, misleading estimates of. core damage.
14 We would agree with that characterization that
(*h
( ,) 15 these mechanisms could bias a sample and could result in 16 misleading information, and therefore we think that the 17 changes to the methodology are warranted. We think that the 18 methodology does better reflect, and it is in an approximate 19 way that it does it, but it reflects the fission product 20 behavior and transport. It would improve the timeliness and 21 the usefulness of the core damage estimates by removing the 22 reliance on PASS, and as such it would create the 23- opportunity to have this information available earlier for 24 the' decision making process. So I think it makes a lot of 25 sense to go back and to relook and revisit this.
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i 46 1 DR. BONACA: If you feel that it is warranted, and tO)'
v-2 I tend.to agree-with that, what about the non-Westinghouse 1
3 owners' groups?
4 'MR. PALLA: _ We've had some discussion, and they 5 are following-very closely-what we're doing here, and ,
6: they -- my understanding is that they intend to be revising 7 .their methodologies as well.
}
8 DR. BONACA: Because here it is not so much what )
9 'you have to look at. I think it's more what you're looking 4 l
10 with that is a problem.
11 MR. PALLA: Yes.
12 DR, BONACA: I mean, PASS is not the right --
13 MR. PALLA: That's right.
I 14 DR. BONACA: Tool. And it's going to be probably O
}q,J. 15 an impediment to a rapid assessment. So I'm saying that, l
16 you know, I am all with it --
17 MR. PALLA: Yep.
i 18 DR. BONACA: But I think itLaffects other' plants 19 too1 {
20 MR. PALLA: Yes. I think they're following. I'm l'
12 1 not 1 sure about'B&W, but CE has definite interest in this.
22 What we've done-in this methodology is essentially l 23 we're looking at the same thing, you could say well, we 24 already in the existing methodology had some reliance on 25 auxiliary' indicators, we were going to look at core exit l 1
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I 47 l 1 temperatures and radiation monitors as confirmation of PASS, i i
2- you know, results. What's been done here is eliminate PASS 3 as any parameter at all that's being considered and to make 4- the primary emphasis be the radiation monitors and the core '
S exit temperatures with secondary reliance on containment 6 hydrogen, reactor vessel level instrumentation, RTDs in the 7 hot leg, and the source range monitor.
- 8. This makes a lot of sense to us. There was still 9 a concern, and I'll talk about it a little bit later, the 10 concern being should we retain some elements of the existing 11 methodology if we in fact might draw a sample late.in the 12 event perhaps to try to structure some kind of recovery 13 strategies, entries, maybe late-term venting or releases of 14 atmospheric -- containment atmosphere. There was some l I 15 reservation about should we completely eliminate PASS from 16 the methodology. I'll talk about it later, but the point is 1
17 it's not in there right now, and we think that you don't !
18 need to have it in order to make these core-damage 19 assessments.
20 DR. KRESS: You know, it would'make sense to me to 21 have two different sets of requirements, one for core damage 22 assessment, and then another one for postaccident recovery l 23 or assessment or guidance. Is there anything in the 24 regulations that requires that second part?
25 MR. PALLA: There really -- I don't think that l
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48 1 there's --
()
. .2 - DR. KRESS: I couldn't recall a particular 3 regulation'that1actually requires something to help you 4 guide the recovery action.
MR. PALLA: I don't believe that -- I don't know 6 of anything. If anybody!-- i 7- MR. O'BRIEN: This is Jim O'Brien for the
- 8. Emergency Preparedness Group in NRR.
9' As far as a regulation, I'm no sure, but emergency 10 plans typically will have instructions on recovery actions.
11 I'd have to look into Appendix E of Part 50 and so forth.
12 Because it may actually be there that that is supposed to be 13 part of emergency plan. But that's where I've seen it used 14 and exercised during emergency preparedness exercises.
-( I- 15 DR. SEALE: One of the -- you just mentioned the 16 fact that you looked at this in terms of being able to 17 assure yourself that you got the information you needed to 18 make the kinds of judgments that'your emergency. plan would
.19 require for you and so on, as well or better than you have 20 with the old PASS system.
- 21l One of the things that's changed in the time since 22_ the_ original initiatives to put sampling in and so on is
~
23 -that there's an awful lot of fission product' chemistry 24 .researchLthat's going on, that is, just understanding the 25 ' behavior of fission products better,.the releases, the whole
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I
l l
49 1 process'we went through in going to a time-dependent fission
( (' 2 product models that are used in accident evaluations and so 3 forth. And there's more understanding of the effects of the 4 chemistry, in particular things like iodine behavior under 5- various conditions of chlorine and things like that, and 6 cesium in the plant and so on. Did you revisit the question 7 of_ fission-product chemistry in looking at this_particular 8 modification?
9 MR. PALLA: Well, what we did here, we didn't go
.10 back and revisit the basic science --
11 DR.-SEALE: Okay.
12 MR. PALLA: But what we did is reviewed what was 13' being done in the methodology to account for that chemistry.
14 And essentially, and I've got it on the next slide there,
() 15. but just to summarize, certain assumptions are made about 16 the-extent'of fission product removal that might occur and 17 approximate value -- you know, recommended values are 18 developed _as to what_ fraction of the fission products would
~
19 get out of the RCS in a high-pressure sequence, how much L20
~
'would get out in a low-pressure sequence. So those numbers 21 are built into the methodology. We looked at that against 22- 'the calculations that we-had available to us to confirm it 23 .was in the right ballpark.
24 Okay. With regard to what do you with the --
=25 _you're going to now look at all these different sources of
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7-50 1 information and you're going to try to convert them into r~%'
( ) 2 some estimate of core damage, and we looked at what was
%/
3 being done in the methodology in that regard. And 4 essentially what the methodology does is after initially 5 classifying the state of the core into either no damage, 6 suspected cladding damage, or suspected fuel overheating, it 7 goes further and it tries to look at these different 8 parameters and what they tell you individually about the 9 extent of core damage, and then each of these individual 10 parameters are cross-compared with each other to see if 11 there's some kind of a convergence on, you know, what the 12 estimate of core damage is.
13 When you look at what's being done with the 14 containment high. area radiation monitor readings, they're O
\_/ 15 compared to some predetermined calculations that each l
16 utility would run for their plant. They would look at where 17 their radiation monitors are located in the plant and what 18 they would see given that you had 100 percent cladding 19 failure as you generate some curves, and then if you had 100 20 percent overtemperature fuel damage, you generate these 21 curves. They would be as a function of time to account for 22- the decay, they're a function of reactor coolant system 23 pressure to account for holdup effects and fission product 24' removal effects, and there's curves that are with and 25 without sprays to account for decontamination of the ANN RILEY & ASSOCIATES, LTD.
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51 j 1 atmosphere by spray operation.
( f 2 DR. KRESS: Hydrogen holdup. Is that anything 3- other than just capacitance? I mean, you're sweeping it out 4 by the flow --
5 MR. PALLA: There is some recognition on hydrogen l 6 as far as whether it's a high-pressure or a low-pressure
{
4 7 scenario -- '
E DR. KRESS: But that's still capacitance.
9 MR.-PALLA: And whether or not you've -- yes, but l i
10 whether or not you've actually had reflood would determine i J
l 11 the extent of hydrogen production. So --
12 DR. KRESS: Oh, yes, production's one thing.
i 13 ' Holdup --
{
14 MR. PALLA: Holdup is it. Now when it comes to ]
l'(s ,/) 15 burning, as in the ice condensers, the guidance basically ~
16 .says once you've exceeded -- I'm not sure where the 17 threshold would end up being set, but above a flammability 18 limit you can't place much confidence or use on the hydrogen !
19 numbers themselves. But when they're very low, you know 20 that you haven't produced anything yet.
12 1 DR. KRESS: Somewhere in there you talked about 22' hydrogen holdup in the RCS, and that seemed a little strange 1
23 to me. j 24 MR. PALLA: Oh, well, I guess it's a concept --
l 25 DR KRESS: I can understand about hydrogen in the NE ANN RILEY & ASSOCIATES, LTD.
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52 1 containment.
[ 2 MR. PALLA- Well, the vessel's at -- let's say 3 it's at a high-pressure sequence and it's still proceeding, 4 it's close to 2,000 psi, what you're seeing out in the 5- containment might just be what's come through the core 6 cycles, but you could have half of the inventory actually 7 sitting there if you had a vessel failure, you know, a 8 minute later, it would be out in the containment. So yes, 9 you know approximately from the various calculations how 10 much is produced, but knowing that you're at a high pressure 11 would lead you to realize that some of what's been produced 12 is still in the vessel. It's not everything that's -- what l
13 you see in the containment isn't everything that's been 14' produced.
15 DR. KRESS: I would guess in a high-pressure 16 accident it is basically everything produced.
17 MR. PALLA: What you're seeing in the containment?
18- DR. KRESS: Well, in a low-pressure accident for 19 sure.
20- MR. PALLA: Oh, yes, low pressure.
21 DR. KRESS: High pressure --
22 'MR. PALLA: And the assumption's made if it's low 23 -pressure, it's all out there, everything produced is out in 24 the containment. I I
25- DR. KRESS: In the containment, and high l
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53 1 pressure -- 1
() 2 MR. PALLA: In high pressure there's an assumption 3 made, and it's a setpoint that's been determined is half, 4 half of it's in the vessel still. And then on the 5 containment hydrogen concentration, you take a measurement, 6- but then you'd compare it to the expected value for the 7 situation you're in, and two factors there are the RCS 8 pressure, which can determine how much is held up, and then 9 the reflood would' determine how much had been produced or, 10 .you know, you increase the amount of hydrogen you produce if 11- you have a reflood.
12 And so these factors lead you to four 13 subcategories of hydrogen that you would compare your 14 measurement against the appropriate category that you think
() 15' you're in to estimate just how much do you have, how much 16 core damage do you really have.
17' .DR. KRESS: Are the hydrogen indicators used for 18- anything other than deciding on the extent of core damage?
-19 MR. PALLA: In a concrete manner I think it's 20 probably -- you'd have to almost talk to somebody that's 21 -dnvolved with the procedures to see if the procedure 22> specifically does something. I think when you turn in an 23 ice condenser plant, for example, actuation of the igniters 24 is done before.that, so I don't think that --
25- DR. KRESS: They're already --
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I I 54 I J
1 MR. PALLA: I don't think you're going to, wait for j ) 21 a hydrogen rending to turn on. igniters. I just think it's 3 .information --
4 .DR. BONACA: I think for venting you would have --
5 DR. KRESS: That's what I was getting at.
6 MR. PALLA: Well, in accident management space 7 -you'd be looking at hydrogen as a potential threat to the
! 8 containment, so I guess --
9 DR. KRESS: Of course. I think decisionsHon 1 10 whether'--
11 LMR . PALLA: Severe accident management guidelines 12 is probably the only procedural or guidance-driven thing 13 that would actually.use that hydrogen information, other 24 than emergency response in general, as you would be doing
,() 15- here with the core damage assessment.
16 Okay So basically we looked at the way that 17 these various indicators are converted over into estimates 18 of core damage, and it looks like it's a reasonable way to 19 ' interpret the data, and what's'done in the methodology is 20 you develop an estimate based of core damage for each one of y 21 these things individually, and then you kind of 22 cross-compare and look for, you know, consistency.
23 With regard to set points and holdup assumptions, '
24 this gets back to a question about do you reflect the latest 25 science,' fission-product science. We looked at the i
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l' 1- assumptions made for high-pressure sequences, 50 percent of t-() 2 3-the' nobles, and the hydrogen would be part of that too, is held.up. Actually these numbers are what's being released L
'4 in the containment. .Only'2 percent-is going to -- of this
! 5 cesium and iodine would be assumed to be released. So when 16 you go and you've got your plant-specific curve that tells
! 7 you how much hydrogen you might have -- or how much 8 radiation level you might have for a low-pressure sequence, ;
9 built into'that curve is an assumption that you're only 10 looking-at 2 percent of what's been produced.
11 We kind of'look critically about that 2 percent.
12 Fifty percent's easier to accept; 2 percent looked like 13; well,,you know, you better be pretty sure you're going to 14
~
.get that much removal. And looking at some of the I 15 calculations that -- we asked Westinghouse for more, and 16 they provided us some additional calculations with MAAP. We 17 looked at what was done with MELCOR. The number 2 percent's 18 probably -- it's on the low side, but one thing that I need 19 to mention is the fact that there is not within the method 20 'an assumption -- any kind of a treatment of fission product 21 removal just by natural processes, gravitational settling, 22 . agglomeration, these kinds of things. So that 2 percent 23 number-is probably not bad when you consider that fission i24 ~ products would be removed due to these natural processes in 25 addition, j'
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l 56 1 Okay. Looking at the low-pressure numbers, 100 n- i 2 p%) percent of the nobles and hydrogen would be released; 50 3 percent of the iodine and the more volatile species would be l i
4 held-up. 'With sprays operating they assumed the 5~ decontamination. factor of 100, which seems reasonable.
6 DR. KRESS: When you talk about best-estimate 7 calculations, are these MAAP or MELCOR or --
8- MR. PALLA: We looked at both of them.
19 DR. KRESS: Both of them. They're consistent?
10 MR. PALLA: There were more MAAP calcs available, 11 but we looked to see what we could find from the 12 calculations done for the source-term rebaselining work. A 13 lot of those tended to have sprays on, so they didn't tell 1 14 us much information about the case without sprays. But we 9
k, ,/ 15 tried to look at what's out there without running more 16 calculations. We didn't go and do any additional 17 calculations for this.
18 The bottom line is their assumed setpoint values 19 and holdup fractions seem to be good approximations. I 20 mean, you can find sequences where they don't match very 21 well. Some of the sequences are higher; some are lower.
22 These numbers.are not bad'.
23 A few residual issues. I call them residual; 24 these are residual as of a couple weeks ago. We did get 25 .some additional.information that we've looked at now, and r
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h 57 1 .I'11 summarize what we've found from that. But the 2 questions that we had was, well, the firnt one was what 3 about retaining some kind of a scheme for converting a PASS 4 sample into a core-damage estimate for the late term. We 5 accept the arguments that in the near term of transient 6 effects a postaccident sample isn't going to be of very_much 7 value. It's going to be several hours old by the time you 8 get it. The conditions would have changed by that time.
9 The only question we had was well, let's say that 10 things have settled down now, the core is stable, you're 11 hours into the event, and now the core cooling's been 12 recovered, and you're thinking of taking a sample to kind of j 1
-~3 1 assess what's in the containment. There really wouldn't be j 14 any.way to do that with the current -- with the revised v 15 methodology, and we asked ourselves well, does that make 16 sense, or should we retain some kind of an element of the --
17 DR. BONACA: Let me just say on that, that's not 18 an emergency planning. issue. Again, that need, that was the 19 need why PASS came about. I'm convinced. If you go back 20 and look. It wasn't because we-felt that you couldn't in 21 the short term make some -- it was because people were )
22 trying to understand what was -- I mean, you know, after )
- 23 TMI, comparing the sump, the RCS, and et cetera. So there 24 was a need for that outside of emergency planning --
25 long-term analysis.
I l l i
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58 1 MR'. PALLA: Except there's a three-hour l
{]v
[2 re'uirement; q I'm not sure'why you'd have a 3- three-hour requirement. 1
-4 DR.-BONACA: The requirement came in the emergency 5 planning, because once the system was available, was made
'6 part of emergency planning -- all I'm trying to'say is that
'I-totally support the idea of removing PASS as a means of
~
7 8 using -- of supporting' emergency planning. But before you-
- 9. scrap it altogether, you've got to really go back and 10 understand, you know, could you need it a week after the 11 accident, or two weeks, depending on what scenarios you've 12L got and what kind of comparisons you want to make. So --
13 MR. PALLA: Okay.
14 DR. BONACA: So that should be outside of 15 emergency planning in my judgment.
16 MR. PALLA: Okay. And I think we're going to hear
- 17. more about that.
18 DR. BONACA: Okay.
19 MR. PALLA: About the fact that even though you 20 may take the PASS sample out of the core damage assessment 21 l methodology, there still is an intent to retain the 2:2 capabilities for late monitoring. What we thought about 23 'here is that -- and Westinghouse's argument is that it's not 24 really credible to have some kind of a core damage
- 25 ' assessment guidance that's dreamed up in advance and that ANN RILEY & ASSOCIATES, LTD.
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59 1 would cover all these different plant conditions that you
.O 2 might have.
U 3 The situation's really too complex. If you relied 4 on PASS, the chemistry and the behavior is complex, results 5 could easily be misinterpreted or misleading, and after the 6 plantcis stable, there's sufficient time to address, you 7 know, the plant-specific -- the actual event that had f 8 transpired. You'd know the actual description, you know, j
- 9. the event and the actual plant conditions that you've got in l
10 this kind of an assessment could be done later, but it need 11 not be part of this core damage assessment methodology. I 12 We do accept that rationale. We think the 13 methodology can serve its purpose without relying on PASS in 14 that the' PASS sample and the ability to translate it into a O).
(, 15 core damage estimate is not really needed as part of this.
16 We think that PASS as used in the longer term is of value 17 primarily for dose assessment and for, you know, confirming 18 protective actions and perhaps in planning recovery 19 etrategies. But that's a different purpose than what we're 20 looking at here. So in fact I think we'll talk about that 21' in a short while.
22 Just to summarize our conclusions, and I will call 23 them preliminary, 'did I skip a slide here -- let me just go 24 back here. .I think I may have.
25 Second bullet was we had a question about this f~h' ANN RILEY & ASSOCIATES, LTD.
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60 conceptjof when assessingLwhether or not you have got clad
~
'l
(} '2 L 3'
' damage-the original WCAP'that we looked at had -- you essentially established a pressure threshold and you say if 4 the pressure is less than that we use one temperature to 5e signify clad damage and if the' pressure is greater than that
'6- we will!use some.different and higher-temperature to signify 7 damage, .and that-is the way the core exit temperatures were 8 used to determine'the extent of core damage 9 We have some questions about the values that-were 10- selected, just the basis for the calculations. They were 11 based on MAAP calculations and we had some questions of what
=12 .if.you went1back and. looked at some of th'e stress / stain 13 criteria-that's used for clad ballooning and rupture, and 14 'how would that compare -- are we getting into a conservative
=
15 estimate that may-give you a kind of misleading estimate or 16 not?-
17 As a result of further discussion of this with 18 Westinghouse, Westinghouse went back. They looked more 19 closely at the bases for the numbers they had developed.
20 They ran some additional calculations looking at effects of 21 higher burn-up and they ended up adjusting the threshold 22 values to be a bit more consistent with the fact that a lot 123 of plants areJoperating at higher burnups than the original 24 number was.taking into account, so I think we are past that 25 .second item -- the revised values which were included on the JUGi RILEY & ASSOCIATES, LTD.
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l 61 a
1- slide you haa seen previously look acceptable to us.
() 2 3
The final bullet there, the issue was that the methodology as provided made these assumptions, as I
- 4 indicated -- 50 percent of the fission products are released
-S in a low pressure sequence, 50 percent are held up still, 6 and 2 percent in a high pressure sequence are released. 3 7 .I had some reservations that there wasn't any 8 accounting for the effect of fission product removal in the 9' containment itself due to gravitational settling, 10 agglomeration. The concern is not with spray because with 11 sprays they did have a separate factor that they put on 12 that.
13 The concern was maybe 50 percent or two percent 14 are good for how much gets out of the RCS, but there could
() 15 be some additional removal in the containment itself.
16 Westinghouse provided us some additional information. It 17 does show that of what i.s released to the containment there 18 is some substantial amounts that become deposited in pools 19 or on surfaces. They are not actually in the air space any 20 longer, but even at that it does seem that the assumed 21 . values, the 50 percent value, the 2 percent value being 22 available for sampling -- I think those are still reasonably 23 good numbers.
24 I think-the effect of these things that are going 25 on in the containment is still -- these numbers are still l'
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62 1 within the right range and I think there is a certain amount
) 2 of uncertainty associated with it in the effect of the 3 . removal in the containment and the case without sprays is 4 within the range of that uncertainty, so I think that that 5 issue is acceptably resolved.
6 DR. FONTANA: I guess the real question, and you 7 touched on'it, is.under what situations could these 8 approximations lead 'you to do probably not the best thing 9 with respect to accident management.
10' Did you run through a kind of a disciplined 11 approach of what the accident management procedure would 12 have told you to do under various circumstances and looked 13 to see where there is a situation that could lead you
'14 astray?
() 15 MR. PALLA: No. No, we didn't, and this 16 methodology is actually separate from basically everything 17 that we do. You have got your protective actions 18 recommendations, your emergency action levels. You have got 19 EOPs. You have got severe accident management guidelines.
20 These -- all of these things are done in isolati.on of the 2 11 core damage assessment methodology, I think i.n essence ;
22 because we had a requirement for PASS, we had a requirement 23 for the procedure. These requirements were met, but because 24 'of the timeliness issue this information isn't really used, 25 so we did not go back and look at the severe accident
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63
'1' management guidelines to see if we would be -- because they
() 2 don't actually tie back into the core damage assessment 3 methodology,_ittis unclear how an assessment of core damage i 4 here relates into an action.
1 5
I think I don't see that it -- because it is not j 6 an input ~to any of these actions, I don't think there would 7 be a --
i 8 DR. FONTANA: _The question is without PASS it '
9 doesn't make any difference?
10 MR. PALLA: PASS does not seem to influence what 11 you do in emergency operating procedures or in severe 1 12 accident management guidance.. That is why I saying the risk I 13 is not impacted by change and if anything the risk would be i 14 improved by going to something that is more timely. Then at ,
(~S q_) 15 least it is an additional piece of information that could be i 16 used upfront in the decision-making process. As it is now 17 three hours after the situation, you know, three hours delay 18 time it adds very little.
19 DR. FONTANA: Thank you.
20 MR. PALLA: Which is the point of our conclusions, 21 that the guideline does provide core damage information that 22 we think is going to be of a sufficient level of accuracy to 23 support short-term decision-making. It is a simpler 24 methodology. It is more timely. It accounts for fission 25 product, hydrogen distributions in an approximate way but at
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64 1 .least it' accounts for them. That approximation looks to be 2 reasonable.
N' )b 3 By making'that information available earlier, it 4 could improve emergency plan decision-making. On the other 5 . hand,.it might not result in any change whatsoever. If a 6 utility has already got this process set up, it makes this l 7 information more' timely but there is no requirement that 1 l
8 they would modify any of their emergency plan to account for 9 this, but it is our hope that when that information is out 10 there and there is an awareness that it is now an additional }
l 11 consideration that they can bring in to bear, they could at {
- 12 their option integrate this better into their emergency l 1
13 plan.
14 This is where we are headed with our SER.
() 15' DR. KRESS: Le'. me ask you about the timing of the 16 SER. When is that supposed to be done or when you project 17 it to be done?
18 MR. PALLA: I think it was supposed to be done 19 already but I am not certain what the actual date -- Peter, 20 do you have any -- maybe the end of May. He said May, 21 right?
22 DR. KRESS; No, he said today.
23 [ Laughter.]
24 DR. KRESS: And basically then this goes to the H25 . Commission?
(}.
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65 1 MR. PALLA: I am not exactly sure of where it 2 heads. It may in fact be.different than -- there is 3 actually an SER that will be written on the core damage 4 assessment methodology and there is an SER that will be i
5 written on the post-accident sampling changes. '
6- I think there was some consideration did we have 7- to send the SER on post-accident sampling to CRGR and I l
8 think 1 there is going to be a waiver there. I 9 On core damage assessment, I don't think it gets 10 any special treatment. I think it is just the change in the 4
11- methodology. .There is no relaxations or increases in
- 12. requirements on these. It's just different, so whatever is 13 normally done with a topical report --
14 DR'. KRESS: Assuming we write-a letter, the
( 15 conmittee, the full committee, at the May meeting, which is 16 what? -- next week?
17 -MR. BOEHNERT: Yes.
18 MR. PALLA: It won't be ready then.
19 DR. KRESS: If we had things to say that might be 20 useful to you, could it influence the SER?
21 MR. PALLA: Oh, yes. Yes, it would be very useful 22 to get the committee's thoughts on this change.
23 Yes, that would be beneficial. In fact, I would
'24 look to take that into consideration, definitely.
25 DR. KRESS: I think at this time we are scheduled
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66 j 1 for a break of 15 minutes, so we will recess for 15 minutes 1 l
1
. /3 -2
~
and ask' people to be back at 10:25.
,y .
3 [ Recess.]
i 4 DR. KRESS: Can we get started again, so we don't 5 run.over too much?
6 I think at this point we're about to hear from the j 7 Postaccident Sampling System requirements, from Mr. Harrison i 8 of. South l Texas Pn ject. And so the floor is yours, sir.
f 9 MR. RARRISON: Thank you. Is this working now?
10 Good.
11 Good morning. My name is Wayne Harrison from
- 12. South Texas Project. I'm the Westinghouse Owners' Group j i
13' Licensing Subcommittee chairman, and I want to talk to you a 14 little' bit about the Postaccident Sampling System. l
. ,em
.( ) 15 I feel-like I might be fighting a losing battle 16 here because everyone's saying well, you don't need the
]
17 Postaccident Sampling System anymore. And however -- give a I 18 little update on that --
I want to give a summary of what
~19' 'the proposed WOG relaxation, the Postaccident Sampling i
20 System includes. And the Postaccident Sampling System I l
. 21 ~ requirements;that the Westinghouse Owners' Group is going to '
22 propose will be properly focused cn1 the public health and 23 safety and accident management needs for such things as 24- emergency operating procedures, action levels, and PARS, 25 ' offset dose, management and SAMGs. l l
(T[
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7 67 L 1 I need to stress and make -- at this point none of L
lO \ /
12 1 these requirements rely on the Postaccident Sampling System
- l. ~3- to achieve their purpose. As Bob told you earlier, 4 basically the in-plant instrumentation provides us with
.5 timely and adequately accurate information for the purposes 6 of all of-these items.
7 Bob also mentioned a little bit about the risk 8 aspects of the_ core damage assessment. That same logic j l _9 applies to the Postaccident Sampling System. The 10 Postaccident Sampling System is not modeled in probabilistic i 11_ safety. assessments. As you would expect, core damage has 12 already occurred, which is certainly one reason, and we feel- ,
13- that it's risk-beneficial from the aspect of during normal 14- ' operations-with these proposed' changes to the Postaccident
() 15 Sampling System that we would be able to keep our resources 16 focused on those things which are of significance and !
17 risk-significance to us.
18 The need for the protection of the public health 19 and safety as Bob mentioned depends upon timely and 20 .sufficiently accurate information. Also as he discussed in 21 his presentation that information was most effectively 22 provided by installed instrumentation, and that. gives us 23- certainly'the most timely information that we .ieed.
24 The owners' group:has, proposed a more realistic 25 ~ application and use'of the Postaccident Sampling System t
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68 1 that's more-in tune with how we think the system would
() 2- actually be used in accident response than is currently 3- prescribed. These requirements that you see here for the 4 reactor coolant system boron containment hydrogen and 5 containment sump are based on the current plant knowledge as .
I 6 we were discussing earlier of accident phenomena, and j 7 they've.been developed in concert with the emergency 8 operating procedures and the SAMGs.
9 As you can see here, we've retained the capability 10 to obtain samples for long-term cleanup and recovery 11 planning. What this does, it allows our technical support 12 engineering people based on existing plant conditions to 13 assess where the plant is and make the appropriate and 14 timely use of the Postaccident Sampling System capabilities. !
I) 15 DR. KRESS: Before you leave that slide --
16 MR. HARRISON: Yes.
17 DR. KRESS: Where do you measure the RCS boron?
18 MR. HARRISON: South Texas Project takes its 19 Postaccident Sampling System -- we have three locations for 20 past samples: the reactor coolant system hot leg --
21 DR. KRESS: Okay.
22 MR. HARRISON: The residual heat removal system, 23 the containment normal sump, and we have a couple of 24 locations similar to what Bob was talking about in the 25 containment atmosphere at a higher elevation and-at a lower
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7..
69
/
1 elevation.
g..
? T 2 DR. KRESS: What's the basis of the eight hours
(,/
4c MR. HARRISON: The eight hours, 'and if I~can I'll 5' 13o to the next~ slide, where I'm going to --
'6 DR. KRESS: Well, okay. Before you leave this 7- slide, though,_I had another question.
8 MR. HARRISON: Okay.
9 DR. KRESS: And that is why the constraint of a 10 - brackish-water plant for the pH measurement? Why is it l 11 constrained to only brackish-water plants and not just every R 12 plant?
13 MR. HARRISON: Well, for most plants where you h._. ~14L know what the quality of the water is, if you're going to be m) (, >15 adding water from other sources,.you'll know what those "16 sources of water are or-what their chemistry is, so you'll 17- have a knowledge beforehand of what the chemistry of the
'18 water'is.
19 When you have brackish water plants, you may not 20, ' have-as good a knowledge'of that chemistry, you may have 21 ionly one barrier between-the containment and that' brackish
- 22 water, so the thought was with brackish water that we have.
23 more needLfor identifying pH.
24- DR.IKRESS: I suspect for any water, for example, 25 the sprays.and the water that collects in the sumps under an (O
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70 1_ accident, I don't -- if you don't have pH control on that
(T 2 water, I think there are things that get added to it from w) 3 the accident itself that will affect the pH. And it seems 4 to me like there would be a pretty good idea to know what 5 that pH is for accident recovery and control.
6 MR. HARRISON: And that's true for accident 7 recovery and control, and we also need to recognize that 8 most if not all of our plants have a passive pH system 9 either in the containment spray system, or trisodium j 10 phosphate added where you already have some pH control 11 present in the system.
12 Do you have anything you want to add to that, Bob? i 13 MR. LUTZ: Yes. This is Bob Lutz from 14 Westinghouse. The primary concern for the brackish-water !
(A)
~-
15 plants -- and he doesn't have one other qualification. It's 16 for those plants that for example use service water to the l l
17 fan coolers, where you may have leakage of brackish water l 18 into the containment sump, that we feel that there's a real 19 need to get a quick sample to make sure that the chloride 20 content isn't getting too high on those. And that's really 21 what that addresses. l 22 DR. KRESS: Well, my only concern was if you're 23 going to measure pH, I think you need to do it whether 24 there's a chance for brackish water there or not. j 25 MR. HARRISON: First we'll address the reactor f ANN RILEY & ASSOCIATES, LTD, i
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1 71 1 coolant. system sampling. As I mentioned, South Texas for.
Eh N,) 2 ' instance takes'our reactor. coolant system off the reactor <
'3 coolant system hot leg or the residual heat removal system.
4 We're probably typical in that regard, although South Texas 5 is often not typical of anything.
6 With respect to boron, I used boron to actually i 7 confirm shutdown margin. This proposal for eight hours 1
8 after reaching a stable condition is consistent with the 9 emergency response guidelines and is primarily for the 10 ' natural circulation cooldown. We don't need the boron for 11 accident mitigation, and'it's not needed for establishing a
'12 long-term -- we would like to know that for establishing a j 13' long-term stable state.
14 The eight hours as you asked was selected because l O
( ,f 15 it's consistent with the need for when we would need this, 16- and it's also consistent with after we reach a stable plant 17 condition and the conditions are not changing rapidly-18 .anymore.
19 Dissolved gases, currently it would be used for <
20' ' determination of voids or the potential for voiding in the 21 reactor coolant system. We've proposed to eliminate the 22 timing and accuracy requirements for the samples. .There are 23' more direct and timely ways of getting that information for 2.-4 .the operators and for engineering. We have level 25 . instrumentation, for instance. We'also have reactor head Ci ANN RILEY & ASSOCIATES, LTD.
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v - ;
72 l' venting, which provides us with an opportunity to certainly 2 eliminate'some of the gases. And our critical safety LQ /')' -
3 ' function uses instrumentation indications.
4 For oxygen and chlorides again we don't use these 5' for any EOPs or SAMGs. The reactor coolant system chemistry 6 coolant is primarily dependent in a recirc mode on what's in 7 the sump. We would also, as was mentioned, asked, we also 8 use this for assessing potential for stress corrosion 9 cracking an iodine retention. So it does provide us --
10- could provide us some information on whether or not we've 11- maintained the sump pH, and that was your -- goes back to 12 your question on sump pH also.
13' DR. KRESS: I don't understand the stress 14 corrosion cracking. I mean I understand it's driven by
() 15- chloride, but that's a --
16 DR. SEALE: A long-term --
17 DR. KRESS: A long-term normal --
18 MR. HARRISON: Exactly.
19 DR. KRESS: Operating problem, not an accident
- 20. problem.
21 MR. HARRISON: Exactly, and that was why -- that 22 was originally part of the purpose of' putting it in there.
23 We don't think we need to have PASS to monitor stress 24 corrosion cracking except for long-term planning and 25 recovery type of actions.
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1 73 i
'It DR..BONACA: 'I have a question regarding accuracy
.[} 2- requirements. I can see. elimination.of timing, but what 3 does'it mean -- you.still will have some accuracy 4 requirements placed on the ability of PASS?
5 MR. HARRISON: We are talking about elimination of 6 -the-accuracy' requirements. Right now there are some.
7 prescriptive requirements on the Postaccident Sampling 8 ' System thatiare imposed by the regulations. We expect that 9 the system.would be able to have an acceptable level of 10L accuracy, but we would propose to eliminate the regulatory
-11 requirements on the accuracy requirements for the system.
- 12. For radionuclides,' we would use radionuclides in 13 the. reactor coolant' system again for confirmatory
' 14 - information. late into the accident. We propose to eliminate
() 15 : timing and accuracy requirements for the samples. We don't 16 really need this information unless we had some sort of 1 17 planned release. As far as using it for protective action 1
18_ recommendations as we talked about earlier you really don't i 19 .get timely information from a PASS sample here. I 20 Proposed containment atmosphere sampling -- I 21 think the main parameter of interest here is.the hydrogen, 22 ~ which we do actually use in emergency operating procedures 23 and SAMGs but:we really get that information from the online 24 hydrogen monitors and take actions based on what we get from 257 ;the online hydrogen monitors. To have a separate.
f JO (d
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i 74 l i
1 requirement in the post-accident sampling system is really
() 2- no longer necessary.
3 We would~use these in the emergency operating 4 procedures to monitor containment hydrogen and the operators 5 will use that information to apprise the technical support 6 engineering staff and I think that we also use that as a i
7 locator point for actuation or starting up the hydrogen
- 8. recombiners.
9' . DR . KRESS: What does that "within 30 minutes of 10 core damage" mean? That'means after you reach the stage 11 where you failed some clad?
12 MR. HARRISON: Where you have indication that you 13 have some core damage where you would actually be
'14 potentially generating hydrogen you would turn on the 15- hydrogen monitors.
16 DR. KRESS: Okay, and the 30 minutes came out of 17 some. sort of a MAAP calculation?
18 MR. HARRISON: Can you elaborate on that one, Bob?
.19 MR. LUTZ: Yes. Bob Lutz from Westinghouse.
20 .I believe.the current requirement is 30 minutes 21 after the initiation of an accident, and what we are doing 22 here is we are recognizing that that is an unrealistic 23 ' expectation for many accident sequences, and we have looked 24- at when you really need to know what the hydrogen is and we 25 looked at' core heat-up transients and when you would get to a
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75 l' those points in emergency operating ~ procedures or in severe
( ' 2' ' accident management guidance, and we felt that having an 3 indication of the containment hydrogen concentration within 4 30 minutes after'the onset of core damage was quite adequate 5 to satisfy EOPs or SAMG activities.
6 MR. HARRISON: As the operators go through their 7' initial EOPs that.30 minute' time, as Bob mentioned, is a
)
8 distraction or can be.
9- DR. SEALE: Didn't we'have some comments on that 10 several months ago, about the unrealistic early l j
J 11 requirements? '
12 EDR . KRESS: Yes, early requirements were 13 unrealistic and were a distraction to the operators. That 14 is why I brought it up, to be sure this was'the same
) -15 , issue --
16 DR. SEALE: .Part of the same issue.
17 'DR. KRESS: -- we talked about before.
18 MR. HARRISON: With regard to the sump sampling, 19 Westinghouse Owners-Group has proposed sump sampling for 20 brackish water plants without passive pH. control within 24 l
21- hours of core damage. We talked about that and just to 22 ' reiterate, there were three criteria, all of which needed to 23 be' met.
24; One is that you have a: brackish water plant; 125 second, is you-have a singl'e barrier between the cooling-
- h.-
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c 76-1 ' water and the containment, and the third requirement was
,[ } 2 that you don't have'a passive sump pH control.
v L3' DR. KRESS: And I would eliminate the brackish 4 water part'of that if it.were me, because I think you need pH' measurements if you don't have pH. control, whether it is
~
5 6 brackish or not.
7 MR; HARRISON: Okay. With regard to boron, there.
8 are currently no EOP or SAMG requirements. It would be 9 useful at'some point perhaps to estimate the overall boron 10 concentration. 'We would also propose to eliminate the 11 timing and accuracy requirements. Boron is not an issue 12 ,
unless we have introduced large quantities of unborated 13 water into the containment but in those cases we believe, as l
14 we mentioned before, you have knowledge of the source of (A,) 15 that water, what the boron concentration was, what the 16 'boration and quantities in the boron concentrations of the 17 original water was, so you have a method to reasonably 18 estimate the boron concentration of the water.
19 With respect to the radionuclides, it was 20 originally I think envisioned that the radionuclides would 21' be used to help determine offsite doses. As we discussed 22 earlier though, the radionuclide capability of their getting 23 thatfsample would certainly not be timely and very 24 supportive of making timely and effective offsite -- excuse 25 me -- calculating offsite doses and making appropriate
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l 77 1 protective action recommendations.
/9 -2 MR. WALSH: Larry Walsh from Northeast Utilities.
O {
3 I would like to just jump back a little bit on l 1
4 that pH control and the reason for the brackish water 5 plants.
6 As we stated very early in the presentation, one 7 of the things we don't want to do is put people out in a 8 hazardous location when we don't need to, and the reason we 9 put the brackish water plants in is for other plants who 10 have an intermediate system like a Compoly cooling system, 11 it is a known quantity of water, it's a known chemistry l
12 composition because if-it's an inhabited area you take daily '
~13 samples so you k now what it is. You can calculate what 14 your pH is for mixing with that known quantity.
15 For brackish plants it is infinity because it is a 16 river. source and you don't know how much leakage there is, 17 so then you have to have the pH.
18 DR. KRESS: Let me understand what this is. You 1
19 intend to continue measuring for pH even in plants without '
20 the brackish. What you are eliminating is the timing 21 associated with it?
22 MR. HARRISON: Correct. Yes, we would do 3 i
23 long-term pH. l 1
224 DR. KRESS: But you would keep that timing for the 25 brackish? Well, I think that is all right. I originally l
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l 78
]
.1- . thought you were going to eliminate the pH measurement for !
-['h.
s )-
2 plants other than brackish but it is just.the timing you are 3 changing?
4 MR. liARRISON: You'll still maintain the 5 capability to take-the sample and analyze it.
6 DR. KRESS: I think that's fine, yes. Appreciate 7 that'.
8 DR. SEALE: Let me understand something. Dr. i 9 Bonaca raised a question a little earlier. You have here l
10 the elimination of accuracy requirements. Is that a true 11 elimination or a relaxation?
12 DR. KRESS: Or a redefinition of what the accuracy 13 requirements are.
14 DR. SEALE: Yes.
(,m) 15 MR. HARRISON: I think, number one, we would like 16 to remove the accuracy requirement, the prescriptive j 17 accuracy requirements from the licensing basis or the
)
18 regulatory basis, and correct me if I am wrong, for the 19 reactor coolant system, for example for boron, I think we 20 were relaxing the accuracy requirements from currently plus 3 1
21 or minus 5 percent to I think 10 percent when the 22 concentration of boron is 1500 PPM or greater, or 20 percent I l
23- with concentrations of boron below 1500 PPM, and that is 24 because at those, when you get closer to the 1500 PPM your
-25 accuracy requirements --
l l
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l 79 I I
1 DR. SEALE: I am in complete sympathy with the l 1
s idea of redefining accuracy requirements so that they are 1
) 2 (G
3 realistic under the circumstances under which you have to 4 make the measurement.
5 On the other hand -- and for example on the boron, 6 that is I think a very straightforward and understandable 7 change in the requirement -- I have some idea what the needs 8 are for criticality assessments anyway, so I don't see any 9 problem with that, but some of these things, you know, if 10 you eliminate the requirements you'd just as well take the 11 meter out.
12 I mean I can guess that close and furthermore 13 there is no basis on which to decide whether my guess is 14 good or not, if you have eliminated the requirement,
', ,y) f 15 MR. HARRISON: For some of these systems -- excuse 16 me, or for some of these requirements such as the estimation 17 of the radionuclides where we had some accuracy 18 requirements, where we lose accuracy is not necessarily in 19 the accuracy of the measurement that after we have taken the 20 sample you can do the count and so forth. It is more 21 difficult to be sure, well how much did I really dilute that 1
22 sample. If I have a requirement to do it to 500 to 1 or 23 1000 to 1 or what have you, the accuracy of that dilution 1
24 factor in that kind of environment can be very difficult, so 25 that also is a part of the_ rationale. j ANN RILEY & ASSOCIATES, LTD.
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80 1 DR. SEALE: Well, as I say, there may be some A
t,v; 2 economy of wording for the chart here, but that disturbs me, 3 DR. BONACA: Yes. I liked the word you used, 4 which was " relaxation" and I am all for it. The point that 5 Professor Seale is making is correct. I mean if you 6 abandon, if you leave the piece of equipment in a way where 7 there are no requirements established either no licensing 8 commitment or internal commitment, you know, what guarantees 9 that if you need it at some point it will be available and 10 will give you some reasonable information?
11 I think I would rather see the word " relaxation of 12 accuracy" than elimination. l 13 MR. HARRISON: From the standpoint of putting it 14 into a regulatory perspective, in general for accident O
! ,/ 15 response or except for looking for long-term recovery, we '
16 really don't need these post-accident sampling functions, so 17 we would still, as we stated, we would be keeping the 18 requirement to be able to take a sample and we would be 19 describing that in our -- propose to describe that in our j i
20 updated final safety analysis reports. j i
21 The sampling I'm sure for a typical plant would l l
22 have procedures that would describe how to take that sample i 1
23 and there would be certainly accuracy requirements and l 24 expectations prescribed in the procedures. l 25 DR. BONACA: Yes. I had a question though. Once i I
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1 I
81 1 you take'out these licensing requirements, as I understand l
() 2 . and I support that, in your graded QA where will this PASS !
3 system go? We don't know right now but I would see the 4- possibility that this PASS system becomes much less 1
5~ important in your graded QA and has much less attention paid l 6 to it.
7 MR. HARRISON: The PASS system, and I can only 8 speak for how South Texas would address that in our graded 9 quality assurance, and when we do, when South Texas does a 10 graded quality assurance review, this would be something we 11 would, since it is not specifically modelled in the PSA it 12 would be looked at by our expert panel or our working group 13 and what do we need that function for in a post-accident, as 14 a. post-accident requirement.
O)
(, 15- And then they,would determine whether that got 16 ~ some additional requirements or they would look at what are
- 17. the critical functions for this system of what would be 18 required for this system as far as accuracy or performance 19 requirements and how we would monitor this system.
20 And I think, Bob, you want to add something there.
21 MR. LUTZ: Yes. If I could try to provide a 22- little bit of a clarification. What we're talking about 23 t here, if the proposal that we're putting forth is approved, 24 we would maintain the capability'to draw a sample under 25 highly radioactive conditions, and we would be talking about
'O
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82 1 grab samples, and most'likely'that would either go and be
() 2 3
analyzed after dilution on the normal equipment that's used every day in the plant to measure pH or chlorides or 4 whatever, or some special facility that would be shipped out 5 of the plant lab to something else that's set up or 6 whatever.
7 So in terms of accuracy requirements for analyzing 8 for pH or something, we're actually using the equipment 9 that's used every day that's calibrated on a quite regular 10 basis. So it's not that we're neglecting accuracy. We're 11 just trying to get it out of the regulatory space, which is 12 actually what's costing the utilities the burden.
13 DR. SEALE: And, you know, that's fine. If you're 14 going to use the normal analytic requirements for your
() 15 laboratory as far as the instrumentation is concerned, then 16 I can understand where truly the dilution is the great 17 unknown, and you may satisfy that in a procedure that 18 requires you to take five samples and take the average or 19 throw out the obvious wild cards if you have an error in the 20 dilution process. And that doesn't have to be in the 21 requirement here.
22 The staff may want to take a look, though, at some 23 point in an annual QA audit as to how you handle those kinds 24 of -- or what your procedures say would be the way you'd 25 handle those things. But eliminate accuracy. That just --
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83
.1 MR. LUTZ: Well, we're not going to eliminate the (f 2 accuracy, we're going to eliminate the requirements.
3 DR. SEALE: All right, we've beat that horse hard
-4 enough, I think.
5 MR. HARRISON: The conclusions with respect to the 6 Postaccident Sampling System are the same as the conclusions 7 that we made with respect to the Core Damage Assessment 8 Program is that the changes actually have improved the j 9 effectiveness of the emergency plan. We still, as Bob 10 presented, we focused on prompt information that we can get 11 from instrumentation and makes the PASS system a practical 12 system for use for long-term recovery.
13 Proposed _ changes support the ability to maintain a 14 safe, stable plant state following a core damage accident in
() 15 the long term. I think that's a practical use for the 16 Postaccident Sampling System. I think that we recognize 17 that it certainly does have some applications for long-term 18 planning and monitoring of the plant status.
19 Are there any questions on that?
20 Briefly go through some -- there were some 21 questions that we'had from the Nuclear Regulatory 22 Commission. I think we were just talking about the first 23 one-on the removal of the Postaccident Sampling System from 24 the licensing basis. What we are working through that issue 25 -with the reviewer is to clarify exactly what that means and
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84 1 .how that should be characterized.
-I m) 2 We talked earlier during the core damage
\ J.
i 1
3 assessment presentation on the plugging of the sample lines
'4 by the aerosols. I guess throughout both of our 5 presentations we've talked about that we do not need the 6 Postaccident Sampling System to support emergency --
7 determination of emergency action levels. It's not timely.
8 The last set of questions that we nave on 9 reactivity excursion events, I think we're talking about 10 events such as a rod ejection or an uncontrolled rod 11 withdrawal. i l
12 In the case of the rod ejection that would follow 13 the same kind of scenario as a loss-of-coolant accident. We 14 would still achieve the appropriate emergency action levels 15 based on that. For like a rod withdrawal if there were core 16 damage-involved we would expect to trigger the appropriate 17 emergency action levels based on high radiation indications 18 in the chemical and volume control system and perhaps in the 19- containment. So we would expect to see those EALs triggered 20 by other parameters.
21 And heat tracing the sample lines I think was a j 22 question, and based on our assessment of the severe accident l
23 phenomena, we don't believe that the hest tracing would !
24 prevent' aerosol deposition in the sample lines.
25 DR. KRESS: I think you can be sure of that. i I
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85 1 MR. HARRISON: And as far as uncertainty, there I I Q
2 was a question on uncertainty quantification. I think --
3 and Bob may want to elaborate.on this -- that we didn't 4 relate it to quantification of the uncertainies. It was 5 .necessary based on -- I think it was based on the broad band
.6 of the general uncertainties.
7 Do you have anything you want to add on that?
8 Okay.
9 DR. KRESS: What was that last bullet related to, 10
~
-the uncertainties in what, the uncertainties in the 11 assessment of the extent of core damage? Is that what that 12 meant?
13 MR. HARRISON: I think actually-in the --
14 DR. KRESS: I mean, I don't understand the issue, 15 . frankly.
16 MR. O'BRIEN: This is Jim O'Brien. Since I wrote 17 the question, I can.tell you what the issue was. It related 18 to the uncertainty in estimation ~of source term inside 19- containment from'the different parameters, either if you're 20 using --
21 DR. KRESS: .From going from these secondary 22- parameters to a natural source term.
23 MR. 6'BRIEN: Correct.
4
- DR. KRESS: -So you need to know what range you 25 .really could interpret those -- because you're making your i, O ANN RILEY & ASSOCIATES, LTD.
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86 1 decisions really based on a source. term.
i.y\ 2. MR. O'BRIEN: Correct'. Because your PASS gives 3 you a certain accuracy vice core exit thermocouple and )
4 subsequent transport --
.5' DR. KRESS: So you'were asking'whether or'not that 6 uncertainty needed to be quantified?
I 7 MR. O'BRIEN: If it had been quantified as part of I i
- 8. their work. I i
9 DR. KRESS: Yes.
l And their answer is it's not j 10 necessary, and how do you feel about that?
Il MR. O'BRIEN: Well, I can come up and go through 12 my whole presentation, or --
13 DR. KRESS: Oh, you're on next. l 14 MR. O'BRIEN: I'm on next. ,
('/T y_ 15 DR. KRESS: Okay. We'll wait. Okay. Sorry about i 16 that.
17 ~MR. HARRISON: That concludes my part of the I 18' presentation. If there are no further questions, I will --
19 I have got us back' on schedule.
20 .DR. KRESS: Yes, thank you for that.
21 DR. SEALE: You sure have.
22 DR. KRESS: We appreciate that.
23 MR. HARRISON: 'And I'll turn it over to the NRC.
24 MR. O'BRIEN: Good morning. Is that loud enough?
25 DR. KRESS: .That's good.
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87 1 MR. O'BRIEN: Okay. My name is Jim O'Brien. I
() 2 work in the Emergency Preparedness and Health Physics 3 Section in NRR, and I'm the lead reviewer on the PASS WCAP 4 from the Westinghouse Owners' Group. But I have several 5 members of other branches in NRR that are involved in this 6- review. I have some expertise I'll call it in the 7 radiological and emergency preparedness areas, but we have 8 . experts in other areas, and they're listed here.
9 We have Kris Parczewski from the Materials and 10 Chemical Engineering Branch to review the pH oxygen 11: conductivity and chlorides aspect of the PASS sampling.
12 From the Probabilistic Safety Assessment Branch and 13 previously the Containment Systems and Severe Accident, when 14 it was called that, Bob Palla, who also looked at the core
() 15 damage assessment. Reactor Systems Branch, we have Lambros 16 Lois, who assisted'in that. From the Materials -- Kris 17 Parczewski is the person from the Chemical Engineering 18 group. And I'm from Emergency Preparedness again.
19 .The Westinghouse presentation didn't really go 20 through the background on PASS. We heard background on core 21 damage assessment. PASS is more than just core damage 22 assessment, so.I thought I'd just touch briefly on that 23 there are several different capabilities. One is -- that 24 were' prescribed in-NUREG-0737, one being to be able to
- 2 5. obtain certain radionuclides in the reactor coolant and
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1 88 1 containment atmosphere, obtain and quantify. To be able to
'M j } 2 do the same for hydrogen levels in the containment 3 atmosphere and for dissolved gases in the RCS.
4 DR. SEALE: And this was within a three-year -- I 5 mean a three-hour time frame. i 6 MR. O'BRIEN: Correct. They were all within a l 7- three-hour time frame. And an important point to that is 8 this three-hour time frame was from the time of the decision 9 to take those samples. It's not from the beginning of the 10 accident necessarily. So depending on the situation, on how 11 things are progressing, you want to have the capability.
12 And I think that's important. It's a capability, and what l
13 is a capability? It's equipment, personnel, and training '
14 really is what involves a capability. So what your time O
(,,/ 15 frame for having to be able to obtain and analyze these 16 samples would prescribe what equipment you might need, what 17 training you might need, and what procedures you might need.
18 So that's the capability. And when we're talking 19 about relaxations of those capabilities or eliminations, 20 then we ask ourselves what does that -- how does that change 21 the capabilities that you'll have at the plant.
22 I'm sorry, I went too fast on that. These 23 requirements, and I call them requirements, they're not 24 requirements, they're guidance, as Westinghouse stated, 25 those 737 criteria were in many times put into license
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L 89 1 conditions and became conditions for license of that 2 specific plant.
3 Regulatory Guide 1.97 also contained a guidance
'4 relationship to PASS sampling. It had very much the same 5 ones as in NUREG-0737, and it had some additional ones 6 related to containment sump and measurement of pH.
7 Now the reexamining of PASS criteria is not trand
.8' ~new. The NRC undertook a study itself under NUREG as 9- reported in -- we contracted out a study performed by 10 Pacific Northwest Laboratories and reported in 11 NUREG/CR-4330. This NUREG looked not only at PASS but a 12 bunch of other regulatory requirements that have marginal i
13 importance to safety, and PASS was one of those that was 14 identified'and looked at. And the results of that study was )
() 15 that the relaxation of sampling time had a marginal effect 16 on' risk to the public except potentially for boron. And it I
17 also looked at the costs of the PASS and it said that it had H l
18 marginal -- it was not a high-cost issue.
- Now Westinghouse 19 has provided new information related to cost under today's 20 current environment. I 21 One thing to be clear, these are contractor 22 reports that we did not act on to,take any regulatory action 23 from, but it is information that we used and consider as far 24' as our current review.
25- SECY-93-087 was a paper we put to the Commission
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90-1~ 'in relationship to pol' icy and technical and licensing issues 2 ' pertain.ing to evolutionary and advanced light-water 3 reactors, and one of the issues that was looked at was the
'4 ~ relaxation of sampling time for advanced reactors.
{
5 In that paper there were relaxations that were 6- recommended to.the' Commission in relationship to -- let ma 7 make sure I've got it right here - for boron relaxation to 8 ~'eight hours for sampling, eight-hour capability, and for ;
9- radio 14uclides and dissolved oxygen relaxation to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, 10 ,and hydrogen was to be -- sampling was recommended to be 11 eliminated, I believe. Is that correct, Jerry? Okay, I'm
- 12. pretty sure it was, but we'll make sure that that's the 13 case. And it had to do with the fact that you had hydrogen 14- monitors in your required.
15- The latest. action is related to this WCAP that 16 . Westinghouse submitted in August of 1998, and now I'm going 17- .to talk about that. Does anybody have any questions on l
-18' previous history?
19' DR. KRESS: Maybe you could talk about the PNL l
1 20 -bullet on boron. They seemed to think that had more than !
21 -marginal risk to be able to sample, measure for boron.
22 MR. O'BRIEN: Yes.
-23 DR. KRESS: Was that for BWRs or PWRs?
24- MR. O'BRIEN: I don't knew the answer to that 25 .question. I don't know -- Lambros, if you've had the j l
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fi 91 1 opportunity to look at that in detail on the boron.
( 2 MR'. LOIS: What is that?
3 MR. O'BRIEN: Under NUREG-4330.
4 MR. LOIS: I don't have that.
5 MR. O'BRIEN: Okay. I'm not sure.
6 DR. KRESS: Okay.
7 MR. O'BRIEN: The Westinghouse report, which I 8 acknowledge I thought did a good job on looking at this 9 issue, is a pretty good document as far as educating me on 10 the scope of how PASS is used and looking at it in 11 accidents -- that's used under accident conditions. I'm not 12 going to go over each one of these, but it did look at the l
)
13 background of the issue, went through that, characterize
]
14 core damage accidents, diagnose conditions, accident (f 15 management guidance, including EOP, severe accident 16 management, and emergency plans, and took a detailed look at 17 evaluation of the PASS requirements and made recommendations 18; out of that. i 19 One of the issues that we have with this report, 20 and it's kind of brought up in the licensing basis 21 discussion we had, is what the actual relaxations are that 22 are being requested. In some case it's -- there was a table 23 provided in the WCAP, Table 7 at the end of the report, that 24 succinctly states in less than a sentence what its
-25 recommendation is for each of the PASS requirements, and it ANN RILEY & ASSOCIATES, LTD.
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F 92 1 would state, for instance, I have it right here, for this
, (-A) .2 'first one that we're going to look at, for RCS dissolved 3 gases the requested relaxation as stated in the table is 4 delete from PASS, but if you look into the text for this 5 ~ statement it'doesn't go into detail what that means. It 6 'says thus PASS for RCS for noncondensable gases is not 7- required'to reach safe stable. state following an accident.
8 So one of the things we're trying to clarify with 9 Westinghouse, and'we will be clarifying, is exactly what it 10 is that is remaining and not remaining and where it's 11 remaining and how it's controlled into_the documents.
12 For this discussion I'm being brief and just 13 taking the words right out of the Table 7 where it says 14 delete from PASS. Because the way we looked at it from a
.(,A) . .15 safety perspective as if it was gone, nothing is there. So 16- that's our review.
17- For deleting of the dissolved gases our 18 preliminary staff positions, and I emphasize that these are 19 preliminary, they have not been through the management.
20- review process, is_it's acceptable for plants with reactor 21' vessel level instrumentation system. And the rationale for 22 that position is that diagnosis and remediation are 23 available via the RVLIS and the head vent to remove the 24 dissolved gases. And then we also recognize that there 25 would be a delay. The delay between any sampling that could x
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93 1 take place and the availability of the results.
() 2 DR. KRESS: How does the RVLIS and head vent give 3 you an indication of dissolved hydrogen?
4 MR. O'BRIEN: It doesn't give you an indication of 5 that, it gives you an indication of its effect, if it's 6 causing it -- go ahead, Lambros.
7 MR. LOIS: Yes. The water level is really what is 8 of interest'here, and should you have evolution of hydrogen 9 or noncondensable gases, the top of the core, then you will 10 suppress the water level. That's where RVLIS comes in. The 11 same time there is the head vent, which you can remediate
.12 that situation.
13 DR. KRESS: I read this the other way, I guess. I 14 read it that you're not going to have much hydrogen unless 15 the water levels pretty low, and having an indication of 16 the water level is probably a good indication of the 17 potential for producing hydrogen.
18 MR. LOIS: That is true. However, there are 19 situations where you may have an arrest of a transient which 20 'you do not realize and something happened, the water went 21 down, you produce some hydrogen, and then water came back 22 in. Now you have hydrogen with an arrested situation.
23 DR. KRESS: Okay. Thank you.
24 MR. O'BRIEN: The second issue is -- or maybe I 25 should clarify that. On the table provided at the end of ANN RILEY & ASSOCIATES, LTD.
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94 1 the WCAP was a succinct listing, it's only one page, of each
() 2 of the sample points and the analysis that were being 3 changed in their document, recommended to be changed, and 4 that's where my presentation is going through, each one of 5 those items. It will be about 13, I think.
6 The second one is RCS hydrogen, sampling for RCS 7
hydrogen, and again the WCAP recommends deleting from PASS.
8 Our preliminary staff position is that it would be 9 acceptable, and the rationale is the same as for the 10 dissolved oxygen -- or dissolved gases, used in the same 11 manner.
12 The RCS oxygen sample, again delete from PASS, and 13 preliminary staff position is it's acceptable. The 14 information is used to evaluate the potential for stress
) 15 corrosion cracking of stainless steel components. The 16 information is only needed when chlorides are present and 17 that the concentration can be fairly accurately estimated 18 through other means. So we're accepting the proposed 19 relaxation from this requirement.
20 Reactor coolant system pH again delete from PASS.
21 It is considered preliminarily as acceptable. The rationale 22 for our accepting this position is most of the incoming 23 order will come from the containment sump whose pH is 24 controlled and the operator will be aware if water with 25 uncontrolled pH is injected to RCS and can take appropriate O ANN RILEY & ASSOCIATES, LTD.
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95 l 1 corrective actions.
( ). 2 DR. KRESS: Is that a general statement for all 3 Westinghouse pla7ts that pH is controlled for the sump?
4 MR. O'h3IEN: I don't know. That's a good point.
.5 We will have to make sure if that is going to be our 6 rationale.
7 DR. KRESS: Actually, I didn't think it was, 8 frankly.
9 MR. O'BRIEN: Okay. Chris, do you want to address 10 that?
11 MR. PARCZEWSKI: Chris Parczewski, Chemical 12 Engineering Branch -- pH in RCS will be determined mostly by 13 the water coming from the sump and the sump water is, the pH 14 .is either controlled by passive control or by injection of
) 15 some of the hydroxides through the distribution, and so 16 therefore it is related to the pH in the sump, mostly.
17 DR. KRESS: We had a hearing some years ago on 18 removing-the requirements for the sodium hydroxide in the 19 sprays. What ever happened to that suggestion?
20 MR. PARCZEWSKI: Well, yes, but in that case there
~21 was a passive control. They used trisodium phosphate.
22 DR. KRESS: In bags --
23 MR. PARCZEWSKI: In the sump, yas.
24 DR. KRESS: In the sump.
25 MR. PARCZEWSKI: Which buffered the solution to l'\~ )/ ANN RILEY & ASSOCIATES, LTD.
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96 JL ~about 7, so you never really completely removed the control
[)
'%.J 2 of pH, 3 DR. KRESS: Is that in all of the Westinghouse f
4 plants?
5 Is that also in_the ice condenser plants?
6 MR. PARCZEWSKI: This applies to all the plants.
7 MR. BRYAN: This is Bob Bryan. In ice condenser
-8 plants the way we buffer the sump is by using sodium 9 tetraborate in the ice and that provides the buffering 10 agent.
11 DR. KRESS: When the ice melts?
12 MR. BRYAN: For the ice melts, so we don't have to 13 add trisodium phosphate or have an active thing. It's in 14 the ice.
( 15 DR. KRESS: Okay. That I didn't realize.
16 MR. LUTZ: Just to clarify -- this is Bob Lutz 17 from Westinghouse -- I don't know of any Westinghouse plant J l
i 18 that does not have some pH control. l 19 MR. O'BRIEN: Next up, the point RCS chlorides and ;
20 the request is to delete from PASS and we find it acceptable !
i 21- preliminarily and the RCS chloride, the reason for it, is 22 the RCS. chloride concentration can be fairly accurately 23 predicted.
24 DR. KRESS: Good you give me a little background I 25 on why they thought that was needed in the PASS system
[~N N
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97
- I anyway?' I know it is a stress corrosion / cracking issue but 2
- isn't that covered by the water chemistry system for the 3 normalioperating plants?.
4- Did someone envision ~that you would have an j 51 accident and the plant would have to sit there for years and 6- years trying-to recover.and you would have to worry about 7 .some sort of stress corrosion issue? Why was it even part 8 of'the. system?L 9' MR. O'BRIEN: I would have to defer to Chris who 10 is the chemistry folk on that one.
11 MR. PARCZEWSKI. I didn't hear your question.
12 DR. KRESS: My question has.to do with concern 13 over chlorides.
14 Is the stress corrosion / cracking problem or is it ;
15~ -a chemistry problem relating to re-evolution of. hydrogen 16 from water sumps? Maybe'you.could be more specific on that.
17 MR. PARCZEWSKI: Really-there are two problems.
18 One is stress corrosion and cracking. The other one is 19: re-evolut' ion but you see what happens, chloride by itself 20 wouldn't effect chemistry of iodine, but chloride comes very 21 often as hydrochloricfacid.
~ 22 It generally:comes from decomposition of
'23- isolation -- -l 24 ~ DR..KRESS: It affects pH.
25 DR..SEALE: Absolutely.
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w 98
.1- MR. PARCZEWSKI: And this affects pH. If pH drops 2 below'7 you have conversion of the iodine in the form of --
3: -into the elemental form.
'4 Iodine elemental form will have very low partition
- 5 coefficient and eventually there is going to be a release 76 'into theLeontainment, so really it is indirect effect of 7 chloride.
8' DR. KRESS: So if you had a buffered system you 17 would;not have worried about this?
10 MR. PARCZEWSKI: Yes, if you'had a buffered system 11 you shouldn't worry'about it.
12 DR. KR.ESS : Appreciate that.
13- MR. O'BRIEN: Reactor coolant system, boron 14 ' sampled. Request is to extend the time for sample and 15' analysis to eight hours after' achieving a safe, stable core 16 condition and to relax sampling accuracy as Westinghouse 17 representatives discussed.
118 The preliminary Staff position is that both these 19 requests would be acceptable and that the rationale.for it 20 is that boron.is used as a backup to other indications of 21L _ criticality concerns and that sample accuracy in difficult.
22 ~ to obtain due to the need for dilution of the sample.
23 DR. KRESS: What are the other criticality 24 indicators?-
- 25. MR. O'BRIEN: The neutron flux.
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p-s 99 1 DR. KRESS: Tae neutron flux-coming out of the w
2 core?
V J3 MR. O'BRIEN: Ex-core, yes.
J4' DR. BONACA: Is this eight hours tied to boron 5- precipitation concerns?
6 MR. O'BRIEN: I have to defer to the technical 7 reviewer, Lambros Lois, 8 i- MR. LOIS: Yes, As a matter of fact we did 9 receive a question and a comment from Dr. Dana Powers on 10 this issue, so I amt glad that this is back on the floor.
11 Let me first clarify that we accept -- what we 12 will be glad to accept -- glad to.suggest to the Owners 13 ' Group is eight hours not after a stable condition has been H14 ' achieved, rather than eight-hours after initiation of the
() 15 transient,. unlike what is written on the viewgraph.
~
16 The other thing is let me bring back the accuracy 17 . situation. The 5 to 10 percent relaxation which was 18- requested by the Owners Group, we find that it is
- 19: technically necessary in the sense that1 if'there is dilution 20 in the rate of let's say 10 to the 3rd, they are retaining 21 that plus;or minus 5 percent accuracy which was written in 22 ~the requirements. It.may become technically impossible. In 23- fact,.to= achieve it one may need to spend a heck of a lot of 24- time and therefore it becomes a "no, nevermind" so therefore
'25 .one -- welwould prefer.to have it plus or minus 10 percent
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'1 rather;than have plus.or minus 5 percent five hours later,
. t. I
[ 2- which'would..be useless.
- 3 Now regarding the plateout and the possibility of l l
4~ ' reaction with fission products, we see that the amount of j 5 ' boron is so large in terms of gram or moles that even if 1
6 there is such reaction, some reactions probably will be that 7 'willisolidify and precipitate boron'it will.be a minuscule
.8 l amount, so with' respect to the amount of boron that is in 9 the RCS it will be practical irrelevant.
"10- With respect to the plateout because.of cold .
I T il- surfaces, in the context of an accident situation the )
.12 . temperatures will be hardly conducive to plateout.
)
13 Temperatures will be extremely high.
1 14 I do have a table we use from time to time. In !
. .D -
j Q 15 fact, it is quite an old one, but I don't think things have 16 ~c hanged, that plateout -- for example -- at about 30 or 40 1' 7 - ' degrees is in the neighborhood of 4400 DPM. That is about 18 three. times more then what you probably need to keep the 19
~
core quiet _under these circumstances.
20 Should there be any loss of core geometry, then-
.21 the amount of boron that you need to keep it quiet will'be 22 .even lower because optimum conditions occur when the core c --2 3 :hasinot changed its geometry, so therefore that contributes 24 in'our'_ decision to accept the plus or minus 10 percent, and I 25'- we also do not-believe that there will be any significant
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101 1 amount of boron precipitation in the timeframe that this ;
() 2 applies to make any difference in the core criticality.
1 3 DR. KRESS: I think Dana's concern is not i
4 criticality. It was with the potential effects on the 5 fission products. j i
6 MR. LOIS: Yes. As I pointed out, the amount of f
7 such precipitation, should it occur, and I am sure some with 8 fission products, but it will be negligible with respect to 9 the amount of total boron that is present in the RCS.
10 DR. KRESS: Could you make some sort of assessment 11 of that some way?
-12 MR, LOIS: Back of the envelope type, yes. Total 13 amount of fission products you assume that they somehow
-14 react, it's.Very small.
O( ,/ 15 DR. KRESS: Boren likes to patch itself to 16 zirconium and stainless steel at fairly high temperatures ;
17 during an accident situation. Did you somehow factor that k I
18, into your back of the envelope calculations?
19: MR. LOIS: That specific reaction, no, I have not f
1 20 seen that. '
21 DR. KRESS: I think Dana's concern was under an 22 accident condition when you are boiling off the RCS water 23 that you are also boiling off, because it has volatility )
l 24 relationships, you are boiling off the boron and it sees a 25 fairly high temperature in the upper parts of the core and I
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102
'l patches _itself there and then you release the fission
[\ f2 products.and it does things to both cesium and the iodine fsi.) o
- 3. fission products that makes them more volatile.
4' ;It impacts this 2 percent release'from the RCS 1 5_ under high. pressure accident conditions. He is questioning I 6' since that 2 percent was developed without considerations of 7 ' th'ose kind of cheniistry' ef fects, he was worried about
~
8 whether it is a good number and:if it actually was much 9 higher, would that affect our conclusions and decisions.
10 MR. LOIS: Right. 1
- 11. DR. KRESS: That is the nature of his question.
'12 MR. LOIS: That's true. That's correct. However,
.13 this scenario envisions and' extends the core damage in 14 extremely high temperatures. This particular case you no
() 115 longer have intact geometry in the core and you no longer 16 need boron to keep it down. I mean if_it's semi-spherical 17 at the' bottom -- in these cases boron is irrelevant.
- 18. When it is relevant is when you have partial core
-19 damage. You have some releases but-by and large the core is 20- .there and you can regain criticality should you put back in 21' water for moderation. I 22 DR. KRESS: But most of your focus was' 23 recreating --
24 MR. LOIS: .Yes, he did. That's right, and that is 12 5 what I still believe is the essence of any meaning of these
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103 1 investigations here.
' /Y 2 MR. O'BRIEN: The next sample point in analysis
.V 3 ,was RCS conductivity and this was never a NUREG-737 or Reg 4 Guide'1.97 specified item. .However, some Westinghouse 5 . plants had the capability to do that so it was evaluated as 6 part of the WCAP and they recommended deleting that
- 7. capability and we find that acceptable, 8 We never had a' requirement on it anyway.
9 RCS radionuclides. That's also being requested 10 delete-from PASS, and staff, we're still considering this 11 issue, and some of our thoughts on this is that that 12 information would be useful in assessing the potential dose
.13 consequences of an accident, and that the information there, that dose-consequence evaluation could be used in assessing l
14 j
( ). 15 the adequacy of. initial protective action recommendations.
16 -DR. KRESS: Was any consideration-given to 1
17 measuring-the RCS radionuclides in a different way than j l
18 sampling? And I.had in mind there direct gammas looking for l 19 just cesium and krypton, which has. pretty good and ,
20 well-defined gammas that you can' differentiate for the total 21 -reactivity very well.
'22 MR.-O'BRIEN: Yes, and your earlier question when 23 you were talking to Bob kind of indicated down the same
.24 line, why did they have a sample taken --
25' DR. KRESS: Yes, ANN RILEY & ASSOCIATES, LTD.
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4 w
3 104
'1' MR.'O'BRIEN: Rather than measure these direct
- /~
t .2- gammas.
3 -DR.,KRESS: .I-would have done the cesium and L4 kryptonimyse'lf, 5 JMR. O'BRIEN: I don't know to that' level of-detail 6 how these systems work as far as -- I know there are some-
'7- inline monitor systems, and that's really where the costiis 8 in the industry that we're seeing,'that could take these 9 samples and'it-would almost be real-time,-and samples get 10 drewn and I guess they go through some kind of a 11 spectrometer.to make a determination. Those things have
-12 been if'I understand hard to maintain and~ keep accurate. So 13 there is a limited number plants that have those. Most of 14 ~them-have grab ~ sample' capabilities.
I 15 So why not do this?- I believe there are some 16 plantsithat go out and.can take a reading on a line to get'a
-gross-idea of whether there's a lot of radionuclides, but 18 not'to do a spectrum analysis.
19 DR. KRESS: ;Yes, well, you know, I didn't really 20 wantLa' spectrum analysis,.I just' wanted to look at the gamma 21 that comes from xenon and krypton. You don't have to do a
.22 ' spectrum analysis. You can make your system do that 23 directly. H l
24 'MR. O'BRIEN: -Okay. You just want a gross --
25 DR. KRESS: Yes.
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{
105 1- .MR. O'BRIEN: Radionuclide content.
2 DR. KRESS: - No , it would give you the cesium and 3 the krypton, because it looks only for those particular 4- ' gammas.
1 5 MR. O'BRIEN: Okay.
{
6 DR. KRESS: And if I had the cesium and the 7 krypton, I could pretty much tell you how much noble gases 8 and how much iodine and how much other stuff is there much.
"9 more accurately than I could from using the thermocouples, '
10, for example.
11 MR. O'BRIEN: I think that's -- it's an insight I 12 didn't have befo're this meeting, and I think it's one we're 13 going to take back and discuss with our -- I'm mostly 14 -emergency preparedness, so I'11 be talking with my 15 radiological health physicist to -- 1
- 16. DR. KRESS: Well, the' thing about it is, it's.--
17 'everything we have now in the proposed revision is an 18 : indirect measure. j 19 MR. O'BRIEN: Correct.
20 DR. KRESS: But most of them are leading measures, i
21- .so.they're real.' good,'and they.can be used as'a way to
~
22 calculate and estimate what you get. But you really don't
.23 have a direct measure anywhere. And that's what you're 24 saying here. It's useful'as a_ direct thing. Well,- I think 25_ you could.have another direct' measure, and that would be O
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106 1 these -- just look for gammas from cesium and krypton. And
(' f U
2 it's the only direct measure you would have.
3 MR. O'BRIEN: Yes, we consider this sample taken 4 as just one of many sources of information regarding the 5 potential radionuclides that would be released in an 6 accident that we are interesting in getting, and other 7 indications if you do have an actual release would be either 8 a vent monitor or field team measurements. And we're trying 9 to consider all these different pieces of information to see 10 what we gain or lose or how much we lose by not having this 11 potentially more direct indication removed. And that's what 12 we're playing back and forth right now in our 13 considerations.
14 DR. KRESS: But you're saying it's still under
() 15 consideration.
16 MR. O'BRIEN: Yes, it is. And what we're looking 17 at, just to. kind of recap again, is the capabi2ity issue, if 1 18 you're deleting the capability. We don't require somebody l 19 to go out and take these samples'three hours after the 20 . initiation of an accident. We have a capability that if it 21 wanted to be taken, it could be taken within three hours.
22 Containment atmosphere hydrogen. This one Bob I 23 3alla had to look at. It was a relatively easy one, I 24 believe. There was actually -- it was a little confusing
- 25. -what Westinghouse was requesting on this, because it sounded ANN RILEY & ASSOCIATES, LTD.
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107 i i like they.were either saying you have to have the capability
(~'t 2 'to have a hydrogen monitor, keep your hydrogen monitor, or V
3 sample and being able to sample within 30 minutes and 15 1 4 minutes thereafter, every 15 minutes. But I think the real 5 request was for elimination of the, since this is a PASS,
'I 6 was elimination of the PASS sample and maintenance of the 7 hydrogen monitor. We found maintenance of the hydrogen 8 monitor and elimination of the PASS sample to be acceptable.
9 The other way around we would not find acceptable.
10 The reason for not finding it acceptable for the other way l
11 around is because there's regulations related to the 12 hydrogen monitor, and it's a more real-time indicator.
13 Atmosphere oxygen, just for completeness, the WCAP 14 addressed this, but it's not required for PWRs, and O)
( 15 therefore we find it acceptable. It was not required under 16 0737.
17 The containment atmosphere radionuclides is the 18 same consideration as what we discussed for the RCS 19 radionuclides. The information we considered to be another 20 piece of information useful in emergency response in 21 understanding'what the potential releases may be upon 22 containment failure, mainly for determining what the 23 radionuclide isotopic compositions would be that would be 24 released to factor into dose assessments.
25' DR. KRESS: Here once again I would say you could I} ' ANN RILEY & ASSOCIATES, LTD.
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l 108 i 1 do that if you just measured the gammas from cesium and r
j 2 krypton.
x/
3 MR. O'BRIEN: Yes, and -- l 4 DR. KRESS: You could make a good assessment of a
5' the radionuclides from that.
6 MR. O'BRIEN: And if that capability was there, I 1
7 think we would find that acceptable. !
i 8 DR. KRESS: Yes. I don't think it is. I think !
I 9 they just look at total gammas.
10 MR. O'BRIEN: Well, they take the sample and they )
1 11 do a spectrum analysis. They go over to the laboratory to f
1:2 ' analyze it. j 13 DR. KRESS: Yes, and that would probably be all 14 right for containment, too. You know, it's not very good j (r'
s_-
) 15 for RCS but for containment that would probably be all l 16 right. I 17 MR. O'BRIEN: Um-hum. That's the current 18 capability, that the idea is to eliminate that capability, !
1 19 is where industry would like to go. As stated in their 20- presentation and in mind, we looked at it from a deletion l 1
21 from PASS. l l
22 DR. KRESS: Yes. l 23 MR. O'BRIEN: Their real indication is they'll be 24 maintaining it, but outside the licensing basis, so being 25 that we're doing a licensing review, we're reviewing it as ANN RILEY & ASSOCIATES, LTD.
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F i 109 1 it's not there, 2 DR. SEALE: And you're still up in the air.
[mxs}
l 3 MR. O'BRIEN: And we're still up in the air on 4 this one. We're considering how -- it's one of the many l 1
5 pieces of information that could potentially be used during 6 an event. We're sorting out how it fits in with all the 7 other information.
8 DR. SEALE: So if we have a strong position on )
9 that one, you'd like to know about it. !
(
10 MR. O'BRIEN: Correct. l 11 DR. SEALE: Okay.
12 MR. O'BRIEN: And in the end I'll recap on that 13 issue a little bit so I can provide a little bit more on -- l 14 as an overview on some of the ideas that we're playing
() 15 around on.
16 Containment sump pH for plants which have the 1
17 brackish water plants as described by Westinghouse, and 18 without passive pH -- well, excuse me, they would like to I I
19 eliminate it except for plants which have the potential for l 1
20 leaking chlorides and without passive pH. l 21 DR. KRESS: When I questioned them on this I got a ,
l 22 difEerent sense of what they want to do. They just want to j l
23 eliminate the requirements for the time but keep the ]
24 capability for sump pH determination.
25 MR. O'BRIEN: It's once again that issue of l
l l
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a r 110 1 licensing basis and outside license basis. Our review was n
2 it's gone because it's out of the license basis.
(v) 3$ DR. KRESS: It's gone because it's out of H
4 licensing basis.
5 MR. O'BRIEN: Correct. Dut the capability as they 6 stated would be --
7 DR. KRESS: Sut if they included it in their 8 updated FSAR, that they would maintain this capability 9 without the timing, then it would be part of the licensing 10 basin?
11 I heard them say they would include it in an 12 updated FSAR.
13 MR. O'BRIEN: That's correct. That's one of the 14 things that as a staff we have to take a close look at, r~T
( ,) 15 because what controls are there under that constraint, 50.59 16 and so forth, is that the controlling factor, and if you 17 look at a 50.59 evaluation, is that really any control for 18 this aspect, when you consider the questions requested and 19 so forth.. So that's -- we're considering it.
20 We find the recommendations provided in the WCAP 21 to be acceptable, ;.n6 the rationale for our staff position 22 is the pH in the sump is controlled and could be estimated 23 for plants with low chloride ingress.
24 I apologize for the repetitiveness of this, 25 because there's different -- same things are taking samples I '
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111 r
-1' at~different locations, but containment sump chlorides, once
'l"lE 2. .again,l delete from PASS,'and we found it acceptable, and the
' \_ /
rationale is it can be estimated from the chloride in
~
3 4 incoming water.
5 We have two more. Containment sump boron and this 6- one'is'to be deleted from PASS, and we found it acceptable 7 .because the boron can be estimated from knowledge of sources
'8 of water being'added to the sump.
9 The last.one is on containment sump radionuclides, ,
10, 'and once'again'that's one being under consideration for the ;
11 same reasons that I discussed before, its potential for use l
12 in dose consequence refinements and subsequent protective 13 action refinements. I 1
14- DR. KRESS: That has the same flavor of if it's f-w
(,
15 deleted from here it's out of the lasting basis -- l 16 MR. O'BRIEN: Correct. I 17 DR. KRESS: Even though they plan to keep it~.
18 So --
19 MR. O'BRIEN: 'Yes, that's correct. And once again 20 it comes into -- it comes into two things. One is that --
21 the deletion is also no timing requirements, so that comes 22 into a capability. What kind of~ capability are you going to
'23 maintain. Are you going to have in-house analysis 12 4 capability or are you going to be sending'it offsite. And 25 questions of that nature that we're looking at.
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]
112 1 That concludes my-review of the indi'ridual items.
2 I was going to provide a brief discussion of the open issues
~3. that we'see.
4 DR. KRESS: Okay. Great.
5 Do you have slides?
6' MR. O'BRIEN: Lo, I didn't have slides.
7 DR. KRESS: Okay. We're all in the dark.
8 MR. O'BRIEN: I didn't realize how much light that 9 thing put off.
10 DR. KRESS: -How's that?
11 MR. O'BRIEN: Thank you.
12 Okay. The issues -- I apologize for not having 13 slides; after I went through this and heard the discussions l
14 I probably should have. But it's two issues that we are
'gA) 15- really focusing on, and one is the clarification of the PASS.
16 capabilities and how they will be controlled, the idea of 17 outer licensing basis, no timing requirements, adequacy !
18 requirements which you guys identified as something that is 19 of an issue. We want to assure that we understand 20 completely what that means. And we've interacted with 21 Westinghouse Owners' Group, and they've been receptive to 22 .that and provided the information that they were keeping it 23- 'in the FSAR. The ball's in our court now to look at that 24 and evaluate what that is as far as its acceptability. ,
25 The second issue is the one related to the l
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113 1 radionuclide sampling, and this is an issue that's, being an
[~T
, s) 2 3
emergency preparedness person, and we're pretty close to it, there's a lot of people who have a lot of different ideas on 4 this, and~we're listening to them all, from all different --
5 NRR. But what we see is that there is -- the poscaccident 6 i sample is potentially the best sample or best quantification
-7 of what you have in your containment or have out in the RCS 8 . which could be potentially released to.the environment.
9 There's certain accident-situations that you would 10 want that information, and the reason you would want it is 11 that after you -- when you get in an emergency and you have !
12 a core damage accident, the first thing you're doing is 13 you're evacuating your personnel or evacuating the public in 14 a two-mile radius, five miles downwind, based upon reaching i 15 a general emergency classification, with the general s-16 emergency classification being an indication of a core melt i
17 accident or loss of two fission barriers with a potential 18' for loss of a third. So you take that action right away 19 because you want to take the people moving before release 20 occurs. You don't wait till you see the release.
21 Next you do is you do assessments to assess what 22 would be the actual impact, consequence on the public if the 23 release occurs or if it is occurring. And the things that 24 you factor into your dose assessment include meteorology and P
25 source term. And there's default source terms you use-to do ANN RILEY & ASSOCIATES, LTD.
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114 1 this analysis, out we're.looking at refining that default
' /' ' ' 2 sourceiterm either based upon the core damage assessment, 3 which.I think that the new core damage assessment will 4 actually as I think stated by Bob improve that, because you 5 have it quicker and it can be better used. But there's 6 still the accuracy of what you actually have in your 7 containment that we want to look at or in the RCS to ensure 8 that if we do not have that' capability, what it is that 9 we're losing as far as potential emergency response actions.
10 And that's it. Those are the two issues.
11 DR. KRESS: Well --
.12 MR. O'BRIEN: Let me add one more thing. You 13 . asked what we're doing with the core damage assessment as 14 far as its SER We're also doing an SER with the PASS,
(. 15 16 WCAP -- this is issues related to -- it's more significant potentially because it relates more closely.to these Three 17- Mile Island action items and so forth. So we're evaluating 18 what is the proper mechanism for approving the WCAP, whether 19 it's just an SER and whose review it needs or what the
~20 mechanism is.
21 DR. KRESS: Well, we thank you. That was very 22 helpful.
I 23 Are there other comments from Westinghouse Owners' 24 Group or anything before we decide on what to do now?
25 MR. BRYAN: This is Bob Bryan. No , we don't have
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115 1 any other_ comments at this point. Thank you. I
'[Qh 2 DR. KRESS: Okay. The thing we need to do right 3 now 'is if we' re to have an ACRS letter we have 'tx) -- we've 4 got an hour and'a half on the May full Committee meeting, S' May 6, to discuss this very issue, and the question is what 6 could we do in an hour and a half and what should we do. I 7 presume the Westinghouse Owners' Group plans to be here, and ,
1 8 of course the staff will be here.
)
'9 My feeling is that we need to discuss both the' l
.10 core damage assessment'and the PASS. We need to do it in an 11 abbreviated way. Looking at the Westinghouse Owners' Group !
l 12 presentation, I think we can -- I think if we could say what I 13 the current requirements are, what the proposed changes are, l
14 and the technical basis for the changes. You had this in
]) 15- there. I'm trying to figure out how to focus it down. I 16 think we have -- we ought to count on maybe a half an hour 17 for the --
l 18 MR, BOEHNERT:
I'd say half an hour --
19 DR. KRESS: For Westinghouse and half an hour for
- 20. the staff.
21 DR. SEALE: Staff. Yes.
22 DR. KRESS: And the other half an hour for 23 questions. Yes. So we count on about a half an hour's 24 ~ worth of presentation on both the PASS and the core damage 25 assessment methodology.
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e 116 l
[ .1 So what was the old method, what the proposed new
'(
! Nse
/~') 2 one is, how they're.different, and what's the technical 3 rationale for'it, which is all contained in your slides.
4 You might want to -- I don't think you.need to
=5 deal with the risk issue at all, because I think it's pretty 6 clear. You'might want to think about addressing the boron .
7 chemistry issue, because Dana's going to bring it up.
I 8 mean, I wouldn't have it in my slides. I'd just be prepared l
.9 to answer his questions. i
.10- I think both Bob Palla's presentation and Jim-11 O'Brien's really only took about a half an hour, I think the 12 ' sum of the two of them, and you could almost repeat those.
13 You might want to see if you could focus them down a little 14 bit.
O
- t. ,) '15 MR. BOEHNERT: They'll have to focus down some.
I 16 Bob was almost-up there an hour.
17 DR. KRESS: Okay. Well, that's because we kept 18 him up there with --
19 MR. BOEHNERT: Jim was up three-quarters of an 20 hour.
21 MR. O'BRIEN: Yes, I thoug"* mine was 22 three-quarters of an hour.
23 DR. KRESS: Okay. Well, I thought that was -- I 24 think in particular your going over each of the items that 25 - were being proposed and telling what your position is on
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p .
s 117 J 1 them and what the current consideration is was good. That b
V 2 helped a lot. So you can do that again.
3 The overview that Bob gave I thought was very
.' 4 'useful, too. Maybe your regulatory basis, this slide would 5 be good. The core damage assessment review scope, I think 6 the Committee wants to know how -- usually wants to know how 7 in-depth of a review you've given it. So I would do that.
! .8 And your findings, preliminary findings.
1 9 MR. BOEHNERT: That's almost everything.
10 DR. KRESS: That's almost everything. Yes. )
11 \
MR. BOEHNERT: I think what they need to get onto l l
12 is the residual issues in both cases. '
13 DR. KRESS: Yes, you need to cover the residual 14' issues pretty good too.
15 DR. FONTANA: Maybe if you go through the list of l
16' what the proposals are, to remind us what they are, just go 17' through the list and then just discuss the ones you have.
18 MR. BOEHNERT: Yes, but my thought was they could 19 summarize, like Jim could summarize --
20 DR, SEALE: One chart.
21 MR. BOEHNERT: Focus on the ones that --
22 everything's acceptable pretty much, focus on the ones that 23 aren't.
24 DR. KRESS: But we need the whole list for the 25 . Committee, .even though we may have made up our minds.
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118 1 DR. SEALE: That's right.
[GT 2 DR. BONACA: One thing that -- one helpful slide, 3 if I:could suggest that.would have helped me and maybe 4- helped the full Committee would be that you're talking about-5 looking at indications of core overheating, loss of fuel 6 cladding,. et cetera, et cetera, and you explain to us you 7; want to use this detector, that detector, in your proposal.
8 It would be nice to have on the other side what is l I
9 doing it now. For example, you would have overheating, I i
maybe you have PASS, ar.d you want to use a detector, you 4
10 ;
i 11 'know, just -- that~ comparison -- if you had just one chart I 12 having that comparison, it would have simplified a lot, you 1
13 know. So this is a suggestion for the purpose of, you know, 14 we have less time next week than now. l e- I (s) 15 MR. BOEHNERT: Yes. -
]
16 DR. BONACA: If you go to that chart 14 I talked l 17 about --
I asked questions about before, that was from the 18 laboratory. You know, that's maybe an opportunity you have 19 four or five things you want to accomplish, and you're 20 proposing to use certain pieces of equipment now. It would 21 be interesting to see where PASS was provided the function 22 before, so that makes it much more summary. Just a 23 suggestion. I mean, it's not.a requirement.
24 Time is short next week, so.
25 DR. KRESS: Yes.
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119 1 DR. SEALE: Yes.
2 DR. KRESS:
( And I think I'd be interested in 3 hearing whether, you know, your assumption was that if it's 4 . removed here, it's gone, the PASS part of it. I'm not so 5 sure that's the assumption one ought to make, and is there
'6 some regulatory basis for keeping some capability of the 7 PAS!'. 3 u s '. as they described and not assume it was all gone.
8 I would like to know if there's a regulatory basis for that- .
9 And the other thing I'd like to hear from the 10 Westinghouse Owners' Group is is there already some 11 capability in the plants to look directly for cesium and 12 krypton gammas. I don't know if it's there or not.
13 I guess unless there are more comments or more 14 questions, we're ready to --
() 15' DR. SEALE: I think that-covers it for me.
16 DR .- KRESS: Well, in that case, I'll thank both 17 , sets of speakers. I think you covered the issues very well, 18 and we appreciate it. Thank you very much. And I'll 19 adjourn this meeting.
20 (Whereupon, at 11:52 a.m., the meeting was 21 concluded.]
22 23 24 25 O
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l l
REPORTER'S CERTIFICATE I
This'is'to certify that the attached proceedings l f]% .
before the United. States Nuclear Regulatory Commission.in '
the matter of:
f NAME OF PROCEEDING: MEETING: SEVERE ACCIDENT MANAGEMENT J
l; l
J CASE NUMBER:
PLACE OF PROCEEDING: Rockville, MD I
were held as herein appec,rs, and that this is the original 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. I N$ %
Mark Mahoney Official Reporter Ann Riley & Associates, Ltd.
I O
r INTP.ODUCTORY STATEMENT BY THE CHAIRMAN OF THE SEVERE ACCIDENT MANAGEMENT SUBCOMMITTEE 11545 ROCKVILLE PlKE, ROOM T-283 ROCKVILLE, MARYLAND APRll 30,1999 The meeting will now come to order. This is a meeting of the ACRS Subcommittee on Severe Accident Management.
I am Thomas Kress, Chairman of the Subcommittee.
The ACRS Members in attendance are Mario Fontana, Robert Seale, and Mario Bonaca.
The purpose of this meeting is for the Subcommittee to discuss the Westinghouse Owners Group's proposed revisions to the Core Damage Assessment guidelines and Post Accident Sampling System requirements for Westinghouse Electric Company nuclear power plants.
The Subcommittee will gather information, analyze relevant issues and facts, and formulate proposed positions and actions as appropriate, for deliberation by the full Committee.
Paul Boehnert is the Cognizant ACRS Staff Engineer for this meeting.
Portions of this meeting may be closed to the public to discuss Westinghouse Electric Company Proprietary Information.
The rules for participation in today's meeting have been announced as part of the notice of this meeting previously published in the Federal Register on April 2,1999.
A transcript of the meeting is being kept. It is requested that the speakers first identify themselves and speak with sufficient clarity and volume so that they can be readily heard.
We have received no written comments or requests for time to make oral statements from members of the public.
(Chairman's Comments-if any)
We will proceed with the meeting and I call upon Mr. Lou Liberatori representing the
' Westinghouse Owners Group to begin.
[DoCUMENTNAME: G:WoEHNERTVNTR4-30.PB)
' ADVISORY COMMITTEE ON REACTOR SAFEGUARDS
' SEVERE ACCIDENT MANAGEMENT SUBCOMMITfEE MEETING:
WOG PROPOSED REVISIONS TO CDAG/ PASS REQUIREMENTS o APRIL 30,1999
) k^ ROCKVILLE, MARYLAND
Contact:
P. Boehnert - 301/415-8065
, e 1
PRESENTATION SCHEDULE
, l ci topic PRESENTER TIME
- l. Introduction T. Kress 8:30 a.m.
i j 11. Westinghouse Owners Group j j Presentations I
! l A. Introduction L. Liberatori, 8:40 a.m. - 8:55 a.m.
Conn.Ed.
l l l B. Core Damage Assessment R. Bryan, TVA 8:55 a.m. - 9:45 a.m.
Guidelines (CDAG)
- Proposed Revisions (Detail)
{ -Impact on Plant Risk !
- Response to NRC Staff I Concerns BREAK 9:45 a.m. - 10:00 a.m.
1 j C. Post Accident Sampling W. Harrison, 10:00 a.m. - 11:00 a.m.
j System Requirements South Texas i
i Project ;
i l I;
- Proposed Modifications (Detail) i
-Impact on Plant Risk I
, - Response to NRC Staff Concems Ill. NRC Staff Presentation 11:00 a.m. - 12:00 p.m.
A. CDAG Review R. Palla l.
l 1
j - Scope, Content, i t
- Key Review issues
-Impact on Plant Risk i' - Results/ Conclusions
T O
NRR STAFF PRESENTATION TO THE ACRS
SUBJECT:
Core Damage Assessment Guideline Review DATE: April 30,1999 O
PRESENTER: Robert L. Palla TITLE /ORG: Sr. Reactor Engineer Probabilistic Safety Assessment Branch Division of Systems Safety and Analysis Office of Nuclear Reactor Regulation TELEPHONE: 415-1095 SUBCOMMITTEE: Severe Accident Management (v~l
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Revised Core Damage Assessment and Post Accident Sampling l l
Lou Liberatori/ Con Ed, Chainnan l l
Westinghouse Owners Group l ACRS Severe Accident Management Subcommittee April 30,1999 i
( i Agenda
. General Overview - Lou Liberatori, WOG Chairman
. Core Damage Assessment Methodology - Bob Bryan, WOG Analysis Subcommittee Chairman
. Post-Accident Sampling System - Wayne Harrison, WOG Licensing Subcommittee Chairman 2
O
/ \
U WOG Core Damage Assessment and Post Accident Sampling Prese itation
. Desired Outcomes ,
+ Show that the WOG proposals are properly focused on protection of the public.
+ Show that WOG proposed CDAM and PASS changes fulfill post-accident needs based on current knowledge of accident behavior.
3
,r's O
. Intended Use of CDA and PASS:
. Emergency Action Levels (EALs)
. Offsite Dose Projections
. Protective Action Recommendations (PARS)
. Assurance that the plant has been placed in a long term safe stable state
. Applicable Regulations / Guidance
. GDC-64
. R.G.1.97 4
2
a em U _
- . Based on current understanding of core damage accidents
. Revised methods will be more effective and timely
. Revised methods will be more cost effective
. CDA based on fixed in-plant instmmentation - no longer reliant on PASS
. Proposed CDA and PASS better supports accident management needs 5
O Revised Core Damage Assessment (CDA)
I I
Bob Bryan / TVA Westinghouse Owners Group Analysis Subcommittee Chairman ACRS Severe Accident Management Subcommittee April 30,1999 I
6 v'
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Core Damage Assessment Methods
. Provides a method for generally quantifying th: )
status of the fuel
. Looks for 3 fuel states 3
+ Clad Intact
+ Clad Rupture
+ Fuel Temperatures > 2400 F 1
. Used for understanding plant conditions l
I l
7 o i WOG Core Damage Assessment Methods
+ Based on early 1980's understanding of core damage accidents
+ Based primarily on analysis of samples of plant fluids o Relies on Post Accident Sampling System (PASS)
+ Meets regulatory requirements
. Revised WOG Core Damage Assessment
+ Based on current understanding of core damage accidents
+ Based on fixed in-plant instrumentation
+ Meets regulatory requirements 8
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. Incorporate new knowledge of severe accidents
+ Fission product release from core
+ Fission product retention / holdup in RCS '
+ Fission product removal from containment atmosphere
. Supports emergency response decision making used l by licensees
+ Emergency Action Levels
+ Offsite Dose Projections
+ Protective Action Recommendations 9
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Emergency Action Levels
. Based on Fission Product Barrier Degradation
. Loss or Potential Loss of Fission Product Barriers and/or
. Abnormal Plant Radiation Levels
. Can be determined from
+ System Conditions
+ Emergency Operating Procedures
+ PlantInstruments 1
+ RCS Liquid Sample
+ Site Emergency Director Judgment 10 l
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< j Offsite Dose Projections
. Real Time Release Data .
. Field Measurements l l
. Projected From Core Damage Assessment
. FSAR Accident Analysis l
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Protective Action Recommendations
. Plant Conditions (EAL)
. Offsite Dose Measurements
. Offsite Dose Projections 12 O
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1 Restised WOG CDA Based on In-Plant Instrumentation
. Information should be timely
+ Represents current plant conditions
. Information should be accurate
+ Representative of actual plant conditions to make reasonable decisions
. Availability ofinformation
+ Information would be available when needed for decision making
+ Manpower required to obtain information
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Available CDA Instrumentation l e Instrumentation that provides information into the amount of core damage
+ Core Exit Thermocouoles -indication of core overheating
+ Containment Radiation -indication ofloss of fuel cladding and RCS baniers
+ Containment Hydrogen -indication of severe core overheating
+ Reactor Vessel Level -indication ofinadequate core cooling
+ Neutron Monitors -indication ofinadequate core cooling
+ Loop RTD - indication of core overheating .
. Underlined instrumentation (above) was chosen for numerical estimate; the remaining instmmentation is used for qualitative validation 14 O
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[o Core Exit Thermocouples (CETs)
. Revised CDA uses CET indications to estimate degree of core damage
+ Approx 50 CETs in the core with useful range to 2000 F j
+ CET indication lags clad temperatures by 200 F to 600 F l
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. Quantitative CDA made from CETs l
+ No Core Damage -Indication from all CETs < 750 F
+ Cf ad Damage - CET between 1200 F /1400 F and 2000 F l
+ Fuel Overtemperature - CET > 2000 F j f 15
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i Containment Radiation Levels . .
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. Containment radioactivity levels are affected by
+ the amount released from the core /RCS
+ the amount retained in the RCS
+ the amount washed-out by containment spray l l
. SGTR and ISLOCA may not result in release to containment i
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O i Containment Hydrogen Monitor l
.' Containment hydrogen levels are affected by
+ the amount hydrogen generated in the core during boildown l
+ additional hydrogen generated during recovery
+ the amount of hydrogen retained in the RCS l
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O Summary of Revised WOG CDA Methodology
. Primary assessment of clad damage and fuel x overheating is made using
+ Core exit thermocouple indications
+ Containment radiationlevels
. For fuel overheating, containment hydrogen is also used to validate the estimate of clad damage
. Numerical estimates of Core Damage account for current knowledge of severe accidents n
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. Proposed CDA provides more accurate and timely information i
. Methodology is estimated to be accurate to plus or minus 50% for the amount of damage
. Level of accuracy is considered adequate for input to Emergency Plan decisions
. Effectiveness of the Emergency Plan is improved using the revised CDA I i
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Revised Post Accident Sampling Wayne Harrison / South Texas Project Westinghouse Owners Group Licensing Subcommittee Chairman ACRS Severe Accident Management Subcommittee April 30,1999 20 0
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l Summary of WOG Relaxation of l Post Accident Sampling
. The PASS requirements proposed by the WDG are properly focused on public health and safety, and accident management needs
+ EOPs
+ EALs
+ PARS
+ Offsite Dose Assessment
+ SAMG 21 O
WOG Relaxation of PASS Requirembnts
. Proposed Post Accident Sampling System would include:
+ RCS boron within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> of attaining a safe stable state
+ Containment hydrogen within 30 minutes of core damage
+ Containment sump pH for brackish water plants without passive pH control within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of core damage
. Retain capability to obtain samples for long-term cleanup / recovery planning
+ RCS liquid sample
+ Containment atmosphere sample
+ Containment sump sample 22 O
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. Capability to sample RCS within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> after reaching a stable condition !
l Parameter Use Comment Boron Confirm 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> after reaching suberiticality stable condition Dissolved None Eliminate timing and Gas, H2 accuracy requirements l for samples Oxygen / Assess Potential Elindnate timing and Chlorides /pH for SCC and accuracy requirements iodine retention for samples Radionuclides Confirmatory Eliminate timing and Information :tecuracy requirements for samples 23
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WOG Proposed Containment Atmosphere Sampling
. Need ability to sample containment atmosphere for hydrogen within 30 minutes of core damage Parameter Use Comment Hydrogen EOP/SAMG On-line hydrogen monitor Radionuclides Confirmatory Eliminate timing and Information accuracy requirernents i
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. Containment sump pH for brackish water plants without )
passive pH control within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of core damage !
Parameter Use Comment pH and Monitor potential Elinunate timing'and Chlorides for SCC and accuracy requirements iodine retention (except forbrackish water plants)
Boron Estimate overall Eliminate timing and Boron accuracy requin:ments concentration Radionuclides Offsite dose Elimmate timing and (not timelv) accuracy regtdrements 25 l
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Conclusions - Revised PASS l 1
. The changes improve the effectiveness of the Emergency Plan.
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. The proposed changes support the ability to maintain a safe stable plant state following a core damage accident.
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WOG Response to NRC Concerns
. Removal of PASS requirements from licensing basis
+ Adequate description / requirements will be contained in UFSAR-
. Plugging of sample lines
+ Primarily a concern for sequences with core concrete ;
interactions I
+ No need for samples at that time to support decisions
+ Not timely; appropriate EALs would be triggered by other parameters 1
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O WOG Response to NRC Concerns (continued) j
. Reactivity Excursion Events
+ Appropriate EALs would be triggered by other j parameters j
. Heat Tracing of Sample Lines
+ Heat tracing does not prevent aerosol deposition
. Uncertainty Quantification l
+ Quantified uncertainties not necessary l 1
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