ML19345D063
| ML19345D063 | |
| Person / Time | |
|---|---|
| Issue date: | 11/25/1980 |
| From: | NRC COMMISSION (OCM) |
| To: | |
| References | |
| REF-10CFR9.7 NUDOCS 8012090009 | |
| Download: ML19345D063 (68) | |
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9 COMMISSION MEETING 2 6.h d:
PUBLIC MEETING DISCUSSION OF SECY-80-409-PRM TO AMEND 10 CFR 50 CONCERNING ANTICIPATED TRANSIENTS WITHOUT SCRAM (ATWS) EVENTS
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1 UNITED STATES OF AMERICA 2
NUCLEAR REGULATORY COMMISSION 3
4 5
6 PUBLIC MEETING:
7 DISCUSSION OF SECY-80-409 - PSM TO AMEND 10 CFR 50 8 CONCERNING ANTICIPATED TRANSIENTS WITHCUT SCR AM (ATWS) EVENTS 9
l 10 11 Commission ers ' Conference 12 Room 13 Washington, D. C.
14 15 Tue sd a y, November 25, 1980 16 17 18 Th e meeting was convened, pursuant to notice, at 19 20 10 :10 a.m. :
21 22 BEFORE:
j 23 24 JOHN F. AHEARNE, Chairman 25 JOSEPH A. HENDRIE, Commissioner VICTOR GIL.T.NSKY, Commissioner PETER A. 3RADFORD, Commissioner ALDERSoN REPORTING COMPANY. INC.
400 VIRGNA AVE,. 3,W,. WASHI MToN. O.C. 20024 (202) S64 2346
I 2
1 PRESENT ON BEHALF OF THE NUCLEAR REGULATORY COMMISSION STAFFS 2
3 S.
CHILK, Secretary to the Commission 4
L.
BICKWIT, General Counsel 5
H. DENTON 8
W.
MINNERS 7
H. SHAPAR 8
E.
ae':3AHA3 9
ASHOK THADAMI 10 11 12 13 l
l 14 15 18 17 18 19 20 21 22-23 24 25 ALDERSON REPCRTING COMPANY,INC.
400 VIRGINIA AVE, S.W., WASHINGTON. D.C. 20024 (202) 554-2346
DISC 1'Et his is an u= official ::a= scrip: of a. =ascing of ha Uni:ad Sca:az Nuclas: Regulaccry Cc:. dssica held on November 25. 1980 in :ha Commission's-officas a: 1717 E.Straec, N. W., Washing:cu, D. C.
na masc 1=g was open es pub 1 *
- attendanca and observacion.
This. ::ansc=ipe has coc baan reviewed, cc :ac:ad, or edi.ad, and -
1: may contain i=accuracias.
nm ::anscrip is i=:anded solaiv for gn=aral info:=a icnal purposes.
A.s p svidad. by 10 C73. 9.1 2,1: is soc par: cf -da formal or *~ der. a1 :nec d of dard =ien of.he =a::ars discussed.
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No plead 1=g er other paper =ay be filad vi:h the Casics in any p ccaadi=g as tha resul: of or add:sssed to any sca:amant er argusant c=n ained harain, except as the. Commission =ay an:horf a.
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CHAIBMAN AHEABNE:
The Commission meets once 3 again, as se of ten has met for many years, on the subject 4 ATWS.
Not to cause any rising ncpes, I don't expect to US 5 reach a decision this morning as to what we will put out in 6the way of a proposal.
7 But briefly seeing all of the papers that are 8 coming, I have rising confidence that in the middle of 9 December we will have in front of us sort of a final version 10 of a proposed rule, draft environmental impact statement and 11 an assessment from the attorneys on the relatives needs of an 12 that statement, and^ analysis from the Probalistic Assessment 13 staff regarding the various ways of looking at th e 14 statistics on the issues raised in ATWS.
b 15 I think this is an essential next step, which I 16 trust will lead us to putting out before the end of this 17 calendar yea r a proposed rule.
18 With that probably overly optimistic statement, 19 Harold.
20 MR. DENTON:
Thank you.
21 Our purpose this morning is to clarify some of the 22 revisions in the rule and in the notice which we suggested 23 in a memorandum to you earlier this month in response to 24 some of your comments at earlier briefings.
25 Warren Minners will discuss the types of changes ALDERSoN REPORTING COMPANY,INC, j
400 VIRGINIA AVE., S.W., WASHINGTON. 0.C. 20024 (202) 554-2345 C
4 1 that have baen sada, and also say a few words about the 2 implementation schedule which we foresee if the rule is 3 adopted.
4 MR. MINNERSs Could I have the first slide 5 please.
6 My purpose is to try to go over the rule as 7 rewritten.
The first thing I would like to do is just 8 reiterate what the main purpose of the rule is, the intent.
9 The rule embodies in it the philosophy that we are 10 going to have design features to both mitigate and prevent 11 ATWS events, which are going to be required depending on the 12 age of the plant.
13 For plants that were licensed before 1969, it was 14 first conceived that we would ha ve requirements that would so@
15 require them 'to mitigate
- ATWS events, and electrical 16 equipment to the protection system to help prevent failures 171u the reactor protection system.
18 In writing the rule, we decided, as the note 19 indica tes, that the staff did not want to take on the burden 20 of showing that thase plants were okay without mitigation 21 features, but were sympathetic to it, and would look at 22 exemptions requested by licensees, if the licensees 23 justified the exemptions.
24 The next class of plants is all plants that were 2511 censed before January of 1984 There are two classes.
In ALDERSoN REPORTING COMPANY. INC.
400 VIRGINIA AVE., S.W., WASHINGTON, D.C. 20024 (202) 554 2345
5 1 the first class, we are going to require f eatures - that. would 2 mitigate most ATWS events, and also have these electrical 3 features that would help prevent common mode failures in the 4 reactor protection system.
5 However, based on -the recommendation of the ACRS, 6 those plants which already have features which can mitigate 7 all or nearly all ATWS events would not be required to have 8 the prevention f eatures, based on their recommendation that 9 adding such a feature might give a net reduction in safety 10 because you are adding features to a plant without getting a 11 great gain in the reduction of risk.
12 The last class of plants is the plants licensed in 13 January and af ter of 198u.
In those plants, we are going to 14 require f eatures that will mitigate nearly all ATWS events, 15 and have the same prevention f eatures that the other classes 16 of plants have.
17 That is the basic intent of the rule.
18 May I have the next slide please?
19 COMMISSIONER HENDRIE:
Let's go back to that 20 previous slide.
21 What distinguishes pre-83 plants that have 22 extensive mitigation measures, and thus it is concluded that 23 fiddling with the protection system may be a marginal gain, 24 or perhaps a loss, and the post-Bu plants which stand in the 25 same category with regard to mitigation measures.
ALDERSoN REPORTING CCMPANY,INC, 400 VIRGINIA AVE., S.W. WASHINGTON. D.C. 20024 (202) 554 2345
6 1
MR. MINNERS.
I think the differentiation is that 2 we were proposing to have the prevention features put on in 3 1982, about two years away.
I think the thought was that 4 having a design process, construction and installation 5 process in that short a period of time maybe would not give 6 you the assurance that you had no t designed something into 7 it, some kind of mode failure.
While by 1984, with the 8 extended design process, you had much more assurance that 9 would not inadvertently put a common mode failure into the to extra electrical equipment.
11 The difference is, I believe, that this would 12 primarily apply to Westinghouse who-have not yet presented 13 us with a design f or wha t we term a " supplementary 14 protection system."
15 Both BCW and Combustion Engineering, very early 16 on, presented designs f or supplementary protections system, 17 although they gave them different names, and presumably have 18 been working on them for a long time. Those are more mature 19 systems.
20 I think that this is the basic idea behind what 21 ma y appear to be an inconsistency between the pre-84 and the 22 post-8 4 plans that can mitigate ATWS events.
23 MR. DENTON:
It is certainly a diminishing 24 pa yo ff.
We struggled with that type of 8u criteria as to 25 wnether we should do anything different at that time or 1
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7 1 no t.
We finally concluded that did provide +.e to pick up 2 some worthwhile electrical changes.
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.y we did not 3 vant to make any precipitous chcnges in plants that seemed 4 to have good mitigation systems to begin with.
5 MR. MINNERS:
Does tha t answer your question?
6 COMMISSIONER HENDRIE:
Yes.
7 MR. MINNERS4 May I have the next slide please.
8 I just want to show this slide with is a copy of 9 what is now Enclosure K to the Commission paper, which gives 10 the staff estimates of what the ATWS rule requirements would 11 probably require on plants.
12 The caveat I want to give is that this is just the 13 staf f's estimates.
The rule.is cast in the form of criteria 14 which allows the designer or the licensee flexibility to put 15 on the plant 'what he thinks is required to meet this.
So 16 where we may say " safety valve," there are other potential 17 things, such as changing physics design, to change the 18 mode rator coef ficient, which may work.
But the designer has 19 to look at that and see what the economic costs are, and 20 what the bases are.
21 CHAIRMAN AHEARNE Does that comment really apply ~
22 only to the items you have indicated as implicit?
23 MS. MINNERS:
Yes.
The other items, like th e 24 supplementary protection system, the SPS, the AMSAC, which 25 is the ATWS mitigation actuation circuitry, those are ALCERSCN REPORTING COMPANY,INC, l
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8 1 specific in the rule and you have to have those.
2 May I have the next slide please.
3 CO MM ISSIO N ER - HENDR IE :
Alternate 2, 3 and 4,
4 iden tify in what way with the proposed rule?
5 MR. MINN ERS :
In the discussion portion of the 6 Federal Register Notice, it discusses altern ates 2, 3 and 4,
7 which is comparable to the NUREO 0460 alternates, although 8 they are modified f rom, tha t.
But they are kind of very much 9 related to alternate 2 in 0460, and alternate 3 is very 4
10 similar.
11 COMMISSIONER HENDRIEs What is the proposal for 12 the rule?
13 MR. MINNERS4 For alternate 3, for example?
I 14 don't quite understand your question.
15 COMMISSIONER HENDRIE.
Which of these is the rule, 16 or is everything in the rule?
17 MR. MINNERSa Alternate 2 is what would be 18 considered, probably, for pre-69 plants, although that is 19 not explicitly addressed in the rule.
That is just to give 20 some diversity in the protection system, and the mitigation 21 circuitry.
22 Alternate 3 would be the pre-84 plants, in which 23 you have most of the ATWS transients nitigated.
It would be 24 something like a 90 percent moderated roefficient.
25 Alternate 4 would be the post-84 plants, in which ALDERSON REPORTING COMPANY,INC, l
9 1 you had a 99 percent moderated temperature coefficient, and 2 would mitigste almost all of the ATWS events.
Alternate 4 3 includes signal f ailures.
4 For SCW and CE, both of them have safety valves, 5 but that would be very plant dependent.
In alternate 3 you 6 would have safety valves in the plant.
In alternate 4 it is 7 more certain that you would have safety valves because of 8 the higher coefficient.
9 In GE, the difference comes in the single failure 10 criterion requires you to go from an automatically initiated 11 standby liquid control system where, although it has two 12 pumps, you need both of the pumps.
In alternate 4, you 13 would have to go to a much higher capacity to take care of 14 single f ailuras, both in the system and in the containment 15, coolin g systems.
16 COMMISSIONER HENDRIE.
Why don't you go on, but I 17 would like to come back to this table at a later time.
18 MR. MINNERSs The next slide please.
19 The other important feature of the rule, and maybe 20 the most important feature is the implementation schedule.
21 The philosophy behind the implementation schedule is 22 installa tion of aquipmen t in the earliest practical 23 timef rame.
24 For prevention, which is mostly electrical 25 equipment, we believe that July 1982 is a practical time to i
ALCERSON REPORTING COMPANY. INC, i
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10 1 have such equipment installed in the plants.
2 For mitigation, some of the mitigation equipment 3 is electrical, such as actua tion circuits for mitigating 4 systems, containment isolation f eature, and modification to 5 the scram discharge volume, which is neither fish nor f owl, 6 I guess.
7 Those things a re all outside containment, and we 8 believe that they ran be implemented by July of 1982.
9 The mechanical aspects of the mitigation features
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10 in pre-84 BWRs, that would be taking the presents" liq uid 11 control system with its two pumps, and changing the piping 12 so that both pumps could operate simultaneously, and also 13 automating the system.
14 COMMISSIONER GIIINSKY:
Is that post-69.and 15 pre-8a?
16 MR. MINNERS:
Post-69 and pre-84, yes, sir.
17 That is mostly outside the containment, and we 18 belle: u that a July 1982 date would be appropriate for that 19 equipmen t.
20 For the'very early pre-69 SWRs, they are plant 21 unique, so we have given more time for installation, until 22 January 1984 They are unusual plants, like Oyster Creek 23 has very limited high pressure water injection.
24 It is probably all right on the pressure because 25 it has got so many valves, but it has a unique standby l
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11 1 liquid control system, and it has no high pressure injection 2 capacity except for the feedwater system.
It is only an 3 isolation condenser.
4 So that presents unique problems, and we have 5 allowed longer implementation time.
6 In the pre-and post-8 4 PW3s, 1-is January 1984, 7 because we feel that any changes are likely to be 8 modifications to the safety valves inside the plant, and 9 that would take considerably longer than the stuff outside 10 the plant..
11 Those are the basic features of the rule.
12 May I have the next slide nieasd.
13 I just wanted to go down the revisions that we 14 made to the original rule as it was sent down to the 15 Commission.
16 We have, as requested by Chairman Ahearne, revised 17 it somewhat, and rewrote the Federal Register Notice.
One 18 of the revisions is in the definition where we added a 19 definition of "ATWS mitigating systems," which seemed to be 20 necessary, which maybe I could discuss now rather than 21 la te r.
22 Cne of the comments that I have heard often from 23 the industry is that they don't want ATWS to be a design 24 basis event.
I think if you pass a rule that includes it, 25 it-is going to be a design basis event.
It does not make ALDERSON REPORTING COMPANY,INC,
12 1 much difference what you call it.
2 I think the th rust of their comment is that once 3 you call it a design basis event, they are going to be 4 subject to having all of these usual design basis 5 requirements put on them, like single f ailure criterion, 6 environmental qualifications, seismic qualifications, and 7 quality assurance programs.
Indeed, many of those things 8will be imposed on the equipment.
9 But I think what is necessary, and what has been 10 added to the rule is a definition of what is required for 11 these systems, so that both the industry and the reviewers 12 understand what safety rules are going to be applied to 13 these plants, whether they are going to be seismically 14 designed, or whether they are no t going to be seismically 15 designed, or'whether single failure is required, or whether 16 it is not required.
17 I think if this is cla rified, it should take care 18 of the industry concern, which is basically that they will 19 be continually ratcheted in the f uture to make these systems 20 higher and higher grade.
We think there is a proper grade 21 for these systems, considering the probability of ATWS 22 events, and we have tried to specify it as clearly as we 23 can.
24 COMMISSIONER GILINSKYs Where do we categorire 25 " design basis accidents," or is there such a thing?
ALCERSON REPORTING CCMPANY,INC, M C~)NIA CSQ GW, WWTS3 @).@. E4 (sis) N
13 1
MR. MINNERS:
I don't think they are defined 2 anywhere.
Ihere is a list of accidents in the Standard 3 Review Plan tha t applicants are required to evaluate.
I am 4 not sure if it says " design basis" in the Standard Review 5 Plan or not, but those a re the design basis events.
But in 6 the regulations or elsewhere, I don 't know of anywhere _
7 " design basis event" is defined or used.
8 CHAIRMAN AHEARNE:
Howard?
9 MR. DENTON:
We don't really have a list of design 10 basis accidants, and they are ones that historically have 11 always been. assumed for purposes of Part 100 calculations, 12 such as a large loss of coolant, or a small loss of coolant, 13 steamline breaks, fuel handling accidents, waste gas to 14 paytank f ailures.
15 It is more practice of certain types of accidents, 16 which have been through the years found to be the limiting 17 cases for that purpose, o r always assumed, and then all the 18 equipment necessary to mitigate those fall within the full 19 panoply of our requirements.
20 CHAIRMAN AHEARNE:
When you say that there is a 21 concern on industry 's part that this might become a design 22 basis accident, it is not that there is some bin where they 23 are formally now put in, but rather that the reviewers will 24 now start using it.
25 MR. EINNERS That is what I understand they are ALDERSON REPORTING COMPANY,INC,
14 1 talking about.
2 COMMISSIONER GILINSKY:
Those obviously would be 3 used and alluded to when you put out a rule imposing 4 requirements on the handling of ATWS events.
5 MR. DENTON:
The question comes on how many ATWS 8 events are you going to handle with how many failures. _That 7 is what is rather unclear in the way you view the design 8 basis events now.
9 I guess the best defined event is the LOCA event, 10 and you have to look at every single failure.
In ATWS we 11 don' t want you to look at every single failure.
We think 12 there are some single f ailures which are of low 13 probability.
14 COMMISSIONER GILINSKYs It sound like this was of 15 concern because it carries with it a whole train of other 18 activities, quality assurance, and so on.
I suppose that if 17 you specify clearly which of those do and don't apply, and 18 to wh a t extent, have dealt with the problem.
19 MR. DENTON:
I think design basis accidents are a 20 sufficiently big umbrella that we are occasionally the shape 21 of the umbrella around the fringes as need be.
22 Here, I think it does make sense for a particular 23 type of accident, where the probability is uncertain, to go 24 ahead and specif y the proper levels of assurance in each 25 category that would put that issue to bed.
Otherwise there ALDERSoN REPORTING COMPANY,INC,
15 1 would be a tendency to become unraveled a round the fringes 2 with regard to some of the details of the implementation.
3 CHAIR 3AN AHEARNE:
Len, did you want to ask a 4 question?
5 hE. EICK*4IT Under Part 100 of the regulations, 6 if there is a credible accident, which has sometimes been 7 equated with design basis accident.
you can postulate that 8 an accident is violative of the dose limitations in Part 9 100, and you are violating the rule.
10 What I think the commentors are saying is that, if 11 you impose specific requirements under this rule, then they 12 vant to be free of the additional requirement of being 13 classed as a credible accident under Part 100.
In o ther 14 words, this is to be the exclusive set of requirements 15 rega rding ATWS events.
16 MR. DENTON:
I think I would agree with that kind 17 of logic tha t if we impose these criteria, which are 18 intended to make the likelihood of ATWS events so remote, or 19 sufficien tly remote, then we would not turn around, and 20 require the. plant to be designed to cope with it 21 nonetheless, as though all these things fail.
22
'! R. BICKWIT:
It is perfectly reasonable for the 23 co mm en tc.
to want it to be made clear in the rule.
24 MR. MINNERS:
The next change that was made in the 25 rule was in the acceptance criteria, particularly in the ALDERSoN REPORTING CCMPANY,INC, SM I
16 1 prescription of the radiation release.
2 In the first version, we had a statement that it 3 had to be Part 100.
This has been changed to limit 4 effectively the number of fuel rod failures in the core.
In 5 other words, the rulefnow written says that you can fail no 6 more than.10 percent of the rods in the PWR or all of the 7 rods in the BWR.
Failure means perforation of the cladding, 8 and releasing, essentially, the gap activity.
9 COMMISSIONER GIIINSKY:
What is the difference?
10 3R. MINNERS:
Because in the PWR there is a more 11 direct release to the environment.
If you take the tech 12 spec leakage of the steam generator tubes during an ATWS 13 event, you will have a direct leakage path from the reator 14 coolant system through the tubes into the steam generator, 15 and then out the safety and relief valves on the steam 16 generator, which is direct to the environmen t.
17 In a 9WR, you don't have that direct p a th, plus 18 you have a secondary containment which has a standby gas 19 treatment system which will take any leakage f rom th e 20 primary containment, and pass it through filters to the 21 atmosphere.
So you have a much higher decontamination 22 f actor in a pressurired reactor than you do in a boiler.
23 The attempt here was to try to decouple this rule 24 from Part 100, and make it clear that the in tent is that you 25 are to meet these requiremen ts and not necessarily Part 100 j
ALDERSoN REPORTING COMPANY. iNC,
17 1 requirements.
2 I don't believe that if f uel f ailure was the only 3 problem in an ATWS event that we would be seriously 4 considering doing very much to correct it.
The question is 5whether you can keep the core cool, and the possibility of a 6 coremelt is the significant event.
7 COMMISSIONER GILINSKYa Is that a more stringent 8 requirement than the Part 100?
9 MS. MINNERS:
It might not be.
In a SWR, if you 10 put the mitigating equipment on, you still would go through 11 a power transient, which might rupture fuel.
GE says that 12 no fuel ruptures, but I am not sure that the staff 13 completely agrees with that.
14 In a PWR you could have the same thing.
So I 15 think you could easily push the Part 100 limits, while still 16 being well within the pressure and have it a long-term 17 cooling mode.
In some cases there is the possibility that 18 it could be the limiting event, and it really is not.
It is 19 really not the thing of concern.
20 So this was an attempt to try to decouple it from 21 Part 100, and say:
For this particular event, this is how 22 the NEC vants this trea ted.
23 The other things that were changed in the 24 rewritten rule were some design criteria.
I spoke about 25 adding ATWS mitigating systems.
ALDERSoN REPORTING COMPANY,INC,
18 1
COMMISSIONER HENDRIEs Did you say 10 percent and 2100 percent?
3
- 33. MINN ER S :
I said that it was one and ten.
4 The rule as it is written talks about 5 radioa ctivity inventory.
It talks about 10 percent of the 6 radioactivity inventory in the fuel rods.
If you assume, 7 and I as told that'it is a conservative assumption, that 10 8 percent of the inventory is in the fuel gap, then if you 9 rupture 10 percent of the rods, you will release about SB cne to percent of.the totel inventory.
11 It sounded like a good way to write it at the 12 time.
Maybe we will get some comments on it, if it is not a 13 very effective way.
14 CHAIRMAN AHEARNE:
First, we will try to 15 understand it, and then we will try to comment on it.
16 MR. MINNERS:
The other design criteria, now the 17 rule contains a specific criterion for containment isolation 18 that was not specifically addressed'in the rule.
The staff 19 believes tha t this is an effective thing that should be done 20 in plants to get an early containment isolation in a t ATWS 21 even t, which would be based probably on radiation in the Z2 containment.
R.< @
23 Then the criteria ^ supplemental protection system 24 was generalired, and the original ruit, it specifically 25 said, Westinghouse.
As we discussed with Dr. Hendrie, the ALDERSON REPORTING CCMPANY,INC.
r 19 1 pre-S4 plants would be exempted.
It has been generalized to 2 try to clarify exactly what the intent w a J,, and wha t the 3 basis for that exemption is.
4 In the implementation saction what has been added 5 is standardized plants.
This was dealt with in the 6 Regulatory Guide.
But it seemed that if this was a spegial 7 requirement, the Regulatory Guide was not the place to put 8 it.
9 The intent was to keep plants on the same site, 10 the same..If you have two plants of the same design, you 11 don' t want them to differ in their ATW5 mitigating 12 capability, and tha is what it says.
If you have a plant 13 that was licensed after 1984, but is standardized to a plant 14 that was licensed bef ore 1984 and it is on the same site, 15 then they should have the same design criteria, which would 16 be the pre-84 design criteria.
17 What was not changed in the rule was some of the 18 implementation dates.
They may have to be changed based on 19 when the rule. was sctually put in the Federal 2egister.
At 20 the moment there are some submittal dates for information on 21 March 1981 and December 1981.
The March 1981 date is 22 obviously getting very close, and th a t would have to be 23 moved, and maybe the December 1981 date will have to be 24 moved.
25 We did not feel that changing them at this time, ALCERSoN REPORTING CCMPANY,INC.
i 20 1 and shifting them every month was a very fruitful exercise.
2 When the final rule goes out, some decision will be nade.
3 May I have the next slide.
4 As we were requested, we also rewrote the Federal 5 Begister Notice, ahd put in an expanded history section in 6 the Federal Eeoister.
We provided a revised basis for the 7 rule.
We gave a revised explanation of the rule, th at is, 8 what the content of the rule s*.ould be.
We also added more 9 description of the implenentation requirements in the rule 10 to try to give a basis.
So maybe that should be looked at.
11 The adde.d history, I am not sure if we'have 12 responded to what the Commission wanted in that respect.
13 CHAIEHAN AHEARNE:
It was fine.
14 MR. MINNERS:
In my personal opinion, I don ' t know 15 if that really adds to a comment, or the understanding of 16 what the rule requires.
17 CHAIEMAN AHEARNEs It just has a sense of neatness 18 abou t it with that in there.
19 COMMISSIONER GILINSKYs What I would have liked toh*4 20 see -- I just read it quickly, and I may not be doing 21 justice to it.
But t he r e.
has been over these dorens years a 22 shif t in our approach toward mitigating ATWS events, 23 preventing ATWS events.
Tha t flow back and forth does not 24 seem to be reflected here.
think it might be nice to put 25 in a couple of words to indicate that shift in emphasis.
i i
ALDERSoN REPORTING COMPANY,INC,
21 1
MR. MINNERS:
That is right.
In volumes 1 and 2, 2 the emphasis was on criteria.
In volumes 3 and 4,
the 3 emphasis was on equipment, trying to be more specific as to 4 equipment.
Now we have kind of gone back to the criteria.
5 MR. DENTON:
let us see if we can't work that inY 6 aER.
7 COMMISSIONER GIIIN SKY:
I don't think that it 8 would take more than a few words.
9 MR. MINNERS:
May I have the next slide please?
10 This is what we think may be an optimistic 11 schedule for issuing the rule.
Having a. commission meeting 12 today.
We have promised to have an environmental impact 13 assessment and also Research has promised to give you peer 14 review comments by the 12th of December.
15 By the 22nd of December, we have been promised the 16 legal recommendations on the environmental impact will be 17 made.
We also hope to have the Regulatory Guide done at 18 that time.
That may be very optimistic because there is a 19 conflict with TMI-I.
20 CHAIRMAN AHEARNE:
By a conflict, do you mean the 21 same people?
22 MR. MINNERS:
Yes, sir.
23 CHAIRMAN AHEARNE:
Ir is not a substantive 24 conflict.
25 MR. MINNERS:
No.
It is not a technical ALDERSoN REPORT 1P G COMPANY. INC.
22 1 conflict.
It is a people conflict.
2 By the middle of April, presuming-that the comment 3 period is the 90 days which was requested, instead of 60, 4 the comment period would end, then,giving the staff two 5 months to respond to the comments, and incorporate them into 6 the rule, and get them issued into the final rule with the 7 Regulatory Guide, and I guess some kind of an environmental 8 impact assessment or statement of whatever final decision.
9 So you would have a final rule by the middle of 10 next year if everything went correctly.
11 MR. SHAPAB:
That contemplates no hearings.
12 MR. MINN ERS :
That is correct, it would 13 contemplate no hearings.
14 CHAIRMAN AHEARNE:
Your March reporting date 15 clearly would --
16 MR. MINNERS:
Yes.
I think the March date was set 17 --
18 CHAIRMA.] AHEARNE:
I think you are absolutely 19 correct.
20 MR, MINNERS:
when we thought that we were 21 going to have something in late fall.
22 CHAIRMAN AHEARNE:
There is no point in 23 continuously revising it until we finally get something 24 out.
25 MR. XINNERS:
I was trying to say that we were ALCERSoN REPORTING COMPANY,INC.
23 4
1 thinking of maybe four to cix months vould be enough tim e 2 for people to get the information together.
3 COMMISSIONER GILINSKY:
Howard, you were referring 4 to the request we had for hearings?
5 MR. SHAPAR.
That is right.
8 MR. MINNERS:
It was not contemplated that there 7 would be such a hearing.
8 COMMISSIONER GILINSKY:
Is there any sense for how 9 long a hearing like th a t might take?
10 MR. SHAPAR:
No.
11 CHAIRMAN AHEARNE Shorter than the development 12 time of the rule.
13 MR. SHAPARa It depends on the complexity of the 14 issues that are developed.. It depends on the de termination 15 of the people who want change in the rule.
It depends on 16 the control of the hearing, the grounds rules that are set 17 for the hearing, and whether or not the Commission vants 18 recommendations from the hearing board, or wants the record 19 just certified up.
20 CHAIRMAN AHEARNE:
That is what you said on TMI-I 21 restart.
22 MR. SHAPAR:
No, I said something quite 23 diff e rent.
24 COMMISSIONER GILINSKY:
When would we be dealing 25 with that raquest?
ALDERSON REPCRTING COMPANY,INC,
24 1
MR. BICKWIT:
That is a request th at is before you 2 now.
You can accede to it, or what this office has 3 recommended you do.
You can wait until the comment period 4 is over and see whether you feel that additional procedures 5 are necessary to bring out the facts which are unclear j n 6 your own mind, or policies that are unclear in your mind, 7 then make the decision at that stage.
8 MR. SHAPAR:
Another intermediate thing, of 9 course, is an option to put something in the statement of 10 consideration noting that such a request for hearing has 11 been received, and specifically inviting comment on that 12 particular proposal.
13 COMMISSIONER GILINSKY:
We could just ignore 14 th a t.
15 CHAIRHAN AHEARNE:
The request for hearing is on 16 the total rule rather than the application to any individual 17 plan t.
In the application to an individual plant, an 18 existing plant, would the mechanism by which it would be 19 done lead to the potential of a hearing as inthe Shelly 20 case ?
21 COMMISSIONER HENDRIE:
It is a license amendment, 22 and you are now guaranteed a hearing for it.
23 MR. BICKWIT:
Not necessarily.
'a' e have had this J
24 discussion before.
25 If what you are requiring is something outside the l
ALDERSoN REPORTING CCMPANY,INC,
25 1 authority of your license, then it is conceivable that the 2 S h olly,t,s, would affect the procedures.
If what you are 3 requiring is something that the licensee could do 4 voluntarily, if he chose to, and it is within the authority 5 of his license, and you are simply ordering him to do it on 6 the basis of your new rule and he is resisting, my feeling 7 is that the Sholly case is inapplicable.
8 MR. SHAPAR:
Of course, it depends on whether the 9 amendment involves significant harard considerations or to not.
If it is a true amendment, and it involves significant 11 hazard considerations, you would prenotice it anyway.
12 Sholly applies to an amendment that does not involve 13 significant hazards.
14 MR. BICKWIT It is also a case of whether there 15 is an amendment at all, or any amendment requirement at 16 all.
17 CHAIRMAN AHEARNE:
All those are caught in the 18 Sholly case, then, or is there some debate on that?
19 MR. BICKWIT There was some broad language in 20 that case, but I don't think ir is the natural reading to 21 take it as barred as this particular hypothetical.
22 CHAIRMAN AHEARNE:
When you said that it is the 23 recommendation of your of fice, Len, you were talking about 24 the paper that you sent up earlier this month?
25 MR. BICKWITs That is right.
ALDERSON REPORTING COMPANY,INC, 6 /Yik ELCL MIXIIMi@2 @k% N OFWh EDfEXD
26 1
MR. DENTON:
We have on occasion required changes 2 poin ting toward an ATWS rule in individual cases where we 3 thought there was a departure from the norm.
4 COMMISSIONER GILINSKYs At what point have we held 5 hearings in the past, let's say, on the clearance rule?
6 MR. SHAPAR:
When the proposed rule is out.
7 COMMISSIONER GIIINSKY:
Did we have a comment 8 period first, or did we simply go to it.
9 13. SHAPAR:
We had a comment period first.
10 CHAIEMAN AHEARNE.
Then on the basis of the 11 comments, we concluded that there was a need ?
12 MR. SHAPAR:
Yes.
I think there has been at least 13 one occasion where it was determined that the hearing would 14 he held when the proposed rule was put out, but I am not 15 sure of that.
16 Then, of course, it is a question of what kind of 17 a hearing you want.
It presents a bunch of subsidiary 18 options.
19 CH AIRM AN AHEARNE:
Does that complete your 20 presentation ?
21 MR. MINNERS:
Yes, it does.
22 COMMISSIONE3 HENDRIEs Let me go back into the 23 front end of your discussion for the basis of the rule, page 24 7, November 7.
25 Would you explain to se the basis on which the ALDERSON REPORTING COMPANY. INC.
27 1 staf f has concluded that the reliability pro tection system 2 is inadequate?
3 MR. MINNERS:
I think the basis is that there is a 4 high challenge rate of transients.
We believe that we want 5 to a void severe consequences, and make that very unlikely, 6 which I admit are rather vague terms but we have trl-ad to 7 quan tif y them sometimes.
8 Then we have looked at the common mode failure' 9 rate of protection systems, and have some suspicions about 10 i t.
We have looked on March 12, 1970, at the two failures 11 considered in there.
Although we dismissed the N reactor as 12 being not directly applicable, it is not to be ignored.
Th e 13 core reactor we think is directly applicable.
The Browns 14 Ferry experience is directly applicable.
15 In'my experience, when we earlier on went out to 16 the vendors and asked them to do common mode f ailure 17 studies, I think some areas were identified as potential 18 areas having very low probability.
But my personal 19 experience was, as I saw more potential areas than I had 20 seen bef ore, and I was more suspicious of their 21 reliability.
22 Then we have taken tha t ma terial, that data, and i
23 have done some statistical manipulation to try to quantify 24 it and understand it better.
Though I would not claim that 25 our conclusion is based solely on the statistical analyses ALDERSoN REPORTING COMPANY,INC,
28 1as supporting evidence, I think there is a good judgnent 2 f actor because things like Browns Ferry cannot h_ handled 3 directly in the statistics -- is it a full f ailure, or what 4 is it.
This has to be recognized.
5 COMMISSIONER HENDRIE:
It represents a 6 considerable change in the staff position over the years.
7 It seems to me that I have not seen an experience or 8 analysis basis in fact for changing the staff position on 9 the reliability of protection systems which I left in July 10 of 1974, which was not that the protection systems, in the 11 considered j udgment of the staff, were inadequate, but 12 rather 'that it was impossible to demonstrate with the kind 13 of certainty that we would like that the protection systems 14 ha d the caliability which made ATWS events insignificant 15 contributors ' to risk.
16 On the basis that we were unable to show that th e y 17 were adequate, as clearly contrasted to a view that they 18 were not adequate, we said:
"let's fix some things."
19 If you step forward at this moment and tell me 20 that it is the considered judgment of the staff that 21 protection systems are inadequate today, n o t', I don't 22 understand why I don't have a recommendation f rom the staff 23 for emergency shutdown of all operating units.
24
- 33. DENTON:
I guess speaking for myself, I see it 25 more along the line that we have not been able to ALDERSoN REPORTING COMPANY. INC.
400 VIRGINIA AVE., S.W., WASHINGTON. D.C. 20024 (202) 554 2345
29 1 demonstrate what is in any low probability occurrence as we 2 are worrying about here.
You can ' t ever demonstrate from 3 evidence what the true probabilities are.
4 I think that it is exactly the point you made.
It 5 is the inability to demonstrate from the few occurrence we 6have at hand that they are sufficiently reliable for this 7 type of accident, and thereby justify the changes.
8' They may well be very reliable, and as reliable as 9 the industry thinks they are.
It is impossible to tell from 10 the data base that we have.
11 CONHISSIONER HENDRIE:
That is where we were in 12 1974, but that is not where you seem to be today.
What I am 13 suggesting to you is, if what you have written down here in 14 this language is, in fact, what you believe, the problem is 15 enormously more urgent and difficult than the whole rest of 18 this other languages on here.
17 It seems to me that the staff has made a leap, and 18 I would regard it as an ill-considered one, frem a position 19 in which for all we know these systems are perf ectly 20 adequate, but because we cannot prove that to ourselves, 21 wi th the level of confidence that we would like to have, we 22 ace going to go ahead, as a judgment matter, and require 23 some additional measures.
24 MR. DENTON:
Let me take another look a t that.
I 25 had not focused on that page.
When we come back in the ALCERSos REPORTING COMPANY,iNC,
30 1 middle of December, I will have a clarification.
2 COMMISSIONER HENDRIE:
I think if we publish a 3 rule, which the basis for the rule is this position, you 4 have a lot of other problems than whether by 1984 you are 5 going to have people doing this, tha t, and the other thing.
6 MR. DENTON:
I think we were trying to lay *:h e 7 basis for a rule.
8 CHAIRMAN AHEARNE:
Yes.
I think that this was the 9 staf f 's attempt to try to respond to the questions that I 10 raised the.last time around.
11 I was trying to track through the logical train to 12 reach a conclusion as to why take the action, and as it 13 says, leading into that, operational experience is not 14 sufficient to determine on a statistical basis whether the 15 protection systems are irraliable.
The analysis methods are 16 inadequate.
Therefore, it reaches a conclusion on 17 engineering judgment.
18 When I read the previous version of September 4th, 19 that is what it seemed to me what the staff was really 20 saying.
It was their engineering judgment that this was 21 nece ssa ry.
I think that is where they ended up.
! think 22 th e la st sentence is a summary of what their engineerino 23 judgment leads them to believe.
24 (Commissioner Bradford joined the meeting at this 25 poin t, 10:55 a.m.)
ALCERSON REPORTING CCMPANY,INC,
31 1
ER. DENTON:
I think we do have to be careful how 2 ve say that, and I would like to have a chance to take a 3 second look at what we conclude.
4 COMMISSIONER GILINSKY:
In some sense there has 5got to be a conclusion of inadequacy if we are going ahead 6to fix things up.
This is a problem that we run into eyery 7 time we try to do something, it does not me=n that we have 8 to shut everything down, to use your dramatic phrase again.
9 You do have to be careful of how you say these 10 things, but in some sense whenever we make an improvement, 11 ve decide that the system is not adequate for the purposes 12 at hand, or to deal with the problem before us, assuming 13 that we go f orward, and I certainly would recommend that we 14 go f orward.
15 MR. DENTON:
It is a product of our Aristotalian 16 logic.
17 COMMISSIONER GIIINSKY:
Some years ago, I thought 18 you talked on the subject pretty eloquently, the regulator's 19 tra p.
20 COMMISSIONER HENDRIE:
I have always rejected this 21 as a' trap, and considered tha t there is a reasonable 22 intermediate ground on which you are prepared to say at any 23 given time, I am not too sure about this object out here, 24 maybe it is all right, and maybe it is not all right.
25 But it is my considered judgment, as a responsible ALDERSON REPORTING COMPANY,INC, 400 VIRGINIA AVE. S.W WASHINGTON. D.C. 20024 (EB 554 2345
32 1 official in charge of the public safety in this area, that 2 until I know more sbout it, I want some fixer around it.
I 3 vant to put a little fence around it, or I will plant a 4 posey on it or something.
5 You could argue with me, and say, you can't prove 6that that is necessary.
All I am saying is that the system 7 of regulation we operate under and the authorities given to 8 the Commission are such that we don't have to prove that it 9 is necessary.
'Je just.ea y that in our judqnent it would be to a good idea to put a little fence around it.
That is it.
11 CHAIPMAN AHEARNE4 I think, perhaps with the 12 exception of the last sentence, that is what the staff has 13 said here.
14 COMMISSIONER HENDRIIs Yes, but I just don't like 15 their last sentence, because I spent a good many years 16 examiring precisely the basis on which one would draw that 17 conclusion, and I decided that I couldn't draw that 18 conclusion.
19 The only conclusion I could draw was that the 20 experience base, together with other methods of analysis 21 that were available, gave some encouragement, but we were 22 not about to reach a level of assurance which would allow me 23 to cheerf ully say, "This is not a problem that we are going 24 to bother with."
But that also did not mean that ! had a 25 basis to say, "No, it is inadequate."
ALDERSoN AEPoRT:NG COMPANY.1NC,
33 1
MR. MINNERS:
That conclusion did not lead me to 2 say that we needed some immediate action.
3 COMMISSIGNER GILINSKY:
You are always forced to 4 say, even if you put it your way, that you think that it is 5 not good enough.
You have thought about it, and you have 6 looked at all the data.
7 COMMISSIONER HENDRIE:
I think that it is prudent 8 to put some additional things there.
Now, you are asking, 9 "Does it mean the scram system is adequate or inadequate?'
10 I will sa y, "Sorry.
Prudence dictates that we put something 11 there."
12 COMMISSIONER GILINSKY.
When it runs to Howard's 13 of fice, it is either going to be adequate or inadequate.
14 (Laughter.)
15 MR. MINNERS:
That is not true.
16 COMMISSION ER HENDRIE He will treat it with his 17 customary subtlety.
18 CHAIRMAN AHEARNE:
I guess there is no 19 disa greement that (a) it is an' engineering judgment; (b) the 20 engineering judgment leads one to conclude that it is wise 21 to make some recommended changes.
It is the right way to 22 characterize that which is your concern.
23 Harold, will you look at that characterization?
24 MR. SHAPAR If the rule comes under attack, as we 25 have to suppose it will, this language becomes very ALDERSoN REPORTING COMPANY. INC.
1 400 VIRGINIA AVE., S.W., WASHINGTON. D.C. 20024 (202) 554-2345 l
34 1 important in summing up what the basis for the rule is.
2 (laughter.)
3 CHAIRMAN AHEARNE:
Joe, do you have further 4 questions ?
5 COMMISSIONER HENDRIE:
Yes.
6 I as a little purried by the evaluation model.
7 ground rules.
8 MR. MINNERS:
Do you mean in the rule itself?
9 C3MMISSIONER HENDRIE I am still up in the front 10 end of the. language.
It says, "The proposed rule rpecifies 11 that realistic values or parameters may be used until the 12 value is known with reasonable accuracy.
But the parameters 13 with large uncertainties must be conservatively treated."
14 How do you decide when the accuracy with which you 15 know a given parameter has gone from a reasonable accuracy, 161n which you presumably use the central value, over to a 17 situation in which there is a large uncertainty, and I 18 assume conservatively treated, that means you have to use a 19 value for the parameter which is at the conservative side of 20 the uncertainty bat.
21 MR. DENTON:
I would assume that we could identify 22 those values by comparing our calculations to the industry 23 calculations, where we agreed on a value.
24 CHAIRMAN AHEARNE:
Do you_think all commentors 25 would agree with that sort of normal mode of approaching the ALDERSCN REPORTING COMPANY,INC,
35 1 problem.
2 MR. DENTON.
Warren has looked at that in much 3 more detail.
4 MR. WINNERS:
The answer to the question is, no.
5 But I think there is agreem,ent between the commenters, that 6means the industry and ourselves, that we would like a _
7 hopefully better way of doing it than we did it in the ECCS 8 models.
The better way is to try to do it " realistically."
9 But I think that everybody must recognire that there are 10 some parameters.
11 I-would use the flow rate out of the safety relief 12 valves, which are not known very well.
The data is very 4
13 limited.
So how do you treat tha t?
If you just took some 14 kind of average value from the limited-data, you would be 15 quite suspirious of that.
So some conservatism should be 16put in there.
17 What we hope to do, when we write up the Reg Guide 18 is to get a good deal more specific about which parameters 19 ha ve to have a conservative factor, and which ones don't, to 20 reduce, at least, tae argument between us and the industry, 21 if not the disagreement.
22~
I think that it is another encineering - judgment 23 situation, where the people are going to have to look at it 24 and say, "Does this require some conservatis m," which will 25 also then say, "If it is an insignificant parameter, why i
ALCERSoN REPORTING COMPANY,INC.
36 1 hassle about it.
If it is a significant parameter, such as 2 saf ety valve flow rate with sub-cooled water, then I guess 3 you are going to have to put some more conservatism, and 4 moderated temperature coef ficient."
5 There are proponents in the staff who would say 6that this is a technique which is not a good way to go,.and 7 that we ought to go back to the old system where you take 8 the bounding analyses, and take a very conservative bounding 9 for all parameters, do your calculation, and then show that 10 you meet tha acceptance criteria.
I think we have a 11 consensus from most of the staf f that that would be 12 excessive.
13 Exactly how to work that out, I think, is going to 14 be a problem, because in some ways it is cutting a new 15 path.
We have not done that with the industry, and we vili y 4'rw 16 have to work out some ++ hec details.
17 1 466%
Three Mile Island helps us a lot in doing that 18 because I think people recognire for Three Mile Island that 19 the over-conservative analyses that we did misled us in a 20 va y, people want to get away from that.
21 Yet, the staff recognires that you cannot throw 22 away all the conserva tism.
But if you have so nuch 23 conservatism that it distorts the results, then we don't 24 want to do that.
25 CHAIRMAN AHEARNE:
Which ever-conservative ALDER $oN REPORTING COMPANY,INC,
37 1 estimates on Three Mile Island are you talking about?
2 MR. MINNERS In doing double-ended breaks, we 3 took all the parameters at the high side, and we calculated 4 what the temperatures would be in the fuel cladding.
5 Hindsight would say that you would have better taken that 6 effort and did some other realistic cases, small breaks _on 7 very unusual situations.
8 COMMISSIONER HENDRIE:
I must say, I don't see why 9 you don 't just go devn the line with central values for the 10 parameters, each with its error estimate.
11 MR. MINNERE:
How would you factor the error 12 estimate into the result?
You would just make an estimate shd 13 of thederror in the result?
14 COMMISSIONER HENDRIE:
Yes, precision of the total 15 result.
16 MB. MINNERS:
That becomes, I think, a difficult 17 problem.
We did that with our multi-barrier analysis, and 18 it just becomes a difficult process to do, to estimate the 19 total error.
You just can't add the errors all together.
20 You have to somehow statistically combine them, and it 21 becomes a more complica ted process.
22 That is the exactly the way the G-tab, the General 23 Electric thermo analysis basis is done.
All of the errors 24 are combined together, hopefully properly, statistically, to 25 give you a statistically correct error on the re sults.
It
.s ALDERSON REPC,RTING COMPANY,INC,
38 1 is a complicated process.
It presumes that you know the 2 errors, and that you have some confidence in the error 3 estima tes.
In ATWS events, in some of them maybe, like flow 4 rates, you have a good estimate of what the error is, and 5 you can put something down.
6 COMMISSIONER HENDRIE:
Wait.
7 If I am unable to choose the central value of a 8 parameter and say that "It is plus X and minus Y,"
and 9 propagate that down the lins, how is it you are going to 10 select a particular value for it?
11 If you have some basis for saying, "Here is the 12 value we will assume for the flow rate," if you can do that, 13 I should think you would be able to say, "He re is the da ta,
14 and it is has a peculiar looking distribution like this.
I 15 am going to tak e th e central value over there, th e mean, or 18 the ' average, or whatever, if it has a variance of such much 17 one way and so much the other way, and I can propagate that 18 through the calculation. "
19 I just getting around to suggesting th a t what I 20 perceive is that after two years of scratching with the 21 vendors, we will have a set of evaluation models on which 22 once again every parameter is taken at the conservative 23 bound, and we are going to end up with a set of ATWS 24 circumstances to f ace where you will discover, "I needed 25 second pressure vessels," or something like that.
Then, you l
ALDERSON REPORTING COMPANY,INC, 1
6 W
..i
39 1 will say, "No, I can't do that."
You will start backing off 2 in peculiar ways.
3 When we talkad about making ATWS analyses years 4 ago, it was always with the view in mind'that we would try 5 for a change to do a realistic analysis, tha t is, a central 6 value analysis.
We recognired that there would be 7 substantial errors, and the though t in those days was to 8 make the error propagation analysis from a base case, which 9 had been done on central values, best estimate values, and to then try to decide what sort of factors of conservatism one 11 vanted on the basis of the overall product, rather than 12 building in unquantified f actors of safety all along the 13 line by taking conservative bounds on parameter af ter 14 parameter, af ter parameter.
15 This language sounds like you are somewhere sort 16 of in-between.
You have not quite made up your mind which 17 things you are driving people to the conservative bound, and 18 which places you are going to say that is realistic.
19 The tenor of what I have read and heard over the 20 last couple of years suggests to me that there would be 21 damned few, so-called, central value parameters, and a hell 22 of a lot of conservative bound parameters.
You are going to 23 end up once again with peak pressures, and a calculation of 24 140,000 pounds per square inch.
These are not going to be 1
25 able to hack it.
ALCERSON REPCRTING COMPANY,INC,
40 1
I really wonder if you would not be better off to 2 say, "In this case, let us try to make our best calculation 3 of the way that nature will work in one of these 4 sequences."
Having made that calculation, then also make a 5 calculation to see if we can get some rough idea of the 6 distribution of that, so-called, best calculation value_of 7 final results.
Then we can see what we want to do, if 8anything, about safety factors.
9 MR. MINNERS:
It is a technique that could be 10 d o n. e.
I think that one of the advantages of trying to put 11 in some conservatism is -- I am not too sure that it has 12 worked well in the past.
But the idea is that if you have a 13 quan tity which is unknown and, therefore, uncertain, go out 14 and do come research analysis, or whatever, and get your 15 error estimate down.
It will give you some economic 16 benefit.
17 Therefere, there la an impetus for the industry to 18 go o ut and find outwhat the true facts are, rather than 19 living with a very uncertain best estimate of some 20 parameter.
21 COMMISSIONER HENDRIE:
It does not work th a t way.
22 MR. MINNERSs It hasn't, I agree.
23 MR. THADAMI:
Dr. Hend rie, I hope I can help in 1
24 this case.
1 25 The approach used here does rely on central value ALDERSoN REPCRTING COMPANY,INC,
41 1 parameters, where we do have sufficient information 2 available to us, pressure, temperature, power levels, etc.
3 It is areas where we do not have data in general, or have 4 very little data, that one gets into difficulties of trying 5 to assess what is central value.
6 Warren gave, I thought, an excellent example of 7 water release through safety valves under these pressure 8 conditions.
We do not know of any data for these devices, 9 for these geometries, which are indeed appropriate to be 10 used.
11 We have utilized information, if you will, at
- 12. lower power level for devices that look somewhat similar in 13 terms of the geometry.
14 We have made some assessments as to which models 15 might be appropriate.
There has been some disagreement 16 between the staf f and the industry.
The industry at one 17 time suggested that it was conservative, while we felt under 18 the conditions it was more appropriate to use that type of 19 model where we did no t have enough information.
20 Another reasonable example is actuation of systems 21 in terms of times.
We do have tech spec limits.
We were 22 trying not to get into the mode of using tech spec limits in 23 terms of actuation times f or systems.
We would have 24 pref erred to have used more realistic values.
25 The recommendation we made was, where we do have ALDERSoN REPORTING COMPANY,INC.
42 as' I substantial data, we would indeedothe central values.
2 Difficulties arised because we were trying to handle this 3 problem in a generic way, and actuation times for systems in 4 diff erent plants are not necessarily the same.
5 In a situa tion like that, it might have been 6 better, and I believe it would have saved a lot of money, if 7 we had done an analysis on the basis, perhaps, tech spec 8 values.
It would be a conservative value.
While not 9 rigorously a parameter, nevertheless it is an input into an 10 evaluation.model.
11 I believe we are saying the same thing.
The whole 12 approach has been to try to assess the realistic course of 13 the event.
Only where we do not know what realism is with 14 any degree of confidence, are we utilizing what might be 15 considered renservative values.
4 16 There is ons exception, and Warren touched upon 17 that also, moderated tempera ture coefficient.
It is a 18 parameter which varies with burn up.
So what is a realistic 19 value ?
At any given time, it ha s got value, and about that 20 value there is some uncertainty.
21 We picked a time in the life of the plant in 22 pre-84 and post-84, as Warren indicated to you, 90 and 99 23 percentile values.
That is, only 10 percent of the time the 24 realistic value of the temperature coefficient would be 25 worse than that which was used in the evaluation model.
But ALDERSoN REPORTING COMPANY,INC, evm.
43 1 the uncertainty in that case was not added on.
So it is a 2 realistic value at that time in life.
3 Again, I just wanted to say these words to make 4 sure that there is a reasonable understanding in that a 5 thorough attempt was made to make as realistic as 4e can.
I 6 do believe there are conservatisms only because we do not 7 know what the realistic values are.
8 MR. MINNERS:
I think, as he pointed out, the 9 problem is the staff is going to have to have some to discipline in applying this rule.
We hope we can have that 11 discipline through a reg guide which is fairly specific.
12 We would not cara to put numbers like there would 13 be in a reg guide in a rule, because when someone comes up 14 with new information, you 'have to go through a lot of 15 analysis, which probably is not worthwnile.
So we would 16 pref er to go that course.
17 But we believe that the staff can have discipline, 18 be reasonable in which things are applied conservatively, 19 and which things are central estinates, and specify those 20 things in the reg guide for better to understand what they 21 are.
22 COMMISSIONE3 HENDRIE:
It is useful for you to 23 keep in mind, as you come to detailed consideration of those 24 thin gs, that when you get through with these calculations, 25 you come out with a li.7ited amount of fuel damage, primary ALDERSoN REPORTING CCMPANY,INC,
44 1 system pressures not over level C service limits versus some g.(**>
2 more condition, creation of releases consistent with the s
3 amount of fuel damage, the containment intact or shutdown 4 and cooling for a long term.
That is the condition which 5 has to result at the end, and the calculation in itself is a 6 pretty conservative one.
7 MR. MINNERSs I think we tried to say that.
We 8 adopted those criteria more because they are easily 9 iden tifiable and that they are really hazardcus conditions.
10 COMMISSIONER HENDRIE.
Most of the design lifetime 11 is 90 percent, and almost all of the design lifetime is 99 12 percent?
13 HR. MINNERS:
Yes, sir.
14 There has been some discussion, mostly with the 15 lawyers, on whether it should-be numbers or whether it 16 should be words.
The technical staff, for the reasons I 17 have stated, would prefer to have some words which give 18 guidance on what should be in there, and then have specifics 19 in the reg guide.
So that when somebody comes in with 99.9,
' 20 he does not have to go back and do a reanalysis.
21 COMMISSIONER HENDRIEs Let me ask you.
If in the 22 fron t end where you explain what you mean, you say the 23 numbers, and even the meanest intellect is able to 24 understand that what you are talking at 90 and 99 percent, 25 using the numbers at the front end, is in fact back here in ALDERSoN REPCRTING COMPANY,INC,
45 1 section bact here, whatever it is, on the design lifetime 2 and most of the design lifetime.
Have you retained that 3 flexibility?
4 I leave it as a question to be answered for 5 yourselves.
6 You would go with seismic and natural event 7 design.
Seismic design, the operating basis is earthquake.
8 MR. MINNERS:
Yes, sir.
Having a ATWS events and 9 an earthquake simultaneously is a very low probability to event.
It does really not'have to be considered.
What is 11 required is to have some kind of a vibration design for the 12 equipment.
It is difficult to specify.
You can't have a 13 truck go by to exaggerate that condition and have the 14 equipment no t work.
That has always been th e dif ficult in 15 specif ying some low level earthquake design.
16 COMMISSIONER HENDRII:
Yes.
/
17 If you put a single f ailure requir ement on the 18 mitigating systems for later plants, what is that going to 19 require, doubling up the standby liquid control system in 20 BWRs ?
21 MP. M!NNERS:
I think that there will be some 22 changes in the RHR systems.
Is that correct.
23 MR. THADAMI:
I am sorry, I did not get it.
24 MR2 5 INNERS:
For single failures in SWR, you 9wa6N1 1
25 would need to have a redundant 411guid control system, and ALDERSoN REPORTING COMPANY,INC,
46 1 also. RHR capability?
2 MR. THADAMI:
I don't lieve so.
On the basis of 3 very preliminary analyses that General Electric performed 4 several years ago, their judgment was that they could 5 withstand single f ailures as long as the standby liquid 6 control system had higher capacity on the order of 300 _
7 gallons per minute, rather than the 86 gallons per minute 8 that we have been discussing under alternate 3.
9 COMMISSIONER HENDRII:
The question was, the 10 requirement to withstand random single f ailures of active 11 components in the post-84 plant series, it required higher 12 capacity in the standby liquid control system as noted on 13 the summary chartshr some, hmt.
14 I was curious, what else do you predict in the way 15 of ATWS mitigation systems you are going to require.
For 16 example, is reserve pump trip a single f ailure resistant 17 now?
18 MR. THADAMI:
It is single f ailure resistant in 19 terms of the electrical aspects.
But we do not postulate a 20 passive or techanical f ailure.
It is a single active 21 f ailure that we have postulated.
The recirculation pomps 22 can, indeed, withstand single active failure in terms of the 23 electrical aspects.
24 The biggest concern we had really was the 25 reliability of high pressure injection system, coolant ALDERSoN REPORTING COMPANY. lNC,
47 1 injection system, or high pressuo, core spray.
We do 2 believe, on the basis of our discussions with GE, that 3 failure of the high pressure core spray system for post-Su 4 plants, the added capability of standby liquid control 5 system in tarms of not only providing the negative 6 reactivity, as well as providing higher quantities of water, 7 would aid in keeping the core covered.
We certainly take 8 credit for other systems, such as control red dry pumps, and 9 so on, in the evaluation.
10 So I don 't believe, on the basir of our 11 understanding which is certainly based on GE calculations, 12 that anything beyond what was identified in that slide that 13 Warren showed you would be required for post-84 plants.
14 There may be alternative ways of achieving the same 15 objective, and possibly cheaper ways.
16 COMMISSIONER HENDRIE Do you think six months is 17 going to be enough to get these evalution models submitted?
18 MR. MINNERS:
What confidence do you want me to 19 put on my answer.
20 COMMISSIONER HENDRIE Make s central estimate.
21 (Laughter.)
22 MR. DINNERS:
I guess I am not as familiar with 23 the models is I should be to answer the question.
In 24 talking to the people, I get various opinions, and six 25 months is what people have quessed would be a proper amount i
i ALDERSoN REPORTING COMPANY,INC, 63NTXikfkR NT@lDi 88 M4 FM) G*M
48 1 of time.
2 It is kind of hard, I think, to estimate until you 3 see the evaluation models and leak at then hard.
If you 4 find some problems, then six months may not be enough.
5 Based on what we have looked at now, and considering that we 6 have had a lot of discussions with people, six months should 7 be able to do it.
8 COMMISSIONER HENDRIE:
It looks like combustion 9 and CE plants are going to have to hang some more relief 10 valves in the system.
I am not sure that there is much else 11 to do.
12 I am not sure that recasting the whole core 13 neutronics design to make the moderator coefficient strongly 14 negative at all times is something that they are going to 15 consider very practical.
'd If they have to go into these plants and hang new 17 safety valves, can it be done?
What does it require -- new 18 pressurizers?
19 MR. MINNERS:
I don't think we have a complet 20 answer to tha t.
My understanding is that some plants have 21 additional nozzles on the pressurizers, and it would be a 22 rela tively easy job to add a safety valve to those plants.
23 In some instances, you may be able to use the same 24 valve, but put a different orifice in it to give it a higher 25 capacity.
ALDERSCN REPORTING COMPANY,INC, 400 VIRGINIA AVE., S.W. WASHINGTCN, D.C. 20024 (202) 554-2345
49 1
COMMISSIONER HENDRIE:
Won't that fall before the 2 single f ailure requirement?
3 MR. MINNERS:
No.
I don't think we would 4 postulatee as a likely single failure a safety valve not 5 opening.
That is a pretty low probability event.
Ther? may 8be cases in which the plants do not have any provision for 7 more valve on the pressurizer, and that would be a difficult 8 situ ation.
We don't have a complete survey and could not 9 tell you plant by plant whether they can or can't put valves 10 on.
11 MB. THADAMI:
In some cases, and I believe in 12 particular the the BEW designs, the safety valves are fairly 13 small size safety valves, and one could use larger size r
14 valves.
15 COMMISSIONEE HENDRIE:
Are the nozzles big 18 enough ?
17 MR. THADAMI:
It is my understanding, but I cannot 18 say that with a high degree of confidence either.
19 Again, in the case of BEW, there may be 20 alternative ways, if it is not possible to add vt!ves, to 21 reduce the calculated pressure.
One example I can give you, 22 I could make sure that the a uxilia ry feedwater system is 23 actuated very early, very quickly.
24 Of course, one would have to look at things like 25 diesels, and at what time one turns on these pumps, load ALDERSCN REPORTING COMPANY,INC, f * #EtTi
50 1 sharing, and so on.
There are alternative ways to reduce 2 the calculated peak pressure, possibly to well below service 3 level C limit.
4 The analyses have not been performed, but you can 5 see the trend from the sensitivity studies that have been 6 cond ucted that there are other possibilities also.
7 We are talking about Sabcock and Wilcox and 8 Combustion Engineering plants, I think there are roughly 15 9 units.
B CW, at least on the basis of my understanding, I am to optimistic that one can just use maybe larger sire valves, it and that should do it, especially because of the physics 12 characteristics.
A 90 percent temperature coefficient is 13 not very severe.
For BCW, they should not be calculating 14 very excessive pressures.
Unfortunately for Combustion, I 15 quess, it is about eight units.
16 The pre-CESSAR designs are going to have very 17 dif ficult time because of the physics characteristics, and 18 the temperature is not very negative.
That is where we have 19 to te careful, because they would be calcula ting such 20 excessive pressures that t ?re is potential for lifting of 21 the head of the vessel, pressures that could be as high as 22 6,000 pounds.
In that case, I think, we do have to be 23 extremely concerned.
24 COMMISSIONER HENDRIEs Is it practical to use some 25 of those reactor head vents for safety valving?
Are those l
ALDER $oN REPORTING CCMPANY,INC, 1
51 1 things big enough?
2 MR. MINNERSs We did not consider that.
I doubt
~
3 if they are.
I will take a look at it.
4 MR. THADAMIs I don't believe they will be big 5 enough.
We did suggest that those be considered in th e 6 analyses as another link path, if indeed it could be 7 actuated in that manner, pressure actuation.
8 COMMISSIONER RENDRIE:
I decided the last time 9 there was a meeting on this that I did not understand what 10 we meant by the supplementary protection system that is 11 required.
Either it has been explained to me and I have 12 forgotten it, or I have never bothered to stop and think 13 what it means.
14 What is it?
Everybody has to have one, and what 15 is this again?
16 3R. MINNERS:
In concept, it is another reactor 17 trip system, which is diverse and independent from the 18 present reactor trip system.
So that if you had a common 19 mode f ailure in one portion, you would still get a rod 20 scra m.
21 COEMISSIONER HENDRII:
Where does it hook to the 22 present system?
23 MR. MINNERS:
Since there is diversity already in 24 the sensors in the reactor protection systems, it would 25 probably use some of the same sensors, because you don't
)
ALDER $oN AEPoRTING CoMPMY,INC, e
52 1 teed all of the sensors in all of the trancients.
2 Then you would have the logic circuits, and the 3 power intorruption divices would be separatekrom the logic 4 and power interruption relays of the present scram system 5 concept.
6 COMMISSIONER HENDEIE:
,So this system would have 7 its own set of scram breakers.
8 MR. MINNERS:
That is the staff's proposal.
In 9 the industry proposal, they would use the same scram 10 breakers.
11 MR. THADAMI.
Just a clarification.
The Babcock 12 and Wilcox designs, we do believe, have diverse means of 13 dropping rods.
So for those plants wo are not requiring any 14 breikers, if you will.
15 But for Combustion Engineering, the supplementary 16 protection system does utilize different type of breakers, 17 but I don't believe that they increase the number of 18 breakers.
They would still utill:e, I believe, eight scram 19 breakers, but two or four breakers would be manufactured by 20 somebody else.
It is diversity of manuf actu re.
21 COMMISSIONER HENDRIE:
What about the Westinghouse 1
22 system, where you come down to that-pair?
23 MR. THADAMI:
Westinghousa, at least so far, as 24 Warren indicated to you, we have not seen any design.
But 25 for post-84 plants, we would expect that they would have to ALDER $oN REPORTING COMPANY,INC, M0m ARR,W WW;ToNJA N4 A 564-fem
53 1 have breakers to meet that requirements.
2 With two breakers, off-hand, I don 't see how they 3 can provide the kind of improvement that we were looking 4 for.
I think you are quite right, for Westinghouse design 5 post-84 plants, they may have to add scram breakers.
6 But so far we.are only talking about logic by_
7 stables, and the actuation portions.
The sensors are still 8 the same.
9 MR. MINNERS:
The design would be a little 10 diff erent ?.
11 MR. THADAMIa It is really not much different on 12 G E.
13 HR. MINNERS:
You sould get a slow scram on the GE 14 Ma,ign rather than a rapid scram.
15 MR. THADAMI.
Yes.
16 MR. MINNERSs The GE design has some va)ves on the 17 air system, which vent the whole air system.
The protection 18 system operates on individual valves on each rod.
Then 19 there is a pair of valvas the whole air system snd, 20 therefore, all of the rods.
But it would be a slower vent, 21 so you would get a slower scram.
22 MR. THADAMI:
A similar improvement for GE is 23 obtained making the ' curren t change Warren described, as 24 vell as recirculation rump. rip.
So their system is a 25 similar system and it is called ARSS, it is an improved i
l t
ALDERSoN REPORTING COMPANY,INC.
e 54 1 protection syrten, and it makes sure that the pumps trip 2 very early.
So you are back with the same situation.
3 COMMISSIONER HENDRIE:
Let me ask a final 4 question.
5 All of this is aimed at driving down the 6 likelihood of a serious ATWS events, and by serious ! mean 7 of f-site consequences.
That must be the aim, by 8 definition.
9 MR. MINNERS:
I think there is more than that.
10 Althcuch we have focused on off-site events, I think there 111s also in the back of everyone's mind that even if you have 12 a carenelt that has no offrite affects, which is unlikely, 13 or small of f-site ef fects, that is something that we are 14 driving toward also.
This is being considered.
It is a 15 small f actor, but it is still in there.
16 COMMISSIONER RENDRIE:
Let me divide it into parts 17 A and B.
18 What is your best estimate of what those fixes in 19 the various classes will do by way of improvement, first for 20 reducing the likelihood of off-site consequences; secondly, 21 reducing severe core damage?
22 MR. MINNERS:
It varies by plant and alternative, 23 and we do have that in one of the documents.
24 Mark, if you would put up 17-A from the back-up 25 slides.
1 ALCERSoN REPORT 1No COMPANY,INC, cevr,mmun-sa m m su.2m i
.o 55 1
Alternate 1 in this case is the current 2 probabilities.
Alternate 2A is just to have a supplementary 3 protection system.
Alternate 2B is to mitigste most ATWS 4 events.
Alternate 2D is to mitigate all or almost all ATWS 5 events.
6 Those are the probabilities that we have made, 7 estimates for.
That is for an ATWS event.
As you have 8 poin ted out, this would be that you would exceed the exceed 9 the acceptance criteria, and there is still some margin to between that and coremelt.
Then there are further margins 11 between coramelt or core degradation and serious off-site 12 consequences.
13 We have chosen not to include that in our 14 evaluations, because we have kind of indexed it on the 15 reactor, safety study, and have said, in a qualitative way, 16 that ATWS coremelts are like any other kind of ceremelt, so 17 we will not go into the consequence modeling, we will just 18 compare coramelt probabilities.
19 MR. THADAMIs May I comment on that.
20 Those numbers represent not really frequency of an 21 ATWS event.
The frequency of at ATWS event sould be 22 approxima tely two times 10 to minus four for all designs.
23 Those numbers represent frequency of a severe ATWS event, 24 on e th a t exceeds the criteria.
25 MR. MINNERS:
One that exceeds the criteria, that i
AI.DERSoN REPORTING COMPANY. INC.
... o 56 1 is right.
2 MR. THADAMI Yes.
These numbers do not take into 3 consideraton the Browns Ferry event.
4 MR. MINNERSa Correct.
5 MR. THADAMIs Warren probably has those numbers.
6 MR. MINNERS; I don't have a slide of that, but it 7 is in Appendix H, or one of those in the back.
8 COMMISSIONER HENDRIEs A factor of 100 richt side 9 of slight, lef t side of the slight.
to MR. MINNEBS:
Yes, sir.
11 MR. THADAMI:
That is correct.
If you want to 12 look at it that way, we believe if you go to alternate 3A as 13 defined in the SECY paper, you would go from roughly 10 to 14 the minus four to 10 to the minus five.
Alternate uA takes 15 you to about '1 0 to the minus six.
16 The pre-84 plants we believe would be at 10 to the 17 minus 5 level, if you will, recognizing the uncertainty of 18 these numbers.
Whereas post-84 would be close to 10 to the 19 minus six in terms of severe consequences from ATWS 20 even ts.
21 MR. MINNERS:
I would like to put a caveat on 22 this.
The numbers were basically developed to be used in 23 the value impact analysis, because to do a value impact 24 analysis you had to have the numbers.
I think they should 25 be looked at f rom tha t perspective.
At. DER $oN REPCRTING CCMPANY,INC, M'
i 57 1
I hate to say it again, but I guess you ought to 2 apply some engineering judgment to some of the numbers, and 3 some will have different confidence than others have.
They 4 are all central estimates, but I believe some more than 5 others.
6 CHAIRMAN AHEARNE:
As I understand your estimated 7 schedule, as far as you know we will be getting a draft I '-
CI p+ever 8 mi th e b y the middle of December?
9 MR. MINNEPS:
That is correct.
10 CHAIRMAN AHEARNE:
I checked with Bob Minogue, so 11 I know that - they are estimating the research on time.
I 12 assume that the legal recommendation will also be coming in 13 on time.
14 We have been having Ed Ha*rahan, as you know, 15 summ ariring a number of things for me,.
I have a modified 16 collection of the alternates that you have put together that 17 I am coing to ask him to talk with you about.
18 MR. DENTONs Fine.
19 CHAIRMAN AHEARNE:
I have no f urther comments.
20 Len, do you have a comment?
21 MR. BICKWIT Just one, to finish up the 22 discussion that we had earlier.
23 If your intent is to rule out the application of 24 Part 100, I think that rather than simply delete the 25 ref e rences in the ea rlier draf t, you ought to state that you i
ALDER $CN REPORTING COMPANY,INC, FN Q M 6 % % M
58 1 are ruling out the application of that part.
Otherwise, I 2 think' the rule will be subject to some smbiguity.
3 CHAIRMAN AHEARNEs Thank you very :c uch.
4 (Whereupon, at 11.45 a.m.,
the meeting was 5 concluded. )
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November 25, 1980 1.
Intent of ATWS Rule Major Requirements 2.
Implementation 'f Rule o
3.
Revisions to Rule
~
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Revisions to Federal Register Notice 5.
Schedule O
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PROPOSED RULEMAKING TO AMEND PART 50 4
CONCERNING ATWS (ANTICIPATED TRANSIENTS WITil0UT SCRAM) 1 i
a
p ATWS RULE INTENT PLAtlT ATWS EVENT MITIGATE PREVENT MOST ALL ELECTRICAL PRE-69 (1)
X PRE-34 X
X X
POST-84 X
X (1) EXEMPTI0t!S CASE-BY-CASE JUSTIFIED BY LICENSEES
g,'
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TABLE K-1
SUMMARY
0F REQUIREMENTS
( INDICATES IMPLICIT REQUIREMENT.)
VENDOR ALT 2
ALT 3
ALT 4
B&W, CE SRS SPS SPS AMSAC AMSAC AMSAC CONT ISOL CONT ISOL CONT ISOL ANALYSIS ANALYSIS ANALYSIS INSTR
- INSTR
- SAFETY VALVE
- SAFETY VALVE
-H AMSAC AMSAC AMSAC CONT ISQL CONT ISOL CONT ISOL ANALYSIS ANALYSIS ANALYSIS INSTR
- INSTR
CONT ISOL CONT ISOL CONT ISOL ANALYSIS ANALYSIS
L0 sic
- L0 sic
- INSTR
- INSTR
- SLCS-AuT0*
INCR. CAP SLCS-AuT0*
HI-CAP
l ATWS RULE IMPLEMENTATION
{
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.I EARLIEST PRACTICAL PREVENTION ELECTRICAL JULY 82 f
MITIGATION' ELECTRICAL JULY 82 ACTUATION CIRCUITS CONTAINMENT ISOLATION
-SCRAM DISCHARGE VOLUME MECHNICAL i
PRE-84
. BWR JULY 82 PRE-69 BWR JAN 84 PRE-84.-
PWR JAN 84 i
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ATWS RULE REVISIONS DEFINITIONS-ADDED "ATWS MITIGATING SYSTEMS" ACCEPTANCE CRITERIA
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1 DELETED PART 100 LIMITS FUEL R0D FAILilRES J
DESIGN CRITERIA r
ADDED ATWS MITIGATING SYSTEMS ADDED CONTAINMENT-ISOLATION GENERALIZED EXCEPTION TO SPS IMPLEMENTATION ADDED. STANDARDIZED PLANTS i
NO CHANGE TO DATES.
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ATWS FED. REG, il0TICE ADDED HISTORY REVISED BASIS FOR RllLE REVISED EXPLAilATION OF RULE ADDED IMPLEMENTATION
b
.ATWS RULE SCHEDULE 11/25 COMMISSION MEETING 12/12 ENVIRONMENTAL IMPACT ASSESSMENT RES. COMMENTS 12/22 LEGAL RECOMMENDATION REGULATORY GUIDE 01/12 PUBLISH NOTICE 04/15 END COMMENT PERIOD I
06/15 PUBLISH-FINAL RULE 8 REG. GUIDE 4
4 L
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i ATWS FREQUENCY ALT. 1 ALT. 2A ALT. 2B ALT. 2D B&W 8
10-5 g. 10-5 q, 10 10-6 C-E 8
10-5 q. 10-5 g. 10-5 10-6 W
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