ML20151B581
| ML20151B581 | |
| Person / Time | |
|---|---|
| Issue date: | 07/14/1988 |
| From: | NRC COMMISSION (OCM) |
| To: | |
| References | |
| REF-10CFR9.7 NUDOCS 8807210028 | |
| Download: ML20151B581 (85) | |
Text
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l4 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION i
Title:
BRIEFING ON FINAL RULE ON 10 CFR 50.46, ECCS ACCEPTANCE CRITERIA (APPENulX K)
Location:
ONE WHITE FLINT NORTH, ROCKVILLE, MARYLAND Date:
THURSDAY, JULY 14, 1988 Pages:
1-50 I
.l J
Ann Riley & Associates Court Repcriers 1625 l Street, N.W., Suite 921 d[f h Washington, D.C. 20006 T
(202) 293-3950 g72g(Qg28680714 PT9.7 PDC i
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. DISCLAIMER This is an unof ficial transcript of a meeting of the United States Nuclear Regulatory Commission held i
7-14-88 in the Commission's office at One on White Flint North, Rockville, Maryland.
The meeting was open to public attendance and observation.
This transcript has not been reviewed, c0rrected or edited, and it may I
contain inaccuracies.
The transcript is intnnded solely for general l
informational purposes.
As provided by 10 CFR 9.103, it is l
not part of the formal or informal record of 4o,'31on of the 1
matters discussed.
Expressions of opinion in tri.>
transcript do not necessarily reflect final determination or beliefs.
L r
No pleading or other paper may be filed with the Commission f
l in any proceeding as the result of, or addressed to, any statement or argument contained herein, except as the i
Commission may authorize.
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UNITED STATES OF AMERICA 2
NUCLEAR REGULATORY COMMISSION 3
4 BRIEFING ON FINAL RULE ON 10 CFR 50.46 5
ECCS ACCEPTANCE CRITERIA (APPENDIX K) 6
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7 PUBLIC MEETING 8
9 Nuclear Regulatory Commission 10 One White Flint North 11 Rockville, Maryland 12 13 THURSDAY, JULY 14, 1988 i
14 r
15 The Coonission met in open session, pursuant to 16 notice, at 10:10 a.m., the Hanorable LANDO W.
ZECH, Chairman of 17 the commission, presiding.
18 COMMISSIONERS PRESENT:
19 LANDO W.
- ZECH, Chairman of the Commission 20 THOMAS M. ROBERTS, Memb'er of the Commission 21 KENNETH M. CARR, Member of the Commission 22 KENNETH C.
ROGERS, Member of the Commission 23 L
24 1
i V
25 i
t f.
4 2
r 1
2 STAFF.AND PRESENTERS SEATED AT THE COMMISSION TABLE:
3 j.
4 V.
Stello W.
Parler I):
5 J. Guttman E.
Beckjord 6-L.
Shotkin B. Sheron 7
D. Ross 8
i 9
10 11 12 13 i.
l 15 j
16 17 18 19 20 21 22 23 24 25
I, i
3 l
1 PROCEEDINGS I
2 (10:10 a.m.)
3 CHAIRMAN ZECH:
Good morning ladies and gentlemen.
4 Today the Commission will.be briefed by the NRC's Office of 5
Research on a final rule on 10 CFR Part 50.46, emergency core 6
cooling systems acceptance criteria, Appendix K.
1 7
Section 50.46'of 10 CFR Part 50 requires licensees to '
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8 perform calculations to demonstrate that the emergency core 9
cooling systems will adequately cool a reactor in the. event of 10 a loss of coolant accident.
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4 11 This final rule is a result of over 12. years of 12 research on emergency core cooling systems and thermal 13 hydraulics sponsored by the NRC, DOE, the nuclear industry and 14 various foreign countries.
15 This research has allowed the staff to develop a more 16 realistic safety assessment of emergency core cooling system 17 performance.
i 18 It is my understanding that the proposed final rule 19 will allow the use of best estimate evaluation methods for
- i' 20 ascessing the performance of an emergency core cooling system.
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21 However, current emergency core cooling system methods included i
22 in Appendix K will be permitted.
23 The Commission will be interested in hearing how 24 comments on this proposed rule have been addressed.
25 Do any of my fellow Commissioners have opening
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1 remarks or comments to make before we begin?
Commissioner 2
Rogers?
3 COMMISSIONER ROGERS:
Yes, very briefly,.that I 4
noticed in the supporting material that the ACRS has indicated 5
that there are safety advantages to the new rule and that they 6
are substantial and in your presentation, would you somehow try 7
to clearly address what.the safety advantages and any safety
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8 disadvantages are that may arise from that rule.
9 CHAIRMAN ZECH:
Are there any other comments?
10
[No response.)
11 CHAIRMAN ZECH:
Mr. Stello, you may proceed.
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12 MR. STELLO:
Thank you, Mr. Chairman.
i 13 Perhaps it is appropriate to stop for d moment and 14 review briefly the history.
There are at least two of us at 15 the table here, Dr. Ross and myself, who are intimately 16 involved in the early years of the ECCS controversy and I guess 17 many have forgotten the intensity of that controversy back in 18 1970.
19 There was considerable debate over the relative 20 safety of nuclear plants because of the question surrounding 21 the emergency core cooling systems and a very long complicated 22 hearing process went on that spanned over a two year period, 23 finally coming out with Appendix K in 50.46, which has been the i
I 24 Commission's regulations on emergency core cooling systems that 25 we have used since that time.
5 1
In these 18 years since then, the total expenditure 2
of money to bring this to the point of understanding where we 3
can now support the changes we are talking about, in excess of 4
$1 billion, and this very often gets to be a controversy of 5
where does our research money go and what is it used for, that
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6 one figure by itself, the amount of money that was spent-in l
7 dealing with this issue because the Commission at that time i
8 indicated that this research had to go on, confirm the 9
conservatisms or identify any further problems.
10 It has been a very, very long process and a lot of 11 money has been spent.
I think we now can say with confidence 12 that tihe controversy of emergency core cooling systems is now 13 behind us.
It was a long process, a complicated one, a lot of
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14 hard work has gone into this to bring us to where we are today.
15 If the Commission finally does go forward with these
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j 16 changes, I think we have brought to rest one of the major 17 controversies that was associated with nuclear power back in i
18 the early 1970's anc in fact has not been a major controversy l
P 19 of reactor safety in the pcst several years.
20 I think that is principally a result of the very hard 21 work and dedicated research.that has gone on to resolve these 22 issues.
23 I think it is a significant occasion that we are at 24 this point in time, at least for me personally and.I guess I 25 could speak for those of us who have'followed this over these
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1 many years.
We are happy to be here with the Commission and I i
2 think can speak with confidence, this is no longer a safety 3
issue where we think this agency needs to' concern itself and
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4 propose to make some significant changes which I think have 5
advantages to them.
6 With that brief introduction, I think Eric Beckjord 1
7 has a few introductory comments and then we will get on with 8
the briel'ing is in two parts, with Brian Sheron doing the first 9
part followed by Lou Shotkin who will get into the substance of 10 that rule.
11 Eric?
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12 MR. BECKJORD:
Thank you, Vic.
13 Actually, the points I was going to make, several of 14 them have already been covered.
I would add that actually 15 there are three of us at the table because I was a member of 16 the AEC Core Cooling Task Force from 1966 to 1968 that 7
17 anticipated the decisions to increase the capacity of emergency l !
l 18 core cooling systems.
19 The other point I wanted to go over was this proposed 20 revision completes the 1974 mandate from Congress an'd the
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21 Commission to quantify the conservatism and margins in the 1974 22 rule.
At that time, in their assessment of the state-of-the-23 art, the American Physical Society concluded that the 24 calculational methods were not satisfactory and that 25 experimental verification was needed.
1 7
]
1 We have now completed this work on the schedule that i
2 was anticipated at the time and also the technical basis for 3
this new rule has received peer review.
4
~I think that covers it.
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MR. STELLO:
Thank you.
Brian?
6 MR. SHERON:
Thank you.
Could-I have the second
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7 slide,.please.
8 (Slide.)
9 MR. SHERON:
What I will be talking to you about 10 first is just the purpose of the meeting and then again to give 11 a little more detailed background on the ECCS rule.
12 (Slide.)
! l 13 MR. SHERON: 'The thir'd slide just states our purpose 14 here, to brief you on the final version of the ECCS rule and i
15 its technical basis and I guess to ask you to affirm 16 publication of the final rule.
17 (Slide.)
18 MR. SHERON:
On slide four, the purpose of the rule 19 as you have heard from Vic and Eric is to provide guidance and i
20 performance criteria for the design of emergency core cooling 21 systems in light water reactors, both PWRs and the BWRs, in the I
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22
- q event of a loss of coolant accident, this is both large break i
23 and the small break.
i f d i 24 The ECCS rule, just for your information, is broken k
25 up into two parts.
There is 10'CFR 50.46, which specifies the g
i
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4 8
1 criteria, and then there is Appendix K to Part 50 which 2
provides the required and acceptable features of an ECCS 3
evaluation model.
4 (Slide.)
i k
5 MR. SHERON:
Prior to 1971, the review of ECCS 6
designs from a regulatory standpoint was sort of ad hoc.
They 7
were I believe challenged on an individual basis many times in 1
8 the hearing process.
There was no criteria guidance.
Also in 9
1970, testing that was done at Idaho National Engineering lab 10 on a semiscale facility, test number 845, showed indications 11 that when ECCS water was injected into the primary system to 12
'ake up for coolant loss by a LOCA, that in fact some of that m
i 13 ECCS water might go right around the annulus of the vessel and 14 out the break and not find its way into the core.
15 (Slide.)
O 16 MR. SHERON:
You will see as a result of what I just 17 told you, that in 1971, there was a Regulatory Task Force which r
18 developed an ECCS design interim' acceptance criteria.
These 19 criteria were pretty much what the final criteria were except 20 they did allow peak cladding temperature of 2300 degrees rather 21 than the current 2200.
22 During the period 1972 to 1973, ECCS hearings were 23 conducted.
They were very extensive as Vic said, they were 24 very emotional at the time, very intense.
I 25 COMMISSIONER ROBERTS:' Who were the major
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9 9
1 participants?
2 MR. STELLO:
The Union of Concerned Scientists, Dr.
3 Kendall and Dan Ford were the principal intervenor organization 4
in the hearing.
There were others that participated but of 5
considerably lesser statute and significance.
6 CHAIRMAN ZECH:
Let's proceed, please.
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7 (Slide.)
8 MR. SHERON:
The current ECCS rule which is embodied 9
in 50.46 and Appendix K was promulgated in December of 1973 and 10 became effective in December of 1974.
The Commission issued an l
11 opinion with the rule that endorsed the ECCS research program 12 that would confirm the margins that were embodied in the rule.
13 Since that time, since this research has been ongoing 14 and it has been rather expensive, we have, I would point out, a 15 number of times received congressional concern over the fact 16 that gee, we had done all this research or were conducting all 17 this research and yet why wasn't it being used in any rules.
18 (Slide.)
19 One of the things that led to our consideration of 20 when to change the rule was when would a substantial amount of 21 the research be finished.
What we didn't want to do was do 22 some research, change the rule and then complete additional 23 research and have to yo back and perhaps change it again for a 24 second or third time.
25 In 1982, General Electric came into the Commission
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10 tI 1
and requested relief from the LOCA restrictions of the BWRs 2
which they designed.
I believe, if memory serves me, they 3
asked if they could have an exception to the decay heat i
4 requirement which says use the 1971 ANS standard increased by I
5 20 percent.
6 That obviously was contrary to the rule and we did 7
not allow it.
However, we were I guess sympathetic to the fact 8
that based on the research that we had seen, we did believe 9
there were margins that could be taken advantage of.
The staff i
10 prepared and sent to the Commission-SECY-83-472 which allowed -
I 11
- said that we were going to propose to allow the industry to 12 use be'st estimate models for calculating ECCS performance.
13 In order to comply with the rule that was still on p
14 the books however, they would have to do an analysis that used 15 perhaps the best estimate model but it had to.use the required 16 features in Appendix K.
Acceptable features were not required.
17 They'were things that the staff would accept without question 18 or review if they were used, but,they were not necessarily 19 required.
However, to make sure that we were not giving away 20 too much margin or making plants unsafe, what we also asked for
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21 was that in addition to that calculation, the industry should 22 supply us with the best estimate calculation plus an
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23 uncertainty assessment.
f 24 What we really wanted to know is what the peak clad 25 temperature at the best estimate value plus the 95 percent
11 1
uncertainty level.
What we wanted to confirm was that the 2
appendix K calculation that they did, namely a best estimate l
3 analysis plus the required features resulted in a peak clad 4
temperature that was still in excess of the 95 percent pj 5
uncertainty level.
6 This assured us that we still had an acceptably l
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7 conservative analysis.
We did this.
General Electric came in 8
with a model.
It was reviewed and appro' red by the staff.
It 9
showed that when they did the calculations in this manner, the 10 peak cladding temperature was substantially lowered and 11 therefore there was additional margin which could be used by 12 the in'dustry.
Namely, peaking factors could be increased -- so 13
- forth, f
l 14 Westinghouse also decided to use the SECY-83-472 l
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15 approach on their upper head injection, I'm sorry, the upper l
i 16 plenum injection plants.
There are, I believe, six of them.
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17 The two-loop plants.
That model, I understand, has just been i
18 recently approved by the staff and it was the favorable 19 experience that we had received from the industry as well as 20 the staff in applying the SECY-83-472 approach that led us to 21 formulate the proposed rule along the same lines of 83-472.
22
[ Slide.]
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23 On slide 9 you'll see that the criteric of the ECCS It 24 rule which are unchanged by the way, specified that the peak P
25 cladding temperature calculated using the ECCS models should be p
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less than 2200 degrees Fahrenheit.
The max cladding oxidation 2
that's allowed should be no greater than 17 percent locally.
3 The maximum hydrogen generation should be les, than one percent 4
core-wide.
That's based on theoretically the amount th6t could 5
be generated by oxidizing all of it -- cladding.
h 6
The coolable gecmetry should be retained and long-7 term cooling should be assured.
8
[ Slide.]
9 On slide ten, just to refresh you, that even though 10 the use of the ECCS rule was designe.d for coming up with 11 acceptable ECCS system performance and even though wo know now 12 for e$ ample that the LOCA is a very low probability event 13 compared to other events which could lead'to chall'nges to the e
14 systems it did provide several regulatory requirements with 15 regard to establishing the design margins that exist in plants 16 today.
17 I think the major one is the containment design.
The 18 ECCS required -- or I'm sorry -- that the LOCA specified the 19 containment design margins, namely for the large dry 20 containments that they be able to withstand the energy releases f
21 from the large break LOCA.
This led to design pressures in the 22 large dry containments of around 50 psi and when you looked at 23 the conservative loadings,that were required in the structural 24 design of the containment, like for example combining SSE plus 25 LOCA loads, we now have large dry containments which have
t 13 1
ultimate strength perhaps three times greater than the design 2
strength.
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3 For the BWRs it 'ed to the suppression pool systems F
4 used to condense the steam.
The ECCS also very strongly 5
influenced the core design, the ritel and cladding diameter and 6
the fuel spacing -- the lattice spacing -- the accumulator 7
capacities and set pressures, the high pressure and low 1
8 pressure systems, and their capacities.
!I 9
(Slide.)
i 10 On slide 11 the other thing that the ECCS rule did 11 and the effect of ECCS on plant operation is that it did put 12 limits on how a plant operated.
On some plants, it puts.a 13 limit on the i:otal power level that the plant can achieve.
I 14 think for most.olants this is usually early in cycle when 15 there's very high peaking factors.
16 It also limits the LOCA power peaking factor in the 17 plant, again because if the LOCA peaking factor would produce 18 several pins th.at would have very high power levels and 19 therefore their calculation in a LOCA would produce 20 temperatures above 2200.
Surveillance requirements were 21 required as a result of the ECCS.
Diesel generator start times L
I 22 and loadings were a very important part of ECCS.
23 In order to meet the 2200 degree limit, diesel A.
24 generator start times and loading times were typically of the 25 order of ten to twelve seconds.
Steam generator tube plugging
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-- when plants plugged too many steam generator tubes, it 2
starts to affect the ECCS performance and indeed puts 3
operational restrictions on the plant.
4 Then component reliability concerns obviously are
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affected by ECCS.
How many systems can be taken out of service f
6 or 111 owed to be out of
'e rvice.
So as you can see, the ECCS,
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7 while providing a number of benefits in the area of system 8
design, structural design of the containment, also did put 9
limits on the way plants could operate.
10 It was the intent when wo went f0:; ward and changed 11 the rule to make sure that we retained the degree of safety 12 necesdary in the ECCS systems to assure that the LOCAs both 13 large and small could be accommodated without any damage to the 14 core and yet did not provide an undue restriction in the 15 operation.
f la 16 Dr. Shotkin will now tell you about the revised rule.
17 COMMISSIONER ZECH:
Before you go on, let me ask if 18 there are any questions, my fellow commiscioners.
Mr. Rogers?
19 Mr. Roberts?
Commissioner Carr?
20 MR. STELLO:
Let me, if I might, Commissioner Rogers 21 asked us to cite some significant advantages for safety.
22 There's one that I particularly think is very significant and 23 was mentioned and I'd like to emphasize and that's diesel
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24 generator start times.
These ten to twelve second start times 25 after the rule was issued required cold fast starting of diesel
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1 generators -- very short time periods.
2 I think they had contributed significantly to the 3
unreliability of the diesel generators.
The new start times 4
that would be calculated using this new rule are like on the
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5 order of a hundred seconds?
And that change in start and 6
loading in the diesels will I think go a long way in making the.
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k 7
diesel generators far more reliable because the demand on the f
8 diesel generator really comes about from the ECCS calculations.
n if 9
So if I could cite one that I would use as a very i
10 significant safety advantage and there are others -- upper head 11 injection, some of the other things that no longer would be l
12 needed in calculations. consistent with this rule but the diesel 13 generators I would cite as potentiially very very significant 14 advantage.
i 15 COMMISSIONER ZECH:
Before you go on, c)uld you talk 16 just a little bit more about the -- on your last slide where 17 you talk about the power levels -- what other requirements 18 other than you have in this rule would have to be met for 19 example to approve an upgrade in power levels?
j 20 MR. SHERON:
Most plants cannot upgra.ie the power 21 mo.re than about 5 percent and this is because their -- the 22 diesel generator capacity is limiting.
23 COMMISSIONER ZECH:
What would the impact of that 24 kind of --
25 MR. SHERON:
I'm sorry, turbine generator capacity.
4
16 1
COMMISSIONER ZECH:
Okay.
What would the impact of 2
say a 5 percent or 10 percent increase in power level be on 3
risk?
4 MR. SHERON:
We've looked at that and it's basically 5
negligible.
The change in fission product inventory which 6
ultimately is a measure of risk is the release.
The fission 7
product inventory change is not as great, okay?
It's not a 5 8
percent increase because of the way the K ratios and so forth.
9 So the fission product inventory really doesn't increase that 10 much and when one looks at the overall uncertainties in our
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11 ability to calculate severe accidents right now, a 5 percent t
I 12 change" in power is really kind of down in the grass.
13 COMMISSIONER ZECH:
So it would have very little, if 14 any impact on risk, then; is that what you're saying?
15 MR. SHERON:
That's correct.
16 MR. STELLO:
And the new ECCS models would allow 17 because most plants at one time or another are in fact limited 18 because of ECCS calculations.
This would allow operating a p1' ant either at higher power level or make the operation of the 19 t
g plant simpler throughout the lifetime because of the problem of 20 21 peaking at various times in life.
22 COMMISSIONER ZECH:
All right.
Thank you very much.
l 23 Please proceed.
24 MR. SHOTKIN:
Before I start, let me add one aspect 25 to Commission Roger's question because of the ability to use
17 1
different peaking of the power in the core we can reduce the j
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2 vessel fluence in the wall and alleviate the concern of 3
pressurized thermal shock so this is one of the po'tential 4
advantages of the use of this rule.
5 (Slide.)
6 If I go to the second slide, I will be talking about i
7 the proposed ECCS rule and the ECCS research that is used for 8
the technical basis for the change.
The two are interconnected 9
for two main reasons.
First, without the research there'd be 10 no possibility of having the rule revisions.
The second is I.
11 that as has been mentioned, the Congressional intent which has 12 been dxpressed several times has been to apply the research 13 results -- any research results we have to remove excessive 14 conservatism in our rules and this is one of the rules that is 15 excessively conservative and we are using research to alleviate 16 that and then I'll come with a conclusion.
17 We go to page three, the key features of the proposed 18 rule require a best estimate calculation plus a measure of the 19 uncertainty and in doing both of these, we have to use the 20 computer codes that have been developed through the research 21 program as well as the data that has been developed.
Later on, 22 I'll be talking about the data that we have obtained has been I.
23 through international as well as domestic cooperative efforts 24 so this has been an international worldwide effort.
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i 25 The uncertainty that we have in the rule is just
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mentioned as to be determined at a high level of probability.
2' The high level is defined in a regulatory: guide that'does 3
accompany.the rule.. We propose to-grandfather the existing-4 rule so we wouldn't disrupt the' regulatory process for those i
l 5
utilities whose plants'are-not constrained by LOCA and there c
6 are most of the-B&W and the CE plants are not constrained by 7
LOCA.
8 It's the Westinghouse and the GE plants that would be 9
-- right now many of them are. constrained by LOCA and would f-10 benefit from this rule.
One of.the major things that we are 11 relaxing are the reporting requirements.
We're not only relaxing them but,we're clarifying them.
12 13 In the past utilities have had to report almost any.
14 change in their model even if it's up to 20 degrees Fahrenheit.
i 15 This has put in too much of a burden on their staff and one of thesafetybenefitsoftheruleisIfweremovetheburdenof 16 17 reporting requirements on their: staff, they can now concentrate 18 on more important safety issues.
19 So, we've raised that 20 degrees Fahrenheit to 50 20 degrees.
Most of the public comments have agreed with that.-
j 21 The reporting is now only annually for all error corrections 22 and changes.
Now if they exceed the 50 degrees they have to 23 report that in 30 days.
24 COMMISSIONER CARR:
How many different models are 25 there?
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MR. SHOTKIN:
The evaluation models are one for each 2
major vendor but the individual models within the codes, there I
3 are hundreds of them.
So any one of them, you could find an 4
error that's either, you put in a two instead of a.three, or 5
new research will say that some of it doesn't fit the data too 6
well --
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7 COMMISSIONER CARR:
Who ends up making these change
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8 reports?
9 MR. SHOTKIN:
The utilities.
I 10 COMMISSIONER CARR:
Each utility is working this 11 model on his own then?
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12 MR. STELLO:
There are six basic, I think, six.
33 Westinghouse, GE, Combustion Engineering, Babcock and Wilcox, 14 Exxon and then we have a set of calculation models -- and 15 Yankee Atomic.
And then we have our own models.
Those are the 16 basic models that are available to the utilities to use in the 17 calculations.
I 18 COMMISSIONER CARR:
I guess my problem is why are 19 they changing so much, the models?
i 20 MR. SHERON:
A lot of times the change is made 21 because they find an error in their model and many times if the 22 error goes in the wrong direction, namely tends to increase the 23 calculated peak clad temperature, what they normally do is go 24 back and look at other models in the code and try and improve 25 on them, I guess sharpen the pencil you might say, in order to
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20 1
come up with a compensating decrease such that the net 2
resulting peak clad temperature doesn't wind up exceeding 2,200 j
3 degrees.
l When they make those compensating changes, that's 4
- f p
what usually results in their having to come in and report a 5
I 6
model change.
7 They're required by other parts of the regulations to 8
report an error; okay?
This is not the error reporting.
Error 9
reporting I think is under 50-72 or something like that.
But 10 it's when they make compensating changes so that they don'c 11 have to suffer the impact of that error that we start seeing
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12 these type of submittals.
'(
L't's proceed.
13 COMMISSIONER ZECH:
All right.
e 14 MR. SHOTKIN:
I guess we're using the term model that 15 has two connotations.
One the computer code itself.
That 16 there are six or seven.
And then the individual models within 17 the computer code and those are the ones that will change on 18 the individual models.
I'd like to go to the next page.
We 19 have had this rule out for public comment.
We received 32 of 20 them, most of them from industry.
Almost all were favorable.
21 As you can see, there were 20 utilities, four 22 vendors, two owners' groups.
Those were all favorable.
Tne
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23 same intervenor sent in two. comments and one individual sent in B
l 24
- two comments of why we weren't considering multiple steam 25 generator tube ruptures in conjunction with a large break LOCA.
l 1 :
21 1
We assigned this a generic issue, GI-141 and that has 2
been prioritized and we're recommending it as a drop primarily 3
because the large break LOCA itself is such a small probability 4
and small contributor to risk.
5 So based on the public comments, we proceeded -- we 6
are proceeding with the rule.
The rule is unchanged.
We did 7
change the regulatory guide to make some of the things more j
8 clear as a result of many of the comments.
The regulatory j
9 guide defines the high level of probability as 95 percent and 10 again, most of the public comments supported this as good 11 engineering practice.
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12 The regulatory guide also details general features of 13 what the best estimate calculation should be and ends with l
14 putting in many acceptable models and data that come from the 15 last 12 years of research that our staff has agreed that if t
16 anyone uses these, we won't challenge them.
17 The research that we have done on page six is
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j 18 detailed in a compendium of ECCS research.
It's 1,200 pages.
j 19 I brought a copy just to show you that it does exist and it's 20 big.
It's primarily a road map for use of the industry and 21 others to help them find where the research is available.
The 22 research as Vic mentioned, the NRC part was about $700 million 23 and took about 12 years to accomplish.
1 24 If you include DOE, industry and foreigners, it's i
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25 about double that.
On the next page, some of the benefits of I
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1:
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the new rule and some of these are safety benefits and some of 2
these are not directly related safety benefits.
First, I think 3
the most intangible or tangible -- however you want to call it 4
-- is a more accurate understanding of ECCS behavior.
5 If we calculate what's going to happen with best 6
estimate codes we feel that the staff and the utilities and the.
~ _..
7 operating crew will have a much better understanding of what's 8
actually happening in their plant rather *han using very 9
overconservative models.
10 Vic mentioned th; longer diesel generator start times j
11 and I've mentioned this reduced neutron fluids at the vessel 12 va'll dhich reduces the PTS risk.
The main thing to keep in 13 mind is that this design basis loss of coolant accident -- this 14 stylized scenario that we're dealing with is a very small 15 contributor to risk.
16 That's primarily because the ECCS system works.
Let 17 me mention here that EPRI has recognized the benefits of this 18 new rule and they are sponsoring a conference in Boston --
19 Cambridge, Massachusetts, August 11 and 12 and it's called 20 "Appendix K Relief Using Best Estimate Methods -- The Revised 21 LOCA ECCS Rule."
22 This conference is being sponsored by EPRI and two 23 utilities, Northeast Utilities and Yankee Atomic Electric 24 Company and they go and discuss the benefits -- pretty much the 25 same benefits that I'm showing you, i
23 1
[ Slide.)
{
2 If we go to the next slide, eight, other benefits of 9
3 this new rule will provide for less stringent power peaking 4
limitations and this will allow more operating flexibility.
5 The utilities can more their fuel around more so it will lead 6
to more efficient fuel utilization.
There'll be reduced 7
monitoring of the flux shape and again, one of these intangible 8
benefits, it will allow industry to more intelligently optimize 9
the ECCS design.
10 one specific example of this has been the upper head 11 injection where the research has shown that the benefits of UHI
(
are no't that great and I believe the utilities are proposing to 12 i
13 remove that from their plants.
14 The next page,' I'd like to cover some of the spinoffs 15 from the ECCS research program.
We're talking today of the 16 ECCS rule revision which of course is the major benefit.
But 17 there have been other spinoffs that are related to the computer 18 codes that have been developed under this program.
19 These computer cod.s have been applied to many other 20 regulatory issues.
A partial list would be the pressurized 21 thermal shock issue, anticipated transient without scram, steam 22 generated tube rupture, decay heat removal using feed and 23 bleed.
Recently the B&W safety reassessment -- we did some 24 calculations far NRR using these codes.
25 3
When there is a transient in a plant like at Davis-1 l
l 24 1
Besse er '.ne recant stability concern of LaSalle we take these 2
codes and use them to analyze what happened in these plants and 3
do "what if" studies.
In addition, and that's NRC use -- in 4
addition these codes that I'll describe later are also being 5
used by other agencies.
i.
p 6
For example, DOE at Savannah River is using these
(!
computer codes, TRAC and RELAP in particular, to analyze the 7
t i
I h
8 safety of their production reactors.
Finally, Knolls Atomic i
n 9
Power Laboratory is using TRAC to analyze the safety of their 10 naval reactors and they've been doing this over the last seven 11 or eight years.
12 In addition, these codes and the research itself will 13 be used to look at severe accident analysis and uncertainty.
14 In the past they have been used to calculate the front end of 15 severe accidents and now we are using them to go into the new i '.
16 field of accident management.
l (Slide.]
17 18 MR. SHOTKIN:
On page 10 we reviewed the mandate for 19 the ECCS research program and I think we can go back to 20 primarily three different sources.
First in 1973 both the 21
' Commission and Congress mandated the AEC at the time to start 22 an Office of Research which would quantify the margin of safety 23 and conservatism in the ECCS rule which was just being 24 published at that time.
25 In 1974 the American Physical Society oppointed a h
25 1
peer review committee which published their report in 1975, a f
2 very detailed report.
It's an excellent report.
It provides 3
to us a measure of the accomplishment we've achieved over the 4
last dozen years.
5 In fact, that report predicted over a decade of 6
research would be needed to quantify this conservatism in the
~ _.
4 7
rule and that's about what it took.
And finally, in 1976 the 8
NRR gave a user need that was developed best estimate computer 9
codes, developed the data, assessed the codes against the data 10 so that we can quantify this margin of conservatism.
t
)
11 (Slide.)
j
~
12 At the end I'll tell you that we feel we have 13 answered this mandate.
On page 11 I will just give you a 14 little overview of some of the test facilities and later, some 15 of the computer codes that we've used to develop the data.
I 16 think there's two points to be made from this slide.
17 First that the facilities that we've used -- the
[
[
18 principal LOCA test facilities have not been only in the U.S.
L 19 There have been several -- Loft, semiscale, FIST, SSTF -- but 20 also in Japan and Germany and in fact, Japan and Germany have i
f 21 been under this 2D/3D program.
The 2D stands for the two-22 dimensional facilities that are in Japan and the 3D refers to 23 the 3D full-scale facility in Germany and I'll describe these 24 in a little more detail later.
25 The point is that in all of the facilities in the i
{
3 26 1
U.S. have closed'now.
We've finished the work.
If you can see 2
the dates there, they show when we finished the work.
LOFT in j
3 1986,, SSTF which was the multidimensional BWR facility and the a
4 counterpart of UPTF finished as early as 1983.
I 5
The Japanese facilities have finished testing this 6
year and the Upper Plenum test facility in Germany is going to 7
finish next year.
Now not only did we have to build these 8
facilities almost from scratch to get the data, we also had to 9
develop our own instruments.
I think one of the major results 10 of this program -- one of the major spinoffs -- is the i
11 instruments that were developed that will be I think used in
~
12 the future for measurements in two-phase facilities and in 13 other industries, not just ours.
14 We have, if you can see in the screen, we've provided 15 some of these -- examples of these instruments -- on a table in 16 the back that you can look at if you have time later.
Some of 17 these are video probes where we can look inside the facility 18 and see what's going on.
We have optical probes that can 19 detect the difference betw" L W
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4 I
j UNCERTAINTY METil0D0 LOGY (CSAU)
PURPOSE:
DEMONSTRATE VIABILITY AND PRACTICALITY OF CONCEPT IN.
PROPOSED RULE.
METHOD:
DETERMINE KEY VARIABLES PREDICTIONS VS. DATA PROBABILITY AND BIAS PEER REVIEW:
ACRS EXPERT PANEL-(TODREAS) 18 I,
4
)
,1 s
4 i
1 i
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i l
l 10-8 i
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i Peak Mecn T(F) 95% FVobcbiEtv T(F) i 5
EBowdown 1G84 1437 l
a First Reflood 903
-1370 y
Second Reflood 660 1301 I
k i
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0 500 1000 1500 2000 i
l Terrperottre (F) l i.
ram 19 i
I
i CONCLUSION O
FULFILLED ORIGINAL MANDATE 0F COMMISSION AND CONGRESS-TO CONFIRM THE SAFETY 0F ECCS DESIGN 0
COMPLETED LARGE RESEACH PROGRAM LEADIt1G TO REVISIO!? 0F MAJOR REGULATION O
RULE IS PERFORMANCE-BASED AllD PROVIDES' INCENTIVE FOR INDUSTRY TO DEVELOP. ACCURATE BEST ESTIMATE ANALYSIS MODELS.
20 f
i
MNWdEEWWWWWWWWAWWWilftWdWdd%WWp(TVgy&;f;(gygggggggggg TRANSMITTAL TO:
Document Control De u, 016 Phillips l<
j ADVANCED COPY TO:
The Public Document Room 7//F/PI b
DATE:
5
/
E FROM:
SECY Correspondence & Records Branch Attached are copies of a Commission meeting transcript and related meeting i,
document (s). They are being forwarded for entry on the Daily Accession List and i
placement in the Public Document Room. No other distribution is requested or required.
84 M. //, EdCJ Meeting
Title:
/dtIc/ A e_ A /0
(&.
.)
' = =w Meeting Date:
7//<4/P/'
Open X Closed E-
!!f Item Description *:
Copies
[-
Advanced DCS
'3 to POR Copy I
g
- 1. TRANSCRIPT 1
1 l
w /h4 d
l 2.
,,i 4.
Si 5.
6.
I i advanced one copy of each document, two of each SECY paper.
- * ^)
Ch dranch files the original transcript, with attachments, withcut SECY
- i papers.
lll 3
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