ML20028D525
| ML20028D525 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/28/1982 |
| From: | Ernst M, Miraglia F Office of Nuclear Reactor Regulation |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20028D338 | List: |
| References | |
| NUDOCS 8301190227 | |
| Download: ML20028D525 (2) | |
Text
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. ENCLOSURE I DEC 2 8 582 N i Docket No. 50-245 MEMORANDUM FOR:
Darrell G. Eisenhut, Director Division of Licensing FROM:
Frank J. Miraglia, Jr., Assistant Director for Safety Assessment Division of Licensing Mal'colm L. Ernst, Assistant Director for Technology Division of Safety Technology
SUBJECT:
MILLSTONE 1 INTEGRATED ASSESSMENT
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.At the ACRS meeting held on December 9, 1982, all issues and resolutions described in the Millstone 1 Integrated Assessment Report (NUREG-0824) were discussed.
During the meeting, the staff described how the Millstone 1 IREP was used in reaching risk judgments on specific. issues.
The SEPB staff described its basis for agreeing-with licensee proposed corrective actions.
where the PRA showed a small reduction in risk.
By letter dated December 13, 1982, from Shewnlon to Palladino (Attachment 1),
the ACRS agreed with all of the.resolutionTpresented in NUREG-0824.
As.a matter of interest however, the ACRS letter (page 2) states that the plant-specific IREP PRA did not provide a more definitive risk basis for judgments on the SEP topic resolutions than did the more limited risk analyses developed for the other SEP Phase II plant reviews.
The DST staff discussed the statement informally with the ACRS on December 21 because of the substantial confusion as to its meaning.
The.ACRS is very concerned about a possible misinterpretation, and this subject will be discussed formally and clarified during the next ACRS meeting, at their request.
Prior to the staff addressing specific issues which utilized PRA in their resolution, the Division of Safety Technology presented an overall perspective on the use of a plant-specific PRA to judge the cost effectiveness of fixes for selected SEP issues (Attachment 2).
As can be seen in Attachment 2, DST has identified two policy questions regarding the application of PRt. results in licensing decisions.
The first policy question was identified in S. Hanauer's December 1, 1982, memorandum and raises the question of whether hardware changes of little safety significance should be pursued, even if the costs of modification are alleged to be small.
In the case of Millstone, any such changes have been proposed by the licensee, and we do not believe that we should deny. changes 8301190227 830112 PDR ADOCK 05000245 O
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DEC 2 5 7; that the licensee desires to make just because we do not see a significant safety benefit.
However, this policy question could influence future SEP reviews, simply because less empnasis could be directed toward those areas where previous reviews have indicated little safety benefit.
DST.'s general rule of thumb for Millstone was that hardware changes that reduc ~ed the estimated core melt frequency or risk by less than 1% generally would not be warranted.
From a risk standpoint, this represented about 1% or less of the Commission's proposed safety goal.
The second policy question involves the mechanism for pursuing potential
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safety issues identified in the IREP study which are outside of the scope of review of the SEP topic reviews.
For Millstone, such issues involve the reliability of the manual depressurization system and the reliability of the instrument power system (ref. memorandum, Ernst to Miraglia, dated November 15, 1982).
Such identified issues need to be^ addressed, in consonance with any final safety goals policy statement issued by the Commission.
., While the above two impcrtant policy questions need to be resolved for the future, only the second is likely to be important for Millstone. The first one would be important only if any such hardware changes are required by the NRC, instead of proposed by the applicant and approved by the NRC.
Ba~ sed on information available to-date,--OST concurrence in the final integrated assessment would be anticipated.
Frank J. Miraglia, Assistant Director for Safety Assessment Division of Licensing Malcolm L. Ernst, Assistant Director for Technology Division of Safety Technology Attachments:
As stated Distribution Central File cc:
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Dec.
13,.1982 Honorable Nunzio J. Palladino Chairman U. S. Nuclear Regulatory Commission Washington, D. C. 20555
Dear Dr. Palladino:
SUBJECT:
ACRS REPORT ON THE SYSTEMATIC. EVALUATION PROGRAM REVIEW OF THE MILLSTONE NUCLEAR POWER STATION, UNIT 1 During its 272nd meeting, December 9-11, 1982, the ACRS reviewed the results,~
, of the Systematic Evaluation Program (SEP), Phase II, as it has been applied to the Millstone Nuclear Power Station, Unit 1.
These matters were also
. ' discussed during Subcommittee meetings in Washington, D.
C. on October 27 and November 30, 1982.
During our review, we had the benefit of discussion with representatives of the Northeast Nuclear Energy Compary (Licensee) and the NRC Staf f.
We also had the benefit of the documents listed below.
The Committee has reported to you previously on reviews of the SEP evalu-ations of the Palisades, Ginna, and Oyster Creek plants in letters dated May 11, August 18, and November 9,198?.,~The first of these reports included comments on the objectives of the SEP and the extent to which they have been achieved.
Our review of the SEP in relation to the Millstone pla.nt has led to no changes in our previous findings regarding this program, as reported in our letter on the Palisades plant.
The. remainder of this letter relates specifically to the SEP review of the Millstone plant.
Of the 137 topics to be addressed in Phase II of the SEP, 31 were not appli-cable to the Millstone plant and 20 were deleted because they were being re-viewed generically under either the Unresolved Safety Issues (USI) program or the TMI Action Plan.
Of the 86 topics addressed in the Millstone review, 48 were found to meet current NRC criteria or to be acceptable on another de-fined basis.
We have reviewed the assessments and conclusions of the NRC Staff relating to these topics and have found them appropriate.
The 38 remaining topics involved 87 issues relating to areas in which the Millstone plant did not meet current criteria.
These. issues were addressed by the Integrated Plant Safety Assessment, and various resolutions have been proposed.
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Honorable Nunzic J. Palladino Deccaler C, =
The Integrated Assessment has not yet been completed for 42 of 'the issues, for which the Licensee has agreed to provide the results of studies, analy-ses, and evaluations,'needed by the NRC Staff for its assessments and deci.
.sions.
All of these issues are of such a nature that hardware backfits may be required for their resolution.
Several relate to structural design, and the Licensee has proposed an integrated structural analysis' program for their resolution.
The resolution of these issues will be addressed by the NRC Staff in a supplemental report that will be available for review in connection with the application for a full term operating 1.icense (FTOL) for the Millstone plant.
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For 23 of the issues included in the Integrated Assessment, the NRC Staff concluded that no backfit is required.
We concur.
3 For the remaining issues for which the as'sessment has been completed, the NRC Staff requires hardware backfits in about half of the cases, and changes
' in procedures or Technical Specifications in the other half.
The Licensee
~, has agreed to make these changes with one exception.
Topics XV-16 and 18 relate to the calculated radiological consequences for certain design basis accidents; thyroid doses, calcul ated in accordance with current criteria, are considerably in excess of the siting criteria. To correct this situ-ation, the NRC -Staff has proposed that-the radioiodine concentration in the reactor coolant be limited to that permitted by the Standard Technical Specifications for BWRs.
.The Licensee has proposed to establish pl ant-
/
specific radioiodine limits based on more realistic dose calculations.
We believe that the NRC Staff's proposal is the more appropriate.
We have noted in previous letters on the SEP program that pl ant-specific probabilistic risk assessments (PRA) were not available for use in con-nection with the Integrated Assessment.
In this case, a pl ant-speci fic I
PRA for the Millstone plant had been developed as part of the Interim Re-liability Evaluation Program (IREP), and the 'results were, used in the as-sessment of 21 of the issues.
Contrary to our previous belief (contained in our August 18, 1982 and May 11, 1982 reports on the Ginna and Palisades-SEP reviews), it does not appear that the plant-specific IREP PRA for the Millstone plant provided a basis for more definitive assessments than the more limited risk analyses developed for the other plants' that we have reviewed.
l Our conclusions regarding the Millstone SEP review are similar to those for the plants previously reviewed:
1.
The SEP has been carried out in such a manner that. the stated objectives have been achieved for the most part for the Millstone plant and should l
be achieved for the remaining plants in Phase II of the program.
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2 The actions taken thus far by the NRC Staff,in its SEP assessment of the Millstone plant re acceptable.
3 The ACRS will defer its review of the FTOL for the Millstone Nuclear Power Station, Unit 1 until the NRC Staff has completed its actions on the remaining SEP topics and the USI and.TMI Action Plan items.
Sincerely,
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P. Shewmon Chainnan 3
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References:
1.
U.S. Nuclear Regulatory Commission Draft Report, NUREG-0824,
" Integrated Plant Safety Assessment, Systematic -Evaluation Pr~ogram, Millstone Nuclear Power Station, Unit 1,"
dated November 1982.
2.
U.S. Nuclear Regulatory Commission Safety Evaluation Reports ~,
Millstone 1 Systematic Evaluation Program Topics, Volumes 1 and 2, received November 1982.
3.
NRC Staff consultants' reports on the Millstone 1 Integrated Plant Safety Assessment Report consisting of consultants' reports from S. H.
Bush, J. M. Hendrie, H. S. Isbin, and Z. Zudans, dated November 22, November 29, November 24', and November.24,1982, respectively.
4.
Science Applications, Inc. report rtDinb'er SAI-002-82-BE, " Interim Reliability Evaluation Program:
Analysis of the Millstone Point Unit 1 Nuclear Power Plant," Volume I, Main Report, Draft dated October 1,1982.
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valve.
It is it. the inside con tainm en t.
2 f.R. EBERSOLE:
Is it?
3 MR. GBIMES:
I believe so, but let me check.
4
. _. MR. EBERS01E:
That chanpas the.Wh le picture,-.-...-.
5 if that is the case.
6 MR. MOELLER:
Excuse me.
For example, on that 7
list, 'th e fi rst item, III-5.B, 55, and 511A, Dr. Zudans 8
raised questions on each of those.
Now, will we hear 9
that later?
-t 10
!!R. GRI,M ES:
They are addressed in the context
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11 of either requiring no action, requiring further 12 evaluation.
I will go into each of the issues in terms 13 of the integrated assessment results after you 14 und erstand-how 've.were give n a risk perspective on each
- 15 of the issues.
16 MR. SIESS:
We will now hear from Mr. Spulak 17 on how they used the PRA.
You are next.
Are we going 18 to hear f rom you on the PRA or not?
19 gtpumnN*M I would like to say a couple of 20 words before we start on the PRA.
It will come out 21 during the PRA presentation th a t there were a number of 22 rather low risk sequences identified that seemed to have 23 some potential hardware fixes associated with them.
In 24 that regard, I think a few introductory remarks are 25 worthwhile.
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First, as was poin ted gu t for M11'1 stone, this 2
was the first ti=e that t h ere h ac,,.be en a quantitative 3
assessment of the SEP potential fixes versus the 4
qualitative matrix kind of approach that was used ~- -
5 before.
For a number of -- a half-dozen or so of these G
issues, DST did,take a look at the risk reduction, and did, b' sed on some judgments that were provided to us, 7
a 8
made some judgments on' cost ef f e ctiv en es's.
We.found a 9
couple of things.
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10 As I mentioned, a number of them did appear to 11 have rather small or insignificant risk reduction 12 potential.
Some of these did appear to have some 13 potential hardware fixes associated with them, based on
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14 a reading of the NUREG.'],5 think there are~some points'
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15 to be made.
16 First, the PRA's are uncertain, as all of us 17 are well aware.
Secondly, in a number of cases, as we 18 understand it, the licensee desires to make some i
19 changes, for whatever reason, whether it be risk or some 20 other reason.
And we understand also that the end 21 result is that some of the potential hardware fixes may 22 not eventually take place anyway.
23 The final point, I guess, is that ma[ing 24 judgments on the usefulness of hardware fixes,'I think 25 PRA is one consideration, but certainly not the ALDERSoN REPORTING CoMPA4Y, INC.
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det ermina tive con sid er a tion.
There are some useful PRA 2
insights, nanely, that in noct if not all of these, the 3
risks are at least on the order of or less, than a couple 4
orders of magnitude less than the safety g o tl, the core 5
nelt proposed safety goal.
6 If one. takes a look a t the individual risk 7
reduction potential and some numbers on cost, whether or 8
not thoroughly documented, may argue that such changes 9
are worthwhile.
It seems to me that there is a point, 10 and I don't know exactly what that point is, but there 11 is a point where the residual risk reduction potential 12 probably is not worth the ball game of looking at it too 13 hard, even if the alleged costs were very small.-
i 14 And I do question whether very small so-called
~ 15 changes in hardware don't have somewhat large costs 16 associated with them anyway.
You just can't do too much
,17 for a little bit of money.
But I just-want a little bit' 18 of perspective th a t the PR A is not determinative.
There 19 are other considerations.
And DST just looked at it 20 basically from a risk reduction potential, and made some i
21 judgments that there were some marginally defensible 22 hardware fixes, and those hardware fixes did take place.
23 There are two issues that remain, I think, 24 looking towards the future, not just Millstone.
That is 25 the policy question of how much initiativ.e should there ALDERSON REPCRTING COMPANY,INC.
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be te consider hardware fixec f or potentially very small
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risk reduction sequences, and if so, there should be 3
some cutoff point at,which you jus't do not,pursu'e 4
hardware changes any more based on your risk assessment
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5 of what would that cutoff point be.
6 I think this is somethi,ng we have to look at 7
in the' future.
8 Secondly, wit 5 respect to Millston'e, there are 9
a couple of residual issuesftha t were outside the scope 10 of the SEP program that were identified in the PRA' 11 analysis.
One of these involves a more reliable 12 depressurization because this particular part of the 13 safety of the p1 nt was paramount in about five dominant 14 accident sequences.
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.15 Secondly, apparently, if one loses instrument 16 power, one also has the potential of losing containment 17 shu tdown cooling systems.
'I th' ink these issues need to 18 be addressed.
The mechanism of address, since it is 19 outside the scope of the SEP, and perhaps even outside 20 the licensing requirements,'is a question that needs t'o 21 be addressad, and in a broader sense, I guess, addressed 22 to the safety goal implemen tation plan, and how do you 23' use PRA in any future safety goals and making decisions 9
24 on that.
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of perspe:/tive for the PBA part.
Thank you.
2 MR. EBERSOLE:
.. a y I ask a question?
Under 3
reliability of the depressurization process which you 4
suggest was very important, and I certainly -agree with.
5 that, was any of that associated with environmental 6
qualification problems with the solenoid. valves that 7
operate the depressurization system?
8 MR. SPULAK:
We have problems with the work 9
time.
?
10 MR. EBERSOLE:
I want to know if one of the 11 major contributors to the unreliability of blowdown is 12 due to a weakness in the solenoid valve design which is 13 inside a hostile environment.
Y 14 MR. A'MICO:
Paul Amico from SAI.
No, it would
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15 not be dominated'by the operator f ailing to initiate the 16 manual blow down process.
17 MR. EBERSOLE:
Did you find qualification of 18 the solenoid valves adequate?
19
- f. R. AMICO:
We didn't go into that much 20 detail.
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21 MR. EBERSOLE '
If you didn't go into it, you 22 don 't k now.
23 MR. AMICO:
We used the data a vaila ble.
24 Exactly w h a~t is included in tha t date is supposedly the 25 actual failures.
I am unaware of any other.
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MP. FiEEFOLE:
Those age type tested.
They 2
are never in situ tested.
Thank 4 ou.
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3 XR. GKRENT.:
What do you mean whei you say you
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use the data that a re a vailable?
5 MR. AMICO:
The data that was available in the 6
IREP study.
7 MR. OKRENT:
Yes, but it seems to me when you 8
answer a question, you should answer the~ question that i
9 is being asked, to say we db.dn' t do that.
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10 MR. AEICO:
We personally did not do tha t.
11 MR. OKRENT:
Fair enough.
That is an answer.
12 5R. SIESS:
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I think there are a. number of 19 questions where if hardware fises are finally the 20 resolution for the issue and there is some question in 21 most of these cases and there are also some cases where t
i 22 apparently the licen see wants to make the change --
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23 MR. SIESS:
That'is his business.
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do it, and this appears to have a very small rish 3
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reduction., I think in that case from a.PRA and cost 4
benefit standpoint we would say th a t i t d oe's n o t appear 5
to be justified.
6 HR. SIESS:
I can think of cases wh,e re there 7
is a very small risk reduction, but also a very small 8
cost.
So the cost benefit may look high.
And I think 9
there are some instances'lik'e that.
Maybe y'ou can just 10 point them out when we get to them.
That would be 11 better.
l 12
- 58. ERNST:
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14 N. Ent' looking ahead, I think one needs to say s
z 15 how small a leve'l of risk reduction do ve vorry about.
16 MR. SIESS:
I think there are some specific 17 examples that will help bring this out.
18 Okay, Mr. Spulak.
Let's see.
'Are you going 19 to be able to give us the relationship between the 20 numbers and the words?
Is that a pa rt of your 21 presentation?
Or will that have to come.from Mr.
22 Russell or Mr. Grimes?
23 MR. SPULAK:
I an.not sure I understand what 24 y ou mean.
25 MR. SIESS:
We were told at the subcommittee l
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