ML20054J190
| ML20054J190 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Crane |
| Issue date: | 02/12/1981 |
| From: | Cutchin J NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| To: | |
| Shared Package | |
| ML20033C447 | List: |
| References | |
| FOIA-82-176, RTR-NUREG-0694, RTR-NUREG-0737, RTR-NUREG-694, RTR-NUREG-737 NUDOCS 8206280266 | |
| Download: ML20054J190 (8) | |
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4 UNITED STATES OF AMERICA J
NUCLEAR REGULATORY COMMISSION BEFORE THE COMMISSION
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In the Matter of
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METROPOLITAN EDIS0N COMPANY, Docket No. 50-289 ET AL.
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(. Restart) 1 (Three Mile Island, Unit 1)
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j REPORT OF NRC STAFF m
On January 28, 1981 Chairman Ahearne and Commissioner Hendrie requested that the parties (particularly the Staff and Metropolitan Edison) provide, by February 12, 1981, reports on the time by which Metropolitan Edison could be expected to be in compliance with each of the following items should such compliance be required for restart:
a, the items contained in the August 9,1979 (CLI-79-8,10 NRC 141) and March 6, 1980 (CLI-80-5, 11 NRC 408) Commission Orders; b.
the items relating to near tenn operating licenses contained in NUREG-0694, "TMI-Related Requirements for New Operating Licenses"
(
as revised by NUREG-0737, " Clarification of TMI Action Plan
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Requirements"; and c.
any other item which the parties believe Metropolitan Edison should be required to implement.
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pi The Staff's response to the request for a report is attached.
Respectfully submitted,
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2 James M. Cutchin, IV Counsel for NRC Staff Dated at Bethesda, Maryland this 12 day of February,1981 9
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m STAFF RESPON. TO C0ti!!ISS10NERS' AHEARNE AtlD...DRIE ETTER OF JANUARY 28, 1981 j
1 In Question 2 of Commissioner's Ahearne and Hendrie letter of January 20, 1981, tiie Co cissioners requested a report op the time by which lietropolitan Edison could be expected to be in compliance with the following items should such conpliance be required ultimately for restart: (a) the items contained in the August 9,1979 and tiarch 6,1980 Comission Orders; (b) the items relating to near tem operating licenses contained in flUREG-0694, "T!11-Related Requirements fo. Deu Operating Licenses" as revised by flVREG-0737, " Clarification of Till Adtion Plan Requirements"; and (c) other items which the parties believe fletro-politan Edison should be required to implement.-
This response, in a large part, is based on infomation provided to the staff by the licensee in discussions on Februliy 6,1981. The staff does not have available to it either written or oral detailed infonnation concerning I
the actual stage of design, engineering and procurement rhlated to
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nany cf the items to be completed prior to restart, as outlined in Question 2.
In addition, it is unclear how many resources the utility could direct to the resolution and implementation of these various req ui rements. Therefore the staff cannot independently assess the like-
. lihood of the licensee meeting the goals it has set for completing these i tems.
T;1e staff has reviewed, with the licensee, a prelininary schedule for completion of ne items contained in the August 9,1979 and liarch 6,1980 Comnission Orders (7tr a of Question 2) and the near tem operating license (NTOL) items (Part b cf hEstion 2). With some exceptions, the licensee has estimated that.it could sz-'st these requirements and be ready to return the plant to operation by Oc :cer 1931.
For an October 1981 restart, the licensee estinates that it would be r.e:essary to tiegin plant heatup in August 1981.
In addition, routine pre-Darat or, of plant systems to support plant heatuo fron such an extended outage can require some six to eight weeks additional lead time before plant hea;u:.
In general, for hardware modifications, the licensee indicated tna engineering and procurement appear to be pacing the completion of -
tnese items, with installation not perceived to be a significant problem.
I After reviewing the status of each item in the Orders and the NTOL requirenents identified above, it is the staff's belief that this schedule appears feasible It should be noted, however, that the licensee's schedule may not allow adequately for contingencies if problems develop during the implementation or testing of plant systems.
In addition, there are a nurber of safety grade conponents recuired for l1ardware modifications for which equipnent delivery dates are not available. T;1ese specific items are discussed in the following paragraphs.
Wita respect to the completion of the items contained in the Comission's Orders, tnere are five items requiring safety grade components for which the licensee eitr.er has no delivery date or the scheduled delivery date for the component would likely impact the above schedule. The first item involves components recuired to ensure diversity of parameters for containnent isolation, and is a
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Category "A" recommendation of fiUREG-0578, " Tit!-2 Lessons Leahied Task Force Status Report and Short Term Recommendations." This iten was required to be incienented on all other operating reactors in early 1980 and is required by tile Orcer to be completed prior to restart. The other four items involve acci-dant ronitoring instrumentation and are Category "B" recommendations of 1
MUREG-0573.
In our Safety Evaluation Report on TIII-l Restart. NUREG-0580, the 4
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2-required implementation date for these items is January 1,1981. However, as stated in NUREG-0737, the schedule for completion of these items has been extended to January 1,1982 for operating reactors, and we believe the latter schedule should be applied to TMI-1.
If the revise'd schedules and technical clarification contained in NUREG-j 0737 for operating reactors is applied to Ti1I-1, these items would not be required to be fully implemented aefore an October '81 restart.
'Of the remaining items identified in.the Commission's Orders, the staff j
has no basis on which to question the licensee's schedule for completion.
1 A number of the items in the Orders do not require hardware modifications.
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While a number of these non-hardware itens remained to be resolved, the i
sta'f does not believe implementation of these itens would be on the critical path assuming an October restart.
With respect to the completion of the items relating to NT0Ls in NUREG-0694, as rev. sed by NUREG-0737, four items were identified which could signifi-cantly impact the licensee's schedule. One of these four, II.K.I.21, l
requires a safety grade anticipatory reactor trip on loss of main feedwater, turoine trip, and on low level in the steam generators. The licensee is in-stalling a safety grade reactor trip for loss of main feedwater and turbine tri; only. The staff is evaluating a generic 85W recort indicating that an anticipatory reactor trip for low steam generator level is unnecessary.
The second item from NUREG-0694, III.D.3.4, Control Room Habitability, would be -e:uired to be completed by NUREG-0737, includina hardware modifications, befers reaching full power.
For other operating reactors, the staff has not yet established a date by which mocification must be implemented. The hard-a were nodification for this item were not considered by the staff to be an l;TC requirement for TMI-l as described in the staff's response to Board Question 21 and further delineated by letter da ed I;overter 25,1983 fron 4
D. G. Eisennut, NRC to R. C. Arnold, GPU. The renaining items are I.D.1, 3
Con rol Room Design Review, II.E.1.1, ARJ Evaluation, and III. A.l.1, Ener-cen:y preparedness. Under Item I.D.1, a Control Roon Design Review was con-duc ed on THI-l during which it was detennined that the plant's renote snu cown panel requires modification.
It is the staff's present position that an improved remote shutdown capability should be installed prior to restart. This item remains to be resolved. Item II.E.1.1 requires a full system upgrade to the AR! system before full power. The staff considers this requirement to be covered by the long range requirement for ARl uporading required by the
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Comnission Order and this would not be a prerequisite for an October restart.
b;R staff Testimony of D. F. Ross, Jr. relative to the sufficiency of the proposed additional requirements (Board Question 2).
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- Under Item III.A.l.1, Emergency Preparedr.ess, a satisfactory finding and deteminatiori by the Federal Emergency Fanagement Agency (FEMA) that I
h state and local emergency plans are adec uate is an essential element in ensuring the adequacy of overall emergency planning for THI-1. The staff will continue to review the TMI-l emerge 1cy olan, which is nearing completion,
,and will continue to follow FEMA's process in reviewing the State and local plans. At present, it is expected that this effort will be completed to support an October startup schedule.
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Ir response to Part c of Question 2 of the Commissioners' letter.Sttachment 1 lists additional items not contained"in the August 9 and March 6 Com-eissien Orders, NUREG-0694, or NUREG-0737, that the staff considers should i
ce resolved to the satisfaction of the staff prior to restart of the facility.
inis listing includes significant IE Bulletins for which actions are required of tne licensee and the list may be modified if other significant safety matters should arise.
In addition, the licensee would be expected to resolve significant findings resulting from IE Inspection activities and, the licen-see needs to establish and successfully conduct a restart test program. The licensee is making reasonable progress toward resolution of these items and no ceficiencies have yet been identified which would preclude restart in 0::ccer of this year.
It is our judgment that the licensee's resource require-ns. s necessary to implement these items should not preclude a restart schedule irti:a.ed above.
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ATTACHMEllT 1 1.
IES79-018 Environmental Qualification of Class 1E Equipment 2.
IES 79-02 Pipe Support Base. Plate
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3.
IE3 79-14 Seismic Analysis for As-Built Safety-Related Piping Systems 1
' 4 IES 79-27 Loss of Non-Class 1E Instrumentation and Control Power System Bus During Operation - NNI/ICS Failure An'alysis, Items:
a) Provide response to Bulletin q
b) Meet requirements of Orders issued to other B&W reactors I
5.
Sna11 Break ECCS !!odification - Exis' ting exemption (March 16, 1979) to 10 CFR 50.46.
c a) Ndifications to ECCS are required prior to restart by J
terms of the Exemotion.
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6.
IES 80-11 Hasonry Walls
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J UNITED STATES OF AMERICA NUCLEAR REGULATORY C0ttilSSION BEFORE THE COMMISSION In the Matt'er of
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METROPOLITAN EDISON COMPANY,
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(Restart)
(Three Mile Island, Unit 1)
)
CERTIFICATE OF SERVICE I hereby certify that copies of " EPORT OF HRC STAFF", dated February 12, 1981, in the above-captioned proceeding have been served on the following, by deposit in the United States mail,'first 4 ass, or..as indicated by an asterisk through deposit in the Nuclear Regulatoryj' omission's internal mail system, this 12th day of February, 1981:
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f John F. Ahearne, Chairman Dr. Linda W. Little U.S. Nuclear Regulatory Comission 5000 Hemitage Drive i
Washington, D. C.
20555 Raleigh, North Carolina 27612 r
Dr. Joseph M. Hendrie George F. Trowbridge, Esq.
U.S. Nuclear Regulatory Comission Shaw, Pittman, Potts & Trowbridge Washington, D. C.
20555 1800 M Street, N.W.
j Washington, D. C.
20006 T
4 Dr. Victor Gilinsky U.S. Nuclear Regulatory Comission Karin W. Carter, Esq.
Washington, D. C.
20555 505 Executive House P.O. Box 2357 Mr. Richard T. Kennedy Harrisburg, Pennsylvania 17120 U.S. Nuclear Reoulatory Comission Washington, D, C.
20555 Honorable Mark Cohen 512 D-3 Main Capital Buildino u
i Peter A. Bradford Harrisburg, Pennsylvania 17120 l
U.S. Nuclear Regulatory Comission L
Washington, D. C.
20555 Mr. Marvin I. Lewis 6504 Bradford Tr.
l.
Philadelphia, Pennsylvania 19149 l
Ivan W. Smith, Esq.
j Atomic Safety & Licensing Board Panel U.S. Nuclear Regulatory Comission Mr. Thomas Gerusky Washington, D. C.
20555 Bureau of Radiation Protection c
Dept. of Environmental Resources Dr. Walter H. Jordan P.O. Box 2063 881 W. Outer Drive Harrisburg, Pentisylvania 17120 Oak Ridge, Tennessee 37830 Steven C. Sholly 4
Union of Concerned Scientists Suite 601 1725 I Street, N.W.
Washington, D.C.
20006 l
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Metropolitan Edison Company Ms. Frieda Berryhill, Chairman Attn: J.G. Herbein, Vice President Coalition for Nuclear Power' Plant i
P.O. Box 542 Postponement Reading, Pennsylvania 19603 2610 Grendon Drive Wilmington, Delaware 19808 i
Ms. Jane Lee-R.D. 3; Box 3521 Gail Bradford Etters, Pennsylvania 17319 ANGRY 245 W. Philadelphia St.
Walter W. Cohen, Consumer Advocate York, PA 17401 Department of Justice Strawberry Square, 14th Floor Jordan D. Cunningham, Esq.
Fox Farr and Cunningham Harrisburg, Pennsylvania 17127 2320 North 2nd Street L
Allen R. Carter, Chairman Harrisburg, Pennsylvania 17110 Joint Legislative Comittee on Eneroy o
Louise Bradford Post Office Box 142 1011 Green Street l
Suite 513 Senate Gressette Building Harrisburg, Pennsylvania 17102 Columbia, South Carolina 29202
.i Thomas J. Germine Ms. Ellyn R. Weiss O;
Deputy Attorney General Harmon & Weiss i
Division of Law - Room 316 1725 I Street, N.W.
1100 Raymond Boulevard Suite 506
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Newark, New Jersey 07102 Washington, D. C.
20006 Atomic Safety & Licensing Appeal Board Ms. Marjorie M. Aamodt U.S. Nuclear Regulatory Commission R.D. #5 Washington, D. C.
I'0555 Coatesville, Pennsylvania 19320 Atomic Safety & Licen:,ing Board Panel William S. Jordan, III, Esq.
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'J.S. Nuclear Regulatory Comission Harmon & Weiss 4ashington, D. C.
20555 1725 I Street, N.W.
i Suite 506 Washington, D.C.
20006 U
ear Regulatory Commission ATTN: Chief, Docketing & Service Br.
Washington, D.C.
20555
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Robert Q. Pollard 609 Montpelier Street Saltimore, Maryland 21218 Chauncey Kepford Judith H. Johnsrud Environmental Coalition on Nuclear Power i
433 Orlando Avenue State College, Pennsylvania 16801
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"E James M. Cutchin, IV i
John Levin, Esq.
Counsel for NRC Staff Pennsylvania Public Utiliti.es Comm.
Box 3255 l
Harrisburg, Pennsylvania 17120 3
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UNITED STATES r
,'t NUCLEAR REGULATORY COMMISSI, d j
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November 17, 19 4'
p CHAIRMAN f.
F The Honorable Morris K. Udall, Chairman
$ w_ f d4 Subcomittee on Energy and the Environment i
Comittee on Interior and Insular Affairs United States House of Representatives g
L Washington, D. C.
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Dear Mr. Chairman:
g This responds to your letter une l 198 in which you asked the Commission again to consider seriously control system failures in nuclear power plants.
Since such failures may have severe consequences, the NRC staff has begun to better define their safety significance. Enclosure 1 summarizes these actions.
Recent operating experience, such as the Crystal River event of last February, and continuing evaluation of the control system failure issue, has led the s
staff to propose to the Commission that the issue has sufficient safety sig-nificance to justify its being designated as an " Unresolved Safety Issue"
-(USI) and reported to the Congress under Section 210 of the Energy Reorgani-zation Act (See Enclosure 2). That proposal is currently under consideration y
by the Comission. Classification as an USI would assure priority for resources needed for timely and effective resolution of this issue.
9 At the present time, the Comission is relying on the consensus engineering judgment of senior staff that the risk associated with control system failures is not sufficient to require immediate corrective actions such as power
.i derating. This judgment is not based on any special analyses or calculations '
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beyond those normally performed in the course of staff review of postulated transients and accidents. We recognize (as you noted in Mr. Denton's October 22, 1979 memorandum) that the analyses do not take into account all events that can be postulated. The program outlined in Enclosure 2 is intended to provide a better basis for judging the adequacy of plant protection features i
and operator actions to mitigate control system failures.
j With respect to the differences you noted between the wording of our May 14 i
response and that of the previous staff statement enclosed with that response, the wording in the May 14 letter does convey a greater sense of certainty about the adequacy of analyses performed to evaluate the interaction between 4
high energy lines and control systems than does the December 19, 1979 memorandum.
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We regret any misunderstanding this may have caused.
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0 The Honorable Morris K. Udall Please be assured that the Comission is evaluating the safety significance of control system failures and, depending on our finding, will take whatever actions are necessary to continue to assure adequate protection of the public i
health and safety.
Sincerely, Origina151g::ea By John 7.Ahearna 1
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John F. Ahearne l
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Enclosures:
As stated c
cc: The Honorable Steven Symms i
1 Cleared with all Cmrs.' Offices by SECY C/R Typed in final in SECY C/R based on Cmr. commerts Re f. -CR-80-156A Distribution:
1 WJDircks EKCornell TARehm EDO 9208 VStello 50 HShapar LUnderwood m
H0enton i
SCavanaugh SECY-80-1267 i
CA BMorris Cross j
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EC_LOSURE 1
.,3 UPDATE OF INFORMATION PROVIDED IN CHAIRMAN'S i
MAY 14 RESPONSE TO UDALL LETTER Significant corrective measures which have been or will be required'as a result of control system malfunction or failure analyses conducted to date include the following:
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1.
For high energy line breaks which may be. exacerbated by consequential i
control system failures, some licensees adopted new operator procedures as needed to assure that the postulated events would be adequately 1
i mitigated.
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In response to Bulletin 79-27, some licens,ees have taken corrective action including hardware changes, and revised procedures to assure H
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that single failures of power supplies will not simultaneously cause transients and failure of instrumentation required to mitigate these transients.
1 3.
Licensees with B&W plants have been required to address changes in the 1
j Integrated Control System to enhance its reliability.
Tne analyses upon which decisions concerning the oregeing. corrective measures i
have been based are as follows:
i 1.
Operator procedures to mitigate high energy line breaks causing additional control system failures were based en an assessment cf required operation 4
actions and small break LOCA analyses.
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Corrective actions resulting from Bulletin 79-27 have not been b.ased on calculations,but rather on deduction regarding the sequence of events o
expected from postulated control system f ailures. A limited amount of testing has been done at Cr.ystal River to confirm some of the conclusions.
3.
Measures to enhance B&W Integrated Control System reliability were based on failure modes and effects analysis and operating history review.
The C'ommission's program for determining the extent to which unanticipated control system failures could aggravate accident sequences currently con-1 sidered in the NRC's regulatory requirements consists of the following:
a.
1.
Creation of a new branch to focus on systems interactions.
2.
Continuatio,n of integrated Reliability Evaluation Program to establish
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the relative risks of control system failures.
3.
Identification of failure modes of safety related instrumentation con-i current with control system failure through reviews of licensee replies to Bulletin 79-27.
4.
Future indepth review of license applications against existing Standard i
Review Plan Section 7.7 acceptance criteria, including failure modes and effects analyses.
5.
Participation with an IEEE working group in development of IEEE standards for control and other non-safety equipment.
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3-The Cor:nission staff is also considering establishing a new unresolvid
.i safety issue, " Safety Implications of Centrol Systems."
A paper which presents this proposal is under consideration by the Corsnission.
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ENCLOSURE 2
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MEMORANDUM FOR:
Chairman John F. Ahearne FROM:
Harold Denton', Director
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Office of Nuclear Reactor Regulation THRU:
William J. Dircks Acting Executive Director.for. Operations
SUBJECT:
ACRS AND AEOD COMMENTS CONCERNING NEW UNRESOLVED SAFETY i
ISSUES In response to your m,emorandum of August 19, 1980, we have reviewed the ACRS and AEOD cc:renents on SECY 80-325 and have the following coments 3
and recomendations.
We recommend that the two issues that AE00 recommended be considered as Unresolved Safety Issues be added to the list'of items requiring further study before de.ciding on designation as USI's. This further study will
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be performed over the next few months. We recomend that the other two concerns raised by AEOD be incorporated into existing or proposed Unresolved Safety Issues as described in Enclosure 1.
The ACRS comments' include a recomendation to add to the list of Unresolved Safety Issues three issues that the staff had initially screened out.
Upon reconsideration we now reco=end that one of these (," Control System Reliability").varrants designation as an Unresolved Safety Issue; Enclosure 3 provides a description of the issue that we propose to add to the Special Report to Congress.
In discussing the issue of Control System Reliability, the ACRS also noted the related issue of the reliability of nonsafety system information displayed for use of the reactor operator.
We recomend that this ACRS concern be added to the list of items requiring further study to evaluate their impact on overall risk before deciding on designation as a USI.. This flPrther study will'be performed over the next few months.
We do not agree that the twc other issues recomended by ACRS (D.C.
Pcwer Reliability and the Single Failure Criterien) warrant designation as Unresolved Safety Issues for the reasons described in Enclosure 2.
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John F. Ahearne.,
Pending receipt of further coments and guidance from the Comission, we are preparing revisions to the draft special report to Congress to.
incorporate discussion of the issues raised by the ACRS and AEOD coments.
Oridn!!!;:sd y 1
i!.._ ca:::n, j C( 3 Y Harold Denton, Director Office of Nuclear Reactor Regulation
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Enclosures:
1.
Consideration of Comments From c
I the Office for Analysis and Evaluation of Operational Data
- 1 2.
Consideration of Coments From l
the Advisory Comittee on Reactor Safeguards 9
3.
Safety Implications of Control Systems cc:
Commissioner Gilinsky Comissioner Hendrie Comissioner Bradford J. Plesset (.ACRS)
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CONSIDERATION OF COMMENTS FROM T..E OFFICE FOR ANALYSIS AND EVALUATION OF OPERAT10NAL DATA (AE00)
By letter of August 4,1980, the AEOD provided coments to Chairman. :
Ahearne concernino the information and recommendations in SECY 80-325.
l These comments may be su=nrized as:
4 (T) Agreement with the six issues recommended by NRR for designation as Unresolved safety Issues.
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(2) Recommendation that two new issues be considered as candidate 1
issues; 1
I (3) Recommendation that two additional concerns be considered, possibly under the umbrella of existing Unresolved Safety Issues.
.l The fdllowing describes how the staff proposes to resolve the concerns expressed by Items (2) and (3) above:
(2)
New Items For Consideration As Unresolved Safety Issues We agree with the AEOD recommendation that two. items, " Safety Implications of Steam Generator Transients and Accidents". and "The Piping and Use of Highly Combustible Gases in Vital Areas," warrant further consideration.
Although we are.'not prepared to recomend their designation at this time, we propose to add them to the list of items recuiring furthe-study. These items will be evaluated along with other newly identified issues to evaluate their impact on overall risk and to determine if they meet the USI definit. ion.
This further study will be performed over the next few months.
It seems likely that this evaluation will shcw that the second item concerning ccmbustible gases has already been addressed in the Fire Protection reviews, although some refinement to the criteria may be required.
(3)
Items That Micht Be. Included'Under Existine Unresolved Safety Issues We agree that these two concerns identified by AE00 probably ' fall under the scope of existing or proposed Unresolved Safety Issues. To assure that AEOD's concern related to failure modes of non-cualified equipment in a seismic event and effects of these failures is not overlooked in j
the proposed Unresolved Safety Issue on Seismic Qualification of Equipment a.: Operating Plants, we will clarify the description of this issue in i
the Special Report to Congress.
It is the intent of this task to look
'I at the seismic qualification of equipment recuired to safely shut down the plant as well as the qualification of equipment for which failure e
could produce unwanted actions.
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c With respect to the AEOD cencern related to effects of a high energy pipe break on small lines (e.g., instrument lines) or in causing unwanted actions by control systems, we agree that this concern is within the:
scope of the Syst' ems Interaction (A-17) Unresolved Safety Issue.
- However, the portion of the concern related to development of unwanted actions in control systems is closely related to a concern raised in the ACRS s
letter of August. 12, 1980 on the subject of "New Unresolved Safety i
Issues." To address these concerns we have proposed addition of another Unresolved Safety Issue, " Safety Implications of Control Systems, as described in Enclosure 3.
We 5elieve that this should be made a separate j
Unresolved Safety Issue from A-17 because it is a separate, specific, and manageable concern that requires significant work to resolve and that may 5e resolved more expeditiously if treated as a separate issue.
The balance of this AEOD concern should be adeouately addressed within j
the scope of Task A-17. To assure that Phase II of Task A-17 considers jet impingement frem a nigh energy pipe break on small lines, including d
i potentiial for simultaneous primary and secondary system blowdown, we will include this in a revision to the Task Action Plan for Phase II of A-17.
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CONSIDERATION OF C0!EENTS FR0!i THE ADVISORY COMMITTEE ON REACTOR SMEGUARDS (ACRS) t
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On August 7,1980; the HRC staff discussed with the ACRS the information j
contained in SECY 80-325 that would be included in this Special Report to Congress.
As a result of these discussions, the ACRS provided several recommendations to Chairman Ahearne by letter of August 12, 1980, concerning
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Unresolved Safety Issues. This letter indicated agreement with the six i
new issues recommended by the staff for designation as Unresolved
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Safety Issues, but also recommended addition of three issues:
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Control System Reliability
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(2) 0.C. Power Supply Reliability (3)
Single Failure Criterion e
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-We have considered the ACRS recommendations and have the following comments:
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Control System Reliability
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The staff agrees with the ACRS recommendation concerning Control System Reliability and recommends that a task, Safety: Implications of Control 1
Systems, be added to the list of new USI's to-te designated in the
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Special Report to Congress. describes the issues that would be addressed in this task.
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The ACRS lei.ter also notes a relateo issue regarding the reliability of nonsafety system information displayed to the reactor operator.
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staff believes that further study of this issue is required to assess the improvements already made by licensees, the extent of the deficiency, and the resultant impact on risk.
Following this further study, a decision would be made as to whether this issue should also be designated as a USI.
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D.C. Power Reliability The definition of an Unresolved Safety Issue includes a statement that it is an issue "for which a final resolution has not yet been developed."
While we agree with the ACRS that D.C. Power Reli+bility is an important issue and one that may have a major impact on overall risk, we continue j
to believe that it should not be designated as an Unresolved Safety Issue prior to review of a draft contractor report that proposes a final resolution of this issue and that is now in the final stages of preparation.
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This report is expected to be ready for NRR and ACRS review in September i
with final issuance shortly thereafter.
If, after review of the contractor c
j report, we find that the proposed resolution is inadecuate or that further work is required to develop a resolution of the issue, then at that time we would recommend designatien of this issue as an Unresolved i
Safety Issue.
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Single Failure Criterion i
The staff believes that the single failure criterion has served well in its use as a licensing review teci to assure reliacie systems is one element of j
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9 the defense-in-depth approach to reactor safety.
The Reactor Safety Study and more recent reliability studies have indicated that the use of the single failure criterion has led to a generally high level of reliability in most systems important'to safety, However, for certain systems it may be 'neceesant j
to postulate more than a single failure in order to provide a sufficient reliability of performing a safety function.
The IREP investigations that are currently underway will evaluate the current system reliability achieved by application of the single failure criterion.
The results of IREP when used in conjunction with quantitative safety goals, will identify deficiencies in systems where improvements beyond the single failure criterion ar'e required in
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order to achieve an acceptable level of risk.
These quantitative safety goals i
will be developed as described in action items IV.E.1 and V.B.1 of the THI-Action Plan.
l Where these deficiencies in sys' tem reliability are identified, they will be c
considered for designation as Unresolved Safety Issues.
One such deficiency 5
has already been designated as an Unresolved Safety Issue.
Because of the significant contribution to risk of loss of all feedwater in PWRs (i.e.,
i multiple failures in main and auxiliary feedwater systems), a separate issue i
concerning requir'emants for an alte. native decay heat removal method has been designated as an Unresolved Safety Issue " Shutdown Decay Heat Removal Require-ments" (See SECY 80-325).
The results of the IREP studies will be carefully reviewed for similar issues.
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'I We believe that the IREP program:
is adequately structured to provide the l'
information required to identify deficiencies in the single failure criterion; is receiving pri'crity and resources for expediticus completion; and is being monitored by a new organizational unit in NRR, the Reliability and Risk Assess-ment Branch.
Additionally, the new Generic Issues Branch has the responsibility to monitor new concerns and issues to identify those that should be designated
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as Unresolved Safety Issues.
Accordingly, we do not recommend that such a broad concern as " Single Failure
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Criterion" be designated as a separate Unresolved Safety Issue; but rather 3
that any specific generic deficiencies identified by IREP be considered as candidate Unresolved Safety Issues as they are identified.
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SAFETY IMPLICATIONS OF CONTROL SYSTEMS 1
This issue concerns the potential for accider.ts or transients to be made more severe as a result of control systems failures or malfunctions.
These f ailures or calfunctions may occur independently or as a result of the accident or transient under consideration and are in addition to any control. system failure that may have initiated the event.
Although it is generally believed that
. control system failures are not likely to result in loss of safety functions leading to serious events or to result in conditions that safety systems are not able to cope w'ith, in-depth studies have' not been performed to support this.
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This issue resulted from recommendations by the Advisory Committee on Reactor Safeguards, the NRC's Office for Analysis and Evaluation of Operational Data, the NRC's Lessons Learned Task Group' on TMI, and Westinghouse Corporation i
1 based on a review of Salem environmental qualifications.
An I&E Information Notice was sent to all licensees concerning the potential 1
unreviewed safety question identified at Salem.
Additionally, in September 1979 all licensees were requested to investiga'te, and report the results within 20 days, the potential effects on control systems of the environment J
resulting from high energy line breaks inside or outside containment and the resulting impact on safety systems.
A survey review of information provided by licensees showed that although no event sequence was identified that clearly leads to an unacceptable consequence, certain concerns were identified:
a variability in the breadth and depth of the reviews by licensees; lack of a consistent metho'dology of review; failure to characterize the relative risks accng the actions considered; and new scenarios generated by some licensees that were not considered by all other licensees.
This Information Notice and l
initial systems review were only directed at the effects on plant control i
systems of the adverse environment caused by the accident.
A related concern is the independent failure of some control system compounding the conditions i
during a transient or accident.
This Unresolved Safety Issue is directed at both concerns.
The potential for an accident to affect a particular control system and the effects of.the control system failure will differ from plant to plant.
It therefore will not likely be possible to. develop generic answers to these concerns.
However, to perform these plant-specific reviews, generic criteria i
will be required.
T_he Durcose of this Um esc 1ved Safety Issue is_to_ define
- e eric criteria that may be used for plant-specific reviews anc wii) include
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Define scenaries that should be considered; (2)
Develop a methodology for evaluating these scenarios; (3)
Develop acceptance criteria for the results; and (d
Develop guidelines for improvements that have to be reade where acceptance criteria are not met.
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Q These guidelines will address:
Measures to improve the reliability of control systems (such a.
as QA criteria, environmental cualification, periodic surveillance, or increased redundancy);-
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Measures to reduce the effects of control system failures; and,
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Measures to improve the capability of coping with the effects j
of control system failures (such as procedural improvements; improvements in information display; human factors improvements; and/or improvements in operator training [.
i Probabilistic assessment may 5e required to define the -independent failures that should be postulated to occur in conjunction with the event and c
failu.res that result from the event.
Failures of control systems will be considered under conditions of normal operation, anticipated operational l
occurrences, and design basis events (pipe Breaks, earthquakes, etc.).
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