ML20024D028

Approves Priority Ranking of Note 2 for Generic Issue 40, Safety Concerns Associated W/Breaks in BWR Scram Sys. Evaluation Encl

ML20024D028
Person / Time
Issue date:	07/18/1983
From:	Harold Denton Office of Nuclear Reactor Regulation
To:	Mattson R Office of Nuclear Reactor Regulation
References
NUDOCS 8307260333
Download: ML20024D028 (10)

Text

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UNITED STATES y

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• ;9.W /,j WASHINGTON, D. C. 20555 s.....l July 18,1983

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MEMORANDUM FOR:

Roger J. Mattson, Director Division of Systems Integration FROM:

Harold R. Denton, Director Office of Nuclear Reactor Regulation

SUBJECT:

SCHEDULEFORRESOLVINGANDCOMELETINGGENERICISSUE

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NO. 40 - SAFETY-CONCERNS ASSOCIATED WITH BREAKS IN THE BWR SCRAM SYSTEM This memorandum approves a priority ranking of " Note 2" for Generic ~ Issue 40,

" Safety Concerns Associated with Breaks in the BWR Scram System." The evaluation of the subject issue is provided in Enclosure 1.

In accordance with NRR Office Letter No. 40, " Management of Proposed Generic Issues," the resolution of this issue will be monitored by the Generic Issue Management Control System (GIMCS).

The information needed for this system is indicated on the enclosed GIMCS information sheet.

Your schedule for resolving and completing this issue should be commensurate with the high priority nature of the work, but compatible with your present division work loads.

Normally, as stated in the Office Letter, the information needed would be provided within six weeks.

This issue is being sent to other NRC offices, the ACRS, and PDR for comments on the technical accuracy and completeness of the prioritization t

evaluation.

Any changes as a result of comments will be coordinated with you.

However, the schedule for the resolution of this issue should not be delayed to wait for these comments.

The information requested should be sent to the Safety Program Evaluation Branch, DST.

Should you have any questions pertaining to the contents of this memorandum, please contact Louis Riani (24563).

/

Harold R. Denton, Director Division of Nuclear Reactor Regulation

Enclosures:

9 1.

Prioritization Evaluation 2.

Generic Issue Management Control System cc:

J. Funches W. Minners

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NOS SeegSe4{O$.0R R. Minogue Z. Rosztoczy R. DeYoung L. Riani XA Copy C. Heltemes, Jr.

R. Capra-

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ROUTING AND TRANSMITTAL SLIP (please route to next person)

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INIT1ALS DATE INIIIALS

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SUBJECT:

PRIORITIZATION OF GENERIC. ISSUE NO. 40 Safety Concerns Associateo with breaks TITLE: in the BWR System 3

fDNs et al. from W. Dircks,

REFERENCE:

Memo to Directors o

" Program Guidance," September 20, 1982.

(, An evaluation of the safety priority ranking of the subject issue is attached and is.being routed to the appropriate NRR division or other NRC office for review and concurrence or comment.

Other offices marked for

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copies and the other NRR divisions are also requested to review the iss'ue and comment if app'ropriate.

Comments on the technical accuracy and completeness of the description of the issue and its safety significance are solicited.

Comments may be noted on the attached copy of the evaluation of the issue or appended.to this routing slip.

Generally, comments will either be incorporated into the evaluation or resolved with the commenter.

Concurrence is not required and unresolved comments will be identified in the final prioritizaticn report by SPEB.

Comments endorsed by the appropriate office or NRR division should be returned to SPEB within ten working days using this routing slip.

This draft is part of the work in furtherance of the Commission's Policy, Planning, and Program Guidance for FY 1983-87,Section III B, Paragraph 1.3, which states that "a fully integrated priority list based on the potential significance of each [ generic]. issue will be eptablished."

NRR/ DST has been assigned responsibility for preparing the recommended priority rankings.

cc:

T. Speis, D/ DST R. Capra, DSI E. Sullivan,- DE -

D. Jones, DHFS

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P t lE ISSUE NO. 40:

SAFETY CONCERNS ASSOCIATED WITH BREAKS IN THE BWR SCRAM SYSTEM i

DESCRIPTION Historical Backoround On April 3, l'981, the Office for Analysis and eveiuar. ion of Operational Data

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(AEOD) published draft NUREG-0785, " Safety Concerns Associated With Pipe Breaks in the BWR Scram System" (Ref. 324).

As a result of the development of these safety concerns and the findings presented in the. report, the Nuclear Regulatory Commission (NRC) staff met with representatives of the BWR Regulatory Response Group and the General Electric Company on April 9, 1981.

A letter was', issued on April 10, 1981 (Ref. 325) to all boiling water reactor reactor (BWR) licensees requiring a generic evaluation of the safety concerns within 45 days of receipt' and a s -

plant-speci'fi.c evaluation withiri 120 days of receipt'

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h A m'eeting was held with General Electric on April 28, 1981 to discuss the status of its generic evaluation.

Subsequently NE00-24342, (Ref. 326), was submitted to NRC' by letter dated April 30, 1981 (Ref. 327).

A multidisciplinary group from the Office of Nuclear Reactor Regulation was assembled to review the generic eval'uation.

A three phase approach was W

developed to identify generic review objectives 'and describe review termination points.

It was agreed that this approach would be based on establishing either'1)~ flow probability f'or the event, or 2) acceptable -

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,e consequences for the event, or 3) alt ~ernate codieg' systems and mitigation p

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equipment for the event.

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As the review progressed, it became evident that a sufficient data base did not exist to conservatively terminate the generic review on the basis of a quantitative risk assessment.

It was equally difficult to show acceptable

~ consequences for all scram initiators, considering the potential for an unisolable leak from the reactor coolant system into'the reactor buildin'g..

Thus, it was necessary to generically evaluate he mitigation capability for.

this scenario.

As the evaluation proceeded, several suggestions for improving and verifying piping integrity, mitigation capability, and environmental qualifications of essential equipment were made,.

These suggestions are discussed in NUREG-0803 (Ref. 328) which begins with a rev ew vf the licensing design b

basis for the SDV piping system.

An evaluation of the SDV-piping system integr.ity.and an assessment of the mitigation capability follow.

Finally, each gestion for improvement is evaluated in NUREG-0803 (Ref. 328)as4'

-;LM-),the final guidance for resolution of this problem is presented.

NUREG-0803 was transmitted to the BWR licensees, CP applicants,.CP holders, 31L and OL applicants by letter (References 329 and uc),awJg iso requested M appropriate responses to the safety concerns and guidelines presented in NUREG-0803.

In these letters it has been noted that an acceptable

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plant-specific. response for.this issue will conform to the final, approved guidance provided in NUREG-0803.

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Oecently, a study was completed (reference 337) which describes the

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l However, an additional submitYA1 wAs forwarded to the NRC staff by GE

-(reference 402) and the BWR Owners' Group in August 1982/fnwhichananalysiswaspresent-ed to demonstrate that the probability of a pipe break in the scram dis-charge volume system was negligibly small and that, therefore, this I

issue should not be regarded as a significant safety issue.

On the basis of its review of the August submittal the NRC staff conn-(*,.,1uded tha t the results of the submittal were unacceptable.

However, before the submittal was formally rejected by the staff, GE-and the BWR Owners' Group'provided additional material which amplified the August submittal with supporting informa(tiong(w pch wa)s, presented at referenc 403 a meeting with the staff on February 8,1983.

At present the staff is j

reviewing all of the recent material provided by GE and the BWR Owners' !

Group wit'h a view towards the resolution of this issue.

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postulated small-break loss-of-coolant accident outside of the primary containment.

This is the first volume of a two-volume study in which a

_ detailed analysis of the accident sequence is presented.

An estimate of the magnitude and timing of the concomitant release of the noble gas, cesium, and iodine-based fission products to'the envirohment will' be provided in' Volume 2 of this report.

W Safety Concern If a break or leak exists or develops in the SDV piping during a reactor scram, this would result in the release of water and steam at 212 F into the reactor building at a maximum. flow rate of 550 gpm, and is postulated to result in 100% relative humidity in the reactor building. 'The principal f **

means of isolating this break would be to close the scram exhaust valves which are located.on the Hydraulic Control Units (HCll); however, this is.

dependent upon the ability to reset scram, which cannot be absolutely ensured immediately following the scram.

Therefore,aruptureofthe55 t,

could result in an unisolable break outside of primary containment, which is postulated to threaten emergency core cooling equipment by' flooding dreas in mL b c.a.u s m o.mbie,a 4,.9A,,

which this equipment is located 3 L M % ymM w nd-JMd.

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NUREG-0803 provides guidance to ensure pipe'inte'grity, detectio.n capability, mitigation capability and qualification of the emergency equipment to the

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4 REFERENCES 324. U.S. Nuclear Regulatory Commission, " Safety Concerns Associated With Pipe Breaks in the BWR Scram System," USNRC Draft Report NUREG-0785, April 1981.

325. Letter from D. G. Eisenhut, NRC, to all BWR licensees,

Subject:

Safety Concerns Associated With Pipe ~ Breaks in the BWR Scram System, dated April 10, 1981.

326. General Electric Company, "GE Evaluation in Response to NRC Request -

Regarding BWR Scram System-Pipe Breaks," NED0-24342, April 1981.

327. Letter from G. Sherwood, General Electric Company, to D. G. Eisenhut, NRC,

Subject:

Safety Concerns Associated With Pipe Breaks in the BWR Scram System, dated April. 30, 1981.

328. U.S. Nuclear Regulatory Commission, " Generic Safety Evaluation Report Regarding Integrity of BWR Scram System Piping," NUREG-0803, August 1981.

329. Letter to all GE BWR Licensees (Except Humboltit Bay), from Darrell G. Eisenhut, Director, DL, Office of Nuclear -Reactor Regulation,

" Safety Concerns Associated With Pipe Breaks. in the BWR Scram System (Generic Letter 81-34)," dated August 31, 1981.

332. Letter 'to all, BWR Applicants to cps, Holders of'.tPs, and' Applicants for OLs from Darrell G. Eisenhut, Director, DL, Office of Nuclear React 5r Regulation, " Safety Concerns Associated with Pipe Breaks in the BWR Scram System (Generic Letter 81-35)," dated August 31, 1981.

337. U.S. Nuclear Regulatory Commission, "SBLOCA Outside Containment at Browns Ferry Unit One - Accident Sequence Analysis" - Vol. I, NUREG/CR-2672 (ORNL/TM-8119/V1).

402. Letter from T. J. Dente to the U.S.N.R.C., At'tention: Darrell G. Eisenhut,

" Analysis of Scram Discharge Volume System Piping Integritt-NED0-22209 (prepublication form)", August 23, 1982.

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403. Letter from T. J. Dente to U.S.N.R.C Attentton:.K. Eccelston$.on to S

" Transmittal of Supporting Information on Applicati%n of Scram Time Fract Discharge Volume (SDV) Pipe Break Probability As Used in NEDO-22209",

January 28, 1983.

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o GENERIC ISSUE MANAGEMENT CONTROL SYSTEM The Generic Issues Management Control System (GIMCS) provides appropriate information necessary to manage safety related and environmental g, eneric issues through technical resolution.

For the purpose of this information system technically resolved is defined as the point where the staff's technical resolution has been issued.

Generally, speaking, this occurs when the technical resolution has been invorporated into one or more of the following:

(a) Commission policy statement / orders (b) NRC Regulations (c)

Standard Review Plan (d) Regulatory Guide (e) Generic Letter GIMCS will provide management information for both active and inactive issues.

Accordingly, the control system consists of two parts:

Active and Inactive.

GENERIC ISSUE MANAGEMENT CONTROL SYSTEM-ACTIVE (GIMCS-A)

The active section of GIMCS will provide information to manage and control High priority generic issues, issues for which possible resolution has been identified for evaluation, issues for which a technical resolution is available (as documented by memorandum, analysis, NUREG, etc.), issues designated by the Director of NRR and previously inactive issues for which resources have become available.

GENERIC ISSUE MANAGEMENT CONTROL SYSTEM-INACTIVE (GIMCS-I)

The inactive section of GIMCS will provide management information for issues awaiting assignment of resources.

These are generally Medium. priority issues that have no safety deficiency demanding high priority attention, but there is a potential for safety improvements or reduction in uncertainty of analysis that may be substantial and worthwhile.

Efforts for resolution of these issues should be planned, over the next several years, but on a basis that will not interfere with the resolution of High priority generic issue work or other high priority work.

Thus, medium generic issues will be inactive until such time as resources become available to resolve the various issues.

As resource allocations are directed at medium issue resolution, they will become active.

The detailed schedule for resolving and completing the generic issue will be developed and the issue will be transferred from the GIMCS-inactive section to the GIMCS-Active section for management and control.

-n Management and control indicators used in GIMCS ate defined as follows:

1.

Item No.

Generic Issue Number.

J

i e

2.

Issue Type -

Safety, Environmental or Regulatory Impact High, Note 1 or Note 2 (From NUREG-0933),

Medium.

3.

Schedule -

Green - Technical Resolution is on schedule.

Orange _ Technical Resolution schedule has l

l slipped 4 to 6 months.

Red -

Technical Resolution schedule has l

slipped 6 to 12 months.

l

-Whi te - Technical Resolution is not scheduled l

during present fiscal year.

4.

Office /Div/Br -

1st listed has lead responsibility for re-solving issue, others listed have input to resolution.

5.

Task Manager -

Name of assigned individual responsible for schedule updating.

6.

Tac Number -

Each issue should be assigned a TAC #

7.

Title -

Generic Issue Title.

8.

Work Authorization -

Who or what authorized work to be done on generic issue.

9.

Contract Title -

Provide Contract Title (if contract issued).

10. Contractor Name/

Identify Contractor Name and FIN Number (as FIN No. -

appropriate).

If contract is not yet issued, ind, tite whether the contract is included in the FIN p'. n.

11. Work Scope -

Descr ~ es briefly the work necessary to tech-nical'/ resolve and complete the generic issue.

12. Affected Documents -

Identifies documents that the technical resolution will be incorporated into to identify new criteria.

13. Status -

Describes current status of work.

14. Problem / Resolution -

Identifies potential problem areas and describes what actions are necessary to resolve them.

15. Technical Resolution -

-IdentifiesdetaileNscheduleofmilestone dates that are required for completing the issue through the issuance of the SRP revision or other change that documents requirements.

16. Milestones -

Selected significant milestones.

The " original" schedule remains unchanged.

Changes in schedule are listed under " Current".

Actual completion are listed under " Actual".

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i GENERIC ISSUE MANAGEMENT CONTROL SYSTEM-ACTIVE Issue Issue Task Number Type Schedule Office /Div/Br Manager Tac No 40 Safety /

NRR/DSI/ASB Note 2 Title ----------------

Safety Concerns Associated With Breaks in the BWR Scram System.

Work Authorization ---

Contract Title -------

Contractor Name/

FIN No. ------------

1 Work Scope -----------

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Affected Documents ---

a Status ---------------

Problem / Resolution ---

Technical Resolution -

Milestones Original Curre'nt Actual 9

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