ML20044C679
| ML20044C679 | |
| Person / Time | |
|---|---|
| Issue date: | 04/23/1993 |
| From: | Palla R Office of Nuclear Reactor Regulation |
| To: | Thadani A Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19303F714 | List: |
| References | |
| NUDOCS 9305060349 | |
| Download: ML20044C679 (28) | |
Text
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April 23, 1993 MEMORANDUM FOR:
Ashok C. Thadani, Director Division of Systems Safety and Analysis THRU:
William D. Beckner, Chief h}
l Probabilistic Safety Assessment Branch Division of Systems safety and Analysisu$
FROM:
Robert L. Palla, Jr.
Probabilistic Safety Assessment Branch Division of Systems Safety and Analysis
SUBJECT:
SUMMARY
OF FESRUARY 23, 1993 MEETING WITH OWNERS GROUPS REGARDING ACCIDENT MANAGEMENT On February 23, 1993, the NRC staff met with representatives of the Nuclear Management and Resources Council (NUMARC), and the PWR Owners groups (B&W, ABB-CE, and Westinghouse). The purpose of this meeting was to discuss:
(1) progress by each owners group on severe accident management guidance development effort, (2) results from the EPRI project on instrumentation and l
computational aids, and (3) the status of INP0's activities on training and decisionmaking.
This memorandum summarizes the most significant results of l
the meeting.
A list of attendees is presented in Enclosure 1.
A copy of the meeting handouts is provided as Enclosures 2 through 8.
Following introductory remarks, R. Shoemaker (WOG) described the structure and features of the severe accident management guidelines being developed by the WOG.
This effort will involve the development of two control room guidelines, and parallel guidance for the Technical Support Center staff.
The two control room guidelines, designated SAMG-A and SAMG-B, are for use before and after the Technical Support Center (TSC) is actuated, respectively.
SAMG-A is intended to focus on fast-moving events such as ATWS and large LOCAs, and is event-based.
SAMG-B is intended to provide more general guidance to enhance control room implementation of TSC recommendations.
The TSC guidance is in two parts:
(1) a step-wise master document and (2) a status tree.
The master document points to the need to evaluate a response guideline for possible implementation.
The status tree takes priority over the master document l
steps, and points to the need to implement a response guideline.
Logic l
diagrams depicting the organization of TSC severe accident guidance, and severe challenge monitoring were presented and discussed.
Copies of an example of a response guidance and an associated calculational aid were provided to the staff.
The viewgraphs arc presented in Enclosure 2.
The example response guideline is presented in Enclosure 3.
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Ashok C. Thadani The following points were raised in ensuing discussions:
Much of the guidance is still draft or under development.
For example, SAMG entry conditions have not yet been defined, and the actions in the logic diagrams have not been prioritized.
There will eventually be about 20 resp 9nse guidelines, some of which will include calculational aids. Westinghouse is presently working on about 10 of these.
The staff noted that in many instances the TSC would be activated prior to core damage, yet the SAMG does not appear to address preventive measures that the TSC should take, such as actions to back up the operators.
The present scheme for severe accident challenge monitoring appeared to be based on comparisons with threshold values.
The staff noted that parameter trends is important and should be incorporated into the guidance.
Industry representatives agreed and indicated that a combination of trends and specific values is being pursued.
H. Crawford (B&WOG) and W. Dove (CE0G) followed with reports on the status of the B&WOG and CEOG SAMG development efforts.
The status and schedule for remaining activities is summarized in Enclosures 4 and 5.
Both owners groups are continuing to work towards a date of June 30, 1993, for submittal of draft SAMG to NRC.
The B&WOG is planning to have a complete draft of their SAMG document for utility review by mid-April 1993.
H. Crawford committed to explore whether the draft could be provided to NRC.
Similarly, significant portions of the CEOG are essentially completed, however, other areas of the guidance, involving assessing plant response and restorative AMG, have just been initiated.
W. Dove indicated that the CE0G would be willing to provide a copy of their SAMG, in its present form, to the NRC if staff would agree to review and comment on the document.
(This document was subsequently submitted by CE0G, with the agreement that staff would attempt to provide high level i
comments by the end of April. A meeting on this topic is presently scheduled l
for April 22.)
S. Oh (EPRI) discussed EPRI's project on computational aids development for severe accident management, and presented examples of some of the generic computational aids currently under development.
These include computational techniques for estimating:
(1) required water addition to restore core l
cooling, (2) containment pressurization associated with water addition to core l
debris, and (3) vent size required to stabilize containment pressure.
Examples of computational aides being developed by each reactor vendor were separately described by W. Dove, R. Shoemaker, and H. Crawford.
Copies of the EPRI and owners groups presentation materials are provided as Enclosures 5 I
through 8.
As the final presentation, L. Walsh summarized the status of INP0's activities in the areas of training and decision-making (Enclosure 9).
The first milestone in the industry plan -- identifying severe accident training program
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j Ashok C. Thadani '-
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attributes for personnel with accident management responsibilities -- is being addressed, in part, through the development of a list of tasks important to
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l severe accident management. A initial set of tasks has been developed based on the accident management strategies (candidate high level actions) treated in the EPRI Severe Accident Management Technical Basis Report. Three different types of individual accident response roles have been defined in conjunction with the task list, namely, " evaluator", " decision maker", and
" implementor".
A draft task training matrix has also been developed.
The matrix represents a first cut at identifying associated knowledge items for each candidate high level action, and responsibilities of personnel in each accident response role.
The accident management task list and training matrix are presently being refined and reassessed to reflect any additional consideration contained in the vendor-specific accident management guidance.
This effort is expected to be completed within the third quarter of CY1993.
Issuance of the revised training / decision-making guideline is still targeted for late CY1993.
Original signed by:
Robert L. Palla, Jr.
Probabilistic Safety Assessment Branch 1
Division of Systems Safety and Analysis
Enclosures:
As stated DISTRIBUTION:
A/M Distribution List (w/o enclosures)
GHolahan WBeckner AEl-Bassioni RPalla NRC PDR (w/o Enclosures 3 & 8)
Central Files
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SPSB r/f 0FC SPSB:DSSA:NRR SC:SPSB:DSSA BC:SPSB:DSgA NAME RPalla:bw 8.l f AEl-BaNidi WBeckneY DATE 04h3/93 04/0/93 04/[/93 0FFICIAL RECORD COPY Document Name:
FEB23 MET
l 1-Ashok C. Thadani i attributes for personnel with accident management responsibilities -- is being addressed, in part, through the development of a list of tasks important to severe accident management. A initial set of tasks has been developed based on the accident management strategies (candidate high level actions) treated in the EPRI Severe Accident Management Technical Basis Report.
Three different types of individual accident response roles have been defined in conjunction with the task list, namely, " evaluator", " decision maker", and
" implementor". A draft task training matrix has also been developed.
The matrix represents a first cut at identifying associated knowledge items for each candidate high level action, and responsibilities of personnel in each accident response role.
The accident management task list and training matrix are presently being refined and reassessed to reflect any additional consideration contained in the vendor-specific accident management guidance. This effort is expected to be completed within the third quarter of CY1993.
Issuance of the revised training / decision-making guideline is still targeted for late CY1993.
W L.PA G Robert L. Palla, Jr.
Probabilistic Safety Assessment Branch Division of Systems Safety and Analysis Enclosures-As stated
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f ACCIDENT MANAGEMENT DISTRIBUTION FOR MEETING NOTICE l
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TSpeis, NLS 007 BSheron, NLS 007 LShotkin, NLN 353 FCoffman, NLN 316 NLauben, NLN 353 DHouston, P 315 i
JKudrick, 8 D 1 RErickson, 9 H 19 DDesaulniers, 10 0 24 MRubin, 8 E 23 RJones, 8 E 23 RGallo, 10 D 18 DMarksberry, MNBB 3206 WPasedag, DOE Alevin, 8 E 23 l
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WESTINGHOUSE OWNERS GROUP SEVERE ACCIDENT MANAGEMENT PROGRESS REPORT Presented to:
Nuclear Regulatory Commission February 23,1993 Rusty Shoemaker A
Chairman, Operations Subcommittee / Westinghouse Owners Group i
Wotinghouw Owners Group NRC Presentation 23 February 93 Uk
TOPICS FOR PRESENTATION Severe Accident Management Guideline Structure o
o Overview of Control Room Actions TSC Diagnosis for Strategy Implementation o
Sample Response Guideline t
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Sample Computational Aid o
Houstadmesme Owners Group NRC Presentation 23 February 93
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Accident Scenario Considerations o
Two accident scenario types may progress to core damage prior to the j
time that the TSC is functional Large LOCAs ATWS events Investigation of WOG ERGS has determined that additional guidance i
o beyond the present ERGS is required for. severe accidents l
Present. ERGS are success oriented and "do-loop" on restoring core cooling (FR-C.1) i s
Need to broaden focus for fission product barrier protection I
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Wens'-7: :w Ownen Group NRC Presentation 23 February 93
I WOG SAMG STRUCTURE Human Factors Considerations o
Decision making process was defined in detail to permit human factors i
considerations to be factored into SAMG structure o
No coincident ERG and SAMG Usage
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Eliminates Possible Conflicts i
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Goal Orientation is clear i
o Need for symptom based guidance
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Plant conditions may not be well known based on instrumentation
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Defines critical parameters to be monitored 4
%Cf a Ownen Group NRC Presentation 23 February 93 1
SAMG STRUCTURE
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Control room guidance to be used if TSC is not functional at the time of o
core damage Provides a broader focus to include fission product barriers Limited to actions until TSC is staffed for Large LOCA and ATWS o
Control room guidance to be used during TSC evaluations Fosters Communication Enhances control room acceptance of TSC recommendations o
TSC Guidance (Main part of WOG SAMGs)
Provides the logic for diagnosis of severe accident challenges and evaluation of possible mitigating or recovery actions i
Wetinghouse Owners Group NRC Presentation 23 February 93
WOG SAMG STRUCTURE TSC NOT OPERATIONAL j
TSC OPERATIONAL
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Plant Chattenges Controlled a:na es woc c.n.rio sa cuidene.
CASE 1 ERGS i
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CONTROL C Ati E 2 ERGS ROOM 5
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SEVERE ACCIDENT Severo Accident i
GUIDELINE FOR 3
1 Symptoms Observed i
CONTROL ROOM SAMG B
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Control Room Guidance Conwnunicotlans Decielons
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TSC Gu! dance l
3 TSC SEVERE ACCIDENT LONG TERM i
MITIGATION GUIDANCE i
PLANT CONCERNS t
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PRELIMINARY DRAFT j
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o For use in ew., which proceed to core damage before TSC is functional o
Limited to considerations and actions for Large LOCA and ATWS events until TSC is staffed Actions well defined Interface with ERG well known j
Priorities easily established 9
Time frame limited to about I hour j
% sus'-f -- -- Owners Group NRC Presentation 23 February 93
CONTROL ROOM SAMG - A; High Level Actions o
Actions fall into two broad categories Fission product barriers (not in procedure being used at core damage)
Re-iteration of important ERG actions (ERGS have been discontinued)
Draft logic covers actions related to:
o RCS Depressurization Containment Spray Operation Containment Fan Cooler and Mixing Fan Operation Containment Isolation Containment Hydrogen Control i
Injection into RCS Steam Generator Water Inventory l
Containment Sump Water Inventory Evaluation of Plant Equipment Status Weasingheene Ownen Group NRC Presentation 23 Febmary 93 t
CONTROL ROOM SAMG - B; High Level Actions
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Actions fall into two broad categories Information used by the TSC 1
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accurate and timely
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Alerting TSC to significant changes in plant status Equipment status and configuration
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appropriate plant equipment is under manual control e
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no unanticipated changes in equipment status have occurred.
o Draft logic is presently being developed:
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1 MwW Ownen Group NRC Presentation 23 February 93
WOG TSC SAMG DIAGNOSIS Based on detailed evaluation of a broad. range of core damage accident o
4 scenarios and potential accident management actions 4
o Step-wise Master Document Simple actions to prevent unexpected challenges Actions for rapid challenges to fission product boundaries Actions to achieve a controlled, stable plant state Transition to long term recovery o
Status Tree Based on indication of severe challenge to fission product boundaries Limited to longer term transient indications
% eid' 7 : _ a Onmen Group NRC Presentation 23 February 93
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SEVERE CHALLENGE MONITORING l
(PARALLEL PATH) l STATUS 1.
MONITOR PLANT STATUS VS. DESIRED PLANT END-STA (E CONDITIONS SEVERE NO a.
CORE COOLING CONDITION CHALLENGE b.
CONTAINMENT CONDITIONS
- c. RADIATION CONTROL YES j
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EQUIPMENT STATUS e.
OTHERS IMPLEMENT 2.
EVALUATE NEED TO APPROPRIATE IMPLEMENT STRATEGIES GUIDELINES i
To ACHIEVE DESIRED PLANT END-STATE o
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EXIT TSC SAMGs PRELIMINARY DRAFT Copyright Westinghesse Owners Greap t
1 RELATIONSHIP BETWEEN DIAGNOSIS AND RESPONSE All diagnosis efforts point to a potential response I
o Master document points to the need to evaluate the need for a response guideline Status trees take priority over master document steps and point to a need for implementation of a response guideline Each response guideline will address o
Urgency of response Factors to be considered in determining the appropriate response l
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i M and'-7 :- -- Ownen Group NRC Presentation 23 February 93
a HIGH LEVEL LOGIC OF TSC SEVERE ACCIDENT GUIDANCE ENTER TSC SEVERE ACCIDENT GUIDANCE J
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II CCNTAINNENT VATER VEL EVALUATE THE NEED FI3t STRATEGY
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y CVALUATE THE EED FDI ITRATEGY a IGNITE HYDROGEN u CCNTAlpeCNT a IstLATE IGNITION SOURCES e HYDROGEN
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1 ENTER SITE NO SAMG-A RELEASES LESS THAN (1) YES
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PRESSURE I
LESS THAN ($ YES CONTAINMENT NO SAMG-C 1
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HYDROGEN LESS THAN (3) YES l
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PRELIMINARY DRAFT C*Pyright Westinghouse Owners Group j'
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KEY FEATURES OF DIAGNOSIS METHODOLOGY
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Relies only on available plant information Does not require diagnosis of reactor vessel failure Can be used if some information is not available i
o Direct relationship to individual response guidelines o
Easy to use i
Westinghouse Owners Group NRC Presentation 23 February 93
RESPONSE GUIDELINE: INJECT INTO RCS 4
o SAMG-1, " Inject into the RCS", is the first guideline developed by the WOG Severe Accident Working Group; it is still a preliminary draft i
Purpose of the Guideline is to provide structure and logic for the TSC to o
make decisions regarding injecting into the RCS during a severe i
accident.
i Determinations made by the TSC in using this guideline:
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4 Is injection possible with the current plant configuration ?
i What are the impacts of initiating injection into the RCS ?
Is injection successful in mitigating the challenges ?
i What are the long, ierm concerns associated with RCS injection ?
H ome W O m mers G reesp NRC Presentation 23 February 93 I
RESPONSE GUIDELINE: INJECT INTO RCS Is injection possible with the current plant configuration ?
o Step I through 5 of guideline Determine the availability of ECCS pumps Determine the availability of any other plant-specific alternate injection pathways Determine potential injection. water sources, and Determine potential injection flow paths me f
INJECT INTO RCS RESPONSE GUIDELINE:
I CS?
f ting injection to the R What are the impacts of initia 8 of the guideline tor tubes ?
o 6 through ture of the steam genera Step a potential for creep rupevaluate the potential i
Is there Guidance is provided to dditional hydrogen t inment to failif a
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a potential for the con a ry ?
Is there is produced during recove evaluate the potential Guidance is provided to other mitigating cts are identified, can
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If any potential negative impad to lessen the im strategies be performe i
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IDELINE:INJECTINTO o
Implement injection RCS Step 9 with available sources Inject with whatever sou maximum rces are available; there isno minimum or Computational aid devel given to recovery of additioped to determine if high onalinjection capability priority shoul RCS depressurization, SG I j been n ection considered prior to other guidelines reaching this strategy;and RWS already no need to network
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H edinghenone O w men Gnsup NRC Presentation 23 Feb ruary 93
RESPONSE GUIDELINE: INJECT INTO RCS Is injection successful in mitigating challenges to the plant ?
o Step 10 through 13 of the guideline Has injection been properly implemented based on monitoring of various plant parameters ?
Are any of the negative impacts greater than expected ?
I WeMinghouw Owners Group NRC Presentation 23 February 93 L________
RESPONSE GUIDELINE: INJECT INTO RCS What are the long term concerns associated with RCS injection ?
o Step 14 of guideline Will injection sources need to be refilled ?
Will containment flooding become a concern ?
What is the minimum flow rate to remove decay heat one the core is recovered (a computational aid is provided) ?
What are the habitability concerns in the auxiliary building is ECCS recirculation is established ?
Is RCS Injection limited due to degraded operation of the injection pump ?
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M end'-7 :n; Owners Group NRC Presentation 23 February 93
,