ML20005B361

Responds to 810427 Request for Short Summary of Severe Accident Sequence Analysis Program as It Applies to Facility.Outlines Objectives,Type of Info Needed,Use of Info,Site Visits & Advantage for Util & Program

ML20005B361
Person / Time
Site:	Arkansas Nuclear
Issue date:	04/29/1981
From:	Murfin W SANDIA NATIONAL LABORATORIES
To:	Disalvo R NRC
Shared Package
ML20005B360	List: ML20005B361
References
NUDOCS 8107070552
Download: ML20005B361 (2)

Text

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Enclosure Sandia National Laborato:ics Albuquerque Ne.* '.ie nco 8 7185 Dr. Ray DiSalvo Iluman Engineering Section Division of Facility Operations USNk; Washington, D. C. 20555

Dear Ray:

In response to your request of April 27, 1981, I am sending you a short summary of the Severe > Accident Sequence Analysis (SASA) program as it applies to Arkansas Nuclear One - Unit 1. .

1. objectives - The primary objective is to improve the

> understanding of reactor accident phenomenology and of the .

human-machine interface during events beyond the design basis.-

Secondary objectives are to evaluate the capability for arrest-ing and mitigating the consequences of severe core damage ac-cidents and to evaluate potential improvements in those capabilities, if warranted. These objectives will be met by

analyzing the plant response to the most Jikely accident initiators, using best-estimate rather than conservative methods. The plant response to operator actions will also be analyzed. The impact of training, procedures, and current regulations on operator action will be considered.

- 2. Type of InEormation Needed - More accurate and detail- ,

ed input information is required for a best estimate analysis than for a consarvative analysis. Detailed primary system layouts are needed for input to the thermal hydraulic codes. ~

Detailed containment drawings are needed for structural analysis.

General systems information (P & ids, etc.) is available from IREP, but is not sufficiently detailed for developing input for the codes. Also, some of the IREP material is illegible. In-i formation in the FSAR is generally conservative, and is hence not usually suitable for best estimate analyses.

3. Use of Information - Realistic plant respons;s to transients, equipment failures, human errors and other accident initiators will be analyzed. Operator actions to arrest or mitigate the accidents will be considered. Sequences leadinga e

to severe core damage will be analyzed in considerable detail.

The effects of plant systems to mitigate the accident will be analyzed. The possibility of damage control and/or repair of systems, and the use of alternate systems in a non-standard

- manner will be considered. The plant responses will be reported, but the detailed input data will not be published. The pro- ,

bability of initiation of accidents will not be analyzed. The i

likelihood of alternative paths will be qualitatively reported.

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4. Relationship to IREP - The IREP analysis will be use-ful in indicating which accid'ent initiators are most probable..

The SASA analysis will be useful to IREP in indicating the con-servatism involved in the IREP estimates of accident outcome.

The IREP and SASA teams will cooperate closely, but it is not expected that IREP results will be directly used by SASA, nor will SASA results be directly used by IREP. Much of the data' needed by SASA is already available to IREP.

5. Site v'isits - Collection of information is expected '

to require a visit.

The needs of all three participating laboratories will be combined so that a single visit for in-formation gathering should suffice. Every effort will be made to preclude the need for follow up visits. A briefing for Arkansas Power and Light technical personnel on the objectives '.

and methods to be used is anticipated. ..AP&L can als'o be briefed on SASA results at any desircd intervals. It is also possible that occasional informal contacts by individual SASA project workers to interested personnel at AP&L would be use-ful; the extent of these informal contacts would be optional with AP&L.

6. Advantages for AP&L - One of the principal advantages is seen to be improved understanding of plant response. SASA will usual also indicatetype licensing howofmuch response conservstism is involved in the calculations. AP&L personnel will become familiar with the type of analysis used in SASA.

AP&L will be able to use the results t,o optimize procedures and training. Utility participation in,the program will be mutually beneficial, in that plant data used in ths 3ASA analysus will be accurate; this will ' obviate the possibility '

! of publication of overly conservative results based on mistaken l information. It will be advantageous to AP&L to be able to i review SASA reports before publication. -

7.

Advantages for SASA - Cooperation of AP&L is vitally necessary if the SASA analyses are to be truly "best estimates".

Without AP&L's cooperation SASA would probably be unduly con-servative. AP&L's cooperation would also ensure greater com-l l

Pleteness joint reviews andof accuracy, SASA. especially if AP&L consents to periodic l

,, Sincerely, 3

/

i i Walter B. Murfin Nuclear Facility' Analysis WBM:4414:ebl Division 4414 Copy to: '

/

USNRC (NRR) John Stolz

4414 G. B. Varnado I

4414 J. L. Darby ,

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