ML20154N459

Forwards Rev 0 to Mark I Wetwell to Drywell Differential Pressure Load & Vacuum Breaker Response for Vermont Yankee Generation Station, in Response to 860117 Request for Addl Info

ML20154N459
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	03/10/1986
From:	Capstick R VERMONT YANKEE NUCLEAR POWER CORP.
To:	Rooney V Office of Nuclear Reactor Regulation
Shared Package
ML20154N464	List: ML20154N459 ML20154N481
References
FVY-86-19, GL-83-08, GL-83-8, GL-83-89, NUDOCS 8603170328
Download: ML20154N459 (2)

Text

f 5 kERMONT YANKEE NUCLEAR POWER CORPORATION RD 5, Box 169, Ferry Road, Brattleboro, VT 05301 FVY 86-19

. ,,go y ENGINEERING OFFICE 1671 WonCESTER ROAD March 10, 1986 FRAWGHAM. MASSACHUSETTS 01701

• T EL E PHONE 617-872-4100 United States Nuclear Regulatory Commission Washington, DC 20555 Attention: Office of Nuclear Reactor Regulation Mr. Vernon L _ooney, Project Manager BWR Project .,irectorate No. 2 Division of BWR Licensing

References:

(a) License L3. DPR-28 (Docket No. 50-271)

(b) Letter, USNRC to VYNPC, NYY 83-23, Ceneric Letter 83-08, dated February 2, 1983 (c) Letter, VYNPC to UONRC, FVY 83-36, dated May 11, 1983 (d) Letter, USNRC to VYNPC, NVY 86-10, dated January 17, 1986

Subject:

Modifications of Vacuum Breakers on Mark 1 Containments (Generic Let.t.ec 83-08)

Dear Sir:

By letter dated January 17, 1983 (Reference (d)), you requested additional information related to the Vermont Yankee torus-to-drywell vacuum breaker modification in order to complete your review initiated under Ceneric Letter 83-08 (Reference (b)). In response to your request, attached please find the information requested in the enclosure to your letter.

We trust this information is satisfactory; however, should you have any quertions or require additional information, please contact this office.

Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION J

R. W. Capstick Licensing Engineer RWC/no Attachment Me 4cb y M (J u t e A M S r i B60317032g gso3go DR ADOCK O #d/

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Response to NRC Request for Additional Information Related to the Modification of Vacuum Breakers on Mark I containment at Vermont Yankee Nuclear Power Station.

Question 1: Is the chugging source rate used in the Vermont Yankee evaluation the same as the one developed in CDI Report

(#84-3)? If not the same, provide the chugging source rate with the supporting justification.

Answer: Yes. The methodology followed in CDI Report Number 84-3 (Reference 1) is identical to the methodology used in the Vermont Yankee evaluation (Reference 2 - attached) and detailed in response to NRC Question Number 5 in Reference 3.  !

Question 2: Did the Vermont Yankee calculation apply the 1.07 load factor to account for the uncertainty in calculating the underpressure (Section IV of the staff's generic evaluation).

Answer: A load factor, used to assure conservative prediction of the '

underpressure and detailed in response to NRC Question 2 in Reference 3, was. applied to the Vermont Yankee evaluation (Reference 2). In fact, the load factor used in the plant unique evaluation was 1.06 and yields a conservative prediction of the underpressure.

Question 3: Have the Vermont Yankee calculations used the drywell model Which results in the most conservative prediction (Section V of

-the generie avaluatinn)?

Answer: Yes. Drywell modeling was examined in response to NRC Question 6 in Reference 3. For the Vermont Yankee evaluation (Reference 2), the capacitance model results in a more conservative forcing function, and was therefore used.

REFREENCES

1. "Kark I Wetwell to Drywell Vacuum Breaker Load Methodology, Revision 0,"

Continuum Dynamics, Inc., Report Number 84-3, February 1984.

2. " Nark I Wetwell to Drywell Differential Pressure Load and Vacuum Breaker Response for the Vermont Yankee Generation Station, Revision 0,"

Continuum Dynamics, Inc. , Technical Note Number 84-24, January 1985

3. " Response to NRC Request for Additional Information on Mark I Containment Program Wetwell to Drywell Vacuum Breaker Load Methodology, Revision 0,"

Continuum Dynamics, Inc. Technical Note Number 84-11, October 1984

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