ML20038C268

Forwards Containment Isolation/Purge Valve Analysis for 18-Inch 2FII Butterfly Valve w/744A-1SR Bettis-Operator & 746A-2SR Bettis-Operator.

ML20038C268
Person / Time
Site:	Prairie Island
Issue date:	12/03/1981
From:	Mayer L NORTHERN STATES POWER CO.
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20038C269	List: ML20038C268 ML20038C270
References
NUDOCS 8112100342
Download: ML20038C268 (3)

Text

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8 47 Northern States Power Company 414 Nicollet Mall Minneapolis. Minnesota 55401 Telephone (612) 330-5500 December 3, 1981 Director Office of Nuclear Reactor Regulation Attn: Document Control Desk U S Nuclear Regulatory Commission Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Containment Purge and Vent System Information

Reference:

(a) Letter from L 0 Mayer, NSP, to Director, NRR, November 7,1980,

" Containment Purge and Vent System Isolation Logic (b) Letter from L 0 Mayer, NSP, to Director, NRR, May 6,1981,

" Containment Purge and Vent System Isolation Logic Modifications" Two containment purge systems are installed at Prairie Island for containment venting and purging:

1 - Containment purge system utilizing 36-inch supply and exhaust 2 - Containment inservice purge system utilizing 18-inch supply and exhaust System (1) is a high volume purge and ventilation system (33,000 cfm) used to ventilate containment following reactor shutdown to permit access for inspection and maintenance. Two containment isolation valves are provided on each supply and exhaust line which receive an automatic closure signal on receipt of a safety injection (SI) or high radiation signal. These valves are of the butterfly type designed to close in 3 seconds.

System (2) is a low volume (4,000 cfm) purge system which provides charcoal adsorption and particulate filtration of containment air prior to release.

This system is used to assist the internal cleanup system in permitting containment access when airborne radioactivity levels preclude entry. It may also be used as a low volume normal purge and vent system. Two contain-ment isolation valves are provided on each supply and exhaust line which receive an automatic closure signal on receipt of an SI or high radiation signal. These valves are of the butterfly type designed to close in 3 seconds.

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NORTHERN STATE 3 POWER COMPANY Director of NRR December 2, 1981 Page 2 Reference (a) contained our commitment to the Interim NRC Staff Position related to containment purge and vert valve operation. Specifically, we committed to keep isolation valves in both purge systems closed with the air supply isolated until:

- Containment ventilation logic modifications have been completed and found acceptable by the NRC Staff

- The evaluation of containment purge and vent valve operability has been completed and found acceptable by the NRC Staff Purge and vent operation, when resumed, would be on an "as low as achievable" basis pending completion of a long-term review of other issues.

Containment ventilation logic modifications committed to in Reference (a) and described in Reference (b) have been completed. Train power supply separation modifications noted in Reference (b) and applicable only to the 36-inch containment purge system are scheduled to begin within the next few weeks.

Evaluation of containment purge and vent valve operability has now been completed for both the 18-inch and 36-inch isolation valves by the valve vendor, the Henry Pratt Company. The results of this evaluation indicate that:

- The 18-inch valves are capable of withstanding combined seismic and LOCA-induced loads

- The 36-inch valves are not capable of withstanding LOCA-induced loads unless valve opening is restructed or an orifice plate is installed in each line A copy of the Pratt analysis of 18-inch valve operability is attached.

Following NRC Staf f review of this analysis and our logic changes, we will resume use of the inservice purge system during plant operation on an "as low as achievable" basis.

Based on the results of the Pratt analyses, we have no plans at this time to resume containment vent and purge operations with the 36-inch system.

The 36-inch valves will remain closed with operating air isolated when the associated reactor is above cold shutdown. A Technical Specification change will be proposed containing this requirement within 90 days of receipt of the NRC Staf f evaluation of our logic modifications and analysis of valve operability.

NORTHERN STATEO POWER COMPANY Director of NRR December 2, 1981 Page 3 We -ask that Staf f review of our May 6,1981 description of logic changes and the attached operability analysis begin soon to permit resolut.i>n of this issue. Please contact us if you have any questions related to any of-the information we have provided.

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L 0 Mayer, PE Manager of Nuclear Support Services LOM/DMM/bd cc: Director IE-III, USNRC NRR Project Manager, NRC Resident Inspector, NRC G Charnoff Attachment i

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