ML20041G154

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Forwards Mark III Containment Ventilation/Purge:Il Power Study of Containment Continuous Vent/Purge Issue as Applicable to Clinton Power Station.
ML20041G154
Person / Time
Site: Clinton Constellation icon.png
Issue date: 03/10/1982
From: Wuller G
ILLINOIS POWER CO.
To: John Miller
Office of Nuclear Reactor Regulation
Shared Package
ML20041G155 List:
References
U-0431, U-431, NUDOCS 8203190336
Download: ML20041G154 (2)


Text

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U-0431 ILL/N0/S POWER COMPANY ., p , 739_g2g93_$9y_t

" b 500 SOUTH 27TH STREET, DECATUR, ILLINOIS 62525 March 10, 1982 Mr. James R. Miller, Chief 6 D Standardization & Special Projects Br'anch E Rs,'N, 4 pb

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Division of Licensing #I Office of Nuclear Reactor Regulation g U. S. Nuclear Regulatory Commission G * / 'T Washington, D.C. 20555 -

Dear Mr. Miller:

Clinton Power Station Unit 1

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Docket No. 50-461 ar-Enclosed is a copy of the Illinois Power Company position paper regarding outstanding issue #10 of the Clinton Safety Evaluation Report (SER-Section 6.2.4.1) on " containment continuous purge." This paper was prepared in response to the NRC Staff's concerns in the CPS-SER regarding continuous purging of the CPS containment during normal operation of the plant.

This report reviews the concerns associated with opera-tion of CPS with the ventilation system isolated and concludes that operation in this mode will have the following effects adverse to safety:

1. Operation of the CPS with the ventilation system isolated will restrict access to the containment for inspection, repair and maintenance of vital instrumentation and equipment. This restricted access could result in plant operation with critical equipment in a degraded state unknown to plant operators.
2. Operation of the CPS with the ventilation system isolated will result in significantly higher airborne activity concentrations in the contain-ment. This will cause higher exposures to operating personnel.

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8203190336 820310 PDR ADOCK 05000461 A PDR

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n Mr. James R. Miller U-0431

3. Operation of the CPS with the ventilation system isolated will have adverse environmental effects.

This is the result of building up of airborne activity during the time the system is isolated, and releasing this inventory in a short period of time, resulting in an increased burden to the environment.

The report furthermore reviews all failures of these valves in operating plants since 1979 and compares the indicated failure mode to the CPS valve design. The result of this effort indicates that the CPS valve design is not susceptible to these indicated failure modes. Furthermore this review indicates that the CPS valve design is signifi-cantly improved over existing designs in the following respects:

1. Corrosion resistance - The CPS valve internals are stainless steel and subsequently not susceptible to corrosion as earlier valve designs.
2. Structural capability - The CPS valves are fabricated from stronger materials resulting in greater assurance against failures that have occurred in earlier designs.
3. Seating capability - The CPS valve design incorporates a teflon seal with a floating backing "o" ring. This design allows the sealing surface to mate positively with the disc upon closure and results in improved seating capability.

Finally we propose to demonstrate the capability of the CPS valve to function as designed through further analysis and through the conduct of an actual test. This test would subject the valve to post accident pressures and demonstrate i t ., capability to operate under these conditions.

In summary we request early staff review of this report and propose to meet with you, as required, such that this outstanding issue can be closed out in a supplement to the CPS-SER.

Sincerely,

/ q. . '/

G. E. Wuller Supervisor-Licensing Nuclear Station Engineering GEW/EWK/lt cc: Mr. J. H. Williams , NRC Clinton Project Manager Mr. H. H. Livermore, NRC Resident Inspector Mr. L. C. Ruth, NRC Containment Systems Branch Mr. W. R. Butler, NRC Chief, Containment Systems Branch

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