ML042380310

Background on RCP Seal Cooling for North Anna

ML042380310
Person / Time
Site:	North Anna
Issue date:	08/10/2004
From:	- No Known Affiliation
To:	Office of Nuclear Reactor Regulation
References
FOIA/PA-2004-0277
Download: ML042380310 (1)

Text

BACKGROUND:

Adequate RCP seal cooling can be achieved by maintaining continuous RCP seal injection or maintaining continuous CCW cooling to the RCP thermal barrier heat exchangers. During normal plant operation, both systems would usually be operating. North Anna's strategy for achieving a safe shutdown of the reactor during a fire stated that the CCW system was only required.to reach and maintain cold shutdown.

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(UPS ca e 1) A ed i SG N. Iehfico ainjgth~ernal f'rjritheiaLt angeaCmooii Recognizing the above issue, North Anna's SSA instead relied upon supplying continuous, uninterrupted ROP seal injection flow to assure adequate seal package cooling. The Unit 1 charging system, through an existing cross-connect, is utilized in the licensee's SSA and procedures to provide charging flow and seal Injectiorl i the Unit 2 charging system were rendered inoperable.

However the team determined that for certain fire scenarios in the Unit 2 Emergency Switchgear Room, ROP seal injection will be interrupted for a significant period of time (30 minutes). The fire contingency action procedure for fire inthis area, 2-FCA-2, directs the operator to initially isolate the RCP seal injection by opening breakers in the Unit 2 Cable Vault and Tunnel (CVT).

Consequently, a finding was identified in that for a significant fire in the Unit 2 Emergency Switchgear Room, the 002 gaseous fire protection system actuation devices and controls located inthe roam could inadvertently actuate to discharge gaseous g02 into the Unit 2 CVT area due a fire-induced electrical hot short circuit condition. This inadvertent release could inhibit station operators assigned to perform the isolation, thus increasing the seal injection interruption duration which could have significant impact on the ROP seal integrity. The fire contingency action procedure does not identify the availability of nor instructions to don self-contained breathing apparatuses.

Industry issued guidance, (Westinghouse Emergency Response Guideline (ERG) Direct Work Request No. DW-94-01 1, dated December 12, 1996),

determined that reestablishing seal injection or restoring CiW to the thermal barrier heat exchangers would not be appropriate if all seal coaling had been lost long enough that the maximum Ri P seal parametersidentified in the RUP Vendor Manual were exceeded. Per this guidance, this was to prevent unintended consequences that could result in additional pump damage or failure of plant safety systems specifically CtWh.

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