ML20198J771

Documents 981214 Discussion with NRC Staff Re Deviation from Emergency Procedure Guidelines

ML20198J771
Person / Time
Site:	Monticello
Issue date:	12/14/1998
From:	Hammer M NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9812300259
Download: ML20198J771 (3)

Text

Northem States Power Company Monticello Nuclear Generating Plant 2807 West Hwy 75 Monticello, Minnesota 55362 9637 December 14,1998 US Nuclear Regulatory Commission NUREG-0737 Attn: Document Control Desk Supplement 1 Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PLAN Docket No. 50-263 License No. DPR-21 Documentation of Discussion Regarding Deviation from Emergency Procedure Guidelines

References:

1. Letter from Carl F. Lyon, USNRC, to Roger O. Anderson, NSP, "Monticello Nuclear Generating Plant - Request for Deviation form Emergency Procedure CJidelines, Revision 4, NEDO-31331, March 1987 (TAC No. MA0168)", December 10,1998

2. Letter from Michael F. Hammer, NSP, to USNRC Document Control Desk,

" Supplement 1 to NSP Response to NRC Request for Additional Information Regarding November 18,1997 Request for Deviation from Emergency Procedure Guidelines," November 10,1998.

In a letter dated November 10,1998 (Reference 2) NSP amended the plant conditions required before primary containment flooding is initiated. This letter states, "If there is not at least one core spray pump injecting water into the RPV [ Reactor Pressure Vessel] and one additional ECCS pump available for RPV injection, Monticello will flood primary containment if RPV water level can not be restored and maintained above the minimum steam cooling RPV waterlevel" In a letter dated December 10,1998 (Reference 1), the NRC responded to the NSP request for deviation from Revision 4 of the BWR Owners' Group Emergency Procedure Guidelines ( EPGs.) In their response, the NRC states [ emphasis added): r

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"Qontainment flooding actions will not be initiated provided the RPV level is maintained at 2/3 [ core height] with two or more ECCS pumps, including at least one core spray pump, injecting into the vessel. If fewer than two ECCS pumps, or no core spray pumps, are operating, containment flooding will be initiated at a higher RPV level, i.e., at minimum steam cooling reactor pressure vessel water level (MSCRWL)."

"By letter dated November 10,1998, the licensee committed to revise its deviation request by modifying the procedural step used to decide when to flood containment to specify that one of the two ECCS pumps available must be a core spray pump."

"As such, containment flooding will not be initiated provided two or more ECCS pumps, including at least one core spray pump, are running. If fewer than two ECCS pumps are running, or if no core spray pumps are running, operators will start to flood the containment if the level cannot be maintained above the MSCRWL."

"If fewer than two ECCS pumps, or no core spray pumps, are available, either initially or as a result of subsequent equipment failures, operators will flood the primary containment if the reactor water level cannot be restored and maintained above the MSCRWL."

"Therefore, the licensee may deviate from the EPGs, Revision 4, and use 2/3 core height for establishing the basis for long-term heat removal with at least one core spray pump running."

In phone conversations with NRC Staff, NSP stated that "available" does not require the system to be currently injecting water into the RPV or that the pump be running. Available means that, to the best of the operator's knowledge, the system will operate correctly if needed. For example, an RHR pump that has been shut-down to allow starting an RHR Service Water pump or an RHR pump that has been re-aligned for primary containment heat removal would both be considered available. In both situations, to the best of the operator's knowledge, RHR could be started and/or re-aligned to inject into the RPV.

Therefore, an ECCS pump that is not running, operating, or injecting into the RPV, might still be available.

In addition, it is NSP's understanding that at least one core spray pump must be injecting into the RPV.

To alleviate the potential for confusion in the future, NSP is providing it's understanding of when containment flooding actions are required, and when containment flooding actions are not required.

a. Containment flooding actions are not required provided RPV water level can be restored and maintained at or above the minimum steam cooling RPV water level (MSCRWL), regardless of the number of ECCS pumps available for RPV injection or the number of core spray pumps injecting into the RPV.

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, b. Qontainment flooding actions are not required provided RPV water level can be restored and maintained at or above 2/3 core height, if at least one core spray pump is injecting into the RPV, and at least one additional ECCS pump is available for RPV injection.

c. Containment flooding will be initiated if RPV water level can be restored and maintained at 2/3 core height but there is either no core spray pump injecting into the RPV, or with one core spray pump injecting into the RPV, there is not a second ECCS pump available for RPV injection.

d. Containment flooding will be initiated if RPV water level cannot be restored and maintained at 2/3 core height, regardless of the number of ECCS pumps available for RPV injection or the number of core spray pumps injecting into the RPV.

The above information was discussed with the NRC Staff on December 14,1998. The Staff agreed with NSP's understanding of the flooding requirements and agreed to acknowledge the discussion on the Monticello docket.

This submittal contains no new NRC commitments, nor does it modify any prior commitments. Please contact Marcus H. Voth, Project Manager of Licensing, at 612-271-5116 if you require additional information related to this request.

t4 W Michael F. Hammer Plant Manager Monticello Nuclear Generating Plant c: Regional Administrator- 111, NRC NRR Project Manager, NRC Sr. Resident inspector, NRC State of Minnesota, Attn: Kris Sanda J Silberg J \ LICENSE \N R.C Misc CorrespiEOP 12-14-98 doc

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