ML062160328

Request for Additional Information Related to Evaluation of Event Notification 42129

ML062160328
Person / Time
Site:	Point Beach
Issue date:	08/29/2006
From:	Lyon C Plant Licensing Branch III-2
To:	Plant Licensing Branch III-2
F. Lyon LPLE X2296
References
TAC MC9035, TAC MC9036
Download: ML062160328 (3)

Text

August 29, 2006 MEMORANDUM TO: File FROM: Carl F. Lyon, Project Manager, Section 1 /RA/

Project Directorate III Division of Operating Reactor Licensing

SUBJECT:

POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION RELATED TO EVALUATION OF EVENT NOTIFICATION 42129 (TAC NOS. MC9035 AND MC9036)

This memorandum documents the telephone conference on March 9, 2006, between J. Lehning and F. Lyon (NRC) and T. Kendall (NMC), to discuss questions from the NRC staffs review of Nuclear Management Company, LLCs (NMC's) letter dated February 16, 2006 regarding Event Notification 42129. The NRC staff requested clarification of the basis for the scaling factor approach used to: (1) reduce the size of the zone of transport (ZOT) around the sump screens, based upon the reduced sump flow rate and assumed increased pool height, and (2) reduce the containment pool flow velocities in the vicinity of the sump screens, based upon the reduced sump flow rate. The scaling calculations were performed in Engineering Evaluation 2005-0024, which was provided in Enclosure 3 to NMCs February 16, 2006, letter.

NMC indicated that the scaling approach for the ZOT was based upon the nodal network calculation used in the current licensing basis for computing containment pool velocities. The NRC staff noted that the scaling approach did not address the geometric convergence of flow near the sump screens or uncertainties associated with the perturbations in nodal channel flow resistance that would result from the perturbation in sump flow rate. NMC responded that no degraded coatings are within 7 feet of the sump screens and further clarified that (1) coating washdown along the liner plate was not predicted to occur and (2) even if coating washdown occurred, these coatings would enter the containment pool over 7 feet away from the sump screens.

The licensee indicated that the scaling approach for the containment pool flow velocity was also based upon the nodal network calculation used in the current licensing basis. The NRC staff noted that this approach did not account for the geometric convergence of the containment pool flow as it approaches the sump screens. The NRC staff also noted that the reduced sump flow rate would induce perturbations in the nodal channel resistance that could reduce the accuracy of NMCs simplified scaling approach. NMC recognized these concerns, but concluded that they would not have a significant effect on the overall debris transport calculation results. NMC stated that its conclusion was based upon engineering judgment.

Docket Nos. 50-266 and 50-301

August 29, 2006 MEMORANDUM TO: File FROM: Carl F. Lyon, Project Manager, Section 1 /RA/

Project Directorate III Division of Operating Reactor Licensing

SUBJECT:

POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION RELATED TO EVALUATION OF EVENT NOTIFICATION 42129 (TAC NOS. MC9035 AND MC9036)

This memorandum documents the telephone conference on March 9, 2006, between J. Lehning and F. Lyon (NRC) and T. Kendall (NMC), to discuss questions from the NRC staffs review of Nuclear Management Company, LLCs (NMC's) letter dated February 16, 2006 regarding Event Notification 42129. The NRC staff requested clarification of the basis for the scaling factor approach used to: (1) reduce the size of the zone of transport (ZOT) around the sump screens, based upon the reduced sump flow rate and assumed increased pool height, and (2) reduce the containment pool flow velocities in the vicinity of the sump screens, based upon the reduced sump flow rate. The scaling calculations were performed in Engineering Evaluation 2005-0024, which was provided in Enclosure 3 to NMCs February 16, 2006, letter.

NMC indicated that the scaling approach for the ZOT was based upon the nodal network calculation used in the current licensing basis for computing containment pool velocities. The NRC staff noted that the scaling approach did not address the geometric convergence of flow near the sump screens or uncertainties associated with the perturbations in nodal channel flow resistance that would result from the perturbation in sump flow rate. NMC responded that no degraded coatings are within 7 feet of the sump screens and further clarified that (1) coating washdown along the liner plate was not predicted to occur and (2) even if coating washdown occurred, these coatings would enter the containment pool over 7 feet away from the sump screens.

The licensee indicated that the scaling approach for the containment pool flow velocity was also based upon the nodal network calculation used in the current licensing basis. The NRC staff noted that this approach did not account for the geometric convergence of the containment pool flow as it approaches the sump screens. The NRC staff also noted that the reduced sump flow rate would induce perturbations in the nodal channel resistance that could reduce the accuracy of NMCs simplified scaling approach. NMC recognized these concerns, but concluded that they would not have a significant effect on the overall debris transport calculation results. NMC stated that its conclusion was based upon engineering judgment.

Docket Nos. 50-266 and 50-301 DISTRIBUTION PUBLIC LPL3-1 RF RidsNrrLADClarke RidsNrrPMFLyon JLehning RidsNrrDorlLpl3-1 ADAMS ACCESSION NO. ML062160328 OFFICE LPL3-1/PM LPL3-1/LA LPL3-1/BC(A)

NAME FLyon:ca DClarke MMurphy DATE 8/29/06 8/23/06 8/29/06 OFFICIAL RECORD COPY