ML20116N719

Responds to Request for Addl Info Re Item 4 of 840711 License Amend Request for Replacement of 2,000 Ppm Boron Concentration Limit w/10% Delta K/K Limit.Boron Concentration Placed in Procedures to Ensure That Limit Met

ML20116N719
Person / Time
Site:	Prairie Island
Issue date:	04/26/1985
From:	Musolf D NORTHERN STATES POWER CO.
To:	Office of Nuclear Reactor Regulation
References
TAC-55445, TAC-55446, NUDOCS 8505070323
Download: ML20116N719 (1)

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Northern States Power Company

• bliet Malt Minneapohs. Minnesota 55401 Telephone (612) 330-5500 April 26,1985 Director Office of Nuclear Reactor Regulation 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 Supplemental Information Concerning License Amendment Amendment Request dated July 11, 1984 Item No. 4 of the July 11, 1984 License Amendment Request, concerned the replacement of the 2000 ppm Boron concentration limit with a 10% deltaK/K limit. This letter responds to an NRC Staff request for additional information concerning the' suggested 10% deltaK/K limit.

Prior to each refueling, our Nuclear Analysis Department prepares a Startup and Operations Report. Contained in this report is the boron concentration required to maintain the reactor shutdown by 10% deltaK/K with the "new" core loaded with all rods in, pressure O psig and the most limiting temper-ature between 68 and 140 degrees F. The boron concentration is calculated by our nodal code DP5, described in NADNSP 8101P Revision 1 (submitted to the NRC on 12/13/82). A bias, determined from hot zero power benchmarks, '

and a bounding reliability factor are added to the baron concentration calcul-ated by DP5. The bounding reliability factor is 100 ppm (approximately 1%

deltaK/K). The standard deviation for best estimate hot zero power calcul-ations is 27 ppm, suggesting that the 100 ppm is conservative. The last three boron concentrationn Nuclear Analysis Department reported to the plant are: 2154 ppm (Unit 1 Cycle 10), 2090 ppm (Unit 2 Cycle 9) and 2150 ppm (Unit 1 Cycle 9). The plant nuclear engineer places this boron concen-tration into plant procedures to ensure that this limit is met.

Please call if you have further questions.

OO Mm David Musolf Manager - Nuclear Supp rt Services DMM/TMP/tp c: Regional Administrator-III, NRC fO of NRR Project Manager, NRC Resident Inspector, NRC *i j MPCA Attn: F W Ferman G Charnoff 8505070323 850426 PDR P

ADOCK 05000282 PDR 4