ML121000243

Request for Additional Information, Request for Change in Reactor Vessel Surveillance Capsule Removal Schedule

ML121000243
Person / Time
Site:	Fort Calhoun
Issue date:	04/09/2012
From:	Lynnea Wilkins Plant Licensing Branch IV
To:	Hansher B Omaha Public Power District
Wilkins, L E, NRR/DORL/LPL4, 415-1377
Shared Package
ML12000239	List: ML121000243
References
TAC ME8219
Download: ML121000243 (1)

Text

REQUEST FOR ADDITIONAL INFORMATION REACTOR VESSEL SURVEILLANCE CAPSULE WITHDRAWAL SCHEDULE REVISION OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION, UNIT 1 DOCKET NUMBERS 50-285 By letter dated February 6, 2012, Omaha Public Power District (OPPD), the licensee for Fort Calhoun Station (FCS) submitted a request for revision to the reactor vessel (RV) material surveillance capsule withdrawal schedule for FCS. The proposed changes were submitted pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix H,Section III.B.3, which requires that: (1) withdrawal schedules be submitted, as specified in 10 CFR 50.4, and (2) the proposed schedule must be approved by the Nuclear Regulatory Commission (NRC) prior to implementation.

The NRC staff has reviewed your submittal and has determined that additional information is needed for the staff to complete its evaluation.

1. ASTM E185-82 recommends that for a reactor vessel (RV) with a five-capsule withdrawal schedule, such as Fort Calhoun Station (FCS), the fourth capsule should be withdrawn at approximately 15 effective full power years (EFPY) or at a time when the accumulated neutron fluence of the capsule corresponds to the approximate end-of-life (EOL) fluence at the RV inner wall, whichever comes first. The proposed schedule for FCS in Reference 1 for Capsule W-275S, the fourth capsule for FCS in terms of fluence, calls for the capsule to be withdrawn in 2028 when it has received a fluence of 3.0x1019 n/cm2. The licensee also stated in Reference 1 that the projected 60-year (48 EFPY) peak RV fluence is 3.5x1019 neutrons-per-square centimeter (n/cm2). Therefore, the proposed withdrawal fluence of Capsule W-275S is approximately 86% of the EOL RV inner wall fluence.

Please provide a technical justification for withdrawing Capsule W-275S at a fluence that is significantly less than the peak projected RV inner wall fluence at EOL.

2. The proposed schedule calls for Capsule W-275S to be withdrawn at 47.2 EFPY, corresponding to the year 2028. Table 2 of Reference 1 provides no lead factor for this capsule (implying capsule fluence is identical to the peak RV inner wall fluence).

Reference 1 also indicates that Capsule W-275S was inserted at 13.6 EFPY. Therefore, the capsule will have been irradiated for 33.6 EFPY at withdrawal. The average fluence per EFPY of the peak RV inner wall location should be (3.5x1019 n/cm2 /48EFPY) = 7.29 x 1017 n/cm2/EFPY. Based on no lead factor, it would appear the fluence received by the capsule would be 33.6 EFPY x 7.29 x 1017 n/cm2/EFPY = 2.45x1019 n/cm2, which is significantly less than the proposed withdrawal fluence of 3.0x1019 n/cm2 . Further, this calculation uses the average fluence per EFPY. With a switch to a low-leakage core, fluence/EFPY would have been higher earlier in plant life. Also, since the projected EOL EFPY is 48 in 2033, the EFPY value of 47.2 for 2028 appears high unless the FCS RV will receive greater than 48 EFPY in 60 calendar years.

Please provide the details of the fluence projection for capsule W-275S.

ENCLOSURE