ML021550388

Master Curve Submittal, NRC Staff Observations

ML021550388
Person / Time
Site:	Beaver Valley
Issue date:	05/17/2002
From:	NRC/RGN-II
To:
References
TAC MB3902
Download: ML021550388 (4)

Text

Beaver Valley Unit 1 Master Curve Submittal i

NRC Staff Observations

• Therefore, based on these observations, the NRC staff requested that FENOC reevaluate their submittal and address, as necessary:

(1) What data should be used to establish RTTO(U) and the baseline data for measuring shifts in To (i.e., ARTTO) due to irradiation for BVPS-1 limiting plate B6903-1 ?

(2) Given the answer to (1), what effect does this have on their characterization of the margin term to be applied in the calculation of ART?

(3) Given the answer to (1), what effect does this have on their characterization of the bias term to be applied in the calculation of ART?

Beaver Valley Unit 1 Master Curve Submittal NRC Staff Observations

• The staff reviewed FENOC's January 25, 2002, submittal and concluded that the general methodology employed by the licensee was consistent with the methodology approved for Kewaunee in the staff's May 1, 2001, safety evaluation.

RTTO(u) + ARTTO + Margin Term + Bias Term = ART

• However, the staff identified significant issues related to FENOC's use of fracture toughness data available from the testing of unirradiated specimens from BVPS-1 limiting plate B6903-1 (plate heat B6317-1).

• The issues raised by the staff may affect the determination of specific values for RTTO(U), ARTTO, the margin term, and the bias term used to calculate ART values for BVPS-1 limiting plate B6903-1.

Enclosure 2

Beaver Valley Unit 1 Master Curve Submittal NRC Staff Observations

° FENOC chose to determine their RTTO(u) value (and their baseline for measuring shifts in To due to irradiation) based using only the data from the unirradiated /2 T-CT specimens.

a

• FENOC claimed that this was "conservative" since it would provide maximum value for RTTO(u).

also claimed that since they were using this "conservative"

• FENOC initial approach to determine RTTO(U) they did not need to account for property variability when establishing the margin term used in their calculation of ART.

Beaver Valley Unit 1 Master Curve Submittal NRC Staff Observations

• The NRC staff disagrees with FENOC's assertion that the use of only the data from the testing of the unirradiated /2 T-CT specimens is "conservative

• While use of the unirradiated /2 T-CT specimen data alone does give the "most conservative" value for RTTo(U), it's use as the baseline for establishing shifts in To due to irradiation results in a minimum (least conservative) value for ARTTO.

• The NRC staff concluded that, when resultant ART values are considered, the use of the unirradiated /2 T-CT specimen data alone results in ART values which are the smallest (least conservative) values which could be determined from the available unirradiated specimen data.