United States Nuclear Regulatory Commission - Protecting People and the Environment

LICENSEE: DUQUESNE LIGHT CO.
SITE: BEAVER VALLEY 1 EN NUMBER: 35359
DOCKET: EVENT DATE: 02-09-99
RX TYPE: PWR EVENT TIME: 18:20
VENDORS: W-3-LP NOTIFY DATE: 02-09-99
EMERGENCY CLASS: N/A REGION:1 STATE: PA TIME: 18:37
OPS OFFICER: DICK JOLLIFFE
10 CFR SECTION: AOUT OUTSIDE DESIGN BASIS
CCCC UNSPECIFIED PARAGRAPH
UNIT SCRAM CODE RX CRIT INIT PWR INITIAL MODE CURR PWR CURRENT MODE
1 N Y 98 Power Operation 98 Power Operation

- Non-conservative dose calculation methodology is a condition outside the design basis of Unit 1 -

As a result of LER 2-97-008 corrective actions, non-conservative inputs have been identified that is associated with the Beaver Valley Power Station (BVPS) methodology in calculating radiation doses for accidents which must analyze for a concurrent iodine spike as part of their radiological analyses. The identified non-conservative factors during past operation, could have resulted in the calculated control room personnel dose values exceeding 10CFR50 Appendix A, Criterion 19 thyroid limits. Since BVPS no longer has reasonable assurance that acceptance criteria for control room personnel dose limits per Criterion 19 would have been met during past operation, the identified non-conservative dose calculation methodology was a condition which was outside the design basis of the plant per 10CFR50.72(b)(1)(ii). This condition is also being evaluated for the criteria in 10CFR Part 21.

For BVPS, the only Design Basis Accidents (DBAs) which involve a concurrent iodine spike analysis are Main Steam Line Break, Small Line Breaks (e.g., letdown line break outside containment), and Steam Generator Tube Rupture. The most significant of the non-conservative issues is purification (i.e., letdown) flow, which was given as 60 gpm. This is the lower limit of the plant design flow rate range of 60-120 gpm. Analysis using 60 gpm results in a significant underestimation of the concurrent iodine spike source term as compared to operation at the upper design limit of 120 gpm. Of lesser importance were underestimated demineralizer decontamination factor, overestimated reactor coolant system (RCS) mass and inadequate use of RCS leakage as an iodine removal mechanism. It has been determined that correcting the above identified non-conservative factor would raise calculated control room personnel dose values of those events analyzed for concurrent iodine spikes by at least 40% and potentially as high as 140%.

Until the BVPS dose calculations can be formally revised to address the identified non-conservative factors, the station has placed administrative controls on the extent of steady state letdown flow to ensure that plant operation remains within past analyzed limits. The influence of the other identified non-conservative factors have also been reviewed and determined not to be an operability concern at this time.

The licensee plans to notify the NRC Resident Inspector.

* * * UPDATE AT 1110 ON 02/19/99 FROM JIM DAUGHERTY TO JOLLIFFE ** *

The licensee is evaluating the above described issue and at 1600 on 02/18/99, they determined that it also meets the reportability criteria pursuant to l0CFR Part 21 specifically for Beaver Valley Unit 1. The generic issue (Westinghouse issue) is applicable to both Beaver Valley Units I and 2. A written report will be supplied pursuant to 10CFR Part 21 and I0CFR50.73 in a supplement to LER 2-97-008.

Until the Beaver Valley dose calculations can be formally revised to address the identified non-conservative factors, BVPS has implemented administrative controls to ensure that plant operation remains within past analyzed limits.

The licensee is continuing to evaluate this issue.

The licensee plans to notify the NRC Resident Inspector.

The NRC Operations Officer notified the R1DO Jim Trapp and NRR

Vern Hodge.


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