Davis-Besse update

["Fill, John (DHS-DDWEM)" <JFill@DHS.CA.GOV>]

April 5, 2002

PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PNO-III-02-006B

This preliminary notification constitutes EARLY notice of events of POSSIBLE

safety or public interest significance. The information is as initially

received without verification or evaluation, and is basically all that is

known by the Region III staff on this date.



Facility

Davis-Besse

FirstEnergy Nuclear Operating Co.

Oak Harbor OH

Docket: 50-346



Licensee Emergency Classification

Notification of Unusual Event

Alert

Site Area Emergency

General Emergency

x Not Applicable



SUBJECT: REACTOR VESSEL HEAD DEGRADATION (SECOND UPDATE)



DESCRIPTION:

The NRC's Augmented Inspection Team presented the preliminary findings of

its review of the reactor vessel head degradation at the Davis-Besse plant

in a meeting with the licensee on April 5, 2002, in Oak Harbor, Ohio. The

AIT began the inspection on March 12, 2002, after the utility reported that

significant corrosion damage had been found while repairs were being made to

a control rod drive nozzle in the reactor vessel head.



The team found that evidence of the corrosion damage was present at least as

early as 1998 and that the utility missed several opportunities to identify

the problem prior to the current refueling outage.



Beginning in 1999, the plant staff observed a gradual increase in the

frequency of filter changes required for the containment radiation monitor

filter from monthly to every other day. The filter changes were required

because of clogging by material identified as corrosion products from

reactor cooling system leakage. Boric acid and corrosion product deposits on

the containment air coolers also increased.



The utility also failed to properly implement the NRC-required boric acid

control program in that reactor vessel head boric acid deposits were not

properly removed and indications of reactor vessel head corrosion were not

recognized or evaluated. In the 2000 refueling outage significant deposits

of boric acid -- different in color and consistency previously associated

with reactor cooling system leaks -- were found on the reactor vessel head.



The utility is continuing its review of the root cause of the reactor vessel

head damage. The Augmented Inspection Team concurred with the utility's

preliminary evaluation that the reactor vessel wastage was caused by

corrosion associated with leakage of primary cooling water containing boric

acid due to cracks in the No. 2 and No. 3 control rod drive nozzles.

Additional issues remain to be addressed, however, in the utility's root

cause evaluation, including factors affecting the rate at which the cracks

and corrosion progressed, the role of deposits left on the reactor vessel

head, and a determination of the chemical process involved in the corrosion.

The utility's evaluation will be presented to the NRC and made publically

available when it is completed.



The State of Ohio will be notified. The information in this preliminary

notification has been reviewed by licensee management.



This information is current as of 9:00 a.m. (Eastern Time) on April 5, 2002.



CONTACTS:

Ron Gardner     John Jacobson

630/829-9751    630/829-9736





************************************************************************

You are currently subscribed to the Radsafe mailing list. To unsubscribe,

send an e-mail to Majordomo@list.vanderbilt.edu  Put the text "unsubscribe

radsafe" (no quote marks) in the body of the e-mail, with no subject line.

You can view the Radsafe archives at http://www.vanderbilt.edu/radsafe/