Event Notification Report for July 20, 1999

OUTSIDE DESIGN BASES - CONDITION OUTSIDE OF APPENDIX R REQUIREMENTS

During an Appendix R baseline project review, a condition has been found that is considered to be outside the Appendix R Safe Shutdown design basis. During a postulated fire on the 26 foot level of the primary auxiliary building, fire related cable damage could lead to spurious opening of a single power operated relief valve (PORV) along with the inability to close its associated block valve. Presently, plant procedures direct operators to isolate air to the containment and vent the instrument air header locally in order to shut the PORV. The local valve operations that are required, however, are in the same area as the postulated fire. Failure to get the PORVs closed in adequate time would place the plant outside of the performance goals of 10CFR50, Appendix R, Paragraph III.L.

The licensee notified the NRC resident inspector.

EMERGENCY SIRENS

All Comanche Peak Emergency Warning Sirens are inoperable. The cause of the failure is unknown, but personnel are working to effect repairs. Hood and Somervell counties have been notified. The licensee notified the NRC Resident Inspector.

NRC BULLETIN 91-01, 24 HOUR REPORT -

At 1430 CDT on 07/20/99, the Plant Shift Superintendent was notified that during calibration of C-335 air plant moisture meter, air was added to C-335 Unit 3 Cell 7 without independently verifying that the enrichment was less than 1.0 weight percent U-235, in violation of NCSA GEN 10-01. Independent assay verification is required if the air moisture content exceeds 1300 ppm or if the moisture meter is inoperable. With the moisture meter out of service, dry air was added to C-335 Unit 3 Cell 7, which had an assay of 1.01 weight percent U-235. The cell was thought to be less than 1.0 weight percent U-235. However, a previously completed independent assay verification was not referenced. Moisture content was less than 1300 ppm prior to removing the meter from service. After placing the moisture meter back in service, it was determined that the dry air never exceeded 1300 ppm while the meter was out of service. During the period of time that the meter was out of service, the air equipment was operated in a steady state condition with no manipulations performed and no abnormal or unusual process conditions observed.

SAFETY SIGNIFICANCE OF EVENT:
Double contingency was not maintained since the independent verification of assay was not performed. Independent verification of assay is required to preclude exposure of an unsafe mass deposit with the enrichment greater than 1.0 weight percent U-235 to wet air. Removal of the moisture meter requires that the system not be pressured with air or independent verification of assay less than 1.0 weight percent U-235 prior to applying air. However, a criticality was not possible because the moisture content did not exceed 1300 ppm.

POTENTIAL CRITICALITY PATHWAYS INVOLVED (BRIEF SCENARIO OF HOW CRITICALITY COULD OCCUR):
In order for a criticality to be possible, a deposit of unsafe mass would have to be present. This deposit would then have to be exposed to sufficient air with a moisture content exceeding 1300 ppm to moderate the deposit.

CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY, CONCENTRATION, ETC.):
Two controls on assay.

ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL (INCLUDE PROCESS LIMIT AND % WORST CASE CRITICAL MASS):
Enrichment of 1.01 weight percent U-235 as determined by Independent Assay Verification.

NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES:
Double contingency for this scenario is established by implementing two controls of assay.

The first leg of the double contingency is based on verification that the assay of the equipment that the air is being applied to is less than 1.0 weight percent U-235. It was believed the cell assay was less than 1.0 weight percent U-235. However, verification of assay was not performed. It was later determined that the cell assay exceeded 1.0 weight percent U-235. Therefore, the control was violated.

The second leg of double contingency is based on the independent verification that the assay of the equipment that the air is being applied to is less than 1.0 weight percent U-235. However, the Independent verification of assay was not performed. Therefore, this control was violated.

Since double contingency was based on two controls on assay, a loss of one or both controls would result in a loss of double contingency. In this instance, both controls were violated and double contingency was not maintained.

CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMENTED:
The moisture meter was returned to service following calibration.

This event is being categorized as a 24 hour event in accordance with Safely Analysis Report Table 6.9-1, Criteria A.4.a and NRC Bulletin 91-01, Supplement 1.

The NRC Senior Resident Inspector has been notified of this event.

PGDP Problem Report No. ATR-99-4250, PGDP Event Report No. PAD-1999-053. Responsible Division: Operations.

STOLEN TROXLER MOISTURE/DENSITY GAUGE

A Troxler Model 3430 Moisture/Density Gauge (S/N 27891) was stolen from the back of a pickup truck in Lima, Ohio. The licensee reported that both the gauge and its transport carrier were missing from the truck. The local police were contacted and responded to the scene.