Event Notification Report for June 10, 2001

POSSIBLE SPENT FUEL STORAGE CAST DEFECT AND POTENTIAL SIGNIFICANT REDUCTION IN EFFECTIVENESS OF THE SPENT FUEL STORAGE CASK CONFINEMENT SYSTEM DUE TO FAILURE OF MULTI-PURPOSE CANISTER (MPC) VENT AND DRAIN CAPS TO FULLY CLOSE (4-HOUR REPORT)

As part of the dry storage project, the licensee has loaded one MPC-68. (This MPC holds 68 fuel bundles.) Subsequent to system vacuum drying and helium backfilling, the vent and drain caps failed to fully close (at 0715). These caps are currently about half closed, and they appear to be stuck in that position.

At this time, the licensee is not aware of the loss of any helium. Licensee personnel have snooped for helium in the area and near the fittings. Licensee personnel are also currently in the process of installing pressure gauges to verify that the proper amount of helium remains in the MPC. The licensee plans to place a helium purge on the system if it is determined that helium is being lost. The licensee also notified the cask supplier (Holtec International). The supplier informed the licensee that the presents of helium will keep the system closed.

The technical specifications that apply to dry storage state that the MPC shall be dry and helium filled, and a helium backfill density limit is also specified. The licensee stated that this technical specification density requirement was met before the attempt to close the vent and drain caps. At this time, the licensee believes that this limit is still being met. However, the licensee is not positive that this limit is being met with the vent and drain caps in the current position. Therefore, the applicable technical specification limiting condition for operation (LCO) was entered. This LCO requires the licensee to perform an engineering evaluation to determine the impact of helium differential within 72 hours and to develop and initiate corrective actions necessary to return the MPC to an analyzed condition within 14 days.

In addition, the applicable technical specifications also specify an MPC helium leak rate limit. The LCO for this specification was also entered. It requires the licensee to perform an engineering evaluation to determine the impact of increased helium leak rate on heat removal capability and offsite dose within 24 hours and to develop and initiate corrective actions necessary to return the MPC to an analyzed condition within 7 days. (The supplier is currently performing an engineering evaluation for the licensee, and the results are expected to be available later today.)

The licensee is making this notification as a 4-hour report in accordance with 10 CFR 72.216(a)(1) and (2) for any instance of a defect in any spent fuel storage cask structure, system, or component which is important to safety and for a significant reduction in the effectiveness of any spent fuel storage cask confinement system during use of the storage cask under a general license issued under 10 CFR 72.210.

HOO NOTE: In accordance with 65 FR 63788 on 10/25/00, the reporting requirements of 10 CFR 72.216 were revised (effective 01/23/01) to require that licensees make initial and written reports in accordance with 10 CFR 72.74 and 72.75. Therefore, more appropriate reporting requirements for this 4-hour report are believed to be 10 CFR 72.75(b)(2) and (3).

The licensee plans to notify the NRC resident inspector.

* * * UPDATE ON 6/20/01 @ 1625 BY GORLEY TO GOULD * * * RETRACTION

Further review of this event it has determined that there was no defect in the multi-purpose canister(MPC) vent and drain caps. The failure of the vent and drain caps to fully close was due to the procedural process used(no lubrication being applied and no torque requirement was used) and a fault tolerant design basis that was less than adequate(thread design and hole locations in the cap). Therefore, the licensee is retracting this event.

NRC Resident Inspector was notified.

Reg 2 RDO(Cahill) was informed.