Event Notification Report for July 24, 2001

AGREEMENT STATE REPORT INVOLVING MISSING SR-90 SOURCES

"Event description: The licensee called the Division to report the loss of 997 mCi of Sr-90 sealed sources. The licensee's records indicate there were 14 individual sources received as brokered material from Stan A. Hauber Consultants, Inc., New Lenox. IL. These sources were received at the facility on June 26, 2000. Physical inventories have been performed and the sources have not been located. It is unknown whether the sources were encapsulated and sent for burial at a licensed disposal facility. This event is reportable under SRPAR 1200-2-5-.140 (1)(a).1.(i)."

TN Event Report ID No.: TN-01-137

24 - HOUR 91-01 BULLETIN - LOSS OF ONE CONTROL OF THE DOUBLE CONTINGENCY PRINCIPLE

On 7-24-01 at 1230 hours, a process operator in the X-330 Building discovered a NCSA-0330_004.A05 noncompliance with cell 29-4-6. Cell 29-4-6 is a shutdown cell at a UF6 negative and was buffered above 14 psia. Over time the pressure decrease to 13.96 psia. This violated NCSA-0330_004.A05 requirement #8 resulting in a loss of one control (moderation) of the double contingency principle. Mass (second control) was maintained throughout the event.

NCSA-0330_004.A05 requirement #8 states in part, "Within 8 hours after cascade equipment shutdown (motor turned off) and with the system at a UF6 negative, the system shall be pressurized with plant air or N2 buffer at > 14 psia, unless the equipment is undergoing maintenance, pre and post maintenance troubleshooting, being evacuated or treated."

Buffer pressure was increased to greater than 14 psia at 1300 hours. Moderation control was re-established for cell 29-4-6.

The safety significance of this event is low. There is no deposit in this cell. The worst case would be contamination on process surfaces exposed to process gas prior to shutdown and buffering.

This event is reportable per NRC BL 91-01 as a loss of one control of the double contingency principle.

SAFETY SIGNIFICANCE OF EVENTS:

The safety significance of this event is low. There is no deposit in the cell (thus is less than a safe mass for an H/U=4 and the cell is isolated from the cascade. The mass in the cell is controlled by virtue of the fact that the shutdown cell is isolated from the cascade which is also shutdown. If the unbuffered condition were permitted to continue for a long period of time, the H/U could eventually reach a maximum of 4. However, since any material in the cell is less than the safe mass H/U ratio, a criticality would not occur even if the H/U reached the maximum through the loss of a buffer.

POTENTIAL CRITICALITY PATHWAYS INVOLVED (BRIEF SCENARIO(S) OF HOW CRITICALITY COULD OCCUR):

The cell would need to be unisolated and UF6 introduced to create a deposit. That deposit would then have to become sufficiently moderated in order for a criticality to occur.

CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY, CONCENTRATION, ETC.):

The parameters controlled are mass and moderation.

ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL (INCLUDE PROCESS LIMIT AND % WORST CASE OF CRITICAL MASS):

There is no deposit in this cell. Worst case would be contamination on process surfaces exposed to process gas prior to shutdown and buffering.

NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES

The NCS control is a dry air buffer >14 psia. Over time the pressure decreased to 13.96 psia.

CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEM AND WHEN EACH WAS IMPLEMENTED:

Buffer pressure was increased to greater than 14 psia at 1300 hours. Control was re-established.

The NRC Resident Inspector was notified along with the DOE Representative.

AUTOMATIC REACTOR SCRAM ON HIGH REACTOR VESSEL LEVEL

The reactor scrammed at 0251 CDT on 7/24/20001 on a level 8 signal, a high reactor vessel level. All rods fully inserted and all systems functioned properly. At the time of the scram there was a surveillance being performed on a level transmitter that feeds the feedwater level control system. Exactly what happened is not known at this time, but an investigation is ongoing.

The plant is stable using the bypass valves to the condenser and level is being maintained with motor driven feedwater pump.

The licensee notified the NRC Resident Inspector.

AUTOMATIC REACTOR TRIP ON HIGH REACTOR COOLANT SYSTEM PRESSURE

The unit received an automatic reactor trip on high reactor coolant system pressure due to a problem with the main turbine control valves. There were no ESF actuations and all rods fully inserted. Steam generator safeties opened for a short period as expected. The plant is stable in hot shutdown with excess heat being controlled by condenser bypass valves with main feedwater system controlling steam generator level.

The problem is being investigated and the cause is unknown at this time.

The licensee notified the NRC Resident Inspector and state agencies.

OFFSITE NOTIFICATION DUE TO EXCEEDING NPDES PERMIT LIMITS

"The EPA and NH Department of Environmental Services (NHDES) were notified this afternoon of a daily maximum exceedence of the NPDES Permit limit for oil and grease at Outfall 025 (Waste Test Tank). The discharge occurred on July 3, 2001. The amount of the exceedence is minor but the significance is still being evaluated so this report is being made as a conservative decision."

The NRC resident inspector has been informed of this notification by the licensee.