Event Notification Report for May 21, 2001

LOST CHEMICAL AGENT DETECTOR(CAD)

The US Army in Aberdeen, Md. Reported that the 7th Chemical Co. 83rd Chemical Battalion at Ft Polk, La. lost a Chemical Agent Detector in the training area during a training exercise. The CAD contained 300 microcuries of Am-241. A 100% inventory and complete search was conducted, but it was not recovered.

FAILURE OF THE EARLY WARNING SYSTEM SIRENS

The operating system for the early warning system sirens failed. This will prevent activation of the early warning sirens. The sirens failed at 0150 on 5/21/01. The failure is currently being investigated.

The NRC Resident Inspector will be notified.

* * * UPDATE ON 5/21/01 @ 1246 BY BAHNER TO GOULD * * *

The system was restored at 0940.

The NRC Resident Inspector was notified.

The Reg 4 RDO(Shaffer) was notified

UNUSUAL EVENT - BOMB THREAT

IMMEDIATE COMPENSATORY MEASURES WERE TAKEN UPON DISCOVERY. AN UNUSUAL EVENT WAS DECLARED AT 1520 CDT.

CONTACT HOO FOR FURTHER INFORMATION.

* * * UPDATE ON 5/21/01 @ 2005 BY HOBBS TO GOULD * * *

The NOUE was terminated at 2000 EDT based on a completed search which turned up no abnormalities.

Notified Reg 3 RDO(Burgess), NRR EO(Zwolinski), and FEMA(Canupp).

FAILURE OF PROGRAMMABLE LOGIC CONTROLLER(PLC) CAUSED LOSS OF ACTIVE ENGINEERED CONTROLS ON CONVERSION LINE 4

24 HOUR 91-01 BULLETIN

At approximately 0759 the decanter tripped off line on conversion line 4. Subsequently line 4 was shutdown at 0805. An error in the display program was initially suspected.

With conversion line 4 shut down, instrument technicians were called. The technicians attempted to correct the problem with the display program to no avail. An instrumentation and controls (I/C) engineer was called and tracked the problem to the line 4 PLC. Since it was determined that the PLC processor for line 4 had faulted, the processor was reset and tested. The test was satisfactory.

Line 4 was restarted at approximately 1000. At approximately 1030 line 4 was shut down due to a plugged duplex valve at the inlet of the calciner. During this shutdown, a process engineer was informed about the earlier events. The process engineer became concerned about the status of the safety significant controls on line 4 and contacted a nuclear criticality safety (NCS) engineer at approximately 1130. The NCS engineer was present in the control room at approximately 1140.

A time-line of events was reconstructed. The NCS engineer reviewed the sequence of events with the I/C engineer. It was determined that an output fault in an I/O card caused the processor to go into fault mode but all outputs did not go to their correct (OFF) state.

The NCS engineer determined that in the time period from 0759 until line 4 was secured at approximately 0805, the active engineered safety significant controls (SSCs) on line 4 were unavailable, and less than double contingency protection existed in the vaporization system during that time period. The SSCs are considered to have been in place for the 1000 startup and remained in place until the shutdown at 1030, although the cause of the initial failure had not been determined. Conversion operators on line 4 were instructed by the NCS engineer to not restart line 4 until the cause of the PLC failure was determined and corrected. Line 4 remains shutdown pending further investigation.

Justification for Continuing Operations on Lines 1, 2, 3 and 5:

Line 4 utilizes a unique Numalogic PLC system while Lines 1, 2, 3, and 5 utilize a different programmable logic system. There is no reason to believe the Numalogic error is possible on the other lines. The manufacturer of the other programmable logic system (utilized on Lines 1,2,3 and 5) was contacted and stated that their cards cannot fail into any state other than all OFF. Conversion Lines 1, 2, 3 and 5 remain in operation.

Double Contingency Protection

Double contingency protection for the vaporizer is based upon control of mass (prevent/detect a UF6 leak) and geometry (prevent/detect accumulation of moderator in a non-favorable configuration in the bottom of the vaporizer). Double contingency protection on the cylinder (in vaporizer) is based upon moderation control (prevent back-flow of moderator from the hydrolysis column into the cylinder). It was determined that less than double contingency protection remain for these systems and greater than a safe mass was involved. In accordance with Westinghouse Operating License (SNM-1107), paragraph 37.3 (c.5), this event meets the criteria for a 24 hour notification because it constitutes a "nuclear criticality safety incident, in an analyzed system, for which less than previously documented double contingency protection remains . . and: greater than a safe mass is involved, but a sufficient number of the controls that were lost are restored within four (4) hours such that double contingency protection is restored."

As Found Condition

See "Reason for Notification" above.

Summary of Activity

An unknown PLC failure led to the shutdown of conversion line 4. It was determined that less than double contingency protection existed on the line 4 from 0759 to 0805. Therefore, the NCS engineer directed that line 4 could not be restarted until the cause of the failure was determined and corrected.

Conclusions

Loss of double contingency protection occurred.
At no time was there any risk to the health or safety of any employee or member of the public. No exposure to hazardous material was involved.
This notification is the result of equipment failure, not a deficient NCS analysis.

***** UPDATE RECEIVED AT 1120 ON 05/23/01 FROM BILL NEWMYER TO LEIGH TROCINE *****

The following text is a portion of a facsimile received from the licensee:

"Westinghouse has proceeded with investigation of the cause of the Numalogic PLC failure on Conversion Line 4. This investigation has discovered that the design of the Line 4 - Numalogic 700 PLC may fault to an undesirable state. A service bulletin update for the Numalogic PLC describes this condition."

"A modification to the PLC (described in the manufacturer's bulletin) is necessary to correct this condition. This modification was completed on the PLC. The PLC was subsequently tested by faulting the PLC, and the correct output condition was achieved."

"Further testing of the control logic was performed to ensure that the output from the PLC, when faulted, will produce the correct valve responses for Conversion Line 4. This functional test revealed that even though the PLC faulted to the correct output values, the valves did not respond correctly."

"Discovery of the problem with Conversion Line 4 prompted investigation to determine if the other Conversion Lines (1, 2, 3, and 5) would experience a similar error (i.e., the PLC faults to the correct output but the valves fail to respond correctly). Testing of Conversion Line 5 (which uses a different PLC logic system) revealed the same deficiency."

"Based on this information, Conversion Lines 1, 2, 3, and 5 have been shutdown pending further evaluation of the correct system response assuming a PLC fault condition. Modifications will be made to each Conversion Line to correct the PLC system response prior to restarting each Conversion line."

The licensee notified onsite NRC headquarters inspectors. The NRC operations officer notified the R2DO (Bernhard) and NMSS EO (Hickey and Broaddus).