On March 4, 1996, at Savannah River, an H-canyon frames waste recovery process operator copied a wrong number from a sample card, resulting in the initial amount of plutonium in the tank being calculated as lower than the actual amount. The frames waste recovery process removes impurities from liquid plutonium. Inattention to detail by the operator resulted in more plutonium in the tank than expected, a violation of an operating limit. This could have resulted in an Operational Safety Requirement violation. (ORPS Report SR--WSRC-HCAN1996-0007)
Before each process run, operators calculate the initial quantity in grams of plutonium in the feed tank. When the operator copied the wrong number used in calculating plutonium concentration, it resulted in the wrong calculated value for the solution. This incorrect result was used in calculations with a tank concentration value taken after chemical adjustment. The resultant calculated values were lower than the actual concentration. After completion of the run, tank samples indicated that the amount of plutonium in the tank had increased instead of decreased as expected.
The facility manager suspended operations and instituted a procedure change requiring independent verification of the plutonium values used for procedure calculations. He also directed a review of related procedures for adequacy.
OEAF engineers reviewed the Occurrence Reporting and Processing System for similar incidents related to procedures and inattention to detail. The following events were found.
On March 9, 1994, an operator determined that the end point for the anion exchange column feed tank was incorrectly calculated. The calculation error was caused when an operator incorrectly transcribed a weight factor in the procedure. This transcription error from the tank calibration chart to the procedure resulted in a 41 gram overfeed. Investigators determined that the direct and contributing causes were inattention to detail and the root cause was an inadequate procedure. (ORPS Report SR--WSRCHCAN-1994-0031)
On June 14, 1994, an operator performing procedure calculations for resin decontamination discovered that the calculations were incorrectly recorded in the procedure. The incorrect weight factor, initially, appeared to exceed the operating limit. The control room supervisor and the separations engineer determined that, after allowing the transfer header to drain back into the tank, the feed limit was not exceeded. Investigators determined that the direct and root causes were an inadequate procedure. (ORPS Report SR--WSRC-HCAN-1994-0077)
A widely used tool used in the commercial nuclear industry to reduce errors caused by inattention to detail is selfchecking. NFS has mentioned this in previous Weekly Summary articles. A recent article appeared in Weekly Summary 95-39, where a commercial technique, called STAR, is in use at the Hanford site. STAR is an acronym for STOP, THINK, ACT, and REVIEW. This program is used at several Hanford facilities because of its effectiveness.
Procedures provide the appropriate direction to ensure operation within the design basis and to support safe operation. Procedures are key factors in operator performance, but the operator must pay appropriate attention when performing procedural steps. To ensure that procedures reflect the best and most current methods of operations, a periodic review and feedback of information is essential. Facility managers should verify that their operating procedures are periodically reviewed for steps which require independent verification because of their importance to facility or personnel safety.
KEYWORDS: operations, procedures
FUNCTIONAL AREAS: operations, procedures