Lesson Learned Statement:Transuranic (TRU) fissile waste material was stored in an airlock that was approved by criticality safety but was not covered by the facility safety basis. Two separate people did not properly apply the complex Unreviewed Safety Question (USQ) screening and evaluation process. Plant personnel did not recognize this vulnerability even after two previous events related to storage in airlocks.
Discussion:On January 14, 2004, a DOE Facility Representative observed TRU waste in poly jars stored inside air lock 108 attached to the outside of the Plutonium Reclamation Facility. Storage of fissile material in airlocks and other similar "outside" storage locations was specifically allowed by Criticality Safety. However, fissile material storage in the airlock was not allowed by the Plutonium Finishing Plant (PFP) Safety Basis because the material was considered dispersible in analyzed accidents such as a fire or spill.
The Safety Basis requirement for outside storage requires the location to be either explicitly authorized or have all three criteria for storage: 1) a confinement ventilation system exhausted through HEPA filters, 2) seismic qualification, and 3) fire protection. Airlock 108 meets none of those three criteria.
Analysis:The Unreviewed Safety Question (USQ) Screening that allowed storage in the air lock should have concluded that a USQ Evaluation was required. The USQ Evaluation would have concluded that the activity was not within the approved Safety Basis. The USQ Preparer and the Evaluator did not perform a thorough and complete USQ Screening for adding the air lock as a storage location. The Safety Basis did not explicitly define storage areas, increasing the difficulty in clearly determining if those areas were within the Safety Basis.
The Safety Basis does not explicitly define "outside storage". Past security requirements prohibited outside storage of fissile material. The need for a formal definition of outside storage was recognized about two years ago when a compressed propane gas bottle was found stored in an air lock. In resolving the question of whether the air lock was an allowed storage location, the Safety Basis Team determined that areas exterior to the main structure would be considered "outside." Three criteria were then established for determining whether an area was outside (negative ventilation, fire suppression, and seismic qualification).
The compressed flammable gas storage issue was a missed opportunity for preventing the recent Airlock 108 storage event because no one connected propane gas with fissile material, no one appreciated the need to incorporate the definition of outside storage in the Safety Basis, and lessons from the non-reportable compressed gas event were informally disseminated within the core Safety Basis Team but not to all USQ Screeners and Evaluators.
Subsequent to the compressed gas storage question, another similar event involving storage of a loaded pipe over-pack in an air lock reinforced the need for definition of outside storage. In that event, transuranic material in Pipe Over-pack Containers was staged for next-day shipment inside an air lock built onto the outside wall of Building 234-5Z. This storage was also allowed by Criticality Safety. This event was a second missed opportunity because the Safety Basis Team did not look at why Criticality Safety allowed this storage but no other controls prevented it.
USQ Screenings prepared before the compressed flammable gas event did not consider outside storage. The screenings were prepared under the prevailing assumption that security requirements would require fissile material storage in a protected area. Since then, storage locations allowed in the Safety Basis must be derived through analyzing the three factors.
Successful application of the USQ process relies on the knowledge and skill of both the Preparer and Evaluator. The complexity of the process creates potential for the Preparer to make a mistake. An Evaluator performing a second review provides a second barrier to an error by the Preparer. The residual risk in the USQ process is that both personnel barriers can fail, resulting in the type of event described in this report.
Other outside storage locations had been allowed for many years. USQ Screeners must not be misled by previous apparently similar changes approved through the USQ process.
Safety Basis documents cannot anticipate all the factors that might eventually have to be addressed by a USQ Screening. Therefore, Screeners must question the lack of specific information, which may lead to elevation of the question to a USQ Evaluation.
Recommended Actions:The PFP Safety Basis will soon be replaced by D&D Documented Safety Analyses (DSA) and will therefore not be changed. The D&D DSAs anticipate outside storage.
All PFP USQ Preparers and Evaluators will be trained to properly apply the USQ process. Training will cover how to answer USQ questions.
Originator:Fluor Hanford, Inc. Submitted by John Lukes (509) 373-3104
Contact:Project Hanford Lessons Learned Coordinator; (509) 373-7664
Name Of Authorized Derivative Classifier:Not required
Name Of Reviewing Official:John Bickford
Priority Descriptor:Blue / Information
Keywords:Authorization Basis, USQ, criticality
References:Occurrence Report RL--PHMC-PFP-2004-0001
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DOE Function / Work Categories:Authorization Basis
ISM Category:Perform Work
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