Oak Ridge Y-12 Plant Review of Lessons Learned of the Tokaimura Criticality Accident Page: 4 of 6
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selected process areas, observation of maintenance activities, and observation
of procedures and other Facility Programs/interfaces to determine effectiveness
of implementation and protection of NCS controls.
Review teams were established consisting of Y-12 Plant personnel
knowledgeable in the areas of Operations, Engineering, Training, and Criticality
Safety. The teams consisted of NCSD engineers, Process Engineers or Subject
Matter Engineers from Operations, Design Engineers from Engineering and
representatives from the Training Department. Since some of these team
members were inexperienced in conducting assessments, training sessions were
conducted in assessment methodology and protocol.
The major emphasis effort was focused on those processes that handle fissile
solutions, processes involving unfavorable geometry containers (generally, waste
collection and handling), and the adequacy of active and passive design
features. Processes reviewed included Chemical Recovery and Special
Processing CSE/CSRs, which have some semblance of the process in
Tokaimura. A sampling method was used for the balance-of-plant areas where
selected processes were reviewed against generic lessons learned from the
Japan accident to ensure adequate controls exist to prevent a nuclear criticality.
Results
The Y-12 Plant review teams noted many positive elements indicative of a
maturing NCS program at the plant. Recent examples include implementation of
the enhanced peer review process and the increased detail and rigor of the
process analysis documentation. Issues identified included the need to continue
the Process Analysis upgrade project; implement improvements in NCS related
postings; develop better documentation of technical basis for equipment used as
passive design controls; improved implementation of the Large Geometry
Exclusion Area program; and planned response to nuclear criticality accidents.
The assessment concluded that no imminent criticality safety hazards involving
fissile solutions were evident. A follow-up DOE review concluded that "the NCS
Division program infrastructure controlling criticality safety was in place and
capable of performing its function of preventing a criticality accident." Y-12 Plant
personnel initiated corrective actions to several of the issues identified during the
assessment.
We have established a well-designed program including joint walk down of
processes by NCS Engineers and Operations, Operations concurrences on our
Criticality Safety Evaluations process descriptions, assumptions and hazards
identification, as well as formal implementation and training on each process.
However, our operators still felt disenfranchise as well as confused on the basis
for requirements. We had not gotten to the f/oor operator (hands on operator).
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Carroll, K.J.; Robinson, R.C. & Hogle, W.M. Oak Ridge Y-12 Plant Review of Lessons Learned of the Tokaimura Criticality Accident, article, November 12, 2000; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc719558/m1/4/: accessed March 28, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.