Nuclear-Criticality Safety Analysis of the Oak Ridge Y-12 Plant Birdcage-Type Containers for Intraplant Storage and Transportation

摘要

The Oak Ridge Y-12 Plant birdcage-type containers include a family of cubic (20-, 24-, and 30-inch) open-framed containers used for the in-house storage and transfer of unirradiated enriched uranium metal. This paper provides insight into the nuclear criticality safety analysis for birdcage usage. All credible contingencies (abnormal events) were analyzed and proven safe (subcritical) in accordance with the requirements and procedures of nuclear criticality safety standards. Examples of the contingencies considered in the analysis include, but are not limited to, full water reflection of any single uranium mass loading, double batching of a loading, water moderation, and misuse of the birdcage. These and other applicable contingencies determine the maximum uranium mass for the 20- and 24-inch birdcages, which is 20 and 28 kilograms, respectively. The maximum number of birdcages stored at one location and the storage array configuration are also determined by the credible contingencies. Stacking restrictions for birdcage storage are three high for the 20-inch birdcage and two high for the 24-inch birdcage. A maximum size for square-based arrays is ten feet by ten feet. Any number of these arrays may be used provided a twelve-foot separation is maintained between each array. Such a storage arrangement results in a floor utilization of 0.42 birdcages per square foot. Better floor utilization, i.e., more birdcages per square foot, is possible with other array configurations that are not square-based. Physical as well as administrative controls, procedures, training, and audits are used to ensure these basic criteria are observed. 1 table. (ERA citation 08:035269)