Gas Tag Identification of Failed Reactor Assemblies—III. Tag Ratios for the Fast Flux Test Facility Cores I Through IV

Gas tagging consists of adding small amounts of gas with a unique isotopic composition for each assembly to nuclear reactor fuel and control assemblies. During subsequent irradiation, when any pin of an assembly fails, the tag gas released along with other gas from the pin plenum enables location of the defective assembly by a mass spectrometric analysis of a sample of the reactor cover gas. The general procedure presented for the design of a gas tag system has been used to produce three designs for the gas ratios for Cores I through IV of the Fast Flux Test Facility. The designs are compared with and without “age tagging,” the use of information from tag gas burnup to help discriminate between failures of different assemblies. A few comments included on the operation of a gas tag system help ensure that the system will operate within the assumptions made in the design of the gas tag ratios.