Application of trace rare gas detection Technique using laser to JOYO

Harano, Hideki; Ito, Chikara   ; Arima, Toshihiro*; not registered

An early detection of fuel failure and subsequent precise identification of the failed fuel subassemblies are important and indispensable for operating fast reactors from the viewpoint of their safety, reliability and plant availability as well. In order to improve the failed fuel detection and location (FFDL) technology, the laser resonance ionization spectrometry (RIMS) has been proposed to use for the trace nalysis of krypton and xenon contained in cover gas. Various promising features have been reported through the fundamental study using the RIMS device at the nuclear engineering research laboratory (NERL) of the university of Tokyo. The results suggest the feasibility of this method to on-power real-time monitoring. Based on the information obtained above, we are developing a new laser FFDL system which employs RIMS, and it is applied to the fast experimental reactor JOY0. By using this system at JOY0, the isotope analysis can be performed with high sensitivity not only for radioactive nuclides but also for stable elements of fission product (FP) and tag gas which are usually diluted in the cover gas argon. This enables to improve irradiation technology and to identify the failed fuel subassemblies immediately. For instance, it becomes possible to identify breached steel capsule to be used for on-line creep rupture experiment of cladding materials under the irradiation condition. The fuel burn-up of failed subassembly can be estimated by measuring the isotopic composition of FP nuclides, which allows the pre-location in the FFDL procedure. The present paper describes the basic design of the laser FFDL system. Some experimental results are also reported from the performance tests to examine the feasibility to fast reactor cover gas analysis.