Simulation Study Of Accidental Tritium Release On Tritium Extraction System Of TBM

The tritium extraction system（TES）is one of the three subsystems of the TBM system,which is the primary function of the TBM system,which separates and stores the tritium produced by the cladding.The occurrence of TES tritium release will result in radiation hazards to staff and the public,and a corresponding tritium system must be designed to control tritium in the safe dose value.In order to analyze the trisaf behavior and the tritium behavior released by the accident,the TES accidental tritium release simulation work was carried out.TES is designed with triple inclusions,tritium components or equipment placed in the secondary containment glove box,the glove box prevents the spread of tritium into the operating room,but the glove box still has a certain leak rate,so tritium release accident occurs when tritium Box and operating room two areas of diffusion.However,the current gas diffusion study only involves the diffusion of a region,and in the use of FLUENT numerical simulation has not been found in the glove box interface to set the leakage rate and other related parameters,so that tritium components leaked after tritium can spread in the glove box Can spread in the operating room,so that the leakage diffusion simulation more realistic.In view of the above problems,this paper has done the following research work:（1）The FMECA method was used to analyze the TBM tritium extraction system,and the TES accident was divided into four grades,namely,gradeⅠwas safe;Grade II was critical;Grade III was dangerous;Grade IV was severe The The results show that the external leakage of the reflux heat exchanger is grade II（critical）accident level;the bed of the low temperature molecular sieve is broken down to grade III（dangerous）accident level;the inner and outer wall rupture of the Pd/Ag diffuser and the separation of the hydrogen isotope separation system The column is broken to grade IV（severe）accident level.The leakage event of Pd/Ag diffuser and hydrogen isotope separation column is the largest trusted event of TES.（2）According to the actual size of TES glove box and operating room,a 3D geometric model was established.Based on the computational fluid dynamics（CFD）method,the FLUENT software was used to simulate the tritium leakage diffusion of the reflux heat exchanger and the tritium of Pd/Ag diffuser and the influence of ventilation on tritium leakage and concentration distribution was analyzed.When modeling,10mm holes were opened in the glove box to solve the problem of tritium spreading in both glove boxes and in the operating room.The tritium leakage caused by the simulated return heat exchanger did not cause radiation damage to the operating room,and the tritium concentration in the operating room was on the order of 10⁴Bq/m³.The leached tritium of the Pd/Ag diffuser begins to rise quickly to the tritium safe dose value in the operating room and then reaches the maximum after the tritium concentration begins to drop.20 times/h and15 times/h of the ventilation can make the indoor tritium concentration down to the safe dose value,the maximum duration of indoor dangers are712s,3020s.2.73×10⁹Bq/m³⁴.43×10⁹Bq/m³ of tirium concentration at the simulated cutoff time of 1800s in the ventilation rate of 20times/h,and8.62×10⁹Bq/m³¹.35×10¹⁰Bq/m³ of tritium concentration of 1800s under ventilation rate of 15times/h;8 times/h ventilation at the cut-off time8400s,tritium concentration 1.47×10¹⁰Bq/m³².34×10¹⁰Bq/m³ range which is still higher than the safe value of2.0×10¹⁰Bq/m³;5 times/h ventilation tungsten concentration in the 10800s when the unit has not yet dropped to the safe dose,the concentration range of 7.42×10¹¹Bq/m³¹.14×10¹²Bq/m³.The concentration of tritium in the glove box is tended in the tritium concentration under four kinds of ventilation conditions,but the tritium concentration is in the order of 10¹⁵Bq/m³,which is much higher than the tritium concentration in the operating room.