Pressure Propagation Behavior Of DFLL TBS Under In-Box LOCA Accident

Breeding blankets are key components of a fusion reactor.They transfer the fusion energy to the heat,breed the tritium and provide shielding against neutrons.Dual Functional Lithium Lead Test Blanket System(DFLL TBS)was proposed by Institute of Nuclear Energy Safety Technology,Chinese Academy of Sciences(INEST)and FDS team,and it was designed to demonstrate the technologies of PbLi blanket concepts.DFLL TBS has two modes,Single-cooled Lithium Lead(SLL)and Dual-cooled Lithium Lead(DLL).Besides,it has the high efficiency of thermal power generation and high Tritium Breeding Ratio(TBR).In-box LOCA accident is considered as a Design Basis Accident(DBA)of fusion blanket for its frequency and serious consequence.When an in-box LOCA accident happens,high pressure helium gas is injected into the low-pressure PbLi zone,and causes the pressurization in PbLi loop system.In this work,multi-scale coupling method was used to simulate the in-box LOCA accident of DFLL TBS,and the behavior of pressure propagation in the system has been analyzed.Besides,the sensitivity analysis of key parameters has been done in this work.The results showed that:1.When an in-box LOCA accident happened in DFLL TBS,the pressure wave propagated into the PbLi system,due to the reflection and superposition of the pressure wave in the PbLi system,the blanket module reached its peak pressure in a short time.Besides,as the PbLi loop is equipped with pressure stabilizers,the peak pressure of key components in PbLi loop was less than 3.0 MPa.2.The key parameters that influence the pressure propagation of DFLL TBS include the position of break,the size of rupture,the blasting pressure and the position of PbLi tank.The influence characteristics of these parameters about pressure propagation are as below:under in-box LOCA accident with different positions,the peak pressure of blanket module inlet could reach 16.71 MPa,and outlet could reach 14.61 MPa.As the size of rupture increased,the peak pressure of blanket module was higher,but the size of rupture only had weak influence on the peak pressure of blanket module.The blasting pressure had a linear relationship with the peak pressure of nearby key components,the higher blasting pressure,the higher peak pressure of nearby key components.The distance between the PbLi tank and the key component had a linear relationship with the peak pressure of the key component,the longer distance,the higher peak pressure of the key component.3.The optimization for the safety design of DFLL TBS is suggested as below:when the pressure stabilizers(1.2E-3 m3 at least)were installed near the inlet/outlet of blanket module,and the maximum allowable pressure of the blanket module was promoted to above 9.0 MPa,the pressure safety of blanket module under in-box LOCA accident could be guaranteed.By arranging key component downstream or in 1.7 m upstream of the pressure stabilizers,and setting the blasting pressure between 1.5 and 2.0 MPa,the pressure safety of key components in PbLi loop could be well protected.In this work,pressure propagation behavior in the DFLL TBS triggered by the in-box LOCA accident was analyzed by the coupling method.And based on the results,the pressure mitigation measures were proposed.This work provided experience for the design of the liquid blanket,and it had important significance and application value.