Coupled hydrodynamic-structural analysis of an integral flowing sodium test loop in the treat reactor

A hydrodynamic-structural response analysis of the Mark-IICB loop was performed for the TREAT (Transient Reactor Test Facility) test AX-1. Test AX-1 is intended to provide information concerning the potential for a vapor explosion in an advanced-fueled LMFBR. The test will be conducted in TREAT with unirradiated uranium-carbide fuel pins in the Mark-IICB integral flowing sodium loop. Our analysis addressed the ability of the experimental hardware to maintain its containment integrity during the reference accident postulated for the test. Based on a thermal-hydraulics analysis and assumptions for fuel-coolant interaction in the test section, a pressure pulse of 144 MPa maximum pressure and pulse width of 1.32 ms has been calculated as the reference accident. The response of the test loop to the pressure transient was obtained with the ICEPEL and STRAW codes. Modelling of the test section was completed with STRAW and the remainder of the loop was modelled by ICEPEL. The ICEPEL representation of the Mark-IICB integral loop included two-dimensional, axi-symmetric, hydrodynamic models for individual pipes and components coupled together to treat the structural response of the loop to the pressure transient originating in the test section. All pipes and components (excluding elbows) were modelled with deformable walls. A burst disc was included in the model at the lower bend of the loop with a rupture pressure threshold of 34.5 MPa. Analyses were performed to investigate the system behavior with and without the pressure of this component. (orig.)