BISON automation to predict transient power history based off prescribed cladding temperature

Abstract

Since the restart of the Transient Reactor Test Facility (TREAT) at Idaho National Laboratory (INL) in 2017, advanced testing using various modules within the minimal activation retrievable capsule holder system has been underway with other types being considered for future work due to customer interest. In this work, one such test module—the Temperature Heat-sink Overpower Response module (THOR)—was simulated within BISON with UO2 fuel with zircaloy cladding and U-10Zr fuel with HT9 cladding, and a steel-alloy heat sink with a desired customer prescribed maximum cladding temperature profile. The THOR module is an instrumented capsule within which fuel rods can be irradiated in a liquid–sodium-filled hole in a thick-wall metal heat sink so that, along with TREAT's unique transient power-shaping capability, experimenters can simulate numerous transient irradiation conditions. For transient testing, specimen temperature history is a primary driver in experiment design, which is primarily driven by the balance of power input to the nuclear heated specimen and the heat-transfer boundary condition associated with a particular experiment design. A simple iterative method was implemented in Python to write a BISON linear heat generation rate (LHGR) power history to produce desired customer-prescribed cladding-temperature values. The BISON LHGR power profile will later be used to write the control rod positions within TREAT to yield the customer-prescribed temperature values. Not all customer prescribed temperature values were achieved when desired temperatures were decreasing due to system limitations of THOR. However, the iterative method shown allows for temporal power histories to be derived, such that all BISON-produced temperatures are within 5% of customer values when increasing or maintaining a constant cladding temperature. The iterative method used allows for the dimensions, materials, and material properties of the THOR module to be customer specific, as well as different customer-prescribed parameters, such as fuel temperature, to be used in place of maximum cladding temperature. This tool allows for different designs and transient scenarios to be explored without manual fitting, allowing for rapid development for customer needs.