The University of Missouri (MU) has been working in conjunction with Argonne National Laboratory (ANL) in the National Nuclear Security Administration (NNSA) Material Management and Minimization (M3) Reactor Conversion Program to support conversion of the University of Missouri-Columbia Research Reactor (MURR®) from highly enriched uranium (HEU) to low-enriched uranium (LEU) fuel. MURR is one of five U.S. High Performance Research Reactors (USHPRR) plus a critical facility that plans to convert to the use of LEU fuel. ANL/RTR/TM-18/16 Safety Analysis of the Mo-99 Production Upgrade to the University of Missouri Research Reactor (MURR) with Highly Enriched and Low-Enriched Uranium Fuel ii ANL/RTR/TM-18/16 Safety Analysis of the Mo-99 Production Upgrade to the University of Missouri Research Reactor (MURR) with Highly Enriched and Low-Enriched Uranium Fuel iv installed. Thus, the upgrade causes a change in the location of the maximum HEU fuel temperature resulting from the limiting LOFA, which is consistent with the shift in the core power distribution that occurs due to the upgrade. For the LEU core, the minimum margin to the fuel temperature safety limit for the limiting LOFA with the 2017-RBM-99 upgrade is 232 °C and occurs in an EOL fuel plate. This is the same margin as was predicted for the limiting LOFA for the PSAR analysis. The location of the minimum margin moves from plate 23 of the fuel element in core position 8 in the PSAR analysis to plate 23 of the fuel element in core position 4 with the upgrade. With more margin than the other scenarios, all LOFA transient results are considered to have very adequate margins to the burnupdependent fuel temperature safety limit. Because there is no change to the HEU or LEU nominal fuel element loadings and an overall negligible effect on the fuel burnup as a result of the 2017-RBM-99 upgrade, the radiological consequences of the maximum hypothetical accident and fuel handling accident were not evaluated in this work. As found in the PSAR analysis, for any event where a release is considered in the current HEU SAR, the radiological consequences after conversion remain lower than the regulatory limits. In summary, the Mo-99 production upgrade to MURR with the 2017-RBM-99 device has been found to cause a shift in the core power distribution for both HEU and LEU cores relative to the PSAR analysis. The predicted steady-state margins to flow instability with the upgrade are adequate for both HEU and LEU cores. The margins with the upgrade are lower than those predicted in the PSAR analysis for both HEU and LEU, but the margin for LEU is larger than that for HEU. For postulated transient accidents, the upgrade causes a slight decrease in the minimum margin to a fuel temperature safety limit based on the fuel blister threshold temperature. There is a 9 °C reduction in the safety margin for HEU for the most limiting accident evaluated under conditions specified in NUREG-1537. For a reference LEU core, the minimum safety margin for the most limiting transient accident with ...

60439. For information about Argonne and its pioneering science and technology programs, see www.anl.gov.

This report contains the results of reactor accident analyses for the University of Missouri Research Reactor (MURR). The calculations were performed as part of the conversion from the use of highly-enriched uranium (HEU) fuel to the use of low-enriched uranium (LEU) fuel. The analyses were performed by staff members of the Global Threat Reduction Initiative (GTRI) Reactor Conversion Program at the Argonne National Laboratory (ANL), the MURR Facility, and the Nuclear Engineering Program -College of Engineering, University of Missouri-Columbia. The core conversion to LEU is being performed with financial support from the U. S. government.In the framework of non-proliferation policies, the international community presently aims to minimize the amount of nuclear material available that could be used for nuclear weapons. In this geopolitical context most research and test reactors, both domestic and international, have started a program of conversion to the use of LEU fuel. A new type of LEU fuel based on an alloy of uranium and molybdenum (U-Mo) is expected to allow the conversion of U.S. domestic high performance reactors like MURR. This report presents the results of a study of core behavior under a set of accident conditions for MURR cores fueled with HEU U-Al x dispersion fuel or LEU monolithic U-Mo alloy fuel with 10 wt% Mo (U-10Mo).For the proposed LEU-fueled core, previous studies [1] have shown that in order to maintain the neutron flux at various crucial experimental locations within the reactor at the same level after the fuel conversion from the HEU to LEU, the steady-state operating power level must be increased from 10 MW to 12 MW. Hence, the accidental positive reactivity insertions, and the loss-of-coolant and loss-of-flow accidents for the LEU core were initiated from an initial steadystate power level of 12 MW. It is noted that all references to the core power level for MURR in this report are the thermal power output of the reactor (i.e., MWt).A search of the published literature and available technical reports was conducted to obtain appropriate values of thermal conductivity and volumetric heat capacity for the materials of 1) the irradiated and unirradiated HEU and LEU fuel meat, 2) the zirconium layers in the LEU fuel plates, 3) the 6061-aluminum of the fuel plate cladding, the reactor vessel walls, and primary system pipes, and 4) the oxide layer on the cladding surfaces of the irradiated fuel plates. This set of material properties was used in the analyses of the reactivity insertion accidents (RIA), loss-of-coolant accidents (LOCA), and loss-of-flow accidents (LOFA).The transient simulations of RIAs, LOCAs, and LOFAs are initiated from the conservative end of the normal operating band for reactor power, reactor primary coolant flow, and reactor core inlet temperature. The typical core state for the MURR was assumed in these simulations. This state has elements with a mixture of burnups, the flux trap is loaded with irradiation samples and experiments, and the control blades are banked in the...

No abstract

No abstract