Conceptual design parameters for MITR LEU-Mo fuel conversion demonstration experimental irradiations

Abstract

The Massachusetts Institute of Technology Reactor (MITR-II) is a research reactor in Cambridge, Massachusetts designed primarily for experiments using neutron beam and in-core irradiation facilities. It delivers a neutron flux comparable to current LWR power reactors in a compact 6 MW core using Highly Enriched Uranium (HEU) fuel.In the framework of its 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 Low Enriched Uranium (LEU) fuel. A new type of LEU fuel based on an alloy of uranium and molybdenum (UMo) is expected to allow the conversion of U.S. domestic high performance reactors like the MITR-II reactor. Toward specifying requirements for Design Demonstration Experiment (DDE) Irradiations in a test reactor, a key set of conceptual design parameters are presented for MITR LEU monolithic U-Mo alloy fuel with 10 wt% Mo.

Irradiation Performance of U-Mo Alloy Based ?Monol

“…Data plotted in the figures and listed in Table 1 were taken from reports recently provided by the 5 USHPRRs. 23,24,25,26,27 The plots also include a trend line that indicates a margin of approximately 15% as an estimate of the range of testing conditions required to demonstrate sufficient margin to failure. In some cases, this margin may not be applicable because it is not possible for fuel to operate under the conditions represented by the trend line.…”

Irradiation Experiment Conceptual Design Parameters for MITR LEU U-Mo Fuel Conversion

“…A representative history of HEU and LEU core states that could exist during steady-state operations of the MITR were examined in [2,4,11]. In this report, irradiation parameters are presented for the LEU elements under the conditions that are expected in steady-state operations to represent the highest plate heat flux, fuel and clad temperatures, fission rate density, and cumulative fission density.…”

“…The most limiting case, in terms of both power and thermal hydraulics was found for a depleted MITR LEU Core 189, and is described below [9]. Since this data was originally compiled for irradiation in a geometry identical to the MITR design that would serve as a prototype partial MITR LEU element, heat flux was used to describe the power distributions [16]. A conversion to fission rate will be discussed after heat flux data is presented in the following sections.…”

“…For the MITR Design Demonstration Experiment (DDE) it was recommended that the starting basis for the size scale of regions of depletion and power distribution correspond with those used in the MITR analyses up to that point in order to represent the various physical phenomena accounted for in the safety basis calculations [16]. Where variations exist the DDE irradiation planning should compare results based on the discretization presented in this work in order to ensure that alterations do not impact accurate modeling of the underlying phenomena.…”