PHWR Reactivity Device Incremental Macroscopic Cross Sections and Reactivities for a Molybdenum-Producing Bundle and a Standard Bundle

Abstract

A new 37-element PHWR fuel bundle, designed for molybdenum-99 production, has been proposed previously. The new bundle has been shown to have lattice properties and reactivity feedback effects equivalent to the standard PHWR bundle. This study looks at the effect the use of molybdenum-99-producing bundles has on the reactivity worth of reactivity devices, through the prism of reactivity-device macroscopic-cross-section increments. The study utilizes three-dimensional supercell configurations and the neutron transport code DRAGON to calculate and compare the incremental macroscopic cross sections and supercell reactivity for adjuster absorbers, shutoff absorber rods and liquid zone controllers when surrounded by molybdenum-99-producing bundles and by regular bundles. Two geometrical representations of fuel bundles are used: a detailed, cluster, representation, whereby all fuel pins are modeled separately, and an annularized representation, whereby each ring of fuel pins and corresponding coolant is represented as a homogeneous annulus. The latter model is the one customarily used in production calculations for finding cross-section increments of reactivity devices.The study finds that reactivity-device cross-section and supercell reactivity increments are very similar (< 2% difference in reactivity increments) for the case of the molybdenum-producing bundle and the regular bundle. The study also finds that the use of a detailed, cluster, geometrical representation of the fuel bundle produces slightly different cross-section increments and supercell reactivity increments than the use of an annularized geometrical representation. The supercell reactivity-increment difference between the two representations is found to be ~8.0% for adjuster absorbers and ~11.0% for shutoff absorber rods.

New strategies for a sustainable 99mTc supply to meet increasing medical demands: Promising solutions for current problems

“…The resulting 99 Mo is called a Non-Carrier Added (NCA) product and possesses high specific activity defined as the 99 per unit molybdenum mass. The fission yield for this reaction is about 6.132% (Haroon and Nichita, 2021;Grummitt and Wilkinson, 1946;Hyde, 1964;IAEA, 2013aIAEA, , 2008IAEA, , 2003.…”

“…Annually, 30-40 million SPECT imaging studies have been conducted worldwide using 99m Tc solely (half of which in the United States). 99m Tc utilization is estimated to increase by 3-8% every year (Banerjee et al, 2000;Eckelman, 2009;Guerin et al, 2010;IAEA, 2013a;Chakravarty et al, 2013;Owen et al, 2014;Dilworth and Pascu, 2015;Gumiela, 2018;Haroon and Nichita, 2021). 99m Tc decays by a relatively short half-life (T 1/2 = 6.01 h) and emits only one-gamma photon at low energy of 140.51 keV.…”