BENCHMARKING MEASUREMENTS AND MCNP6 SIMULATIONS OF A REACTOR GATE DISCHARGE MONITOR

A Reactor Gate Discharge Monitor (RGDM) for spent fuel measurements has been developed at Los Alamos National Laboratory and previously presented at the 46th and 47th Annual Institute of Nuclear Materials Management meetings. The measurement objective of the RGDM is to count fuel rods and determine their direction of motion. This RGDM consists of two nearly identical detector modules. Each module contains an ion chamber and silicon detector, providing redundant gamma detection capabilities. Additionally, each module houses a 3He tube capable of measuring neutrons emitted from fresh mixed-oxide fuel. These detectors are housed in high-density polyethylene with a tungsten shield. Differential shielding enables determination of the direction of motion of passing spent fuel with only a single detector module. The original data acquisition hardware has been replaced with a Next-Generation ADAM module (NGAM) with a < 200 ms sampling rate. The full paper will describe the new monitor hardware, benchmarking measurements, and their MCNP61 simulations.