Quantifying Burst Repeatability for Godiva IV

Abstract

The minimum resolvable relative change in the neutron source emission of Godiva IV between bursts, i.e., burst repeatability, was quantified using a combination of activation monitors and a resistance temperature detector (RTD). Measurements support changes in the neutron source emission between bursts can be determined with a precision of 2.7%. The measurements were performed during a series of twelve Godiva IV bursts and were a collaborative effort between Los Alamos National Laboratory, Sandia National Laboratories, and Pacific Northwest National Laboratory. Gold, iron, nickel, and sulfur activation monitors were positioned in a sample holder in the central cavity of Godiva IV for each burst. The RTD is part of the Godiva burst diagnostic system and is in a fixed location in the safety block of Godiva IV. It is used to determine the temperature rise of the burst, i.e., the difference between the maximum temperature recorded during the burst and the initial temperature prior to the burst. Differences in either the specific activity of the activation monitor reactions, or the temperature rise can be used to determine the relative change in the neutron source emission for separate bursts, but historic results have proven that each method is susceptible to various sources of biases which generally cannot be isolated using a single method. We address this issue by applying both measurement methods and analyzing the correlation between them. The results presented in this work will be used to support future experiments with Godiva IV at the National Criticality Experiments Research Center (NCERC).