Determining reactor flux from xenon-136 and cesium-135 in spent fuel

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 690; pp. 68 - 74
• Main Authors: Hayes, A.C., Jungman, Gerard
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 21.10.2012
• Subjects: Exact solutions; Flux; Fuels; Isotope dilution; Isotopic ratios; Nuclear engineering; Nuclear power generation; Nuclear reactor components; Nuclear reactors; Reactor spent fuel; Reprocessing activities; Spent fuels; Isotope dilution; Reactor spent fuel; Isotopic ratios; Reprocessing activities
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2012.06.031

The ability to infer reactor flux from spent fuel or seized fissile material would enhance the tools of nuclear forensics and nuclear nonproliferation significantly. We show that reactor flux can be inferred from the ratios of xenon-136 to xenon-134 and cesium-135 to cesium-137. If the average flux of a reactor is known, the flux inferred from measurements of spent fuel could help determine whether that spent fuel was loaded as a blanket or close to the mid-plane of the reactor. The cesium ratio also provides information on reactor shutdowns during the irradiation of fuel, which could prove valuable for identifying the reactor in question through comparisons with satellite reactor heat monitoring data. We derive analytic expressions for these correlations and compare them to experimental data and to detailed reactor burn simulations. The enrichment of the original uranium fuel affects the correlations by up to 3%, but only at high flux.