PNNL

Abstract

Radioxenon emissions from industrial sources such as fission based medical isotope production (MIP) facilities and nuclear reactors are generally known to be well below levels of public health and safety concern. However, the global background of radioxenon produced by MIP interferes with nuclear explosion monitoring by the International Monitoring System (IMS) developed for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) (CTBTO, 2024). It was calculated that xenon emissions levels of 5×109 Bq/day 133Xe were low enough to have minimal impact on International Monitoring System (IMS) stations (Bowyer et al, 2013). There are several technologies currently used to abate radioactive xenon emissions to meet regulatory release levels, and some alternative methods have been investigated to reduce xenon release levels well below required regulatory levels (Doll et al, 2014, Gueibe, et al, 2014). While MIP producers are sympathetic to the issue of radioxenon interference with IMS monitoring, the cost to implement and maintain additional abatement systems has resulted in limited implementation. Therefore, more cost-effective options for xenon abatement are needed to help reduce the impact of these emissions on nuclear explosion monitoring. In this paper study, two options for lowering 133Xe emissions at a hypothetical MIP facility were investigated. The releases at the facility were reduced from regulatory levels the facility was designed to meet, to significantly lower voluntary 5×109 Bq/day 133Xe release levels to minimize the impact on nuclear explosion monitoring (Bowyer et al, 2013) – this is considerably lower than the required regulatory levels that typical facilities are designed to achieve. The two options considered in this study are 1) doubling the number of charcoal delay beds and 2) cooling the vault that contains charcoal delay beds in order to increase the holdup time of radioxenon. This longer holdup time allows more of the short-lived xenon isotopes to decay prior to being released to the environment, and therefore reduces the total xenon inventory released from the facility. As part of this comparison, we estimate costs to install each option and discuss their potential impact on the operational facility.