1. Introduction

Nuclear forensics (NF) is by no means new. It is as old as the first use of nuclear materials in weapons. For example, in 1944 the U.S. Air Force searched for evidence of radioactive xenon gas (¹³³Xe) in the atmosphere to monitor the German nuclear program [1]. Such monitoring activities are being practiced both internationally through the framework of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) [2] and nationally by many countries across the world. For example, in September 2017, South Korea’s radionuclide monitoring system recorded and reported the detection of ¹³³Xe subsequent to nuclear bomb tests allegedly performed by North Korea (see [3]).