Gamma spectroscopy measurements of fresh charcoal samples from the Hartlepool advanced gas-cooled reactor

Radionuclides are emitted from nuclear power reactors to the atmosphere and are often measured on the International Monitoring System (IMS) - the primary tool of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) for monitoring for signs of nuclear explosions around the world. During refuel of an advanced gas-cooled reactor (AGR) the coolant gas is processed and filtered before being exhausted to the atmosphere. Charcoal and filter paper samples from the processing plant have been measured using high purity germanium γ-ray detectors to identify which radionuclides are present and the activities calculated. Isotopes of radioxenon generated primarily by fission (¹³³Xe, ¹³⁵Xe, ^131mXe, ^133mXe) and by activation (¹²⁵Xe, ¹²⁷Xe, ^129mXe) were identified, as well as ¹³⁷Cs, ⁶⁰Co and ⁷⁵Se. In addition, radionuclide identification confirmation and activity quantification was made using γ-γ coincidence measurement, which provides a more sensitive measurement for low-activity radionuclides.