A method and system detects failures in nuclear fuel assemblies (600). A water treatment device degasses/removes fission gases from water used in the canister (500) of a vacuum sipping device (30). A sipping procedure then detects a failure in a fuel assembly in the canister. The degassing improves a signal-to-noise ratio of the detector used during the sipping process, and improves the failure detection sensitivity of the system. Additionally and/or alternatively, gas may be recirculated through the canister water before the vacuum is applied so that fission gas concentration in the recirculating gas reaches a baseline equilibrium with the canister water. The vacuum is thereafter applied and the sipping procedure proceeds such that an increase in detected radioactivity over the baseline equilibrium indicates a leak in the fuel assembly.

An apparatus to test for defects in irradiated nuclear fuel includes a submerged sipping canister, a first recirculation system and a degassing device to remove and discharge pre-existing dissolved fission product gases from the fluid in the system and canister prior to a sipping test, a second recirculation system and a degassing device to extract and detect fission products from the fluid in the canister during the sipping test, a flow control valve to maintain a partial vacuum in the canister when the second recirculation system is operating, and a radiation detector monitoring the output gas from the degassing device. The fluid-contacting surfaces of selected components may be pretreated or modified to reduce adsorption or adherence of radioactive noble gases on wetted surfaces to decrease background radiation levels and contamination of the apparatus. A related method is also disclosed.

An apparatus to test for defects in irradiated nuclear fuel includes a submerged sipping canister, a first recirculation system and a degassing device to remove and discharge pre-existing dissolved fission product gases from the fluid in the system and canister prior to a sipping test, a second recirculation system and a degassing device to extract and detect fission products from the fluid in the canister during the sipping test, a flow control valve to maintain a partial vacuum in the canister when the second recirculation system is operating, and a radiation detector monitoring the output gas from the degassing device. The fluid-contacting surfaces of selected components may be pretreated or modified to reduce adsorption or adherence of radioactive noble gases on wetted surfaces to decrease background radiation levels and contamination of the apparatus. A related method is also disclosed.