The IAEA Workshop on Requirements and Potential Technologies for Replacement of 3He Detectors in IAEA Safeguards Applications

The International Atomic Energy Agency (IAEA) held an internationalworkshop March 22–24, 2011, to address the questionof a possible replacement for helium-3-based neutron detectors.Within this wider scope, the workshop was focused on those applicationsused in IAEA verifi cation activities. There were twoprinciple objectives of the workshop: 1) to determine the specifi crequirements that a potential replacement technology would haveto satisfy, and 2) to identify alternative detector technologies thatappear promising for meeting those requirements. The workshopwas successful in achieving both objectives. A set of detailed andquantitative specifi cations was developed and achieved a generalconsensus among the conference participants. These includedoperational considerations such as temperature stability, safety,weight, and cost in addition to a number of performance requirements.The performance requirements were derived from ananalysis of the spectrum of IAEA applications that use neutrondetectors. After analyzing these applications, it was determinedthat the most common application for 3He detectors was for neutroncoincidence counting, comprising over 95 percent of 3Heuse. The details and rationale for this assessment will be provided.The performance requirements for neutron coincidence countingcan be directly calculated from the standard variance expressions.From these, a basic fi gure of merit (FOM) was developed thatcan be used to rank various different options. For neutron coincidencecounting, the fi gure of merit is: , where ε is thedetection effi ciency and is the detector die-away time. Boththe FOM and the calculations will be presented. The full list ofrequirements is included in this paper. The second purpose of theworkshop was to identify promising replacement technologies.There were multiple presentations of candidate detection technologiesover the course of the workshop, covering a wide spectrumof approaches and detection physics. These technologieswere judged relative to the performance of a 3He-based system,as well as its ability to meet the replacement technology requirementsas developed in this workshop. The paper will present asummary of this assessment.