Neutronics characteristics of a 165 MWth Xe-100 reactor

Abstract

The Xe-100 is a high temperature, helium-cooled, graphite moderated, pebble bed reactor (HTGR) featuring a 6-times through, multi-pass (MEDUL = MEhrfachDUrchLauf) fuelling scheme. It is designed for delivering heat in the form of superheated steam at 565 °C and 16.5 MPa. This steam can be used to generate electricity, provide process heat for petrochemical application, or for cogeneration applications, such as the treatment of contaminated water resources, whilst simultaneously generating electricity.The design is characterized as a Generation IV reactor, with a core that cannot melt and featuring safety characteristics that will eliminate the need at any time to evacuate or displace the public, or that will cause unallowable contamination of the land. The technology is based on proven technology that has demonstrated these safety claims both experimentally and in commercial deployment. The foundation of proof ensures high levels of design and technical readiness.In the overview presented below a parametric comparison is offered of a 165 MWth design against that of X-energy’s 200 MWth reference Xe-100 design. The excess reactivity in both cases is shown to be limited by the continuous fuelling regime, whilst the core geometry and selected core power density enables passive heat removal. In this way the desired intrinsic safety design features of a typical GEN IV design are guaranteed. It is shown that even in the event of a depressurized loss of forced coolant (DLOFC) design basis event, no significant amount of radiological material will be released. A larger margin of tolerance is afforded in the 165 MWth design case, as expected.The coupled core neutronic and thermo-fluid dynamics design for the Xe-100 is performed with the VSOP-A and MGT systems of codes. For the equilibrium core, VSOP results demonstrate that the spherical fuel powers (maximum 3.0 kW) and operational temperatures (<1000 °C) fall well within the envelope of the design criteria. Adequate reactivity control and long-term, cold shutdown are provided by two separate, independently actuated systems, while the overall negative reactivity temperature coefficient is illustrated over the total operational range.