Irradiation programme studies IMSR graphite behaviour

09 October 2019

Terrestrial Energy and NRG have begun an irradiation programme to analyse the behaviour of graphite under the conditions it will experience during the seven-year life of a Terrestrial Energy Integrated Molten Salt Reactor (IMSR) core unit.

The graphite irradiation programme is being carried out by NRG (Image: NRG)

The graphite irradiation study is part of a comprehensive test programme supporting the design of IMSR being conducted at NRG's facilities in the Netherlands. The programme will provide data that demonstrates to nuclear quality standards the structural changes of graphite under the irradiation conditions experienced during the 7-year life of an IMSR Core-unit. Terrestrial Energy and NRG presented the programme at the 20th International Nuclear Graphite Specialists' Meeting in Brugge, Belgium.

NRG, operator of the European Union-owned High Flux Reactor at Petten, is providing technical services to support Terrestrial Energy for "in-core" materials testing and development the IMSR power plant. "NRG has been supporting the nuclear power industry since 1955 and has extensive experience of the requirements for successful nuclear technology development and specially for graphite," Commercial Director of NRG Vinod Ramnandanlal said. "Innovative Generation IV reactors have truly transformative potential and Terrestrial Energy's IMSR is a leading design."

Molten salt reactors (MSRs) use fuel dissolved in a molten fluoride or chloride salt. As the fuel salt is a liquid, it functions as both the fuel (producing the heat) and the coolant (transporting the heat away and ultimately to the power plant). Terrestrial's IMSR, which builds on 50 years of MSR experience at the USA's Oak Ridge National Laboratory, integrates the primary reactor components, including the graphite moderator, into a sealed and replaceable reactor core unit with an operating lifetime of seven years.

The graphite irradiation programme aims to enable Terrestrial to select most suitable graphite grade for use in the IMSR reactor, as well as qualifying graphite for IMSR use. Different graphite grades will be subjected to neutron irradiation at elevated temperatures and characterised on a range of material properties. The data set created will cover the lifespan of the graphite components in the IMSR.

The collaboration between Terrestrial Energy and NRG is part of a wider partnership between Terrestrial and the European Union’s scientific community, following a March 2018 technical services agreement with the European Commission's Joint Research Centre (JRC) in Karlsruhe, Germany to perform confirmatory studies of the fuel and primary coolant salt mixture for the IMSR.

Terrestrial plans to commission the first IMSR power plants in the late 2020s.

Researched and written by World Nuclear News