Investigation on structural integrity of graphite component during high temperature 950 °C continuous operation of HTTR

Abstract

Graphite material is used for internal structures in high temperature gas-cooled reactor. The core components and graphite core support structures are so designed as to maintain the structural integrity to keep core cooling capability. To confirm that the core components and graphite core support structures satisfy the design requirements, the temperatures of the reactor internals are measured during the reactor operation. Surveillance test of graphite specimens and in-service inspection using TV camera are planned in conjunction with the refueling. This paper describes the evaluation results of the integrity of the core components and graphite core support structures during the high temperature 950• C continuous operation, a high temperature continuous operation with reactor outlet temperature of 950• C for 50 days, in high temperature engineering test reactor. The design requirements of the core components and graphite core support structures were satisfied during the high temperature 950• C continuous operation. The dimensional change of graphite which directly influences the temperature of coolant was estimated considering the temperature profiles of fuel block. The magnitude of irradiation-induced dimensional change considering temperature profiles was about 1.2 times larger than that under constant irradiation temperature of 1000• C. In addition, the programs of surveillance test and ISI using TV camera were introduced.

In situ measurement of elastic and total strains during ambient and high temperature deformation of a polygranular graphite

“…GEMINI and GEMINI+ between EU and USA), with the latter focussed on the design and regulatory framework of the first modern HTGR 8 . Reliable structural integrity assessment of graphite components is critical for new build designs 9,10 and also for the safe operation and eventual decommissioning of the graphite cores in the current and retiring fleets 11 . This must be underpinned by a sound understanding of the deformation and fracture of graphite under conditions that represent its service in the reactor environment of a high temperature gaseous coolant and fast neutron irradiation 12,13,14,15 .…”

The Evaluation of the High Temperature Gas Cooled Reactor Safety to Fulfill the Requirement of the Next Generation Nuclear

“…Sumita, Shimazaki and Shibata [27] tested the integrity of the core components and graphite core support structures of HTGRs using high temperature Engineering Test Reactor (HTTR). They confirmed that during the high temperature of 950 O C continuous operations, the structural integrity of the core components and its graphite support structures was still maintained and, therefore, there was no challenge to the core cooling capability.…”

Assessment of the fracture toughness of neutron-irradiated nuclear graphite by 3D analysis of the crack displacement field

“…Due to the effects of irradiation, tensile stresses can develop within graphite components during the reactor lifetime that may be sufficient to initiate and propagate fracture [10][11][12][13].…”