Present Status of the High Temperature Engineering Test Reactor (HTTR)

Abstract

With growing concerns about global warming due to emission of greenhouse effect gases like CO₂, it is especially important to make efforts to obtain more reliable and stable energy supply by extended use of nuclear energy including high temperature heat from nuclear reactors because they can supply a large amount of energy and its plants emit only little amount of CO₂ during their lifetime. Hence, efforts are to be continuously devoted to establish and upgrade High Temperature Gas-cooled Reactor (HTGR)technologies. It is also expected that conducting basic research at high temperatures using HTGR will contribute to innovative basic research in future. The construction of the High Temperature Engineering Test Reactor (HTTR), which is an HTGR with a maximum helium coolant temperature of 950°C at the reactor outlet, was proposed by the Japanese Atomic Energy Commission (JAEC) in 1987 and is now under way by the Japan Atomic Energy Research Institute (JAERI).

The construction of the HTTR started in March 1991 and essentially completed in 1996.Functional test operations were performed in 1996 and 1997. Some refurbishments have been required to remedy the control rod drive standpipe internal structure heat-up event.

The HTTR will become critical in June 1998. A test program has already been largely defined. Physics tests will concern the first criticality measurements at zero power and during rise to power to confirm the nuclear design and the compliance to regulatory limits. In loading fuel an intermediate stage with an annular core will be created, and some physics tests be carried out. Thermal hydraulics tests will confirm the plant design and validate the respective codes. Safety tests will demonstrate the typical HTGR safety features, and tests at power operation will confirm the integrity of the high temperature components.