RRFM 2009 Transactions - European Nuclear Society

Irradiation Growth of Graphite in Reflector Elements of JRR-4
Hironori HORIGUCHI, Taiju SHIBATA *1 , Masahiro YAGI,
Kenji YOKOO, Koji OYAMA and Tsuyoshi KUSUNOKI
Department of Research Reactor and Tandem Accelerator,
Japan Atomic Energy Agency
Tokai, Ibaraki 319-1195, JAPAN
*1: Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency
O-arai, Ibaraki 311-1393, JAPAN
ABSTRACT
A crack was found on the weld of aluminum cladding of a reflector element of
graphite in Japan Research Reactor No.4 (JRR-4). A survey on the reflector
element confirmed that the crack was caused by a growth of the graphite reflector.
The growth was observed in other reflector elements by radiographic testing. We
measured the dimensions of irradiated graphite reflectors after dismantling the
reflector elements. We found that the sizes had increased with fast neutron fluence
under the JRR-4 operation condition which was estimated lower than 200 ˚C.
1. Introduction
Japan Research Reactor No.4 are used for medical irradiation (Boron Neutron Capture
Therapy), education and training for engineers, activation analysis and researches in various
fields. The JRR-4 is a 3.5 MW pool-type reactor which is cooled and moderated by light water.
The JRR-4 core consists of fuel elements, reflector elements, control rods and irradiation
tubes. The top view of the JRR-4 core is shown in Fig.1. The reflector element is composed of
reflector part, handle part, joint part and plug part as shown in Fig.2, all of which are made of
aluminum alloy except for the graphite reflector set in the aluminum cladding. The graphite
material is a fine-grained and isotropic one (IG-110) manufactured by Toyo Tanso Co.. The
reflector is a rectangular shape of 691x72x72 mm.
Fig.1. Top view of JRR-4 reactor core.
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