Measurement and evaluation of the irradiation test parameters for a specimen in a HANARO material irradiation capsule
A material capsule system has been developed for irradiation tests of nuclear materials in the core region of the High-flux Advanced Neutron Application Reactor (HANARO) and has been actively utilized for the various material irradiation tests requested by numerous users. For an irradiation test in the reactor, nuclear characteristics and irradiation temperature of the capsule parts are basically necessary for the safety analysis of the capsule and capsule detail design. The irradiation temperature and neutron fluence of the specimens are key parameters required by a user to analyze any neutron irradiation damage effects. Based on a basic design of a capsule, the reactivity effect, neutron flux/fluence, and gamma heating of specimens are calculated by the MCNP code. To compare the calculated neutron fluence of the specimens, thermal and fast fluence monitors (F/Ms) are installed in a capsule. After an irradiation, the F/Ms are dismantled and analyzed to obtain a neutron spectrum. The obtained fast neutrons (E>1.0MeV) by using the SANDII code are located within about a 20% error range of the theoretical values calculated by the MCNP code. The irradiation temperature of the specimens is analyzed preliminary by using the GENGTC or ANSYS codes based on the basic design of a capsule and gamma heating. During an irradiation test, the temperatures of the specimens in a capsule are measured and monitored by thermocouples. The DPA (Displacement Per Atom) and activation of the irradiated specimens are also evaluated by using the SPECTOR and ORIGEN2 codes, respectively, at HANARO.
Neutron Irradiation of Electronic Materials at HANARO
HANARO, a 30 MW open-pool type multipurpose 
research reactor, has been operated as a platform for nuclear researches in 
Korea, and irradiation facilities have been mainly utilized for various nuclear 
material irradiation tests requested by users. Although most irradiation tests 
have been related to national R&D relevant to nuclear power, demand for 
neutron irradiation of electro-magnetic materials is increasing rapidly at 
HANARO. Another research reactor, which is named the KIJANG research reactor 
(KJRR), is under construction in Korea. KJRR is dedicated to increasing the 
national radio-isotopes supply capacity and to the irradiation facilities 
including Neutron Transmutation Doping (NTD) facilities for power semiconductor 
production in a large scale and fast neutron irradiation (FNI) facility for 
fast neutron irradiation. The NTD and FNI facilities in the KJRR reactor can be 
effectively utilized on the study of separated effect of thermal and fast 
neutron irradiations on the properties of electro-magnetic materials. HANARO 
will also specialize more on irradiation research, including neutron 
irradiation of electronic materials. The research status and possibility of new 
electro-magnetic materials using neutron irradiation at HANARO are surveyed to 
ascertain the utilization of neutron irradiation technology in electro-magnetic 
material researches.
Observation of the crossover from two-gap to single-gap superconductivity through specific heat measurements in neutron-irradiated MgB2.
We report specific heat measurements on neutron-irradiated MgB2 samples, for which the critical temperature is lowered to 8.7 K, but the superconducting transition remains extremely sharp, indicative of a defect structure extremely homogeneous. Our results evidence the presence of two superconducting gaps in the temperature range above 21 K, while single-gap superconductivity is well established as a bulk property, not associated with local disorder fluctuations, when Tc decreases to 11 K.