In the nuclear
reactor environment, due to irradiation, the mechanical properties of the
material are degraded. For the safe and long-time operation of the nuclear
reactor, the material properties should be known to us. The non-instrumented
irradiation gas-gap capsule in the research reactor, fast breeder test reactor
(FBTR) in INDIA has used the evaluation and prediction of the irradiation
behavior of the material in the reactor core and the development of new nuclear
materials for the next-generation reactor. An irradiation capsule is loaded
with the tubular and disc types of test specimens. In the reactor, mainly due
to the gamma rays and neutrons irradiation the capsule and specimens work as a
The design of the irradiation
capsule has a main body 1045mm long, and 20 mm diameter which contains four (4)
irradiation sub-capsules of diameter 14.5 mm and length 167 mm in a cylindrical
shape. The irradiation capsule consists of an end plug, sub-capsule holder
along with the specimens, insulator gas gap region. A schematic view of the
capsule main body considered in this study is shown in figure 1. The test
specimens are in two shapes.
A. Disc shape-
which diameter is 8mm and width is 0.5 mm and there are 28 numbers.
shape- 6.6mm outer diameter and 5.7mm inner diameter and there are 2 two
numbers. A schematic view of the irradiation sub-capsule shown in figure 2.
After the specimens kept in the sub-capsule and irradiation capsule are
irradiated into the reactor core, the heat generation due to the gamma and
neutrons flux in the irradiation capsule. This gives in a different temperature
distribution among the specimens. The nuclear reaction profile in the reactor
core is known that in the middle of the core is higher than the top and bottom
of the core . In the irradiation sub-capsule specimens are kept in a mixture
of helium and argon gas environment for controlling the particular temperature
In the study, the thermal analysis
of the instrumented capsule for the irradiation test of the specimens materials
are studies in the COMSOL Multiphysics Computer Code. The temperature
distribution in the irradiation capsule is evaluated and found the percentage
of gas mixture of helium and argon for the particular specimen’s temperature.