Gamma-Irradiation device JBE10 at the research neutron source Heinz Maier-Leibnitz     

The study of rock salt is a field with a lot of open questions. The irradiation of rock salt lays the foundation for a wide field of microscopic studies.

Untreated rock salt is more or less transparent and colorless, which makes microscopic research difficult. High energetic ionizing radiation causes the formation of color-centers inside the crystals. Free electrons get trapped by the potential of surrounding ions. This electrons absorb parts of the visible light which changes the color of the crystals. After this treatment the color is changed and a significant amount of valuable information (fluid inclusions, micro-tectonic etc.) become visible.




For the irradiation a high energetic and stabile gamma ray–source is needed, but irradiation with neutrons, which could radioactively activate the samples, must be avoided. Perfect requirements are provided by the research reactor FRM2 in Munich. The spent fuel–elements are stored in a basin near the reactor. The neutron flux density of this spent fuel-elements is so low that the rock salt samples are not activated but the dose output of gamma-rays is still in the needed kilo Gray dimension. Due to the tabular design of the fuel-elements the JBE10 with the salt rock samples can be placed inside the fuel-elements. The JBE10 is equipped with a heater which heats the samples with temperatures up to 150°C during the irradiation.

The rock salt samples are in a sample cage (for safe charging) inside the inner cylinder. This inner cylinder is waterproof and is equipped with a heater. The inner cylinder fits inside the outer cylinder.

The outer cylinder is also waterproof, so there is no risk of getting the rock salt samples in contact with the reactor-basin water. The JBE10 is connected with an cable to a control-box during the irradiation to regulate the heater and to control the sensors.
 

Maximum charge:          70mm diameter, 500mm height
Maximum heat-temperature:          150°C
Maximum dose output depends to the fuel-element.
It is tested with a dose output up to 45 kGy/h

• Dr. Guillaume Desbois

• Alexander Raith