Radiation Protection Group

Since its foundation the J. Stefan Institute has been engaged in research and application of radioactive materials and other sources of ionizing radiation. Several accelerators have operated at the Institute: betatron, Van de Graaff and a neutron generator. Only Van de Graaff accelerator is still in operation. In 1966 the research reactor TRIGA MARK II of 250 KW was commissioned and in 1991 it was upgraded for pulsed operation. Adjacent to the reactor there are radiochemical laboratories, producing isotopes used in medicine and performing activation analysis of samples. Since 1986 there is a temporary storage facility for low and intermediate radioactive waste for small users in Republic Slovenia (hospitals, industry). There are some other smaller laboratories dealing with sources of ionizing radiation.

For these reasons Institute has done a pioneering work in the introduction of contemporary radiation protection principles and practices. At present the radiation protection is performed by independent Radiation Protection Group, responsible to the director of the Institute. It consists of four radiation protection workers (head and three technicians, all specialized in radiation protection. The main activities of the group are:

• personal dosimetry of radiation workers,
• area radiation survey of laboratories, dealing with ionizing radiation sources,
• control and receipt of radioactive sources in the temporary radwaste storage facility,
• environmental monitoring of the Reactor center Podgorica.

There were about 150 radiation workers monitored by personal dosimetry in the recent years. Termoluminiscent dosimeters and TLD reader of our own production are used. There has not been a single case of overexposure, typical annual doses being very low, usually of the order of natural background or slightly above it.

The area radiation surveys (surface contamination, concentration of radionuclides in the air) are performed in places where open radiation sources are handled.

Environmental monitoring of the Reactor center is based on two types of measurements:

• Source term or measurements of emissions. There are atmospheric releases of 41Ar during the operation of the reactor and liquid releases of some neutron activation products to the river Sava from radiochemical laboratories. By continuous monitoring of releases and temporary high resolution gamma spectrometry of samples it is assured that environmental impact is within the authorization limits. By use of source term data and conservative modelling it has been estimated that a typical annual dose to the population from the released radioactivity has not exceeded 1 micro Sv per year for each of the pathways -- 1 micro Sv per year represents only 0.1% of annual dose limit for population.
• The second type of measurements consist of controlling the immisions -- the radiological situation in the environment. On-site measurement of external radiation are performed continuously (GM detector) and monthly (TLD); besides air concentration of radionuclides, soil radioactivity, radioactivity in rain, river sediments are measured. The purpose of this control is to confirm the results of source-term based predictions and to detect any source of contamination from off-site. Environmental monitoring of the Reactor center in Podgorica could not reveal any environmental impact of the activities of the center. Only natural radioactivity and radioactive contamination due to test nuclear explosions in the past and Chernobyl accident were found in the environment.