RESEARCH REACTORS AND ASSOCIATED RADIOLOGICAL HAZARDS

Not all of the types of radiation sources mentioned in the following sections are relevant for all types of research reactors, nor will the importance of each source be equal for all types of research reactors or their utilization. A careful evaluation of the hazards, their magnitude and their impacts for the specific type of research reactor should be carried out to ensure the proper implementation of adequate programmes for radiation protection and radioactive waste management. 

The type of reactor significantly influences needs for radiation protection. While most research reactors of low and medium power levels will have similar characteristics, some designs, in particular at higher power levels, should have particular radiation protection features and programmes. 

This applies, for instance, to heavy water moderated reactors, for which special attention should be paid to the production of (tritium), including its monitoring. This also applies to liquid metal cooled reactors, for which special precautions should be prescribed for coping with incidental leaks of coolant. Another example is that of light water reactors, for which gamma radiation dose rates from Ar and should be taken into consideration. 

Power excursions (transients) may lead to comparatively high power levels and consequent high levels of direct radiation if the core is not well shielded. Power excursions may be of particular importance for research reactors or critical assemblies of low power level, which in normal operating conditions do not require significant shielding. In the design of the irradiation facilities (e.g. beam tubes), the direct radiation caused by transients should be considered. 

If such power excursions are part of the design for normal operation, the equipment and installations for both monitoring and protection should be able to withstand high power levels. Power excursions give rise not only to intense direct radiation fields, but also to fuel degradation and the release of fission products from the fuel if it is not designed to cope with such excursions. 

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