Radiological releases magnitudes

A log-log graph showing the relative magnitudes of the radiological releases from four major reactor accidents. 

A D—T fusion reactor is expected to have a tritium inventory of a few kilograms. Tritium is a relatively short-Hved (12.36 year half-life) and benign (beta emitter) radioactive material, and represents a radiological ha2ard many orders of magnitude less than does the fuel inventory in a fission reactor. Clearly, however, fusion reactors must be designed to preclude the accidental release of tritium or any other volatile radioactive material. There is no need to have fissile materials present in a fusion reactor, and relatively simple inspection techniques should suffice to prevent any clandestine breeding of fissile materials, eg, for potential weapons diversion. 

It appears that the quantities of radioactivity which can be potentially released are not negligible, even if they are lower by an order of magnitude than the con esponding quantities of fission (Table 24-4). The evaluations in the table have been made as best estimates of important accidents. In any case, however, the lower radiological risk of radioisotopes released by fusion reactors has to be taken into account. 

The release of about 0.1 gm of plutonium and 0.001 gm strontium does not represent a serious radiological hazard in the context of a maximum accident result. Furthermore, the aerosol would settle and deposit on surfaces before it is released. In any event, calculations at a typical reactor site show these values to be at least one order of magnitude below acceptable accident limits. 

The public can usually be protected from an uncontrolled release of radiological material only by some form of intervention (e.g. evacuation) that disrupts normal living. Such intervention is termed protective action. This subsection presents basic radiation protection objectives and protective action guides that establish the magnitude of radionuclide releases requiring early protective action. A more complete discussion of protective actions that may be appropriate during or after a severe reactor accident is presented in Section 5.4. 

In addition, procedures shall be implemented for assessing releases of radiological and non-radiological hazardous materials, including methods for measuring contamination levels at the SR reactor facilities, onsite and offsite, and for determining the magnitude of the source terms and projected doses that may be released. 

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