Radiological hazard potential

APPLICATION OF THE RADIOLOGICAL HAZARD POTENTIAL (RHP) TO RADIONUCLIDES IN MAGNOX REACTOR DECOMMISSIONING... 

The paper considers how the updated metric, named Radiological Hazard Potential (RHP), can be summated for the radioactive waste streams on a particular site and used to help set priorities for future waste management activities. Uncertainties in RHP values may be utilised to prioritise further sampling and radio-analytical measurements. The paper outlines the difficulties in dealing with hazards posed by non-radioactive materials, and some cautionary advice is given on the correct application of the RHP, particularly in avoiding its use as the sole criterion for establishing work priorities. 

Since the formation of the Nuclear Decommissioning Authority (NDA) there has been an emphasis on a demonstrable process for prioritisation of remediation work on UK decommissioning sites. As part of this process, the HI has now been re-named the Radiological Hazard Potential (RHP) and is one of five metrics which are combined numerically to produce a prioritisation metric, the Safety and Environmental Detriment (SED), see below. This paper relates only to the RHP. It is a quantitative measure of the potential for a material or plant item to cause harm, but does not address the risk of that harm occurring and has universal application irrespective of facility type. 

Figure 2 Radiological Hazard Potential - Top impacting Waste Streams...

Instruction for the Calculation of the Radiological Hazard Potential, Nuclear Decommissioning Authority, 13 July 2006, Document No. EGPR02-W101, Rev. 2. 

A D—T fusion reactor is expected to have a tritium inventory of a few kilograms. Tritium is a relatively short-lived (12.36 year half-life) and benign (beta emitter) radioactive material, and represents a radiological hazard 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. 

Accurate estimates of the accumulation of tritium on the surface and in the bulk of the materials of the various PFCs of ITER and the degree of tritium permeation to the coolant are very important for determining the tritium supply requirements, for assessing the radiological hazards from routine operation and from potential accidents, and for decisions regarding the de-tritiation system. 

Use risk assessment of potential biological, chemical, or radiological hazards in the community to determine roles and responsibilities of those involved in public health BT response. 

The Chemical Hazard Potential (CHP) addresses chemical hazards associated with a material and can be applied to non-radioactive and radioactive materials. For a material that has both a radiological and a chemical hazard potential (e.g, radioactive asbestos) both of these hazard potentials must be taken into account in deriving the Safety and Environmental Detriment (SED). 

In terms of their potential radiological hazards the above alpha emitters are divided into five long-lived alpha-emitters i.e. 

D. All levels of ACE command should keep a totally open flow of information regarding the existence and status of radiological hazard areas within the military structure. However, Commanders should be aware that potential belligerents could use radiological hazards to increase tensions. Therefore, Commanders shall apply an appropriate level of security with regards to release of this information to civil authorities and the general public. 

The NBC Defense Officer of each operational headquarters in theater shall maintain a current list of all confirmed, suspected and potential radiological hazards within his area of operations. The NBC Defense Officer at the highest operational headquarters shall monitor the status of these areas and make periodic updates for issue to ACE units. 

E. Once the determination is made that a suspected radiological hazard area is in fact clear, it may be removed from the current list of radiological hazard areas. However, if it is confirmed that there is radioactive material present but is not currently hazardous, the site shall remain on the current list of radiological hazard areas as a potential site. Units operating in the vicinity of potential radiological hazard areas shall initiate periodic monitoring. 

Type of potential exposures to chemical, biological, and radiological hazards types of human responses to these hazards and recognition of those responses principles of toxicology and information about acute and chronic hazards health and safety considerations of new technology. 

The Regulations provide an acceptable level of control of the radiadon and criticality hazards associated with the transport of radioactive material. With one exception (UFg) the Regulations do not cover hazards that may be due to the physical/ chemical form in which radionuclides are transported. In some cases, such subsidiary hazards may exceed the radiological hazards. Compliance with the provisions of the Regulations therefore does not absolve its users from the need to consider all of the other potential dangeions properties of the contents. 

The safety and biocompatibility of the dmg delivery system and its components have been extensively tested according to Tripartite Biocompatibility Testing Guidelines (Center for Devices and Radiological Health, 1993). Specifically, these studies have shown that PLA is nontoxic and the hazard potential of NMP is insignificant. Additional preclinical tests to evaluate tissue irritation potential, implantation effects, and biodegradation have been completed for formulations prepared with PLA, PLG, and PLC polymers dissolved in NMP or DMSO. The pharmacokinetics of these formulations have also been tested for specific dmg delivery applications. 

The metabolic constraints that control the quantity of iodine in the thyroid gland and the low specific activity of I restrict the amount of I that can be concentrated in the thyroid gland. Considering these factors, and given the lack of effects in the thyroid glands of rats fed I for life, the potential for a radiologic hazard from exposure to I appears to be limited. 

---