Radioactive materials protective measures

Values for yields of 20 to 10,000 extrapolated from NCRP, Management of Terrorist Events Involving Radioactive Materials, Report 138, 2001, National Council on Radiation Protection and Measurement. With permission. 

The use of radiation dispersal devices, commonly referred to as dirty bombs, is particularly concerning for disaster planning and emergency preparedness personnel. An RDD is an explosive device designed to spread radioactive material without a nuclear explosion (Briggs Brinsfield, 2003). The initial blast from the explosion can kill or inflict mechanical trauma on those who are close in proximity to the explosion while the radioactive material is dispersed. Please refer to chapter 27, Radiological Incidents and Emergencies, for further information on decontamination, radiation sickness, and personal protective measures. 

National Council on Radiation Protection Measurements (NCRP). (2001). Management of terrorist events involving radioactive material (Report 138). Bethesda, MD Author. 

Radioactive materials released to the environment are sources of exposure and potentially harmful. Such releases may be from different activities in the nuclear fuel cycle, mining operations or industrial users. Strict control measures must be employed to keep the resulting doses as low as reasonably achievable . This implies the implementation of protective and control measures and includes the setting of limits for radiation exposure. 

The intermediate phase covers the period which starts from the first few hours after the commencement of the release and could extend for several days or weeks. During this phase, environmental measurements of radiation levels from deposited radioactive materials, as well as levels of radioactive contaminants in food, water and air, will become available. It is also during the intermediate phase that the plant is expected to be restored to a safe condition and the protective measures, based on the environmental measurements, will be implemented. In this phase the results of the prediction calculations by ESR will be very important to design and check the environmental monitoring plans and to carry out the appropriate evaluations of environmental consequences in conjunction with environmental monitoring activities. 

Now there is growing realization of the possibility of the use of radiological weapons (dirty bombs) by terrorist organizations. With such weapons, radioactive material could be dispersed in populated areas. Such acts could lead to a variety of problematic health and environmental consequences. The National Council on Radiation Protection and Measurement has recently published a valuable reference entitled Management of Terrorist Events Involving... 

Dose is uniform to the entire body due to whole body radiation. This table does not consider the intake of radioactive material. This is assumed due to employment of effective respiratory protection and other measures as necessary. 

However, the text of the convention that was finally adopted, the 2005 International Convention for the Suppression of Acts of Nnclear Terrorism (ICSANT), while maintaining the reference to aU radioactive material, contains language requiring States Parties to make every effort to adopt appropriate measures with respect to physical protection, leaving snbstantial State disaetion when... 

External release of radioactivity resulting in a dose to the critical group of the order of tenths of milHsievert. With such a release, off-site protective measures may not be needed. On-site events resulting in doses to workers sufficient to cause acute health effects and/or an event resulting in a severe spread of contamination for example a few thousand terabecquerels of activity released in a secondary containment where the material can be returned to a satisfactory storage area. Incidents in which a further failure of safety systems could lead to accident conditions, or a situation in which safety systems would be unable to prevent an accident if certain initiators were to occur. 

Preventive controls 1 and 2 both represent measures to avoid a crash. Preventive control 3 represents the ability of a safety structure, the cask, to prevent release of hazardous radioactive material. The cask, depicted in Figure 3E.1-1, was only designed to provide shielding for the target in transit and not to contain volatile material. In fact, no seal is installed on the lid during cask loading and no leak test is performed. The target will be protected in a crash if it remains in the cask and the cask is not breached or broken open in the crash. 

Where a sealed capsule constitutes part of the special form radioactive material, it should be ensured that the capsule offers no possibility of being opened by normal handling or unloading measures. Otherwise the possibility could arise that the radioactive material is handled or transported without the protecting capsule. 

In order to assess the efficiency of the safety design and the planned protective measures, the occurrence of accidents is assumed in analyses and the resulting plant responses are examined. The analysed accidents are characteristic with respect to the possible release of radioactive materials and to the loads they impose on components and systems. 

The key characteristics that need to be known about any radioactive material to plan the appropriate radiation protection measures are principal emissions and their energies half-life annual limit on intake (ALI) shielding requirement [e.g., halfvalue layer (HVL)] monitoring requirements and special considerations (e.g., physi-... 

The Reactor Tank has drained therefore, no liquid release potential exists. The sources of airborne and liquidpersonnel protection measures and doselassessment. Procedures and design are the primary measures used to ensure that exposures are kept ALARA during anticipated personnel activities in areas of the site containing radioactive materials. 

Provisions to promptly measure the amounts of radioactive material released and implement additional protective measures for the public if needed. 

Those who have learned to work with radioactive material can treat it on the same objective basis as for other toxic material. They adopt self-protective measures and precautions which avoid their suffering any detrimental effects. 

A Radiation Protection Programme shall be established for the transport of radioactive material. The nature and extent of the measures to be employed in the programme shall be related to the magnitude and likelihood of radiation exposures. The programme shall incorporate the requirements of paras 301, 303-305 and 311. Programme documents shall be available, on request, for inspection by the relevant competent authority. 

It is widely accepted by the scientific community that the risk of negative effects occurs on the health of workers as a result of their exposure to low doses of ionizing radiation. Sometimes this exposure results from the proximity or handling radioactive materials that occur naturally in the environment. It is therefore of utmost importance to identify these radioactive materials, assess their danger to exposed workers and to take measures to protect them against this exposure. 

The measures that are included in the design to provide an optimized level of radiation protection for operational states will be more than adequate for addressing the requirements for the commissioning phase (in which radiation levels are generally lower because of the lower power levels and the low buildup of radioactive material in the plant s components). 

The FSFs are essential for defence in depth and as a measure of the appropriate implementation of defence in depth through the various provisions for the design and operation of the plant, as indicated by the underlying relevant safety principles. The aim of the defence in depth provisions is to protect the barriers and to mitigate the consequences if the barriers against the release of radioactive material are damaged. 

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