Radiation mitigating exposures

Another approach that has been adopted in the IC industry for mitigating the effects of aberration, particularly chromatic aberration, is line narrowing of the incident radiation. The basis of this approach derives from the realization that an illumination radiation with extremely narrow spectral bandwidth is associated with very low chromatic aberration, obviating the need for color correction of the refractive elements associated with such a system. The required degree of spectral purity increases with increasing NA. For instance, KrF (248-nm) exposure systems with NA 0.7 require spectral bandwidth on the order of a picometer... 

With respect to mitigating oxidation, Bajt et al. have reported that oxides, once formed, are difficult to remove, while Nishiyama et al. reported that Ru oxidized by electron cyclotron resonance (ECR) O2 plasma can be successfully reduced by exposure to atomic H, raising the hopes for a practical mitigation method. Mertens et al. " have reported that under identical gas exposure and radiation conditions, a Si-terminated mirror shows oxidation, whereas a (unspecified) capped mirror shows carbon growth, implying that the surface chemistry plays a critical role in determining the nature of the contamination process a particular surface will undergo under EUV exposure conditions. 

This industry too had its share of corrosion costs. For boiler reactors capacity factor losses because of corrosion problems averaged over 6% between 1980 and 1991, reaching a peak value of 18% in 1982. It is estimated that corrosion problems have cost the nuclear utility industry more than 5 billion since 1980. In addition, repairs and mitigation cost the average US light water reactor > 0.5 billion in the industry with radiation exposures of about 100 rem per year. 

J F ortunately, through metal shielding, encapsulation, or hermetic sealing of electronic assemblies, radiation exposures can be largely mitigated. 

The Radiation Protection Objective is to ensure that in all operational states radiation exposure within the installation or due to any planned release of radioactive material from the installation is kept below prescribed limits and as low as reasonably achievable, and to ensure mitigation of the radiological consequences of any accidents. 

To achieve the Safety Objectives, measures need to be taken to control radiation exposure in all operational states to levels as low as reasonably achievable and to minimize the likelihood of an accident that might lead to the loss of normal control of the source of radiation. Nevertheless, accidents can happen. Measures are therefore required to ensure that any radiological consequences are mitigated. Such measures include on-site accident management procedures and off-site intervention measures in order to mitigate radiation exposure after an accident has occurred. The greater the potential hazard from an uncontrolled release of radioactive material, the lower the likelihood must be of its occurrence. 

For the next few weeks the world watched as, gradually, more details came out of the Soviet Union about the accident. Television cameras on board Soviet military helicopters looked straight down into the core of reactor 4, where the burning graphite could be seen. Other helicopters dropped sand and boron into the reactor. The world saw Soviet soldiers receiving large radiation exposures as they tried to mitigate the consequences. 

Ringer W, Simader M, Bernreiter, Kaineder H. (2008) Mitigation of three water supplies with high radon exposure to the employees. Radiation Protection Dosimetry 3 26-29. 

This shall ensure, as far as reasonably achievable, the control of radiation exposures, of radioactive releases and of the generation of radioactive wastes for all anticipated operational states, and control at the end of the useful life of the source. The design and construction shall also ensure, to the extent possible, the prevention of accidents that could affect site personnel, patients, the public and the environment, as well as mitigate the consequences of accidents if they do occur. 

The protection of people against exposure to ionizing radiation or radioactive substances and the safety of radiation sources, including the means for achieving such protection and safety, such as the various procedures and devices for keeping people s doses and risks as low as can reasonably be achieved and below prescribed dose constraints, as well as the means for preventing accidents and for mitigating the consequences of accidents should they occur. 

The design shall have as an objective the prevention or, if this fails, the mitigation of radiation exposures resulting from design basis accidents and selected severe accidents. Design provisions shall be made to ensure that potential radiation doses to the public and the site personnel do not exceed acceptable limits and are as low as reasonably achievable. 

In general, application of the optimization principle in radiation protection implies that a choice is to be made from a set of possible protective measures. To this end, feasible options should be identified, the parameters to serve as criteria for comparison and their appropriate values should be determined and, finally, the options should be evaluated and compared. The optimization principle should also be applied to design features whose purpose is to prevent, or to mitigate the consequences of, accidents at the facility that could lead to radiation exposure of the site personnel or the public. 

With a view to ensuring the protection of people and the environment from harmful effects of ionizing radiation, the IAEA safety standards establish fundamental safety principles, requirements and measures to control the radiation exposure of people and the release of radioactive material to the environment, to restrict the likehhood of events that might lead to a loss of control over a nuclear reactor core, nuclear chain reaction, radioactive source or any other source of radiation, and to mitigate the consequences of such events if they were to occur. The standards apply to facilities and activities that give rise to radiation risks, including nuclear installations, the use of radiation and radioactive sources, the transport of radioactive material and the management of radioactive waste. 

Through appropriate stabilization methodologies, e.g. modification of polymer properties and use of high quality light stabilizers, the mitigation of deleterious effects induced by increased UV radiation levels upon polymer materials can be attained with maintenance of their lifetime under outdoor exposure conditions [1]. 

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