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Radiation Protection Glossary

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Cherenkov Radiation
Cherenkov radiation is Electromagnetic (non-ionising) radiation emitted when a charged particle (e.g. an Electron ) passes through a medium (e.g. water) at a speed greater than that of light in the medium. This can be seen as the characteristic "blue glow" where sources of large activity (e.g. irradiator sources or spent nuclear fuel) are stored under water.
Chronic Exposure
Exposure to sources of Ionising Radiation over a long period of time, possibly resulting in adverse health effects such as cancer or genetic disorders in offspring of exposed parents. Likely result of a Probabilistic / Stochastic effect of ionising radiation.
Closed Source
With respect to Radiation Protection , a closed source is is a source of Ionising Radiation in the form of Radioactive material which is encapsulated or otherwise contained. The implication is that closed radioactive material can not escape and will not cause a Contamination hazard. Closed sources have many applications including use in irradiators (food and products), medical blood irradiators and density gauges. Whilst the term 'Closed Source' is comparable with 'Sealed Source' , it is defined in a particular way in some of the UK legislation (e.g. see Exemption Orders).
Collective Dose
More accurately known as Collective Effective dose . This quantity is derived from summing the individual effective doses within an exposed population (or workforce). One type of unit to express this quantity is the man Sv. This quantity has been used to assess overall detriment and therefore as an aid to decision making techniques in optimising radiation protection (e.g. Risk Assessment ). It is less well used nowadays where dose constraints are preferred instead .
Consumer Products
Any household product that contains a quantity of radioactive material yielding Ionising Radiation for reasons of functionality of that item. Examples include ionisation smoke detectors and luminising items such as watches and clocks which contain radium . Consumer products from by-gone-days are a potentially significant radiation hazard.
Contamination
Usually an undesirable situation where radioactive material in an Unsealed Source (open source) state is present in the working environment, or otherwise un-contained and not required. Contamination can either be loose (easily removed) or fixed. Loose contamination is usually of more concern since intakes of radioactive material through Inhalation , Ingestion and Injection may occur.
Contingency
With respect to Radiation Protection , contingency means preparing for, and taking action, in the event of an unplanned release of Radioactive material or other unplanned Radiation incident which could lead to radiation exposure to the individual, the population or environment. Contingency may be determined by simple risk assessment or by a more comprehensive Probabilistic Safety Assessment (PSA) as part of a Safety Case. Usually contingency arrangements deal with Reasonably Foreseeable (credible) events, although for some industries (e.g. nuclear), the contingency plans have to be extendable.
Controlled Area
Controlled Area is defined in the Ionising Radiations Regulations 1999. A Controlled Area is an area where any person is likely to receive more than 6 mSv Effective dose (or 3/10 of any other UK Dose Limit ) and / or an area where specific and detailed procedures need to be followed in order to restrict exposure from Ionising Radiation and ensure that doses are ALARP .
Cosmic Rays
Radiation originating from outside the Earth's atmosphere. The term 'cosmic ray' can actually include a number of classes of high energy radiation including Gamma Rays , Electrons and Ions .
Credible
The term 'credible' is used in a number of areas of Radiation Protection , including Risk Assessments , Safety Cases and Probabilistic Safety Assessments . Credible can be taken to mean an incident or accident which is thought to be Reasonably Foreseeable . Credible can be expressed numerically and this value will differ depending on the situation being assessed (but perhaps in the range of 10-5 to 10-6).
Curie
The Curie (Ci) is the traditional unit of Activity (where its SI equivalent in the Becquerel ). 1 Ci is equivalent to 3.7 E10 disintegrations per second (dps) and since 1Bq=1dps it follows that 1Ci = 3.7 E10 Bq (approximately). The Ci was based on the activity found in 1 g of Radium .