Exposure Situations Flashcards
What is a ‘practice’ in terms of radiation safety? Give some examples.
An activity that adds radiation exposure to that which people normally receive due to background, or that increases the likelihood of incurring an exposure. Broader activities are typically considered such as:
- Medical.
- Industrial.
- Agricultural.
- Educational, training and research.
- Nuclear power.
- Irradiation installations.
- Mines and mills processing radioactive ores.
- Radioactive waste management facilities.
What is an ‘intervention’ in terms of radiation safety? Give some examples.
An activity that seeks to reduce the level of an exposure, or the likelihood of incurring an exposure. Examples include:
- Protective actions applied in radiation emergencies (e.g. nuclear installation accident) to reduce or avert temporary exposures.
- Remedial action to avert or reduce long term radiation exposures from chronic situations (e.g. from radon in buildings).
What should be considered in the justification of practices and interventions?
The risks and benefits associated with many factors should be considered such as:
- Radiological aspects.
- Social aspects.
- Political aspects.
- Health impacts.
- Economic impacts.
What should be considered in the justification of CT screening for asymptomatic individuals?
- Detriment from radiation dose.
- Disadvantages of false positives which could cause unnecessary concern or false negatives which may lead to the ignoring of symptoms once they appear.
- Benefits from the early detection of cancers.
- Individuals who may be at increased risk (e.g. due to age or family history).
- Follow-up after screening.
- Information provided to individuals in order to allow them to make an informed decision.
How is individual risk of exposure to radiation limited?
- Dose limits are set for which should not be exceeded. Exposure above these limits would correspond to a level of unacceptable risk.
- These are not applicable to the patient undergoing the medical exposure or to interventions to reduce exposure (e.g. in a radiation emergency).
How did ICRP103 evolve from a process-based approach (i.e. involving ‘practices’ and ‘interventions’)?
The ICRP103 approach is to use a situation-based process with the following exposure situations defined:
- Planned exposure situations.
- Emergency exposure situations.
- Existing exposure situations.
What is a planned exposure situation?
- This includes activities previously considered as ‘practices’ (i.e. some use of radiation that is planned in advance such as medical or nuclear exposures).
- Includes potential exposure situations resulting from reasonably foreseeable accidents (e.g. exposure due to equipment fault).
- Dose limits apply.
- Optimisation applies (e.g. through use of dose constraints).
What is an emergency exposure situation?
- These tie in with previously defined ‘interventions’ and include exposures resulting from major accidents or malicious acts (e.g. terrorism).
- They are not subject to dose limits.
- Dose reference levels for optimisation.
What is an existing exposure situation?
- This includes exposures we have little control over (e.g. naturally occurring radon, exposure from past events or accidents).
- Exposure through practices outside of ICRP recommendations are also included (i.e. uncontrollable exposure or exposures that are so low that protection is unwarranted).
- Optimisation is applied through dose reference levels.
How is protection optimised in terms of different exposure situations?
- Radiation doses should be kept ALARP with economic and social factors taken into account.
- This is achieved through the application of constraints to dose or risk to prevent an unfair distribution of exposure or risk, respectively.
What are dose constraints and reference levels?
- These are restrictions that apply prospectively to exposure of a nominal individual or reference person from specific source.
- They are used to limit the range of options considered in optimisation of the exposure.
- For public exposures, they apply an upper bound to the annual dose received from the planned operation of a controlled source.
- Reference levels, in particular, apply to emergency situations (the concept is the same).
What is a critical group?
- A group of individuals expected to receive the highest dose from a source.
- Dose constraints/reference levels are applied to this group.
- This terminology is typically used when considering the impact of radioactive discharges.
- An example with regards to the disposal of aqueous waste might be a sewage work.
What are Naturally Occurring Radioactive Materials (NORM) and what is of most interest for the medical physicists role?
- NORM: Radioactive materials containing no significant amounts of radionuclides other than those that are naturally occurring.
- Radon is most pertinent for medical physicists.
What is radon and why does it pose health risks? What can be done about this?
- Radon is a colourless, odourless gas from the Uranium decay series that emits high energy alpha particles. Radon can, therefore, cause damage to the lungs (e.g. lung cancer) if breathed in.
- Maps exist to show radon affected areas.
- Domestic action levels are set at 200 Bq/m^3.
- Workplace action levels are set at 300 Bq/m^3 (averaged over a working year).
- Radon risk assessments are required in the workplace.
- IRR17 applies in workplaces where radon levels are above action levels. The HSE must be informed. Other employers working in the area must also be informed.
What would a radon risk assessment include?
- If in a radon-affected area, measurements should be carried out in a number of occupied ground floor areas.
- If site is not in a radon-affected area, only basements need to be checked as there are higher levels of radon underground.
- Risk is typically recorded as low with no action needed.
- Remediation may be required or exposure control via local rules (e.g. limiting of time in affected area and monitoring) if high levels found.
- Review dates.
