We provide instructions for monitoring your radiation levels.
- Instructions for monitoring personal radiation (PRM)
- Actions on receipt of new monitoring cards
- Thermoluminescent dosimetry (TLD)
- Lost or extra cards and holders
- Special issue monitors
- Monitoring records
- Radiation doses
Instructions for monitoring personal radiation (PRM)
- Monitoring cards and forms will be sent to your school for the new monitoring period. The dates of the monitoring period, name of wearer, registration number and occupation code (details on back of form) will be printed on the forms. There will also be a control card sent with each issue.
- The control card is to be placed in a dry area away from radiation sources (typically in the desk of the officer administering the service in the school).
- Monitoring periods are for three calendar months and begin on 1 March, 1 June, 1 September, 1 December. Replacement cards should arrive at the University on the 20th of the preceding month.
- UWA Safety, Health and Wellbeing provides a central distribution and collection service for all personal monitors at the University.
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Actions on receipt of new monitoring cards
- Check the names are correct and that the correct number of cards has been received.
- Remove the old cards from their holders and place the new cards in the card holders with the name facing the front.
- Enter the type of radiation or isotope in the space provided on the form for the monitoring period just concluded.
- The cards and forms collected from the previous issue should be returned immediately to ARPANSA, not those just issued. Check that you have returned all the cards listed on the form including the controls. Thermoluminescent dosimetry (TLD) cards from users and the school control card need to be returned promptly at the end of the monitoring period. Send these to the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). If for some reason they are not all accounted for please include a short note explaining why.
- Changes to your list of people being monitored should be made on the following form and sent to Safety, Health and Wellbeing. Two weeks notice is required for the changes to take affect.
- All Personal Radiation Monitoring Service forms
- Schools will be invoiced directly for cards used and for new holders or lost badges.
- Results will be provided to departments and will also be retained in Safety, Health and Wellbeing. Monitoring results should also be kept in a file in the school.
- Regarding the dose reports received it should be noted that:
- The minimum reporting levels are 10 uSv for X-rays and 70 uSv for high energy gamma and beta radiations. A blank field indicates either no dose or a dose less than these was received.
- The control is used to subtract background radiation doses from the total dose recorded. Note that during the three month monitoring period the average background dose received from terrestrial, cosmic and internal radionuclides is less than 300 uSv and when radon is included it is around 500 uSv.
- Radiation workers are not allowed to receive more than 20,000 uSv per annum, averaged over five years, with no more than 50,000 uSv in any one year from both internal and external radiation exposures.
For all doses 300 uSv and above received in a three month monitoring period the Radiation Safety Committee requires that the circumstances of the exposure be investigated and a written report provided to Safety, Health and Wellbeing.
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Thermoluminescent dosimetry (TLD)
Thermoluminescent dosimetry (TLD) is a phenomena by which solid state detectors can be used to detect and measure exposures to ionising radiations. When exposed to these radiations, free electrons in the TLD crystals become trapped in lattice imperfections. When heated (typically to 300 °C) the electrons escape the traps and release light which can then be measured using a photomultiplier. The amount of light detected is related to the radiation received. TLDs can be used for personal radiation monitoring. They consist of a plastic TLD holder incorporating a number of filters and TLD card into which is imbedded the TLD materials.
Some points to observe when using TLD badges:
- Wear the badge at chest or waist level, and if a lead apron is used in an X-ray area, under the apron.
- Wear only the badge assigned to you. Don't share badges.
- Replace the badge in the rack at the end of each day - this should be in a low radiation background area. Monitors that are taken home are frequently lost or damaged.
- Don't move the card within the badge except when changing cards.
- When cards are changed, the number should be visible, the right way up in the front open window of the badge when the hinge is at the bottom.
- Damaged holders should be replaced as soon as possible.
A TLD badge does not provide protection against radiation. It measures the radiation dose received and is used to:
- establish that the radiation doses received by personnel are within permissible limits.
- verify that the facilities for radiation protection are adequate.
- show that radiation protection techniques are acceptable.
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Lost or extra cards and holders
- The charge to the school for replacement holders is $15 and for a lost holder with card is $20.We suggest you make users aware of these charges and make it clear who will be required to pay should holders and cards not be returned.
- Queries on invoices and payments should be made direct to ARPANSA on 1800 678 112 (free call).
- Schools will be charged for cards that are returned 'unused'.Control cards are used to determine background radiation for each school's issue. These must be returned with the user cards at the end of the monitoring period.
- If you have any holders you do not require, return them to Safety, Health and Wellbeing and we will make these available to schools as required.
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Special issue monitors
- Special issue monitors can be arranged – these are unnamed and come with their own control monitor. Wearing dates need to be entered onto the form and the user's name written in soft pencil on the card wrapper.
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- Monitoring records are kept for at least 30 years.
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- Accuracy is typically 20 per cent and varies depending on the radiation types being measured.
- Minimum detectable dose ranges are from 10 uSv to 70 uSv depending on the radiation types being measured.
- Natural background radiation from terrestrial gamma rays and cosmic radiation is approximately 300 uSv during a three month period.
- Recorded doses above 300 uSv for a monitoring period should be investigated by the School Radiation Safety Officer and a written report forwarded to Safety, Health and Wellbeing.
TLD wearers should not be particularly concerned at doses recorded on their badges below 300 uSv.
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