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RADIATION SAFETY MANUAL
Section 3: Personnel Monitoring Service

INDEX
3.1 Principles of Thermolumnexcence Dosimetry (TLD)
3.2 Organisation of the Personal Monitoring
3.3 Handling of the TLD Badge
3.4 Significance of the TLD Results
3.5 Maintenance of Records

3. GENERAL
Film badges which have been used for personal dosimetry are now completely replaced by TLD badges. They are distributed by the Personal Radiation Monitoring Service of the Australian Radiation Protection and Nuclear Safety Authority (ARPANSA):

619 Lower Plenty Road, Yallambie, VIC 3085
Phone: 1800 678 112
Fax: 03 9432 1835
Email: prms@health.gov.au
Website: http://www.arpansa.gov.au/prms.htm

There is a charge for this service and payment is not the responsibility of the University.

As part of the service ARL is keeping a register of the personal doses received by all persons registered with them. This is a personal (and confidential) register, ie it is not linked to the employment of a person with a certain employer.

3.1 PRINCIPLES OF THERMOLUMNEXCENCE DOSIMETRY (TLD)
The thermoluminescent dosimeter (TLD) is a device which allows much faster evaluation than the film badge, with a lower threshold.

When a TLD material is exposed to ionising radiation at room temperature, part of the energy absorbed is used in changing the energy state of electronics in the material. If the TLD is heated, these energy states revert to their normal level accompanied by the emission of light. Portion of this light emission may be measured and is directly proportional to the amount of radiation energy received by the dosimeter.

TL dosimeters may be used in the form of a body badge similar to a film badge, a finger badge to measure extremity dose, or tiny rods or chips which may be sued to check internal doses using dummies.

3.2 ORGANISATION OF THE PERSONAL MONITORING
The School/Discipline/Building Radiation Safety Officer is responsible for the personal monitoring of staff in the different departments. This responsibility includes:

As a rule of thumb, only persons required to work in a medium level laboratory need to be constantly monitored - see Section 5.

Each member of staff is responsible for wearing the TLD badge all the time when at work. Since TLD badges are a record of the occupational exposure they should not be taken home.

Any member of staff should contact the Departmental/building or the University Radiation Safety Officer if they feel they should be monitored.

In most areas the TLD badges are changed every 12 weeks. However, in exceptional circumstances (such as a radiation accident) the Radiation Safety Officer can organise for an immediate readout. Please contact the RSO if this is required. If a member of staff is engaged in a procedure involving higher than usual radiation levels, or had a need to double check their radiation exposure, eg if pregnant, then further advice can be obtained from the Radiation Safety Officer.

TLD badges are the main personal monitoring equipment. However, other means of personal monitoring, such as finger rings, may be more appropriate for certain tasks. This can be arranged by the Radiation Safety Officer on request.

Laboratories or sections that handle a numer of short-term visitors from other institutions requiring a report on radiation exposure must make arrangements ahead of time to ensure that the visitor has a badge to wear or purchase one immediately registering personal dosimeter to be worn for the length of stay.

3.3 HANDLING OF THE TLD BADGE
The radiation TLD badge is used to measure the amount and type of radiation received by the wearer over a period of time (typically 3 months). It plays an important part in radiation safety, providing a check of the adequacy of protection measures, and in the case of a radiation accident an assessment of the dosage received by the wearer. Failure to observe these rules can result in misleading assessment of radiation exposures.

Precautions to be taken

  1. Always use the TLD sachet inside the holder supplied. The holder incorporates filters which allow an assessment of the radiation quality.
  2. Wear the holder correctly. The ARL symbol should face away from the body.
  3. Do not damage the badge. Pin holes, water, pressure, chemicals and heat can damage the TLD badge and prevent evaluation of the dose.
  4. Do not store TLD badges near radiation sources when not being worn.
  5. Return the TLD badges promptly. Badges must be returned to ARL upon receipt of a new batch. Extended delay increases the chances of accidental exposure of the badge. Also, in case of a dose recorded by the badge it is important to evaluate it as soon as possible so action can be taken to prevent exposure in the future. If it is suspected that a person has received a significant radiation dose, please return the TLD badge for assessment immediately!
  6. Always wear the TLD badge under a lead apron, if used. Since the badge is used to measure radiation exposure to the body, it should not be worn outside of protective clothing. Similarly, care should be taken not to shield the badge by pens, buckles etc.

3.4 SIGNIFICANCE OF THE TLD RESULTS
The permitted levels of radiation allowed for occupationally exposed workers and members of the general public have been laid down by the ICRP (report 60, 1991) as amended in the "National standard for limiting exposure to ionizing radiation" (National Occupational Health and Safety Commission publication 1013 (1995)). They are incorporated in the NSW Radiation Control Act Regulation (2003). The permitted levels are as follows:

 Effective dose limit 20mSv per annum
Averaged over a period of 5 consecutive calendar years 
Effective dose limit in a single year 50mSv

Equivalent dose limit:
In the lens of the eye
In the skin
In the hands and feet

 150mSv per year
500mSv per year
500mSv per year

(When an employee declares that she is pregnant, the embryo or foetus should be afforded the same level of protection as required for members of the public.)

In general, TLD badges provide a measure of the whole body dose received. For practical purposes the allowable limit can be taken to be 0.5 mSv per week, for radiation workers. However, it is recommended that any radiation dose received by a person should be kept to the minimum value practical. The School/building or University Radiation Safety Officer is available to assist in the minimisation of radiation exposure to personnel.

3.5 MAINTENANCE OF RECORDS

  1. It is the statutory duty of the School/Building X-Ray Centre Radiation Officer to ensure that appropriate personal records are maintained of each individual's radiation exposure for whom they are organising a monitoring service.
  2. Such a record must contain:
    • The full name, sex and date of birth of the occupationally exposed person.
    • The current home address of the occupationally exposed person, or if no longer employed, the last known address.
    • The date of commencement of employment or commencement of activities possibly leading to occupational exposure and the date of cessation of employment or cessation of those activities.
    • The kind of work performed by the occupationally exposed person .
    • Details of the types of ionising radiation to which the person has been occupationally exposed including the type of unsealed isotopes involved.
    • Details of any radiation accidents in which the person was involved in which may have affected their exposure in the workplace.
    • Details of the personal monitoring devices worn during the time when the person may have been occupationally exposed.
    • Results of monitoring the levels of radiation exposure.

  3. When an employee leaves employment or a student who has been monitored completes the period of study during which they may have been exposed the employee or student must be given a copy of their records relating to the period of possible occupational exposure.

    If the employer/Radiation Officer is aware that the person is taking up further employment on study involving possible exposure then a copy of the exposure record must be given (if the employee/student consents) to the future employer or student supervisor.

    The record of exposure given to the employee or student must contain the statement:

    "THESE RECORDS SHOULD BE KEPT SAFELY AND BE GIVEN TO ANY FUTURE EMPLOYER OR SUPERVISOR OF STUDY/WORK PERFORMED IN AN AREA WITH RISK OR EXPOSURE TO RADIATION. THEY CONTAIN INFORMATION OF PERMANENT APPLICATION."

    The Radiation Officer must ensure that records are maintained in a form and place where they are available for inspection by the person to whom they relate at reasonable times during normal working hours.