Radioactive Materials - Dosimetry
Exposure to radiation must be closely monitored to ensure that no one receives an exposure which could have a potential adverse health effect. In recognition of this, CNSC has set dose limits for members of the general public and nuclear energy workers (any individual likely to receive an exposure in excess of the general public limits). The following table outlines those limits:
Dose Limits Assigned by CNSC
| Member of General Public | Nuclear Energy Worker * | |
Whole body, gonads, bone marrow |
1 mSv | 50 mSv |
| Skin, thyroid, bone | 50 mSv | 500 mSv |
| Tissues of hands, feet and forearms | 50 mSv | 500 mSv |
This section will also provided specific information concerning:
Thermoluminescent Dosimetry (TLD)
The University issues thermoluminescent dosimeter badges to individuals who are exposed to radiation, and who may receive a dose. Dose records are closely monitored. ORM may elect to monitor(short or long term) individuals who do not directly work with radiation but may be in proximity to radioactive sources. These individuals include support staff, contractors, and trades personnel. Authorised users of radioactive material are listed on the second page of the Internal Radioisotope Permit. The type of dosimeter is also listed on this page, i.e. whole body, extremity or ring badge. CNSC requires a ring dosimeter to be worn by a person who handles a container whose content is 50 MBq of phosphorous-32, samarium 153, strontium 89, or Yttrium 90.
It is important to note that hydrogen-3 and carbon-14 emit such weak beta particles that they can not penetrate the shielding of the tld badge to be detected. The shielding incorporated into the dosimeter badge is intentionally designed to mimic the natural shielding provided by your skin, fat and other organs. Thus a tld badge will not be assigned to those individuals who use these radioisotopes. Although the risk of external exposure is minimal, proper procedures must be followed to avoid an internal exposure ie., due to consumption, absorption.etc..
CNSC has produced a poster to assist you in storing and wearing your dosimeter badge correctly.
Dosimetry service to the University of Ottawa is provided by Health Canada - National Dosimetry Service (NDS). CNSC requires suppliers of dosimetry services to be registered and approved by them, as is NDS. To enroll in this service, NDS requires the following information to be submitted: Name, Sex, Date of Birth, Place of Birth, Social Insurance Numbers etc... Contact ORM in order to register into the appropriate university dosimetry group and to arrange for the receipt of a badge.
Dose records are sent to ORM every three months, where they are review for any abnormal readings. Should a questionable reading be noted, ORM will contact you to determine if the exposure reading represents a personal exposure due to experimental design or singular incident, or non-personal due to storage practices or damage. ORM also monitors reading to ensure exposure readings do not exceed the CNSC dose limits. Should a reading approach this value the experimental design and your work scheduling will have to be reviewed and modified if necessary. Should you wish to see your dose record, please feel free to contact ORM.
In addition the Health Canada - National Dose Registry (NDR) also maintains a central database of dose received by Canadians. This is tracked using individual social insurance numbers, thus ensuring readings are assigned to only one person. Individual names can not be used due to the multiple individuals with the same name. Due to the privacy of your dose records, should you wish a historical record to be released the individual must make an application directly to NDR. This is easily undertaken by using NDR's own Dose History Request Form.
As unbound thyroid is volatile and easily concentrate in the thyroid if the appropriate containment procedures are not used. Thyroid monitoring is required for anyone using iodine -125 or iodine-131, such that an activity of greater than 10 kBq could be detected in the thyroid. As this is a CNSC reportable value it is necessary to be extremely diligent in the monitoring and use of radioactive iodine. As the risk of a dose is dependent upon the activity used and the procedures followed, contact ORM to discuss the procedures to be followed and to determine if direct involvement in a thyroid monitoring program is required.