Accidental exposure includes:
- contamination of the environment, or of a person's skin or clothing by radioactive material, for example following a spill of radioactive liquid;
- intake of radioactive material by ingestion, inhalation, injection or through a cut or wound; or
- an external source of unwanted irradiation such as an X-ray machine or radioactive source.
Any Radiation Users or Nuclear Energy Workers who know or suspect that they or any one else, have been involved in any abnormal situation as described above, should immediately report the fact, with as much detail as possible, to the Permit Holder. If skin, clothing or shoes may be contaminated, it is preferable to remain on the spot (moving away from the immediate area of contamination) and to call for assistance. In this way the spread of contamination to other rooms is prevented.
All incidents involving abnormal exposure and/or contamination must be reported to Environmental Health & Safety, either at the time (if immediate assistance is needed) or as soon as possible afterwards. Environmental Health & Safety will:
- assist in emergency procedures, including decontamination where necessary;
- estimate the radiation dose(s) received by the person(s) involved. This may necessitate the immediate read-out of personnel (TLD) dosimeters and/or the provision of special bioassay procedures for the individual(s) concerned;
- advise on the necessity, or otherwise, of medical examination and arrange such examination if appropriate; investigate the incident with a view to determining its cause and advising on remedial measures to prevent a recurrence;
- in co-operation with the Permit Holder prepare a full report to the Radiation Safety Officer to ensure adequate documentation; and
- if required, the Radiation Safety Officer will submit a report to the CNSC.
The most difficult and crucial step is to recognize that an abnormal situation has occurred; for example that an X-ray machine has failed to switch off, or the shutter of an irradiator failed to close, or a sealed source is on the floor instead in its container.
It is therefore important for radiation workers to become thoroughly familiar with the normal appearance and operation of the sources and/or radiation-emitting devices with which they are working, especially if the devices or sources are capable of delivering a high dose-rate. It is highly desirable for an X-ray machine or irradiator to be equipped with an "emergency off" button in a prominent and accessible position.
Once an accidental external exposure has been recognized, proceed as follows:
- immediatelyperform all necessary actions to prevent further exposure, e.g. withdraw the exposed part of the body from the beam, switch off the X-ray beam or irradiator, shield the radioactive sources, etc. In some circumstances, the exposed person cannot perform these actions on their own and must first call for assistance;
- report the incident to the Permit Holder who, in turn, will inform Environmental Health & Safety;
- make a preliminary estimate of the radiation dose(s) received by the exposed person(s), in co-operation with Environmental Health & Safety. It is better, at this stage, to overestimate rather than underestimate. A more definitive dose estimate is usually made later, when the dosimeter reading for the exposed person is determined;
- steps 3, 4 and 5 of the general procedure set out in Section 12.1 should be followed; and
- bioassay procedures are not required when the accident does not involve radioactive materials.
In situations where the total activity is less than 100 exemption quantities of a radioisotope and there is no apparent contamination of personnel, the following procedures should be adopted:
- estimate the activity involved and the nature of the contamination;
- confine the spill and prepare to decontaminate;
- wear disposable gloves and lab coat and clean up the spill using absorbent paper and place the contaminated materials in a radioactive waste container;
- wash with an appropriate detergent and disposable towels. Care should be taken not to contaminate oneself and to avoid the spreading of contamination;
- perform a test of contamination (wipe test) as described in Sections 5.4 and Section 5.7, and then repeat step iii until contamination levels are acceptable.
- check hands, clothing and shoes for contamination;
- report the spill and clean up to the supervisor and to the RSO (He/she will verity if actions taken will not allow a similar accident to reoccur in the future);
- record spill details and contamination monitoring details; and
- adjust inventory and waste records appropriately.
Where the total activity is more than 100 exemption quantities and/or there is a non-negligible risk of radiation exposure, the following applies:
- notify at once all other persons in the room and/or area;
- clear the area, and persons not involved in the spill should leave immediately;
- close off and secure the spill area to prevent entry and post warning signs;
- monitor with a suitable detector the persons suspected to be contaminated and, if appropriate, proceed with the personnel decontamination measures described in Section 12.3.3;
- estimate the activity involved and the nature of the contamination;
- monitor the area with a suitable detector and estimate the total exposure expected for the personnel involved in the decontamination measures; this is not a simple procedure and it must be performed by trained personnel only;
- if the decontamination procedures are not expected to lead to a significant exposure for the personnel (i.e. less than 100 millirem or 1mSv) and if no airborne contamination is expected (in cases of doubt, ask for assistance from the Environmental Safety Office), proceed as described in Section 12.3.1. Otherwise, proceed as described in Section 12.4 (accident involving radioactive dusts, fumes or gases); and
- notify the RSO of the incident at the end of clean up procedures, so that the RSO can send a complete report to the CNSC.
The following procedures apply for personnel decontamination:
- estimate the activity involved, the nature of the contamination and the affected area;
- wash the affected area with mild soap and lukewarm water. Take care not to injure the skin, as it would provide a direct pathway for radioactive contamination into the body. If the spill is on clothing, the article must be discarded at once and left on the premises in a plastic bag or other closed container. Any spill on the skin must be flushed thoroughly. Showering is not advised before the local contamination is thoroughly cleansed; and
- notify the Radiation Safety Officer of the incident.
- Notify all other persons and vacate the room immediately. Call emergency number 3000 (Downtown) or 7777 (Macdonald).
- Ascertain that all doors giving access to the room are closed and post warning signs to prevent non-authorized access. If possible, switch off air circulation devices.
- The RSO will provide assistance for decontamination, air monitoring, surveying persons suspected of being contaminated, laboratory inspection, and accident investigation and reporting.
The emergency instructions applicable to the building concerned must be followed exactly. It is essential to report the location of radioactive sources to the fire fighting teams and to estimate any additional risk, which these sources may present. The Radiation Safety Officer will survey the premises at the end of the emergency and, before authorizing access to the premises, will ensure that there is no significant risk of radiation exposure.
In any emergency situation, which could result in fatalities, the radiation hazard may be taken into account only if anyone could receive a large whole-body dose, I.E. 0.5 Sv (50 REM) or more. This level is greatly in excess of the normal limits for Nuclear Energy Workers.
The risk of receiving a life-threatening dose of radiation at McGill University is extremely remote. In the event of a life-threatening accident (such as heart attack or serious fall), measures to save the life must be of primary consideration. Then the radiological aspects of the accident (such as possible spread of contamination) are secondary.