111.1.3.1. Exposure in a normal situation

For pure beta radioactive tracers used in a normal situation, there will be no exposure to radiation during transport and injection because the soft beta radiation will not penetrate the walls of the bottles and equipment in which the tracers are kept before injection.

For gamma radioactive tracers, appropriate shielding has to be applied to reduce the dose to the personnel involved to below an acceptable limit.

111.1.3.2. Exposure due to a transport accident

For pure beta radioactive tracers, the tracer is shipped in a sealed 95 mL Monel bottle surrounded by water absorbent material and placed in a steel container. This container is again placed in a steel barrel surrounded by shock absorbing Ethafoam.

For gamma radioactive tracers, the volume of the tracer solution will be similar to the beta emitting tracers, i. e. 50-75 mL, and the packaging and containment are the same except for a higher level of shielding surrounding the inner steel container in order to give an acceptable transportation index (see necessary shielding thicknesses above).

If an accident occurs during the transport of the tracers, the radioactive material is supposed to be retained in its containment. Even in a major accident it is very unlikely that radioactive material will be dispersed. The situation will be dealt with in a normal way according to national and international laws and rules.

There are two scenarios that could result in the release of tracer:

(1) Very small leakages of tracer containing liquid at tube connections, etc.

(2) Breakage or destruction of injection equipment due to some accident

onboard the platform.

(a) Scenario 1

As a general rule, injection of radioactive tracers should always be performed by at least two persons with the necessary technical skills and safety competences. One person is implementing the injection process while the other is handling monitoring instruments and safety precaution equipment.

In case a leakage occurs, valve B (Fig. 7) connecting the tracer injection equipment to the water injection pipe on the platform will be closed. This will stop the leakages and the released fluid will be removed and treated as contaminated material by operators carrying personal protective equipment. It is supposed that this type of tracer dispersion will not cause any significant exposure to radiation or intake of radioactive material by the operators.

(b) Scenario 2

If a serious accident (e. g. an explosion) occurs in the vicinity of the injection site during the few seconds when the tracer is being flushed from the tracer bottle to the water injection pipe, causing destruction of the injection equipment, there could probably be a release of tracer.

It could also be envisaged that a valve or pipeline failure on the high pressure side would cause extensive leakage in the form of an unidirectional ejection of tracer-containing fluid.

The action to be taken, if possible, in this case will be to stop the flow through the injection cylinder by closing valve B. Then the injection equipment and the site will be flushed with large quantities of water to disperse the tracer into the sea (for offshore installations). As the tracer will be diluted with water very rapidly in this case, it is believed that there will be no significant intake of tracer by the operators. If the injection operator, who wears the mandatory protective water repellent clothing, has been splashed by tracer-containing fluid, the nearby support person immediately starts decontamination of the operator according to established procedure, including dousing of the operator with water followed by removal of the protective clothing. The support person also operates

monitoring equipment to ensure that the operator is clean before they leave the injection site.

In the case of onshore operations, injection equipment should be mounted in a trough in order to collect any spillage from the injection equipment itself. In addition, the nearby surface area should be covered with a plastic sheet with absorbent tissue paper on top to collect any spillage and facilitate site decontamination after a spillage. If soil contamination occurs, the area should be evacuated for a time long enough that the remaining activity in the soil has either evaporated (in the case of volatile tritiated liquids) or disappeared deeper into the ground (in the case of non-volatile beta and gamma emitting tracers). Surface monitoring of gamma radiation and/or vapour samples taken by radiation safety workers and analysed with respect to the content of volatile tritium labelled tracers will decide when the area is opened for general and normal work.