Basic safety concepts

As discussed in the first chapter, the core philosophy of the transport of radioactive material is that it should be performed safely. Safety can be achieved in a number of different ways. Some would argue that not transporting radioactive material at all is the only way to be assured of safety. However, this disregards the very significant benefits of using radioactive material and the ultimate need for properly treating and disposing of the existing material when it is no longer needed.

To properly understand the basic concepts for safely transporting packages containing radioactive material it is essential to always keep in mind a clear picture of the package components. These are shown in Figure 5.1

• • Package - The packaging with its Package - radioactive contents as presented for transport

• • Packaging - The assembly of components Packaging - necessary to enclose the radioactive contents completely

+ =

PACKAGING PACKAGE RADIOACTIVE

CONTENTS

FIG. 5.1. Radioactive contents, packaging and package.

5.1.1. Inherent safety

While such aspects as administrative and procedural controls such as marking, labelling, notifications, and communications have their place, it is clearly best to have as much reliance on inherent safety as possible. This minimizes the human factor and the tendency to make mistakes. An example of inherent safety would be shipping the material in such a way that even if all the controls failed, and an individual ingested the material it would not have a detrimental effect. The difficulty is that radioactive material has a very large variety of properties and a very large range of specific activities. To incur a small dose the quantity of ingested material could range from a few milligrams to many kilograms. Because of this phenomenon, the accurate characterization of radioactive material type is a basic safety aspect of the IAEA TS-R-1 Transport Regulations, as will be seen later.

5.1.2. Passive safety

Once one can no longer rely on the inherent safety of the radioactive material itself, then the next best step is to use passive safety. An example of passive safety is packaging. If the quantity of radioactive material is such that it is not inherently safe, then it could be made part of a package that can withstand all the assaults to which it is likely to be exposed. It then does not matter how the radioactive material is treated during the transport process. The difficulty with this is that such a packaging may be extremely expensive compared to the value of the radioactive material content. It is also unreasonable to have a very tough packaging for material that might only be marginally hazardous.

This leads to the concept of a graded approach to packaging requirements. In other words, the package integrity is a function of the hazard associated with the radioactive material. The more hazardous the material, the tougher the packaging. Packaging ‘toughness’

is measured in its ability to withstand various conditions of transport. There are three basic conditions used in the IAEA Regulations with some variations within each condition (see para. 106 of TS-R-1):

- Routine conditions of transport (incident free);

- Normal conditions of transport (minor mishaps); and - Accident conditions of transport.

Routine conditions of transport are those that are totally incident free, apart from the conventional stresses and strains resulting from the conveyance operation. Normal conditions of transport include the typical small incidents that a package might endure during shipment.

These include such things as being rained upon, being dropped, and having other packages stacked on top.

The graded approach to packaging in the Regulations is illustrated pictorially in Figure 5.2. The packaging at the top of the figure is typical of that used for small limited quantities of radioactive material posing a minimal hazard. This package is designed to withstand only the routine conditions of transport. If the packaging fails, the consequences are insignificant because of the levels of radioactivity involved. The packaging in the centre of the figure is typical of that used for moderate quantities of radioactive material posing a small hazard. This package is designed to withstand both the routine, and the normal conditions of transport. If this packaging fails in an accident, there may a release of radiation, but they are unlikely to cause any measurable biological effects. The packaging at the bottom of the figure is typical of that used for more significant quantities of radioactive material, which would pose a large hazard if released. This package is designed to withstand not only the routine and normal conditions of transport, but also accident conditions of transport.

FIG. 5.2. Pictorial representation of the graded approach to packaging.

5.1.3. Active safety

Once all that is reasonably possible has been done with respect to inherent safety and passive safety, then the next level of safety is that associated with active controls. This generally requires the implementation of procedures of some sort. Included in this category would be labelling; marking and placarding; loading, stowage, storage, and segregation provisions; Quality and Compliance Assurance controls, and shipping documentation.

5.1.4. Summary of objectives of Transport Regulations

In summary, the objective of the Regulations is to protect persons, property and the environment from the effects of radiation during the transport of radioactive material (paragraph 104 of TS-R-1). In the words of the Regulations, this protection is achieved by requiring:

- Containment of the radioactive contents;

- Control of external radiation levels;

- Prevention of criticality; and

- Prevention of damage caused by heat.

In terms of this chapter, this can be thought of as applying the principles of inherent safety, passive safety, and active safety controls. The IAEA Regulations incorporate these principles by:

- Limiting the nature and activity of the radioactive material which may be transported in a package of a given design (see Section IV of TS-R-1);

- Specifying design criteria for each type of package (see Section VI of TS-R-1);

- Providing information on hazards by labels, marking, placards, and shipping papers (see Section V of TS-R-1);

- Applying simple rules of handling and stowage of the packages during transport and in-transit storage (see paragraphs 562–569 of TS-R-1).