Type B(U) and B(M) packages

As far as the contents limits and the types of contents are concerned, Type B(U) and Type B(M) packages can be considered together.

7.7.1. Contents limits

With one exception, the Regulations do not specify activity limits for Type B(U) and Type B(M) packages. The activity limits are generally established during design, and are included in the safety documentation supporting application for approval, which is submitted to the Competent Authority (see paragraph 415 of TS-R-1) requesting a certificate of approval. In other words, the contents limit is specific to a particular certified package design.

The exception concerns the carriage of radioactive material in Type B(U) and Type B(M) packages when transported by air (see paragraph 416 of TS-R-1). In this instance, there are two specific limits and one situation that allow variations from these limits. The two limits are:

- For special form radioactive material, the limit is either 3000 A1 or 100 000 A2, whichever is the lower; or,

- For all other radioactive material, the limit is 3000 A2.

The situation that allows variation from these limits is when the radioactive material

While the A1 and A2 values are not used directly to define the activity limits for Type B packages (with the exceptions given above), they are used to define the acceptable release limits. Therefore, they are involved in the design process. Under normal conditions of transport, the release limit is 10^–6 A2 per hour (see paragraph 656(a) of TS-R-1). The maximum allowable release under accident conditions of transport from a Type B package is A2 in a period of one week (see paragraph 656(b)(ii)(ii) of TS-R-1). Release limits are discussed in the next chapters.

7.7.2. Types of contents

Type B(U) or Type B(M) packages are needed whenever the activity level exceeds the A1 or A2 levels. Therefore, a Type B(U) or Type B(M) package is required both for small quantities of alpha emitters which require virtually no shielding, as well as for large quantities of beta/gamma emitters which require significant radiation shielding.

The contents of typical Type B(U) and Type B(M) packages include:

- Bulk supplies of un-encapsulated medical or research radioisotopes such as ¹³¹I, ³H,

24Na;

- Encapsulated sources such as ⁶⁰Co or ¹⁹²Ir for non-destructive testing or ⁶⁰Co for teletherapy;

- Unirradiated nuclear fuel involving highly enriched uranium, plutonium or mixed oxides;

- Irradiated nuclear fuel or research samples for post-irradiation examination.

The contents come in a multiplicity of forms, radionuclide composition, and radioactivity.

Another instance where a Type B(U) or a Type B(M) package must be used is the transport of LSA material or SCO when the external radiation level at 3 m from the unshielded material exceeds 10 mSv/h (paragraph 521 of TS-R-1). A typical example is provided by waste, such as ion exchange resin, which might comply with the criteria applicable to LSA material, but because of the quantity and dose rate, cannot be transported in an Industrial package.

As previously stated, the total activity in a conveyance, or in a hold or compartment of an inland watercraft, is limited when the LSA material or the SCO are transported as Type IP-1, 2 or 3. However, sometimes it is desirable to ship quantities of LSA or SCO that exceed these limits. To avoid dividing the cargo and multiplying the number of shipments, a Type B(U) or a Type B(M) package has to be used. One example of this might be waste contaminated with alpha emitting material that can be classified as LSA-II material. If the waste is made of plastic sheets or gloves, or tissues, it is combustible and instead of multiplying the number of shipments to comply with the 100 A2 limit per conveyance, it might be advisable to use a Type B(U) package.

7.7.3. Lightweight Type B(U) and B(M) packages

Lightweight Type B(U) and Type B(M) packages are not specifically defined as a type of package in the Regulations. Nevertheless, some special testing requirements apply to such packages, and therefore, they need to be identified in this document. In essence, a lightweight Type B package (paragraph 656(b) of TS-R-1) is one which:

- has a mass not greater than 500 kg;

- an overall density not greater than 1000 kg/m³ based on the external dimensions; and, - radioactive contents greater than 1000 A2 in other than special form.

Typical contents of a lightweight Type B(U) and Type B(M) packages are alpha emitters. These include for example, plutonium oxide powders and plutonium nitrate solutions.

7.7.4. Type B(U) packages containing very large quantities of activity

Earlier versions of the Regulations required an enhanced (200 m) immersion test for packages containing more than 37 PBq of irradiated nuclear fuel. This requirement was imposed to minimize the hazards associated with a spent fuel package being sunk on the continental shelf.

As a result of a number of studies the scope of the enhanced water immersion test has been extended in the 1996 Edition of the Regulations to cover any radioactive material transported in large quantity, not only irradiated fuel. Type B(U) packages designed to contain an activity greater than 10⁵ A2 are required to pass the enhanced immersion test discussed in Chapter 8. It should be noted that this test is also required for all Type C packages.

7.8. Type C packages 7.8.1. Contents limits

The 1996 Edition of the Regulations (TS-R-1) introduced a new, Type C, package specification. When adopted by Member States and the International Civil Aviation Organization (ICAO), this package type will apply to the transport of large quantities of radioactive material by air. As discussed above, the introduction of the Type C package places a content limit on Type B(U) and Type B(M) packages being transported by air. The content limits are expressed as:

- 3000 A1 or 100 000 A2 (whichever is lower) for material in special form; or - 3000 A2 for all other forms of radioactive material.

The choice of 3000 A2 for non-special form was linked mainly to an older version of the Regulations that defined a large source as being 3000 A1 or A2. This quantity is retained in the Regulations as the threshold quantity for which shipment approval of Type B(M) packages is required. Also, a study undertaken in France suggested that at typical impact speeds for aircraft crashes the release fraction might be as high as 3 × 10^–2 for a Type B(U) package. This release fraction in combination with the assumption that a release of 100 A2

represents a significant hazard gave a further basis for the 3000 A2 content limit. For special form radioactive material, the same content limit is used. However, there is recognition that the properties of the special form material may be impaired in an aircraft accident, so a cap of 100,000 A2 has been placed on the content limit.

Variation from these limits is allowed with another new feature of TS-R-1, namely low dispersible radioactive material (LDM), as defined in paragraph 225 of TS-R-1. If the material is classed as LDM, it could be safely carried in large quantities by air in a Type B(U)

As with Type B(U) and Type B(M) packages, the Regulations do not specify activity limits for Type C packages. The activity limits are generally established during design, and are included in the safety documentation supporting application for approval that is submitted to the Competent Authority (see paragraph 417 of TS-R-1) when requesting a certificate of approval.

In addition, the same release limits specified for Type B packages apply to Type C packages, both for the normal conditions of transport and the accident conditions of transport.

7.8.2. Types of contents

7.8.2.1. Plutonium and mixed oxide fuel

Plutonium, coming from the reprocessing of spent fuel, can be used to manufacture mixed oxide fuel assemblies. In this process, the mixed oxide will sequentially be in the form of powder, pellets, fuel pins, and fuel assemblies. According to the locations of the different processing plants, the mixed oxide will need to be transported. For instance, it may need to be shipped from a fuel pin fabrication plant to the place where the pins are assembled into a fuel assembly.

Plutonium and mixed oxides have a high activity in terms of A2, so that 3000 A2 will typically represent about one hundred grams of plutonium or two kilograms of mixed oxide.

For reasons of physical protection, it could be best transporting these materials by air, especially if they have to be transported over a very long distance (for instance from one continent to another).

For these reasons, plutonium and mixed oxide fuel are candidates for transport in a Type C package.

7.8.2.2. Very large sources

Another candidate for transport in a Type C package is the very large source. Some sources have to be transported very rapidly due to their short half-life. Nevertheless, it must be recognized that 3000 A2 represents a large amount of activity for this kind of material.