M15.2
TRANSPORT OF RADIOACTIVE MATERIAL
(Target audience: Persons forwarding uranium hexafluoride: Mode: Sea)
Introduction
Transport radioactive material is governed by national and international regulations. The International Atomic Energy Agency (IAEA) has published the Regulations for the Safe Transport of Radioactive Material [1]. All references to “Regulations” in this module pertain to the IAEA Regulations. The objective of the Regulations is to establish requirements that must be satisfied to ensure safety and to protect persons, property and the environment from the effects of radiation in the transport of radioactive material. This protection is achieved by requiring, among others:
a)containment of the radioactive contents; and
b)control of external radiation levels.
These requirements are satisfied first by specifying -
a)performance standards for package design based on the radioactive contents and
b)administrative controls and
c)approval by competent authorities.
Confidence in this regard is achieved through quality assurance and compliance assurance programmes.
Scope of this module
This module relates to the regulatory requirements for the safe transport of uranium hexafluoride.
This moduledescribes how the transport of this materialcan be carried out in conformity with the applicable regulatory requirements.
The requirements for the fissile nature of the material are not included in this module.
Tasks before the consignor
The consignor should –
a)Familiarize himself with the regulations
b)Select the package in which the radioactive material has to be transported
c)Procure an appropriate package
d)Prepare the package for transport (e.g. load the radioactive material in the package, fasten the closure, decontaminate the exterior of the package)
e)Mark and label the package
f)Conduct the tests before the shipment
g)Complete the transport documents including consignor’s declaration and information to the carrier.
h)Forward the package through a carrier
i)Implement radiation protection requirements and quality assurance
Familiarization with regulatory requirements
IAEA Regulations
The IAEA Regulations [1] form the basis of many national and international regulations for transport of radioactive material.
The Agency has published a Safety Guide advising the user about how the regulatory requirements can be satisfied [2]. In order to guide the consignor through the regulatory requirements, IAEA has published the Schedules for the Regulations as a Safety Guide [3]. The schedules provide specific guidance on the regulatory requirements for each type of consignment.
National Regulations
Transport of radioactive material is governed by national regulations of each State. Member States of IAEA adopt the IAEA Regulations within the frame work of the local laws and the international conventions to which the nation is a party. Accordingly, responsibilities are assigned in the National regulations to consignor, carrier and consignee.. Consignors, carriers and the concerned public authorities ensure that the shipments are made in compliance with the applicable national regulations. There could be some differences between the national regulations and the international regulations for the safe transport of radioactive material because of the difference in the legal system among the states.
International Maritime Organization (IMO)
The International Maritime Organization (IMO) is a United Nations agency. The regulations, standards and recommendations (IMDG Code) that it has developed, are recognized, followed, and observed by ships of many nations. This code includes provisions for the transport of radioactive material by sea.
In addition, there is the MERCOSUR/MERCOSUL agreement that concerns road, rail, air and sea transport among certain South American countries.
Definitions of terms
Certain terms are assigned specific meanings in the Regulations. For example the terms contamination means the presence of a radioactive substance in excess of 0.4 Bq/cm2 for beta, gamma and low toxicity alpha emitters or 0.04 Bq/cm2 for other alpha emitters. The term conveyance includes road vehicles, rail cars, vessels or aircraft. A packaging together with the radioactive content is defined as package. Many definitions are provided in the Regulations. It is necessary to understand the meanings assigned to various terms in the Regulations.
A1 values and A2 values
Familiarity with A1 and A2 values defined in the Regulations would be useful. The values of A1 and A2 have been determined for most common radionuclides and are listed in the Regulations. Radioactive material may be transported either in special form (essentially indispersible) and other form. The A1 value refers to the activity of special form radioactive material and the A2 value refers to the activity of other than special form radioactive material.
Selection of Package
The type of package for the transport of radioactive material is determined by the radionuclide and its activity to be transported. Uranium hexafluoride (UF6) is radioactive and could be also fissile. Depending on the degree of enrichment and amount of fissile uranium, uranium hexafluoride may be transported, from radiological standpoint, in an excepted package, industrial package or Type A, B(U) or B(M) package.
Specific design requirements for packages containing UF6
The package should satisfy the design requirements specified for the type of package. The design specifications include the test requirements which the package has to satisfy. The Regulations prescribe the design requirements for the type of package to be used for the transport of UF6 The requirements given below pertain only to the physical properties and the chemical associated with an unintended release of UF6 to the atmosphere or with the reaction of UF6 with water or water vapour. These packagings are pressurized during loading and unloading operations, although they are not pressurized under normal transport conditions, they have to comply with the standards required for a pressure vessel. The design of the package should, in addition, take into account the requirements, appropriate to the fissile properties of the material, specified in the Regulations.
The design requirements specified below apply to packages containing UF6 in quantities of 0.1 kg or more.
a)Uranium hexafluoride should be packaged in accordance with the provisions of the International Organization for Standardization document ISO 7195: “Packaging of Uranium Hexafluoride (UF6) for Transport” [7].
b)The package should withstand the structural test specified in this module.
c)The package should withstand the free drop test specified in this module.
d)The package should withstand the thermal test specified in this module.
e)The package should not be provided with pressure relief devices.
For packages containing UF6 in quantities of 0.1 kg or more which do not satisfy the design requirements specified above, the design requirements are as follows:
a)the package should be designed to international or national standards equivalent to the standards of safety specified in ISO 7195 [7]; or
b)the package should be designed to withstand a test pressure of less than 2.76 MPa as specified under structural test in this module (That is there should be no leakage and no unacceptable stress);
c)the package should withstand the free drop test specified in this module;
d)the package should withstand the thermal test specified in this module;
e)the package should not be provided with pressure relief devices.; and
f)the competent authority approval should be obtained.
The prescribed tests are structural test, free drop test and thermal test.
Test requirements for packagescontaining UF6
The test requirements are given below. The specimen to be tested has to be first prepared. After conducting each the response of the package should be evaluated against the acceptance criterion specified for each test.
Preparation of a specimen for testing
All specimens should be inspected before testing in order to identify and record faults or damage. The following aspects should be given due consideration:
a)divergence from the design;
b)defects in manufacture;
c)corrosion or other deterioration; and
d)distortion of features.
The containment system of the package should be clearly specified.
The external features of the specimen should be clearly identified. This will help in making clear reference to any part of the specimen.
Structural test
Specimens that comprise or simulate packagings designed to contain 0.1 kg or more of uranium hexafluoride shall be tested hydraulically at an internal pressure of at least 1.38 MPa but, when the test pressure is less than 2.76 MPa, the design shall require multilateral approval. For retesting packagings, any other equivalent non-destructive testing may be applied subject to multilateral approval.
Acceptance criterion: There should be no leakage and unacceptable stress, as specified in the International Organization for Standardization document ISO 7195 [7].
Free drop test
The specimen should drop onto the target so as to suffer maximum damage in respect of the safety features to be tested.
a)The height of drop would depend on the mass of the specimen. The height of drop measured from the lowest point of the specimen to the upper surface of the target should be not less than the distance specified in the table given below for the applicable mass. The target should be unyielding as specified in the Regulations.
b)For rectangular fibreboard or wood packages of mass not exceeding 50 kg, a separate specimen should be subjected to a free drop onto each corner from a height of 0.3 m.
c)For cylindrical fibreboard packages of mass not exceeding 100 kg, a separate specimen should be subjected to a free drop onto each of the quarters of each rim from a height of 0.3 m.
Free drop distance for testing packages to normal conditions of transport
Package mass (kg) / Free drop distance (m)Package mass < 5000 / 1.2
5000 Package mass < 10, 000 / 0.9
10000 Package mass < 15, 000 / 0.6
15000 Package mass / 0.3
Acceptance criterion: There should be no loss or dispersal.
Thermal test
The specimen should be in thermal equilibrium under conditions of an ambient temperature of 38°C, subject to the solar insolation conditions specified in the Regulations. The specimen should further have the design maximum rate of internal heat generation within the package due to the radioactive contents. If any of these parameters are different from the above values prior to and during the test, due account should be taken of these variations in the assessment of package after the test. The thermal test should consist of: exposure of a specimen to a thermal environment of an average temperature of at least 800°C for a period of 30 minutes. The heat flux should be at least equivalent to that of a hydrocarbon fuel/air fire in sufficiently quiescent ambient conditions to give a minimum average flame emissivity coefficient of 0.9 fully engulfing the specimen. The surface absorptivity coefficient of the specimen should be 0.8 or that value which the package may be demonstrated to possess if exposed to the fire specified. Then the specimen should be exposed to an ambient temperature of 38°C, subject to the solar insolation conditions specified in the Regulations for a sufficient period to ensure that temperatures in the specimen are approaching initial steady state conditions. Alternatively, any of these parameters are allowed to have different values following cessation of heating, provided due account is taken of them in the subsequent assessment of package response. During and following the test the specimen should not be artificially cooled and any combustion of materials of the specimen should be permitted to proceed naturally.
Acceptance criterion: There should be no rupture of the containment system.
Procurement of an appropriate package
The consignor should procure an appropriate package which satisfies the design requirements. The package should be of approved design. The competent authority design approval certificate should be valid until the completion of the shipment.
Tests before first shipment
Before the first use of a package certain tests have to be carried out.These tests are intended to confirm that the package has been manufactured in complete conformance with the approved design. These tests have to be performed in respect of each manufactured packaging. If the packaging is procured from a vendor, the consignor has to confirm that it has been subjected to these tests and found to be satisfactory.
Following the fabrication of the packaging the effectiveness of shielding should be assessed.
Special arrangement
If conformity with some of the provisions of the Regulations is not practicable, the consignment can be transported but only under special arrangement. Approval for transport under special arrangement should be obtained from the concerned competent authorities.
Approval requirements
Competent authority approval is required for packages containing 0.1 kg or more of UF6. If the UF6 transported in the package is fissile, then appropriate competent authority approval should be obtained in respect of the package design.
Approval of Shipments under Special Arrangement
If the consignment is transported under special arrangement multilateral approval is required. The competent authority needs to be satisfied that the overall level of safety in transport is at least equivalent to that which would be provided if all the applicable requirements of these Regulations had been met.
An application for approval of shipments under special arrangement should include:
a)A statement of the respects in which the shipment cannot be made in full accordance with the applicable requirements and the reasons; and
b)A statement of any special measures which are to be implemented to compensate for the failure to meet the applicable requirements.
Preparation of the package for transport
Limits on package content
Packages containing uranium hexafluoride should not contain:
a)A mass of uranium hexafluoride different from that authorized for the package design;
b)A mass of uranium hexafluoride greater than a value that would lead to an ullage smaller than 5 % at the maximum temperature of the package as specified for the plant systems where the package shall be used; or
c)Uranium hexafluoride other than in solid form or at an internal pressure above atmospheric pressure when presented for transport.
Control of external exposure
External exposure that may result from the transport of radioactive material is controlled. The Regulations impose two limits on the radiation level outside the package. One limit restricts the radiation level at the external surface of the package. The other limit restricts the radiation level at one metre from the external surface of the package. The latter number is referred to as the transport index of the package.
Transport Index (TI)
The TI is an indicator of the radiation level in the vicinity of a package. It is useful in determining the segregation distances from packages. The segregation distance is calculated using the inverse square law of reduction of radiation level from package.Segregation distances should be calculated on the basis of the TI indicated on these loads.
Here is the procedure for determining the TI of a package or overpack or freight container:
Determine the TI of a package on the basis of measured radiation levels, considering the package in isolation. Scan the package, including the top and bottom, at a distance of 1 m from the external surface. Ignore protrusions on the exterior of the package in determining the 1 m distance.
Determine the maximum radiation level in units of millisieverts per hour (mSv/h) at a distance of 1 m from the external surfaces of the package.Multiply it by 100. The resulting number is the transport index of the package.
The value obtained above should be rounded up to the first decimal place (e.g. 1.13 becomes 1.2), except that a value of 0.05 or less may be considered as zero.
Limits on T I and Radiation Levels
The transport index of any package should not exceed 10. If this limit is exceeded, the consignment could be permitted only under exclusive use.
Exclusive use means that -
a)a single consignor will have the sole use of any hold, compartment, or defined deck area of a vessel or of a large freight container;
b)all initial, intermediate and final loading and unloading will be carried out in accordance with the directions of the consignor or consignee; and
c)the consignor has primary responsibility for ensuring compliance.
While under exclusive use, the radiation level on the external surface of the package or overpack or freight container should not exceed 10 mSv/h.
If the radiation level at any point on the external surface of a package or overpack or freight container exceeds 2 mSv/h, it may be transported only under special arrangement.
There is a special case of exception to this requirement. That is, if the radiation level at any point on the external surface of a package or overpack exceeds 2 mSv/h, it may be transported by ship without the need for special arrangement provided the following conditions are met:
a)The packages or overpacks should be carried in a vehicle on board the vessel.
b)The packages or overpacks should be transported in the vehicle under exclusive use conditions as per the regulations for transport by road/rail.
c)The packages or overpacks should not be removed from the vehicle at any time while on board the vehicle.
Controls for Contamination
Consignments of UF6 are unlikely to cause the spread of contamination on the package or vessels or storage areas. It is good practice to check and confirm that such transfer has not occurred.
The non-fixed contamination on the external surface of any package should be kept as low as practicable. The most effective way to ensure this is to prevent the surfaces from becoming contaminated. It is advisable to check gloves or other items of clothing of personnel routinely handling packages. Under routine conditions of transport non-fixed contamination on the external surface of any package should not exceed the following limits:
a)4 Bq / cm2 for β and γ emitters and low toxicity α emitters and
b)0.4 Bq/cm2 for all other α emitters.
Low toxicity alpha emitters are: natural uranium; depleted uranium; natural thorium; uranium-235 or uranium-238; thorium-232; thorium-228 and thorium-230 when contained in ores or physical and chemical concentrates; or alpha emitters with a half-life of less than 10 days. These limits are applicable when averaged over any area of 300 cm2 of any part of the surface. These limits apply also to the external and internal surfaces of overpacks, fright containers and vessels.
Transport of other goods with radioactive shipment
Only items that are necessary for the use of the radioactive material should be contained in the package.There should be no interaction between these items and the package which could reduce the safety of the package.
If packagings are to be used for the storage or transport of other goods, then the package should first be decontaminated to ensure that the level of contamination is below these limits: