Packages containing not more than 1 000 g of plutonium are excepted from the application of 
6.4.11.4
to 6.4.11.14 provided that:
 
(a)      Not more than 20% of the plutonium by mass is fissile nuclides;
 
(b)      The criticality safety index of the package is calculated using the following formula:
 
 
(c) If uranium is present with the plutonium, the mass of uranium shall be no more than 1% of the
mass of the plutonium.

 

Where the chemical or physical form, isotopic composition, mass or concentration, moderation ratio
or density, or geometric configuration is not known, the assessments of 6.4.11.8 to 6.4.11.13 shall be
performed assuming that each parameter that is not known has the value which gives the maximum
neutron multiplication consistent with the known conditions and parameters in these assessments.

For irradiated nuclear fuel the assessments of 6.4.11.8 to 6.4.11.13 shall be based on an isotopic
composition demonstrated to provide either:
(a) The maximum neutron multiplication during the irradiation history; or
(b) A conservative estimate of the neutron multiplication for the package assessments. After
irradiation but prior to shipment, a measurement shall be performed to confirm the
conservatism of the isotopic composition.

The package, after being subjected to the tests specified in 6.4.15, shall:
(a) Preserve the minimum overall outside dimensions of the package to at least 10 cm; and
(b) Prevent the entry of a 10 cm cube.

The package shall be designed for an ambient temperature range of -40°C to + 38°C unless the
competent authority specifies otherwise in the certificate of approval for the package design.

 
For a package in isolation, it shall be assumed that water can leak into or out of all void spaces 
of the package, including those within the containment system. However, if the design incorporates 
special features to prevent such leakage of water into or out of certain void spaces, even as a 
result of error, absence of leakage may be assumed in respect of those void spaces. Special 
features shall include either of the following:
 
(a)    Multiple high standard water barriers, not less than two of which would remain watertight if 
    the package were subject to the tests prescribed in 6.4.11.13 (b), a high degree of quality 
control in the manufacture, maintenance and repair of packagings and tests to demonstrate the 
closure of each package before each shipment; or
 
(b) For packages containing uranium hexafluoride only, with  maximum enrichment  of 5 mass  percent 
uranium-235:
 
(i) packages where, following the tests prescribed in 6.4.11.13 (b),  there  is no  physical  
contact between the valve and any other component of the packaging other than at its original point 
of  attachment  and  where,  in  addition,  following  the  test  prescribed  in 6.4.17.3 the 
valves remain leaktight; and
 
(ii) a high degree of quality control in the manufacture, maintenance  and  repair  of  packagings 
coupled with tests to demonstrate closure of each package before each shipment.
 

It shall be assumed that the confinement system is closely reflected by at least 20 cm of water or such
greater reflection as may additionally be provided by the surrounding material of the packaging.
However, when it can be demonstrated that the confinement system remains within the packaging
following the tests prescribed in 6.4.11.13 (b), close reflection of the package by at least 20 cm of
water may be assumed in 6.4.11.10 (c).

The package shall be subcritical under the conditions of 6.4.11.8 and 6.4.11.9 with the package
conditions that result in the maximum neutron multiplication consistent with:
(a) Routine conditions of carriage (incident free);
(b) The tests specified in 6.4.11.12 (b);
(c) The tests specified in 6.4.11.13 (b).

(Reserved)

 
For normal conditions of carriage a number "N" shall be derived, such that five times "N" packages 
shall be subcritical for the arrangement and package conditions that provide the maximum neutron 
multiplication consistent with the following:
 
(a) There shall not be anything between the packages, and the  package  arrangement  shall  be 
reflected on all sides by at least 20 cm of water; and
 
(b) The state of the packages shall be their assessed or demonstrated condition if they had been 
subjected to the tests specified in 6.4.15.
 

For accident conditions of carriage a number "N" shall be derived, such that two times "N" packages
shall be subcritical for the arrangement and package conditions that provide the maximum neutron
multiplication consistent with the following:
(a) Hydrogenous moderation between packages, and the package arrangement reflected on all
sides by at least 20 cm of water; and
(b) The tests specified in 6.4.15 followed by whichever of the following is the more limiting:
(i) the tests specified in 6.4.17.2 (b) and, either 6.4.17.2 (c) for packages having a mass not
greater than 500 kg and an overall density not greater than 1 000 kg/m3 based on the
external dimensions, or 6.4.17.2 (a) for all other packages; followed by the test specified
in 6.4.17.3 and completed by the tests specified in 6.4.19.1 to 6.4.19.3; or
(ii) the test specified in 6.4.17.4; and
(c) Where any part of the fissile material escapes from the containment system following the tests
specified in 6.4.11.13 (b), it shall be assumed that fissile material escapes from each package in
the array and all of the fissile material shall be arranged in the configuration and moderation
that results in the maximum neutron multiplication with close reflection by at least 20 cm of
water.

 

The criticality safety index (CSI) for packages containing fissile material shall be obtained by dividing
the number 50 by the smaller of the two values of N derived in 6.4.11.12 and 6.4.11.13 (i.e. CSI =
50/N). The value of the criticality safety index may be zero, provided that an unlimited number of
packages is subcritical (i.e. N is effectively equal to infinity in both cases).

Test procedures and demonstration of compliance

Demonstration of compliance with the performance standards required in 2.2.7.2.3.1.3, 2.2.7.2.3.1.4,
2.2.7.2.3.3.1, 2.2.7.2.3.3.2, 2.2.7.2.3.4.1, 2.2.7.2.3.4.2, and 6.4.2 to 6.4.11 must be accomplished by
any of the methods listed below or by a combination thereof:
(a) Performance of tests with specimens representing LSA-III material, or special form
radioactive material, or low dispersible radioactive material or with prototypes or samples of
the packaging, where the contents of the specimen or the packaging for the tests shall
simulate as closely as practicable the expected range of radioactive contents and the
specimen or packaging to be tested shall be prepared as presented for carriage;
(b) Reference to previous satisfactory demonstrations of a sufficiently similar nature;
(c) Performance of tests with models of appropriate scale incorporating those features which are
significant with respect to the item under investigation when engineering experience has
shown results of such tests to be suitable for design purposes. When a scale model is used,
the need for adjusting certain test parameters, such as penetrator diameter or compressive
load, shall be taken into account;
(d) Calculation, or reasoned argument, when the calculation procedures and parameters are
generally agreed to be reliable or conservative.

 

After the specimen, prototype or sample has been subjected to the tests, appropriate methods of
assessment shall be used to assure that the requirements for the test procedures have been fulfilled in
compliance with the performance and acceptance standards prescribed in 2.2.7.2.3.1.3, 2.2.7.2.3.1.4,
2.2.7.2.3.3.1, 2.2.7.2.3.3.2, 2.2.7.2.3.4.1, 2.2.7.2.3.4.2, and 6.4.2 to 6.4.11.
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