Fissile material packaging

Increase by a factor of two in the total number of criticality safety indices for fissile material packages in a number of cases. 

A KENO computational study, was made to demonstrate the nuclear criticality safety of a fissile material package. The study revealed certain expected results, but also hightiig ed the pitfalls of anticipating that the results would be consistent under varying circumstances.. Various parameters (dimensions) were varied, and the KENO-calculated k ff values were observed. The independent variables of the packages within the reflected arrays studied were ... 

Allowable fissile materials packaging is described in 49 CFR 173.417. A fissile-rated Type A or Type B packaging is required for fissile material. Recall that fissile materials cannot be shipped as LSA unless they are fissile excepted per 49 CFR 173.453, so industrial packages do not qualify (with the possible exception of IP-3 packages shown to comply with Type A and fissile requirements). Limitations on the use of Type A packagings for fissile shipments are set forth in 10 CFR 71. 

Small quantities of fissile material are excepted fissile excepted) from some fissile packaging requirements. They are not, however, excepted from the requirements appropriate to their other radioactive properties. Reduced requirements also apply to the following excepted packages ... 

Radioactive Material, name of radionuclides, description of physical and chemical form, activity, label category, transport index, Fissile exempt, package identification markings, and/or appropriate warnings Class 7 materials... 

The leaktightness requirement for a containment system in a Type B(U), Type B(M) or Type C package depends on the radiotoxicity of the radioactive contents for example, a Type B(U) or Type C package under accident conditions must have the release limited to a value of in the period of a week. This connection to the A2 value means that for highly toxic radionuclides such as plutonium and americium the allowable volumetric leak rate will be much lower than for low enriched uranium. However, if fissile material is able to escape from the contaimnent system under accident conditions, it must be demonstrated that the quantity that escapes is consistent with that assumed in the criticality safety assessment in applying para. 682(c). 

A fission chain is propagated by neutrons. Since a chain reaction depends on the behaviour of neutrons, fissile material is packaged and shipped under requirements designed to maintain subcriticality and, thus, provide criticality safety in transport. In the Regulations the term fissile material is occasionally used to refer both to fissile... 

If certain equipment is attached during transport for handling purposes, it also may be necessary to consider its effect in normal and accident conditions of transport. In the case of Type B(U), Type B(M), Type C and packages designed to carry fissile material, the designer must reach agreement with the competent authority for certification. 

In the 1996 edition of the Regulations the TI no longer makes any contribution to the criticality safety control of packages containing fissile material. Control for criticality safety is now provided by a separate criticality safety index (CSI) (see paras 218.1 and 218.2). Although the previous approach of a single control value for... 

The approval certificate should identify any requirements for closure of a package containing fissile material which are necessary as a result of the assumptions made in the criticality safety assessment relative to water in-leakage for a single package in isolation (see para. 677). Inspections and/or tests should be made to ascertain that any special features for prevention of water in-leakage have been met. 

The labels carrying the CSI should appear on packages containing fissile material, as required by para. 541. The CSI label is additional to the category labels (Categories I-WHITE, II-YELLOW and III-YELLOW), because its purpose is to provide information on the CSI, whereas the category label provides information on... 

Segregation of packages containing fissile material during transport and stori e in transit... 

For packages containing fissile material, the programme should also take appropriate account of the need for nuclear criticality control. 

The requirements for packages containing fissile material are additional requirements imposed to ensure that packages with fissile material contents will remain subcritical under normal and accident conditions of transport AU other relevant requirements of the Regulations must be met. The systan for implonenting criticality control in transport is prescribed in Section V of the Regulations. 

Packages containing fissile material are required to be designed and transported in such a way that an accidental criticaUty is avoided. Criticality is achieved when the fission chain reactions become self-supported due to the balance between... 

The effects of temperature changes (para. 671(a)(vi)) on the stability of fissile material form or on the neutron interaction properties are required to be examined. For example, uranium systems dominated by very low energy (thermal) neutrons have an increase in neuUon multiphcation as the temperature is reduced. Temperature changes may also influence the package integrity. The temperatures which should be considered include those resulting from ambient condition requirements specified in para. 676 and those of the tests (paras 728 or 736, as appropriate). 

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