Packaging Process - Continued

DOE-STD-3013-2000

to result from catalytic or radiolytic decomposition of water (see Section A.6.1.2 of

this appendix). This also makes corrosion pitting highly unlikely.

Unlike general corrosion, stress corrosion cracking (SCC) is not mass limited. While

SCC is a definite issue for stainless steel in moist oxidizing environments, Kolman's

evaluation concludes that SCC is not a concern if conditions within the storage

containers are maintained above the dew point of the contained atmosphere. This

conclusion holds even in the presence of chloride salts and temperatures as high as

250C. The stabilization and packaging criteria of this Standard, the anticipated

elevated temperatures during storage, and the affinity of plutonium oxide for water

provide confidence that dew points will never be exceeded within the packages. A

recent review of experience in storing pyrochemical salts at numerous sites in the

DOE complex showed that chloride corrosion has not presented a significant storage

problem in the past when liquid water (and other corrosive agents) were avoided, in

agreement with the predictions of Kolman [Kolman 1999] regarding storage of

materials under this Standard [also see Tandon et al. 1999b].

Kolman's paper also addresses radiation induced SCC and hydrogen embrittlement.

These are not anticipated to be issues if, as expected, significant plastic strain is not

introduced into the containers and large hydrogen pressures (well above that

predicted by the pressure equation) do not develop in the containers. Preliminary

accelerated corrosion susceptibility tests of stainless steel weld specimens support

this conclusion. Kolman's paper states that it is critical that welding practices do not

result in sensitization of the stainless steel container. To avoid sensitization, the use

of low carbon grades of stainless steel is strongly recommended, as is the use of

weld filler material. Moreover, the use of stress-relieved container materials is

strongly recommended.

Likewise, it is concluded that gallium embrittlement is unlikely to be a significant

issue.

4. To promote material homogeneity for facilitating MC&A measurements and

stabilization tests (such as for adsorbed water content), and to preserve

characterization information to the greatest extent possible, only similar materials

(comparable in form and composition, for example) should be packaged together.