Vitrified Waste

DOE-HDBK-3010-94

4.0

Solids; Nonmetallic or Composite Solids

levels of thermal stress considered here are those commonly associated with industrial-type

fires. More rigorous conditions that may be generated in nuclear reactors or other more

severe events are not considered. Although some spent nuclear fuel within the DOE complex

are composed of other materials (metals and alloys), the overall material composite is

covered in this subsection because it deals with the airborne release of all radionuclides

rather than the base material.

4.3.1.1

V itrified W aste

Data from the experimentally measured airborne release from heating this form were not

uncovered. The stresses that are generated by subjecting the canister to the conditions

generated by an industrial-type fire do not appear to be adequate to breach the heavy-wall

stainless steel canister enclosing vitrified high level (HL) waste. The impact of fire-

generated conditions on the behavior of container holding other types of vitrified waste (e.g.

products of slagging pyrolysis) should be considered and the consequences of any breach

mechanism evaluated. If the vitrified HL waste canister is breached by large pressurization

from the heating of the gases in the free-volume, a fraction (ARF 1E-1, RF 0.7) of the fines

present in cooled, vitrified HL waste (estimates as high as 0.035%, WHC, 1993) on the

surface of the vitrified HLW waste held in the canister could be expelled.

Monolithic borosilicate glasses incorporating high-level waste do not appear to have the

potential to release any significant amount of non-volatile radionuclides. These materials

would have been heated to temperatures exceeding those anticipated for most fire situation

during formation and are not anticipated to undergo any chemical change under fire

conditions. Borosilicate glasses are more resistant to thermal shock when cool but could be

affected by very rapid cooling rates (molten glass poured into large bodies of cool water).

Molten glass does not appear to possess the characteristics to generate a physical (vapor)

explosion; it does not remain plastic over the required temperature range to generate fine

(100 m diameter) drops of molten glass adequate to result in the rapid heat transfer

necessary for vapor explosions. Molten glass poured in pools of water would lead to

vigorous boiling that could suspended solid particles carried in the liquid (see Borkowski,

Bunz and Schoeck, May 1986). A possible method to estimate the fragmentation of glass by

rapid cooling is to calculate the energy from cooling the glass and use that value in the crush-

impact correlation outlined in section 4.3.3. Notwithstanding, a bounding ARF and RF

cannot be assessed at this time due to the lack of applicable data. From the information

available, however, any release under industrial-type fire conditions appears to be negligible.

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