Management of Commercially Generated Radioactive Waste - U.S. ...

4.32
Center has been set up to provide techniques for comparing important waste form materials
characteristics on a common basis (Nelson et al. 1980). The first issue of the Nuclear
Waste Materials Handbook will be published in approximately two years. It will contain
materials data, not only for candidate waste forms, but also for other waste package com-
ponents.
Since the most likely mechanism for release of radionuclides to the biosphere is reac-
tion with and transport by ground water, resistance to leaching of radionuclides by ground
water is the performance characteristic of major interest. Leach resistance can be highly
dependent upon the physical, chemical, mechanical, and radiation stability of the waste
form. The stability of a waste form depends upon its response to radiation, temperature,
and the chemical environment (Mendel et al. 1975). The factors influencing long-term sta-
bility are: 1) transmutation by radioactive decay, which may alter the chemical structure
of the waste form; 2) recoil from alpha decay, which may break chemical bonds and alter the
physical structure of the waste form; 3) heat generated by radioactive decay, which may
cause the waste form to change to a more thermodynamically stable state and which may accel-
erate potential chemical reactions, including leaching; and 4) the chemical environment,
i.e., water plus dissolved ions, which ultimately determines the rate of release of radioactive
materials into the repository.
4.3.3 TRU Waste Treatment in the Reprocessing Cycle
When spent fuel is reprocessed for uranium and plutonium recycle, the non-high-level
and nongaseous wastes that result from these operations and from the mixed oxide fuel fabri-
cation must also be treated and packaged. This section addresses the treatment of these
solid and liquid TRU wastes. Treatment and packaging processes for such wastes are
described in detail in DOE-ET-0028 (Section 4.0), where wastes are discussed in four cate-
gories: 1) fuel residue (the fuel hulls and assembly hardware), 2) failed equipment and
noncombustible waste, 3) compactable and combustible waste, and 4) wet and particulte solid
wastes. Brief descriptions of the treatment processes for these wastes are given in the
following sections; the referenced document may be consulted for details. Both TRU and
non-TRU wastes of the latter three categories result from operation of fuel reprocessing
plants (FRPs). Only the treatment of the TRU wastes is considered in this Statement; the
treatment of the non-TRU portions would be similar, however.
4.3.3.1 Fuel Residue Treatment
Packaging without compaction is the example fuel residue treatment process used in this
Statement. Mechanical compaction of hulls and melting of hulls are also described to illus-
trate other alternatives. The fuel residue packages have surface dose rates well above
0.2 R/hr. Remote handling of these wastes is thus required.
Fuel Residue Packaging Without Compaction (Example Method)
Packaging without compaction is a treatment concept in which the nonsegregated fuel
residue is monitored for undissolved fuel, dried, and sealed without compaction in stainless