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Table 2.8. Potential Hazards or Damage to Materials from Exposure to Radiation - doe-std-1128-98_ch10036
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DOE Standard Guide of Good Practices for Occupational Radiological Protection In Plutonium Facilities
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Miscellaneous Radiolytic Reactions - doe-std-1128-98_ch10038


DOE-STD-1128-98
0.001M (0.24 g/L) of plutonium solution is on the order of 2 x 1014
eV per minute. Thus, the hydrogen evolution would be
approximately 3.8 x 1015 molecules per liter per day for a 1M
solution, or about 73 cm3 of hydrogen per year.
The G-values for H2 in solids irradiated by gamma rays are lower:
0.1 for ice (Johnson, 1970) and 0.01 for the hydrates of a large
number of sulfates (Huang and Johnson, 1964). Because the stability
of PuSO4 . 4H20 was found to be remarkably high (Cleveland, 1970),
one of the sulfates may well serve as an alternate interim waste form.
Dole (1974) summarized the radiation chemistry of polyethylene,
quoting G-values for hydrogen as 5 molecules per 100 eV.
Destruction of plutonium hexafluoride as the solid phase amounts to
about 1.5% of the material per day (Weinstock and Malm, 1956).
Cleveland (1970) calculated the mean change in average oxidation
number in 0.52M of perchloric acid to be 0.018 moles per day,
corresponding to a G-value of 3.2 equivalents per 100 eV. The
formation of hydrogen peroxide from the radiolysis of water is
believed to be the mechanism for the reduction of plutonium (VI)
ions. Lower oxidation states are formed by the disproportionation of
the plutonium (V) species.
Pressurization of storage containers holding TRU wastes is a
potential hazard for both long and interim storage periods (Kazanjian
et al., 1985). Sampling of TRU waste drums shows that hydrogen is
usually created (Roggenthem et al., 1989). Waste drums with
pinholes can "breathe" when the atmospheric pressure changes,
thereby introducing water vapor. Water vapor adsorbed on plutonium
compounds is radiolytically decomposed, thereby producing
hydrogen. It may be possible to add pressure relief valves and
appropriate in-line filters to waste drums. (See Section 2.7 for more
information on storage and containment.)
2.5.2.2 Redox Reactions
In most chemical processes for purifying plutonium, it is essential to
maintain its valence state. The formation of hydrogen peroxide from
the radiolysis of water is believed to be the mechanism for the
reduction of plutonium (VI) ions. Lower oxidation states are formed
by the disproportionation of the plutonium (V) species. Cleveland
(1970) calculated the mean change in average oxidation number in
0.5-2M of perchloric acid to be 0.018 moles per day, corresponding
to a G-value of 3.2 equivalents per 100 eV.
In the radiolysis of solutions, the presence of other ionic species can
accelerate or inhibit the disproportionation of plutonium valence
states. For example, the presence of the chloride ion in plutonium
(VI) solutions prevents reduction to plutonium (IV). Reactions may
reverse after long irradiation periods, in which case a steady-state
condition should ultimately be reached, resulting in a net
decomposition rate of zero. An excellent review of the radiation
2-23


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