Oxides - Continued - std301320000034

DOE-STD-3013-2000

Therefore, impure materials packaged under this Standard with weapons grade

isotopic compositions will never experience the bounding temperatures

calculated for the 19-watt solar scenario. The vast preponderance of higher

specific wattage material (e.g., fuels or power grade material) to be packaged

under this standard is relatively pure "product quality" material at PFP.

The mechanism of gas formation from water adsorbed on plutonium oxide and

impurities is highly relevant to both this Standard and to DOE-STD-3013-96. In

both standards, a chemical mechanism described by Stakebake, Haschke et al. in

several peer-reviewed publications is assumed to define the bounding pressure

assumption (hydrogen only, no other gases formed). [Stakebake et al. 1993;

Haschke/Ricketts 1995; Haschke and Martz 1998] The pertinent chemical

reaction is:

PuO2 + x H2O ------> PuO2+x + x H2

As indicated in this equation, decomposition of adsorbed water occurs by a solid

state chemical reaction that generates hydrogen gas and retains oxygen as a

superstoichiometric plutonium oxide. The temperature stability field of this oxide

is not firmly established, but the compound appears to be stable from room

temperature to about 400 C [Morales et al. 1999]. A value of x up to about 0.3,

corresponding to about 2 wt% moisture in plutonium oxide, appears to be

possible in plutonium storage environments [Stakebake et al. 1993;

Haschke/Ricketts 1995; Haschke and Martz 1998].

Recent work by Morales on the rate of the hydrogen/oxygen reaction in

air/hydrogen mixtures over plutonium oxide supports earlier conclusions by

Haschke, et al. that the surface of plutonium oxide, like many other surfaces, is

an effective catalyst for this reaction [Morales 1999; Haschke/Martz 1998].

Accompanying work on hydrogen oxidation in the absence of plutonium oxide

shows that stainless steel and other surfaces readily catalyze this reaction at

temperatures of interest [Quigley 1998]. A recent literature search also shows

conclusively that the H2/O2 reaction is readily initiated by alpha and gamma

radiation [Lloyd et al. 1999 and references contained therein]. Indeed,

remarkably high G values (the yield of product for 100KeV of adsorbed radiation

energy) for recombination (in excess of 100) have been reported, compared to