Utilization of Valuable Metals from High Level Waste-Decomposition of Water Using Semiconductor Photocatalytic Method In
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UTILIZATION OF VALUABLE METALS FROM HIGH LEVEL WASTE -DECOMPOSITION OF WATER USING SEMICONDUCTOR PHOTOCATALYTIC METHOD INDUCED BY GAMMA RAYY.WADA, K.KAWAGUCHI AND M.MYOCHIN
Power Reactor and Nuclear Fuel Development Corporation Tokai, Ibaraki, 319-11, Japan
ABSTRACT
The technique of radiolytic decomposition of water leading to hydrogen production was demonstrated to explore a new field in the utilization of radioactive platinum group metals recovered from high level radioactive waste (HAW) and radioactivity of HAW. The radiation photocatalytic method is based on the technique to decompose water on platinized semiconductor particles under UV-light irradiation which has been widely investigated to develop an alternative energy source. In this study gamma radiation from Co-60 source was applied to produce hydrogen instead of UV-light and a significant amount of hydrogen evolved from catalyst-water suspension. Our preliminary experiments proved a possibility of converting the energy of radiation ionization into chemical energy (hydrogen) by the radiation photocatalytic method. INTRODUCTION
A number of works on the decomposition of water on platinized oxide semiconductors suspended in water under UV light have been performedfl-3) since the study by Honda and Fujishima [4] was reported. They showed photodecomposition of water into hydrogen and oxygen on a titanium dioxide electrode and a counter electrode by photosensitized oxidation and reduction due to the electron-hole pairs generated in the irradiated n-type semiconductor. On the other hand we have been developing the techniques to recover and utilize the platinum group metals from high level radioactive waste (HLW) as a part of the program of the partitioning and utilization of HLW. Spent nuclear fuels contain significant quantities of valuable metals; the platinum-group metals and technetium. The recovery of the platinum-group metals, palladium, rhodium and ruthenium, leads to a new source of these three metals which have uncertainty in supply because of world's limited producers and are increasing in demand of the growth of
high-technology industry. Thus there is considerable incentive to recover the platinum group metals from spent nuclear fuel and various processes to recover them have been evaluated on a laboratory scale. Table I shows the isotopic abundance of the platinum group metals recovered Table I Platinum group metals recovered from spent nuclear fuels U235 4%, ORIGEN-79 28000MWD/t, 1-year Cooling Yield (g)
Activity (itq)
Mass Yield (g) No.
99 5.02X10-3 34.4 100 101 658
-
102 1.56X10-3
-
103
102
-
629 2
103
7.80X10"
104
401
106
60.5
10 3
9.21X10
106
15
5.68X10-
fl- 106pd
102
5 5
Rh
9.25X10 7.4X10
6
10 Rh
13 15
Mass No.
Yield (g)
Activity (Bq)
104
163
-
105
222
-
106
232
107
138
2.59X10
108
89.8
-
110
26.1
-
9
l.•1 2.9y
103mRh
10
-
126d
57m
368d
6.99X10
13
-
7.4 X10
Activity (Bq)
396
103m 7.65X10-
-
Ru .g.-103Rh 39.8d lO3mRh 31i1038h
106Ru 3--- 1°6Rh
Pd
Rh
Ru Mass No.
lI. -
57m
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