Nuclear Energy for New Europe 2009

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No: 912

Conference: Nuclear Energy for New Europe 2009

Title: Compact Tritium Waste Disposal Using Hydride-Forming Materials

Theme: Radioactive Waste Management

Author(s): Valentina Golubeva, Alexej Stengach, Anna Tarrasova, Stanislav Vesnovskiy

Contact : Stanislav Vesnovskiy

E-mail: lbudr@rol.ru

Address: Russian Research Center “Kurchatov Institute”
123182 Moscow

Country: Russia

Tritium-facing equipment and structural components of nuclear reactors, such as beryllium neutron moderator and reflector assemblies, are saturated with tritium. When replaced, these components can be handled both as middle-level and high-level waste. The cost of high-level waste disposal is rather high. In order to reduce activity of the waste and convert it to the low-level grade, it sometimes would suffice to carry out thermal detritiation of structural materials. This would require trapping (compacting) the tritium being released. Hydride-forming metals constitute the most compact tritium sorbent. Following tritium adsorption by hydride-forming metals, the latter are expected to be disposed of in tight casks. At that, metal hydrides should possess high chemical stability and not produce considerable amounts of helium-3, being a product of the radioactive decay of tritium.
The paper presents the results of investigations with titanium being used as the hydride-forming metal. Data on kinetics of helium release from titanium ditritide are given. Active helium release to the gas phase is shown to begin when helium concentration in the solid phase gets as high as to correspond to the atomic ratio He sol.ph./Ti ? 0.3. Such helium concentration in solid-phase titanium ditritide is achieved in 3 to 3.5 years. It is shown that when titanium adsorbs tritium, the total saturation should not be higher that the atomic ratio T/Ti = 0.3. In order to provide more uniform tritium distribution over titanium before disposal, it is suggested to additionally saturate the sorbent with protium, thus bringing the total saturation of titanium hydride to the atomic ratio ? (H+T)/Ti = 1.8-1.9. It is shown that there will be almost no helium-3 release to the gas phase for a long time (at least, 100 years). This precludes the risks of casks containing titanium hydride-tritide becoming leady under helium pressure. Optimal tritium-protium-titanium ratios to enable compact and safe disposal have been determined.

No:	912
Conference:	Nuclear Energy for New Europe 2009
Title:	Compact Tritium Waste Disposal Using Hydride-Forming Materials
Theme:	Radioactive Waste Management
Author(s):	Valentina Golubeva, Alexej Stengach, Anna Tarrasova, Stanislav Vesnovskiy
Contact :	Stanislav Vesnovskiy
E-mail:	lbudr@rol.ru
Address:	Russian Research Center “Kurchatov Institute” 123182 Moscow
Country:	Russia

Tritium-facing equipment and structural components of nuclear reactors, such as beryllium neutron moderator and reflector assemblies, are saturated with tritium. When replaced, these components can be handled both as middle-level and high-level waste. The cost of high-level waste disposal is rather high. In order to reduce activity of the waste and convert it to the low-level grade, it sometimes would suffice to carry out thermal detritiation of structural materials. This would require trapping (compacting) the tritium being released. Hydride-forming metals constitute the most compact tritium sorbent. Following tritium adsorption by hydride-forming metals, the latter are expected to be disposed of in tight casks. At that, metal hydrides should possess high chemical stability and not produce considerable amounts of helium-3, being a product of the radioactive decay of tritium. The paper presents the results of investigations with titanium being used as the hydride-forming metal. Data on kinetics of helium release from titanium ditritide are given. Active helium release to the gas phase is shown to begin when helium concentration in the solid phase gets as high as to correspond to the atomic ratio He sol.ph./Ti ? 0.3. Such helium concentration in solid-phase titanium ditritide is achieved in 3 to 3.5 years. It is shown that when titanium adsorbs tritium, the total saturation should not be higher that the atomic ratio T/Ti = 0.3. In order to provide more uniform tritium distribution over titanium before disposal, it is suggested to additionally saturate the sorbent with protium, thus bringing the total saturation of titanium hydride to the atomic ratio ? (H+T)/Ti = 1.8-1.9. It is shown that there will be almost no helium-3 release to the gas phase for a long time (at least, 100 years). This precludes the risks of casks containing titanium hydride-tritide becoming leady under helium pressure. Optimal tritium-protium-titanium ratios to enable compact and safe disposal have been determined.