Safety_Series_015_1965 - gnssn - International Atomic Energy ...

More documents

Recommendations

Info

This publication is not longer validPlease see http://www-ns.iaea.org/standards/II.INCORPORATION OF HIGH-LEVEL LIQUIDS IN GLASSThere are no sites where high-level liquids are operationallyconverted into solid glass, but there are two experimental proceduresthat are worthy of note in their association of this method with grounddisposal.(1) Glass manufacture at Chalk River, Ontario, CanadaIn this process an aged fission-product solution of concentration20C i/litre, containing 8N nitric acid, was converted into glasshemispherical blocks of 14 cm diam. The glass was made fromnepheline syenite mixed with 15% lime, pelletized by tumbling inwater and introduced into crucibles in alternate layers with the radioactivesolution. The nitric acid reacted with the syenite pellets toform a gel of silicic acid, which was dried at 900°C. This was thenfused at 1350°C and the volatilized gases were passed through firebrickabsorbers containing iron oxide to remove ruthenium andcaesium.Twenty-five of these blocks (1000 Ci) were then buried in sandysoil and leaching was deliberately encouraged by ensuring that theylay beneath the water table. They were placed in a vertical gridoriented normal to the direction of ground water flow, which wasfound to be 23 cm/day. After 2. 5 years, only 4 mCi was releasedto the surrounding soil and ground water, representing a leachingrate of 2 X 1 0 ' 8 g/cm 2 day or about one-tenth of the value anticipatedfrom previous short-term leaching experiments with distilled water.The front of strontium-90 migration was less than 5 m from theblocks and the experiment was felt to be a successful demonstrationof safe disposal into the ground [47].(2) Glass manufacture at Harwell, EnglandA conceptual waste treatment is envisaged [61] that will converthigh-level liquid wastes from fuel processing into glass cylinders15 cm diam. X 1. 5 m long. The specific activity of the glass wouldbe 600 times as large as that in the Chalk River experiment, witheach cylinder incorporating an estimated 9X105 ci after one year'sdecay.A pilot plant using inactive materials was developed until thereliability and reproducibility, necessary for the final process, were60
This publication is not longer validPlease see http://www-ns.iaea.org/standards/achieved. From the experience attained engineering componentswere developed suitable for the commissioning of a full-scale plant.In the process the waste solution and a silica/borax slurry are premixedand introduced at an appropriate flow-rate into a stainlesssteelcylindrical casing placed in an electric furnace (Fig. 15). TheFISSION PRODUCT WASTESILICA/BORAX SLURRY-© ©-STAINLESS STEELCYLINDER6* I D » 5'LONGT 5PRIMARYfilter/absorber; TFURNACE WITH — .6 INDEPENDENTLY \CONTROLLED __ iHEATINGELEMENTSFig. 15Sim plified flow -sheet o f process for incorporation o f fissionproduct wastes in glass.heating applied to various levels of the casing is adjustable to ensurethat evaporation, ' denitration, sintering and melting occur simultaneouslyover a narrow zone to form a bubble-free glass.The resulting blocks of glass would be self-heating and it is intendedthat they should be stored permanently underground or inappropriate structures where convective air-currents would c ir culate naturally and so provide the necessary cooling. It is envisagedthat the soil be used only as a shielding medium but leaching experimentsindicate that if ground water came into contact with the exposedend of a cylinder, the estimated release would be 10 mCi/week.If, however, the entire container corroded, leaching from the exposedsurface would be increased to an estimated 500 m Ci/week.61
Page 1 and 2:
This publication is not longer vali
Page 3:
Page 6 and 7:
Page 8 and 9:
Page 10 and 11:
Page 12 and 13:
Page 14 and 15:
Page 16 and 17:
Page 18 and 19:
Page 20 and 21: This publication is not longer vali
Page 120 and 121:
Page 122 and 123:
Page 124:
show all

Safety_Series_015_1965 - gnssn - International Atomic Energy ...

Create successful ePaper yourself

Delete template?

Save as template?