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Sugaya, Atsushi; Horiguchi, Kenichi; Tanaka, Kenji; Kobayashi, Kentaro
Materials Research Society Symposium Proceedings, Vol.1107, p.173 - 179, 2008/00
In Nuclear Fuel Reprocessing Plant, it is necessary to dispose of a large amount of low level radioactive effluent containing nitrate as a major ingredient, safely and economically. Therefore, engineering developments concerning a cement based encapsulation process have been carried out in JAEA. From the viewpoint of disposal cost decrease, a low level radioactive effluent is passed through the nuclide separation process before cementation to concentrate the radioactivity into the minimum volume for conditioning and disposal. Two kinds of effluents are generated as a result of the nuclide separation; Non-radioactive simulants were prepared for each of these waste streams, and used in encapsulation trials to investigate a special slag cement, on a beaker scale and at full scale (200-litres). The results have confirmed that the nitrate effluent, evaporated up to a predetermined density, can be successfully encapsulated at a salt filling rate of 50wt%, to produce a wasteform which satisfies the required conditions. In the slurry effluent, the strength of the product decreased when carbonate concentration was high. However, it was confirmed that the product made at salt filling rate 50wt% satisfied the required conditions, if the carbonate concentration in the effluent was decreased to 10 g/L or less.
Miyahara, Kaname; Kato, Tomoko
Materials Research Society Symposium Proceedings, Vol.1107, p.673 - 680, 2008/00
Radionuclide fluxes can only be estimated on the basis of models. H12 generic conceptual model for radionuclide transport pathway with conservatively simplified assumptions for geological structures is chosen for this purpose; each waste package is hypothetically assumed to be located 100 m from the downstream major water-conducting fault (MWCF). All radionuclides released from the repository are assumed to migrate upwards through the MWCF, traveling shortest distance to the biosphere. At discharge point from the MWCF to aquifer, these fluxes are compared with fluxes of natural radionuclides in corresponding groundwater flow by conservatively assuming that a groundwater flow rate at the depth of repository is prevail in shallower depth up to the aquifer. This yardstick does not include any geological processes in the surface environment which are practically independent of radionuclide migration processes from the repository up to the discharge point. This paper discusses the relevance of this yardstick to illustrate the effectiveness of barrier performance.
Lim, D.-H.*; Uchida, Masahiro; Hatanaka, Koichiro; Sawada, Atsushi
Materials Research Society Symposium Proceedings, Vol.1107, p.567 - 575, 2007/00
Miyahara, Kaname; Kato, Tomoko
no journal, ,
The effectiveness of barrier performance of a disposal system can be estimated by fluxes of disposal facility-derived radionuclides as a complementary safety indicator, if appropriate yardsticks for comparison are used. Natural radionuclide fluxes due to geological processes such as erosion and river flow have potential for use as yardsticks. However, since those geological processes are variable in different locations and time, it is possible to define a range of environmental fluxes which provide alternative yardsticks. H12 conceptual model is chosen for estimating radionuclide fluxes. At discharge point from major water-conducting fault to aquifer, these fluxes are compared with fluxes of natural radionuclides in corresponding groundwater flow by conservatively assuming that a groundwater flow rate at the depth of repository is prevail in shallower depth up to the aquifer. This paper discusses the relevance of this yardstick to illustrate the effectiveness of barrier performance.
Sugaya, Atsushi; Horiguchi, Kenichi; Tanaka, Kenji; Kobayashi, Kentaro
no journal, ,
In Nuclear Fuel Reprocessing Plant, it is necessary to dispose of a large amount of low level radioactive effluent containing nitrate as a major ingredient, safely and economically. Therefore, engineering developments concerning a cement based encapsulation process have been carried out in JAEA. From the viewpoint of disposal cost decrease, a low level radioactive effluent is passed through the nuclide separation process before cementation to concentrate the radioactivity into the minimum volume for conditioning and disposal. Two kinds of effluents are generated as a result of the nuclide separation; a nitrate effluent of which the principal ingredient is nitrate with a comparatively low radiation level, and a slurry effluent including several kinds of salts with a comparatively high radiation level. Non-radioactive simulants were prepared for each of these waste streams, and used in encapsulation trials to investigate a special slag cement, on a beaker scale and at full scale (200-litres). The results have confirmed that the nitrate effluent, evaporated up to a predetermined density, can be successfully encapsulated at a salt filling rate of 50wt%, to produce a wasteform which satisfies the required conditions. In the slurry effluent, the strength of the product decreased when carbonate concentration was high. However, it was confirmed that the product made at salt filling rate 50wt% satisfied the required conditions, if the carbonate concentration in the effluent was decreased to 10g/L or less.