Method of use of radioactive ion-exchange resins in rapid hardening cements

 

The invention relates to the field of processing radioactive ion exchange resins (IOS) method cementation. Radioactive IOS is mixed with rapid hardening cement, water and sorption mineral Supplement. Then the resulting mixture utverjdayut. As a quick use aluminous cement when water-cement ratio 0,72-0,78, as well as mineral supplements - Cambrian clay. The use of this invention will increase the degree of incorporation of radioactive IOS, decreasing rapidly hardening cement and reduce the leachability of radioactive caesium while maintaining a sufficiently high strength cement compounds. table 1.

The invention relates to the field of processing radioactive ion exchange resins (IOS) method cementation.

Waste kationoobmennika and asianavenue resins are the most radioactive (up to 10-3CI/kg and more) waste resulting from the operation of nuclear power plants (NPP) [1]. Therefore, their inclusion in a binder securely insulated from the environment, is an important environmental problem.

The known method include radioactive IOS in Portland. Otechestvo is b>O3. The best performance for the curing of resins obtained when the water-cement ratio 0,52-0,56 using rapid hardening Portland cement, allowing you to include up to 10% of IOS (by weight of dry resin). Rapid hardening Portland cement differs finer grinding of its constituent minerals and due to this more rapid curing at the initial setting. To reduce the leachability of radioactive cesium from cement compounds should enter them as sorption vermiculite mineral supplements [2] . This mineral in the northwestern regions of Russia contains 34-36% SiO2, 14-16% Al2O3+TiO2up to 1% Cao, 25-27% of MgO, up to 6-8% Fe2O3+F, up to 0.5% K2O+Na2O and has a total exchange capacity of up to 1.6 mEq/g This way by its technical essence and the achieved effect closest to the proposed and selected as a prototype.

The disadvantage of this method is high even when the sorption mineral Supplement of the vermiculite BaselCement of radiocaesium from cement compounds, a low degree of inclusion of IOS and increased consumption of expensive rapid hardening cement (1.8 to 1.9 wt. including cement to 1 wt. including water). Should ammatitaitoista ion-exchange groups with cement to ensure the water resistance of the solidified products must withstand not less than the standard 28 days.

According to the domestic technical requirements RD 95 10497-93 mechanical strength of the radioactive cement compounds should be not less than 50 kgf/cm2even after 90 days exposure to water and BaselCement radiocesium less than 10-3g/cmday, which ensures the safety of their burial in a typical concrete storage [3] . At the same time, the disposal of radioactive concrete blocks in the simplest ground burial is considered to be quite safe when BaselCement radiocesium not more than 10-4g/cmday [4].

The problem solved by this invention is to increase the degree of inclusion of IOS, reducing consumption, rapid hardening cement and reducing the leachability of radioactive caesium while maintaining a sufficiently high strength cement compounds.

The invention consists in that in the method include radioactive IOS in rapid hardening cement with sorption mineral Supplement, as a quick-use aluminous cement when water-cement ratio 0,72-0,78, and as sorption supplements - Cambrian clay.

Domestic aluminous cement is a rapid hardening due b>O3. Cambrian clay in the North-Western regions of Russia contains of 57.5-59.5 per cent SiO2, 18-20% Al2O3+Tio2, 0,7-3,0% Cao, 1.8 To 3.0% MgO, up to 6-8% Fe2O3+FeO, to 2.8% and 6.2% K2O+Na2O and has a total exchange capacity of about 1 mEq/g

The method is as follows.

Radioactive IOS is mixed with aluminous cement and water, with water-cement ratio 0,72-0,78 and add Cambrian clay in an amount up to 10% by weight of cement. In salt-free form of IOS (H+for cation and HE-for anion exchange resin) in aluminous cement include up to 17.5% by weight of dry resin, and salt forms of IOS to 19% by weight of dry resin. The mixture is stirred until homogeneous, and then utverjdayut to a strength sufficient for safe transportation (not less than 50 kg/cm2). BaselCement radiocesium through 150 days shall not exceed 10-4g/cm2day, which ensures their safe disposal in the simplest ground burial.

In comparison with known methods include radioactive IOS in rapid hardening cements used for this purpose, aluminous cement when water-cement ratio 0,72-0,78 with sorcio the cement consumption (1.3 to 1.4 wt. h cement to 1 wt. including water) at 35-38% while maintaining a sufficiently high strength (not less than 50 kg/cm2after soaking in water and leachability quite low (no more than 10-4g/cm2day) for burial in simple earthen mounds that not obvious from the prior art (exchange capacity Cambrian clay 1.6 times lower than the capacity of vermiculite), i.e., the proposed method meets the criterion of inventive step.

Examples of specific performance.

Example I (a prototype). A mixture of radioactive cation exchange resin KU-2 (H+form and Na+-form) anion exchange resin (in the HE--form and SO42-form) in the ratio of 1:1 was stirred with rapid hardening Portland cement grade 400 and water, with water-cement ratio of 0.52-0.56 and sorption mineral Supplement - vermiculite (Kovdor Deposit in the Murmansk region) in the amount of 10% by weight of cement. Stirring is carried out until a homogeneous mass and utverjdali up to full strength. Cement compounds were tested for strength in accordance with GOST 310.4-81 after soaking in water for 90 days and BaselCement according to GOST 29114-91 within 150 days. Characteristics of the cement compounds listed vinsanity cement when water-cement ratio 0,72-0,78. Characteristics of the cement compounds are given in table.

Example III. Differs from example II the fact that as sorption additives used Cambrian clay (Pulkovo field Leningrad region). Characteristics of the cement compounds are given in table.

Example IV. Differs from example II the absence of sorption supplements. Characteristics of the cement compounds are given in table.

From the data given in the table, it follows that when used as a rapid hardening cement high alumina cement (example IV), with increased Vodolaga ability, durable and water-resistant cement compounds are obtained when up to a 19.5-20% wt. IOS, even without the introduction of sorptive mineral supplements BaselCement137Cs is less than 1.0-10-3g/cmday, which provides a safe disposal in a standard concrete vault. When used as a sorption mineral supplements vermiculite as rapid hardening Portland cement (example I prototype) degree vklucheniya 9.5 to 16% wt. IOS and aluminous cement (example II) the degree of inclusion of 17.5-19% wt. IOS, BaselCement137Cs is more than 1.0 to 10-4g/cmday, which ensures the safe disposal of radioactive cement blocks even in the simplest ground burial.

The proposed method can be implemented on the same hardware as in the use of rapid hardening Portland cement with the addition of vermiculite, aluminous cement and powder Cambrian clay is produced on an industrial scale, i.e., the method is industrially applicable. The use of this method improves environmental safety of radioactive waste storage and reduces the cost of disposal.

Sources of information 1. Nikiforov, A. S., Kulichenko centuries, Zhikharev M. I. Disposal of liquid radioactive waste. - M, Energoatomizdat, 1985, S. 110-111.

2. Bonnevie-Svendsen M. , E. A. Studies on the incorporation of spent ion-exchange resins from nuclear power plants into bitum and cement. - In: Symposium on the ion-site management of power reactor wastes, Zurich, 26-30 Marh, 1979, Paris, 1979, p. 155-174.

3. The quality of the compounds formed by the cementation of liquid radioactive waste of low and intermediate level waste. - Technical requirements. - RD 95 10497-93. M: Minatom of the Russian Federation, 1993.

4. Y. Bazhenov, M., Volkova, O. I., Dukhovich F. C., and other Conditions of safety in the storage of radioactive cements. - Iznik ion-exchange resins in rapid hardening cements, including a mixture of cement, water and sorption mineral Supplement with subsequent curing, characterized in that as a quick-use aluminous cement when water-cement ratio 0,72-0,78, as well as mineral supplements - Cambrian clay.

 

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