Intermediate-level Waste Disposal Facility Research Articles

Long-Term Experiments for Demonstrating Durability of a Concrete Barrier and Gas Generation in a Low-and Intermediate-Level Waste Disposal Facility

Long-Term Experiments for Demonstrating Durability of a Concrete Barrier and Gas Generation in a Low-and Intermediate-Level Waste Disposal Facility

Evaluation of efficient cementation of fission 99Mo production process waste and feasibility disposal of cement waste form

The Korea Atomic Energy Research Institute (KAERI) is planning the construction of the KIJANG Research Reactor (KJRR), which is currently undergoing licensing procedures. The fission 99Mo production process (FMPP) of the KJRR generates intermediate-level liquid waste (ILLW) and alumina residue (Al2O3 cake), which is a solid waste. In the present study, an efficient method of reducing the amount of generated cement waste form by mixing the ILLW and Al2O3 cake together, into low-level waste, was developed. The purpose of this study was to determine if the cement waste form produced by mixing cement with the waste from the FMPP would satisfy the acceptance criteria of a low- and intermediate-level waste disposal facility in Korea. The process operating range and the optimum operating conditions were found by investigating the mixability of the cement waste form, by considering the presence of free standing water after curing, and by performing a water immersion test depending on the mixing ratios of Portland cement (type I), ILLW, and Al2O3 cake. The feasibility of treating the cement waste form produced under the optimum operating conditions was evaluated in relation to the acceptance criteria of a low- and intermediate-level waste disposal facility in Korea. The results showed that the cement waste form satisfied the acceptance criteria with regard to structural stability (compressive strength test, thermal cycling test, water immersion test, and irradiation test) and leachability (leaching test).

Large scale in-situ experiments on sealing constructions in underground disposal facilities for radioactive wastes – Examples of recent BfS- and GRS-activities

This paper shows examples of in-situ constructions and laboratory tests that have been designed and implemented by BfS and GRS in order to demonstrate the technical feasibility of special constructions for the sealing of drifts and shafts in different salt formations.Since it is often not possible to directly verify the long-term functionality (for times scales envisaged in long-term safety assessments) of such constructions, an overall understanding of the main chemical and physical processes involved needs to be developed. Such an understanding is required in order to extrapolate the evolution of a sealing system with a sufficient degree of reliability. Laboratory tests and large-scale in-situ tests are necessary and integral parts of the procedures for enhancing the process understanding.Based on a safety case, BfS has developed a robust decommissioning concept for the closure of the low- and intermediate-level waste disposal facility Morsleben (ERAM) which also takes into account the retention of radionuclides by combined effects of different sealing components.GRS has contributed to this concept with laboratory tests and modelling of the long-term behaviour of the sealing material “salt concrete” foreseen for the sealing constructions in Morsleben. Salt concrete is based on the cement Portlandite i.e., on CaO. Furthermore GRS has also investigated the MgO based “sorel concrete” employed by BfS for the Asse project. The chemical corrosion path and the subsequent permeability changes for both concretes have been investigated with test procedures developed in the GRS laboratory. GRS has also developed a new Self-Sealing material “Selbst Verheilender Versatz – SVV” (SVV, German for Self Sealing Backfill) and tested in laboratory and in-situ experiments. With this material it is possible to achieve an instantaneous and long-lasting permeability reduction within the complex system consisting of the sealing construction and the Excavation Demaged Zone (EDZ) upon brine intrusion.The presentation demonstrates details of the concepts and highlights results from the BfS in-situ experiments in Morsleben and the preceding GRS laboratory and in-situ tests.

보조지표를 활용한 중·저준위 처분시설 성능평가: 방사성 핵종 플럭스 사례연구

The use of complimentary indicators, other than radiation dose and risk, to assess the safety of radioactive waste disposal has been discussed in a number of publications for providing the reasonable assurance of disposal safety and convincing the public audience. In this study, the radionuclide flux was selected as performance indicator to appraise the performance of engineered barriers and natural barrier in the Wolsong low- and intermediate-level waste disposal facility. Radionuclide flux showing the retention capability by each compartment of the disposal system is independent of assumptions in biosphere model and exposure pathways. The scenario considered as the normal scenario of disposal facility has been divided into intact or degraded silo concrete conditions. In the intact silo concrete, the radionuclide flux has been assessed with respect to the radionuclide retardation performance of each engineered barrier. In the degraded silo concrete, the radionuclide flux has been explored based on the performance degradation of engineered barriers and the relative significance of natural barrier quantitatively. The results can be used to optimally design the near-surface disposal facility being planned as the second project phase. In the future, additional complimentary indicators will be employed for strengthening the safety case for improving the public acceptance of low- and intermediate-level waste disposal facility.

Experiment on gas entry pressure and gas permeability of concrete silo for a low- and intermediate-level waste disposal facility in Korea

After closure of an underground disposal facility, it would be saturated with ground water and gases would be generated by various mechanisms. As the generated gases are accumulated, internal pressure of the concrete silo would increase and integrity of the silo could be damaged by overpressure. Therefore, an effective gas permeable seal is necessary to prevent the overpressurization of the concrete silo. For designing the gas permeable seal, experimental study and computer modeling on the gas migration through the concrete should be performed. In this study, in order to obtain the specific characteristics of the concrete silo which are necessary for computer modeling, gas entry pressure and gas permeability of the concrete silo were measured by using specimens which have a same composition with the concrete silo. The results of this study could be utilized to the simulation of gas migration and design of the gas permeable seal for a LILW disposal facility in Korea.

Gas threshold pressure and gas permeability of silo concrete specimens for a low- and intermediate-level waste disposal facility in Korea

In order to simulate gas migration at an underground disposal facility, the characteristics of a medium such as the gas threshold pressure and gas permeability need to be measured in advance. In this study, the gas threshold pressure and gas permeability of silo concrete specimens for a Korean LILW (Low- and Intermediate-Level Waste) disposal facility were measured. The concrete specimens had the same composition as the concrete used in the construction of the silo. The gas threshold pressure was measured by injecting a constant gas flow into cross sections of the specimens. To measure the gas permeability, selected pressures were applied to the specimens and the apparent permeability was calculated using the Hagen-Poiseuille equation. The intrinsic permeability was calculated with the Klinkenberg empirical equation. The gas threshold pressure and gas permeability ranged from 30 to 40bar and from 10−17 to 10−18m2, respectively.