Various types of solidifying materials are used to stabilize and solidify low and intermediatelevel radioactive dispersible waste. Portland cement is generally used to solidify various radioactive wastes because its facilities and processes are simple, less dangerous, and it has excellent compressive strength after curing compared to other materials. However, it is difficult to use Portland cement in radioactive waste containing highly water-soluble harmful substances such as sodium fluoride because it is prone to leaching harmful ingredients in immersion tests due to its low water resistance. In this study, solidification was achieved using an organic-inorganic hybrid solidifying binders consisting of inorganic binders such as Portland cement, blast furnace slag powder, silica fume, and organic binders such as epoxy resin. This material was then compared with a solidification material made of Portland cement alone. The mixing ratio of inorganic binders, water, and organic binders to simulated waste is 35%, 20%, and 25%, respectively. The mixing ratio of inorganic binders and water when using only Portland cement for simulated waste is 100% and 80%, respectively. The mixed paste was poured into a cylinder mold (Φ 5 × 10 cm) to seal the upper part, cured at room temperature for 28 days to produce a solidification specimen, and then subjected to various tests were performed, including compressive strength, immersion compressive strength, hydration peak temperature, length change, and immersion weight change. The compressive strength of the organic-inorganic hybrid solidification test was 13-17 MPa, the immersion compressive strength was 15-18 MPa, the hydration peak temperature was 33-36°C, the length change rate was -0.086%, and the immersion weight change rate was –2.359%. The compressive strength of the Inorganic solidification test using only Portland cement was 16-18 MPa, the immersion compressive strength was 20-21 MPa, the hydration peak temperature was 23-25°C, the length change rate was -0.150%, and the immersion weight change rate was -5.213%. The compressive strength and immersion compressive strength of the organic-inorganic hybrid solidification materials were slightly lower compared to those of Portland cement solidification materials, they still met the compressive strength standard of 7-12 MPa, taking into consideration the strength reduce and economic feasibility of the core drill process. Furthermore, it indicates that the rates of change in length and immersion weight decreased to about 1% and 5%, suggesting an improvement in water resistance. The above results suggest that applying the organic-inorganic hybrid solidification method to radioactive waste treatment can effectively improve water resistance and help secure long-term stability.

Domestic NPPs had produced the paraffin-solidifying concentrate waste (PSCW) for nearly 20 years. At that time radioactive waste management policy of KHNP was to reduce the volume and to store safely in site. The PSCW has been identified not to meet the leaching index after introducing the treatment system. PSCW has to be treated to meet current waste acceptance criteria (WAC) for permanent disposal. PSCW consists of dried concentrate 75% and paraffin 25% of volume. When PSCW is separated into a dried concentrate and a paraffin by solubility, total volume separated is increased twice. Final disposal volume of dried concentrate can reach to several times when solidifying by cement even considering exemption. Application of polymer solidification technology is difficult because dried concentrate is hard to make form to pellet. When PSCW is packaged in High Integrity Container (HIC), volume of PSCW is equal to the volume before package. The packaging process of HIC is simple and is no necessary of large equipment. It is important to recognize that HIC was developed to replace solidification of waste. HIC has as design goal a minimum lifetime of 300 years under disposal environment. The HIC is designed to maintain its structural integrity over this period, to consider the corrosive and chemical effects of both the waste contents and the disposal environment, to have sufficient mechanical strength to withstand loads on the container and to be capable of meeting the requirements for a Type A transport Package. The Final waste form is required for facilitating handling and providing protection of personnel in relation to solidification, explosive decomposition, toxic gases, hazardous material, etc. Structural stability of final waste form is required also. Structural stability of the waste can be provided by the waste itself, solidifying or placing in HIC. Final waste form ensure that the waste does not structurally degrade and affect overall stability of the disposal site. The HIC package contained PSCW was reviewed from several points of view such as physicochemical, radiological and structural safety according to domestic WAC. The result of reviewing shows that it has not found any violation of WCP established for silo type disposal facility in Gyeongju city.

A unique porous material with controlled pore characteristics can be fabricated by the freeze-drying process, which uses the slurry of organic material as the sublimable vehicle mixed with powders. The essential feature in this process is that during the solidification of the slurry, the dendrites of the organic material should repel the dispersed particles into the interdendritic region. In the present work, a model experiment is attempted using some transparent organic materials mixed with glass powders, which enable in-situ observation. The organic materials used are camphor-naphthalene mixture (hypo- and hypereutectic composition), salol, camphene, and pivalic acid. Among these materials, the constituent phases in camphor-naphthalene system, i.e. naphthalene plate, camphor dendrite, and camphornaphthalene eutectic exclusively repel the glass powders. This result suggests that the control of organic material composition in the binary system is useful for producing a porous body with the required pore structure.

본 연구는 원자력 시설 해체 시 발생되는 저준위 및 극저준위 폐토양, 점토와 산업부산물인 고로슬 래그를 이용하여 방사성 폐기물을 안전하게 담지할 수 있는 비소성 시멘트의 제조 가능성을 평가하고 광물· 형태학적 분석을 통하여 생성된 반응 물질에 대하여 고찰하였다. 본 연구에서는 (1) 폐토양, 점토 및 고로슬 래그의 특성 분석, (2) 폐토양, 점토 및 고로슬래그를 고화재 및 성분조정제로 이용한 원전 해체 폐기물 담지를 위 한 비소성 시멘트 제조 및 최적의 배합 비율 도출, (3) 제조된 비소성 시멘트 고화체의 수화반응 생성물질에 대하여 광물·형태학적 분석 등을 수행하였다. 비소성 시멘트 고화체의 광물·형태학적 분석 결과, 폐토양과 점 토는 수화반응 생성물이 관측되지 않았으며, 고로슬래그의 경우 고화체의 강도를 발현시킬 수 있는 수화반응 생성물질인 calcium silicate hydrate (CSH), 에트링가이트(ettringite)가 생성되는 것을 확인하였다. 폐토양, 점 토를 고화재로 이용한 비소성 시멘트의 재령 28일 후 고화체는 최적의 배합 비율에서 약 3 MPa의 강도를 나 타내 처분장 인수기준 압축강도인 3.44MPa를 만족하지 못하는 것을 확인하였다. 그러나, 고로슬래그를 고화 재로 이용한 비소성 시멘트는 모든 실험 조건에서 처분장 인수기준 압축강도를 만족하며, 최적의 배합 비율 에서는 약 27 MPa로 높게 나타나는 것을 확인할 수 있었다. 이러한 결과를 통하여 비소성 시멘트 고화재로 고로 슬래그, 방사성 핵종에 대한 흡착제 역할로 폐토양 및 점토를 이용한다면 방사성 폐기물 처분을 위한 최적의 비소성 시멘트를 제조할 수 있을 것으로 판단된다.

This study aims to develop solidifying agents of sewage sludge using industrial By-Products and evaluate applicability of the solidified sewage sludge. The result of this study shows that it was possible to reduce water content of the cover materials to more than 50% in a short time as a result of the excellent hygroscopic function of inorganic binder made from industrial by-products and the granulation of sludge. The result suggests that the appropriate mixed ratio of (PSA + CPA) − (GBFS + SM1) − (SAS + SM2) is 60-25-15, and input ratio of solidifying agent is 48%, considering the applicability of the facilities, including mixing performance and availability of discharge, as well as the percentage of moisture content of the solidified sewage sludge, pH, and exothermic temperature. The solidified sewage sludge made using industrial by-products met more than the standard of unconfined compressive strength 0.5 kg/cm2 (as for cover materials 0.1 MPa) in 7 days due to ground granulated blast furnace slag, high-calcium fly ash, and SAS. As a result, valid resource recovery is possible through the land treatment of sewage sludge by inducing in-situ stabilization of heavy metals and property strengths through the reactivity of industrial by-products.

연약지반의 점토퇴적물을 시멘트와 함께 생석회, 소석회, 석고, 고령토, 제올라이트, 규조토 등의 광물재료를 혼합하여 고화 반응시킨 후 양생시간에 따른 물성변화와 반응생성물을 조사하였다. 그 결과, 시멘트로는 포틀랜드 시멘트보다는 슬래그시멘트가 점토의 고화반응에 따른 강도발현이 큰 것으로 나타났다. 그리고 슬래그시멘트와 함께 각종 광물재료와 고화 반응시킨 실험결과에서는, 석고가 가장 높은 강도발현을 나타냈다 따라서 슬래그시멘트와 석고에 대해 이들의 혼합비를 달리하여 고화 실험을 수행하였다. 그 결과, 슬래그시멘트 70%, 석고 30%의 비율에서 가장 좋은 강도발현을 보이는 것으로 나타났다. 이 실험의 고화반응물에서는 에트린자이트 등의 반응생성물이 포함되었다. 이것은 석고가 슬래그시멘트의 효율적인 수화반응을 촉진시켜서 높은 강도 발현에 기여 한 것으로 생각된다. 이러한 실험 결과는 연약지반의 안정화 처리에 유용한 자료로 이용될 것으로 보인다.