Radwaste Storage Research Articles

Radioecological Studies in the Murmansk Littoral of the Barents Sea as Part of Environmental Monitoring in Radwaste Management

The state of the marine environment in Motovskii Zaliv and Kol’skii Zaliv was studied within the framework of the monitoring and assessment of the radiation contamination of the Barents littoral. The indicated bodies of water as well as the Guba Zapadnaya Litsa and the Guba Andreeva as parts of the Motovskii Zaliv are included in the maritime transit shipment routes of spent nuclear fuel. The Guba Andreeva, where a radwaste storage facility is located, is considered to be the main source of radioactive contamination of the Barents littoral. The current radioecological status of the bodies of water used for transit operations is determined and the initial concentration level of radionuclides in the water and bottom deposits is established. It is shown that the radwaste storage facility in Guba Andreeva has the strongest impact on the radioecological state of the marine environment in Motovskii Zaliv. The obtained data can be regarded as necessary information for the development of maritime economic activity and comprehensive management of the littoral zones.

Modeling of 14C Diffusion from the Core of the Decommissioned ad Reactor

A mathematical model of the diffusion of radionuclides through engineered safety barriers is developed for 14C in order to determine the long-term safety conditions and characteristics of a decommissioned commercial uranium-graphite reactor. Dry and wet mixtures and concrete are used as the barrier materials. Diffusion is studied as the dominant mechanism for the transport of the radionuclides. The 14C concentration at the boundary between the radwaste storage site and the environment is determined computationally and the effect of the modeling conditions on the specific activity of the radionuclide is analyzed. The decomposition sequence of the safety barriers for which the 14C concentration is much lower than the admissible value is determined.

Low-cost radioactivity monitoring with scintillating fibers and silicon photomultipliers

A new detector technology was developed, particularly suitable for low-cost radioactivity monitoring in radwaste storage sites. It consists of a scintillating optical fiber coupled at each end to a silicon photomultiplier (SiPM). The single-photon sensitivity of the SiPM, along with the left-right coincidence constraint, allows the achievement of a reasonable sensitivity to gamma radiation even though a thin 1-mm-diameter plastic scintillating fiber is used. Simulation results are in perfect agreement with the measured behavior, and several implementations are under way. The possibility of choosing the fiber length and shape makes them very flexible both conceptually and mechanically. Any improvement in the SiPM development technology reflects immediately into an improvement in the detector performance.

On-line remote monitoring of radioactive waste repositories

A low-cost array of modular sensors for online monitoring of radioactive waste was developed at INFN-LNS. We implemented a new kind of gamma counter, based on Silicon PhotoMultipliers and scintillating fibers, that behaves like a cheap scintillating Geiger-Muller counter. It can be placed in shape of a fine grid around each single waste drum in a repository. Front-end electronics and an FPGA-based counting system were developed to handle the field data, also implementing data transmission, a graphical user interface and a data storage system. A test of four sensors in a real radwaste storage site was performed with promising results. Following the tests an agreement was signed between INFN and Sogin for the joint development and installation of a prototype DMNR (Detector Mesh for Nuclear Repository) system inside the Garigliano radwaste repository in Sessa Aurunca (CE, Italy). Such a development is currently under way, with the installation foreseen within 2014.

On-line remote monitoring of radioactive waste repositories

A low-cost array of modular sensors for online monitoring of radioactive waste was developed at INFN-LNS. We implemented a new kind of gamma counter, based on Silicon PhotoMultipliers and scintillating fibers, that behaves like a cheap scintillating Geiger-Muller counter. It can be placed in shape of a fine grid around each single waste drum in a repository. Front-end electronics and an FPGA-based counting system were developed to handle the field data, also implementing data transmission, a graphical user interface and a data storage system. A test of four sensors in a real radwaste storage site was performed with promising results. Following the tests an agreement was signed between INFN and Sogin for the joint development and installation of a prototype DMNR (Detector Mesh for Nuclear Repository) system inside the Garigliano radwaste repository in Sessa Aurunca (CE, Italy). Such a development is currently under way, with the installation foreseen within 2014.

Formation of filtration fields in the near zone of radwaste storage facilities during decommissioning

Information is presented on the formation of filtration fields on sections of near-surface radwaste storage facilities with different degrees of degradation of engineered barriers. The initial geological-hydrogeological data for building models of filtration flow field formation near groups of storages facilities. Scenarios of the filtration field formation for decommissioning storage facilities are examined. It is shown that the restoration of engineered barriers to their initial state during decommissioning is a technogenic action which produces definite changes of the hydrogeological conditions on adjoining sections of the storage facilities. It is noted that restoration of the protective properties of a part of the facilities can result in the formation of secondary peripheral sections of radionuclide contamination. The character of the change in the hydrogeological conditions of the technogenic water-bearing horizon in the near-zone of storage facilities must be taken into account when taking corrective actions.

Real-Time Online Monitoring of Radwaste Storage: A Proof-of-Principle Test Prototype

A prototype array of modular sensors for online monitoring of radioactive waste was developed at INFN-LNS. We implemented a new kind of gamma mini-sensor, based on Silicon PhotoMultipliers and scintillating fibers, that behaves like a cheap scintillating Geiger-Muller counter. It can be placed in shape of a fine grid around each single waste drum in a repository. After simulating the counting response of thin scintillating fibers to gamma radiation, we verified our simulation results with measurements using radioactive sources. Front-end electronics and an FPGA-based counting system were developed to handle the field data, also implementing data transmission, a graphical user interface and a data storage system. A test of four sensors in a real radwaste storage site was performed with promising results.

방사성폐기물드럼 핵종재고량 평가시설 구축에 따른 방사선차폐 영향평가

한국원자력연구원 내 저장중인 중 저준위방사성폐기물의 안전한 영구처분을 위하여 방사성폐기물처리시설에서는 이들 저장폐기물의 핵종재고량 평가를 위한 드럼핵종분석장치의 도입을 기획하고 있으며, 이 장치를 운영하고 유지보수하기 위한 전용의 평가시설 구축을 추진하고 있다. 이 평가시설 외부에는 제1방사성폐기물저장시설이 인접하여 있으며 내부에는 평가대상드럼들과 드럼핵종분석장치의 밀도보정용 선원 등이 존재함으로 이들이 방사선원항으로 작용하여 평가시설 내 외부의 선량률에 영향을 미치게 된다. 따라서 방사선원항 주변의 콘크리트 구조물에 대한 방사선차폐 영향을 평가하여야 한다. 본 연구에서는 MCNP 코드를 이용하여 해당 방사선원항으로부터 평가시설 내부 방사선관리구역을 둘러싸고 있는 콘크리트 구조물에 대한 방사선 안전성을 평가하였다. 평가결과 현재 고려되고 있는 콘크리트 구조물의 약 30 cm 두께는 해당 방사선원항으로부터의 방사선을 차폐하기에 충분한 것으로 확인되었다. In order to dispose of the LILW(low and intermediate level radioactive waste) stored at KAERI, the radwaste drum assay system will be introduced to evaluate the radioisotopes inventory of stored drums. At present, the construction project of the dedicated assay facility to operate it and carry out routine maintenance of that equipment has been conducting at the radwaste treatment facility. Since that facility will be constructed in front of a 1st radwaste storage facility as well as the radwaste drums to be assayed and the transmission source in the radwaste drum assay system are in that facility, they could act as the radioactive sources and then, would affect the dose rate at the inside and the outside of the facility. Therefore, the radiation shielding should be evaluated through the concrete wall near to the radioactive sources whether the wall thickness is sufficient against the regulations. In this study, the radiation safety for the concrete wall around the radiation controlled area in the radwaste drum assay facility was evaluated by the MCNP code. From the evaluation results, the thickness of those concrete walls which are under consideration of about 30 cm was enough to shield the radiation from the radioactive sources.

Sensing and Monitoring of Radwaste Storage: A Realtime Online Demonstrator

ABSTRACTAt INFN-LNS we have developed a new kind of gamma mini-sensor, which allowed to implement a prototype array of modular sensors for online monitoring of radioactive waste. The sensors are based on Silicon PhotoMultipliers and scintillating fibers sensitive to gamma radiation, that have to be placed in a repository in shape of a fine grid, around each single waste drum. We simulated the counting response of thin scintillating fibers and verified the results with measurements using radioactive sources. Front-end electronics and an FPGA-based counting system were developed to handle the field data, also implementing data transmission, a graphical user interface and a data storage system. Moreover a test of four sensors in a real radwaste storage site was performed with promising results.

Long-term prediction of the migration of radionuclides from solid radwaste storage sites at the Siberian Chemical Works

The results of a calculation of the migration of radionuclides from a repository for solid radioactive wastes from the reactor plant of the Siberian Chemical Works, performed using a method recommended by IAEA with the AMBER 4.4 computer program and by finding an analytical solution, are presented. Three scenarios for migration of radionuclides from the repository are described and estimates of their specific activity in the uppermost water layer and the results on an analysis of the sensitivity of models to a change in the input parameters are presented.

From Thorium Phosphate Hydrogenphosphate Hydrate to β‐Thorium Phosphate Diphosphate: Structural Evolution to a Radwaste Storage Ceramic.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

From thorium phosphate hydrogenphosphate hydrate to β-thorium phosphate diphosphate: Structural evolution to a radwaste storage ceramic

β-Thorium phosphate diphosphate ( β-TPD), considered as a very promising radwaste storage material, was obtained from thorium phosphate hydrogenphosphate hydrate (TPHPH) precursor through dehydration and hydrogen phosphate condensation. The structures of TPHPH, intermediate α-thorium phosphate diphosphate ( α-TPD) and its hydrate ( α-TPDH) have been resolved ab initio by Rietveld analysis of their synchrotron diffraction patterns. All were found orthorhombic (space group Cmcm) and similarly composed of [ThPO 4] 4 4+ slabs alternating with disordered layers hosting either [HPO 4·H 2O] 2 4− (TPHPH), [P 2O 7·2H 2O] 4− ( α-TPDH), or [P 2O 7] 4− ( α-TPD), unlike the 3D structure of β-TPD. The diphosphate groups of α-TPD and α-TPDH are strongly bent. The irreversible transition to the final β-TPD consists in a shearing of the slabs and a reduction of the interslabs cavities that explains the stability of this high-temperature form.

Development of the technology for localisation and isolation from biosphere of outdoor liquid radwaste storage basins

The approaches were proposed for localisation and isolation of outdoor liquid radwaste storage basins from the biosphere. The lab research findings showed immobilisation of radioactive sludges into a compound and drying-up of liquid phase using porous vitrocrystalline forms (VCF) using as example actual solid and liquid phases from the MCC's storage basins. The effectiveness of the radionuclide immobilisation in the solidified compounds and their mechanical strength were verified. It showed the possibility of disposing of the liquid phase from the liquid radwaste storage basins by the drying-up method using VCF.

Modelling of the shielding capabilities of the existing solid radioactive waste storages at ignalina NPP

There is only one nuclear power plant in Lithuania--Ignalina NPP (INPP). The INPP operates two similar units with design electrical power of 1500 MW. The units were commissioned in 1983 and 1987 respectively. From the beginning of the INPP operation all generated solid radioactive waste was collected and stored at the Soviet type solid radwaste facility located at INPP site. The INPP solid radwaste storage facility consists of four buildings, namely building No. 155, No. 155/1, No. 157 and No. 157/1. The buildings of the INPP solid radwaste storage facility are reinforced concrete structures above ground. State Nuclear Safety Inspectorate (VATESI) has specified that particular safety analysis must be performed for existing radioactive waste storage facilities of the INPP. As part of the safety analysis, shielding capabilities of the walls and roofs of these buildings were analysed. This paper presents radiation shielding analysis of the buildings No. 157 and No. 157/1 that are still in operation. The buildings No. 155 and No. 155/1 are already filled up with the waste and no additional waste loading is expected.

방사성 폐기물 작업 중의 피폭서량 예측 프로그램 개발

In spite of the importance of nuclear power as one of major electric energies in Korea, the nuclear safety has become the most serious social issue in the operation of the nuclear power plant. In this paper, a virtual work simulation program was developed to predict exposure dose during radiation work in radwaste storage. The work simulation program was developed. using applet and VRML-virtual reality modeling language. A numerical algorithm to find the optimal work path which minimize exposure dose during the given work, was developed and exposure dose on the optimal work path was compared with that on the shortest path. Comparing with the shortest path for the given work, the predicted optimal path consumed longer work time by II% but reduced total exposure dose by 46%. The simulation result showed that the exposure dose depended on not only work time, but also the distance between the worker and the radiation source. The developed simulation program could be a useful tool for the planning of radioactive waste work to increase the radiation safety of workers.

Study of Th4(PO4)4 P2O7 and Solid Solutions With U(IV), Np(IV) and Pu(IV): Synthesis, Characterization, Sintering and Leaching Tests

AbstractIn the framework of radwaste storage, the thorium phosphate-diphosphate Th4(PO 4)4P 2O7 (TPD) has been synthesized in the ThO2 – P2O5 system. This material is very resistant to aqueous corrosion. In this paper we report the conditions of synthesis of TPD doped with small amounts of trivalent actinides and of solid solutions with uranium (IV), neptunium (IV) and plutonium (IV). Sintered samples of TPD and Th4_xUx(PO4)4P2O7 (TUPD) have been prepared after pressing at 100-800 MPa at room temperature then heating at 1250°C for 10 hours. The corresponding density varies from 87 to 93% of the calculated value from crystal data. Leaching tests of Th4 (PO4)4P2O7 doped with Am3+ or Cm3+ and solid solutions Th4_xUx(PO4)4P2O7 (TUPD) or Th4-xPux(PO4)4P2O7 (TPPD) have been performed in water and in several acidic media at room temperature and at 90'C. The dependence of the leaching rate on the pH has been determined: the partial order related to [H3O+] is in the 0.35 – 0.44 range while the apparent leaching rate is equal to about 1 x 10–5x–4 x 10–5 g/(m2d).

Chemical Conditions of Synthesis of Th4(PO4)4P2O7. Preparation of Thorium Phosphate−Hydrogenphosphate as Precursor

Thorium phosphate−diphosphate, Th4(PO4)4P2O7, is obtained, at high temperature (800−1250 °C), for a given ratio r = PO4/Th equal to 3/2 from a thorium compound and a phosphating reactant whatever the chemical conditions. This compound, whose solubility is very low, can be loaded in situ and used as a host matrix for radwaste storage. One of the methods for its synthesis involves the precipitation of a precursor, thorium phosphate−hydrogenphosphate. This precursor is used as an adsorber for low concentrations of radionuclides and, after heating in air in the range 800−1200 °C, it is transformed into doped Th4(PO4)4P2O7. The optimum conditions for the precipitation process have been determined. Starting from 0.5−2 M solutions of thorium nitrate or chloride and (NH4)2HPO4 at pH = 9−9.5 at the ratio r = 3/2, a compound of general formula Th2(PO4)2HPO4·nH2O (n = 3−7) is synthesized. Its physicochemical properties have also been studied.

The role of risk perception and technical information in scientific debates over nuclear waste storage

This article examines how members of the lay public factor risk perceptions, trust and technical information from differing scientific sources into policy judgements about potentially hazardous facilities. Focusing on radwaste storage repositories, we examine how members of the public filter new information about potential hazards through risk perceptions, and adjust their own beliefs about risks in light of that information. Scientists play a large (and increasing) role in public policy debates concerning nuclear waste issues, in which public perceptions of human health and environmental risks often differ substantially from scientific consensus about those risks. Public concerns and uncertainties are compounded when scientists from competing groups (government agencies, scientific institutions, industries, and interest groups) make different claims about the likely health and environmental consequences of different policy options. We show the processes by which the public receive and process scientific information about nuclear waste management risks using data taken from interviews with 1800 randomly selected individuals (1200 in New Mexico, and 600 nationwide). Among the more important findings are: (1) members of the public are able to make quite reasonable estimates about what kinds of positions on the risks of nuclear waste disposal will be taken by scientists from differing organizations (e.g. scientists from environmental groups, government agencies, or the nuclear industry); (2) in assessing the credibility of scientific claims, members of the public place great emphasis on the independence of the scientists from those who fund the research; and (3) prior expectations about the positions (or expected biases) of scientists from different organizations substantially affects the ways in which members of the public weigh (and utilize) information that comes from these scientists.

Estimation of unknown activities by comparative calibration method

Among the stored radioactive wastes in the Atomic Energy Authority Radwaste Storage Facilities, several sources were identified as unknown. These sources were brought to the storage facility 1 yr ago. γ-Ray spectroscopic radioassays of these sources showed two main γ-energy lines of 1.17 and 1.33 MeV, which are the main characteristic feature of 60Co radionuclides. Estimation of their activities were carried out using a simple intercomparison technique with a 60Co reference source of activity 146 MBq (3.95 mCi). The sources' activities were found to be in the range 2.70-3.50 GBq (73 to 95 mCi). The authors beneficially found and planned for future use of these sources in research, routine radiation protection programs as well as in calibration.

Cultural Gap and Public Involvement: The Case of Lan-Yu Radwaste Storage Site, Taiwan

Undoubtedly, culture is a vehicle that helps people adapt to their environment From the standpoint of cultural ecology, the unique culture embodied by the Yami people in Lan-Yu is actually composed of a set of adaptive strategies developed specifically for the sake of present-day survival. Even though Lan-Yu is an island known as “the last paradise for cultural preservation,” acculturation has driven the Yami to confront selective elimination, particularly following the promotion of tourism by the Taiwanese government. Outside cultural influences as well as technology have gradually changed Lan-Yu's social structure in terms of people, space, and activities. On the one hand, technological advancement has brought a variety of positive improvements to the island, yet, on the other hand, it has also introduced some negative influences. The Lan-Yu Radwaste Storage Site (LYRSS) has become a much debated issue due to the conflict between traditional culture and modern civilization. Since the LYRSS was established through an inflexible and top-down decision-making process without following any consideration of cultural values or rituals, it has brought about social entropy in Lan-Yu. In other words, because of LYRSS, the Yami public seems to have developed cultural resistance rather than public acceptance. The article is an attempt to explicate the social entropy within the cultural context by looking into the anti-LYRSS movement. In particular, four issues are addressed: public involvement as it relates to limiting factors and promoting factors associated with the Yami culture; the cultural gap between the “etic” and “emic” perspectives; the underlying determinants of the Anti-LYRSS movement; and aspects of public involvement in Lan-Yu.