Molten salt immersion technique has been tested with several Sr oxides, SrZrO3, SrMoO4 and U2SrOy, and MgCl2 based molten salts for the Sr nuclide separation. Reaction time, temperature, and salt composition were varied to effectively separate Sr in chloride forms. ICP-OES, XRD, and SEM analysis were conducted for the conversion efficiency and structure and morphology analysis. It is confirmed that all experiments of SrZrO3 with MgCl2 at 800°C for reaction time 5, 10, 20 hours showed higher conversion efficiency than 99% and in LiCl-KCl-MgCl2 and NaCl-MgCl2 molten salts at 500°C or 600°C, conversion efficiency higher than 97% was obtained. SrMoO4 in MgCl2 immersion experiments for 10 hours showed higher conversion efficiency than 99% when the molar ratio of salt/oxide powder is 7. U2SrOy was also tested with MgCl2 molten salt at 800°C and higher efficiency than 99% and mainly MgUO4 were produced as a reaction product.

Prior to the investigations on fuel degradation it is necessary to describe the reference characteristics of the spent fuel. It establishes the initial condition of the reference fuel bundle at the start of dry storage. In a few technology areas, CANDU fuels have not yet developed comprehensive analysis tools anywhere near the levels in the LWR industry. This requires significantly improved computer codes for CANDU fuel design. In KNF, in-house fuel performance code was developed to predict the overall behavior of a fuel rod under normal operating conditions. It includes the analysis modules to predict temperature, pellet cracking and deformation, clad stress and strain at the mid-plane of the pellet and pellet-pellet interfaces, fission gas release and internal gas pressure. The main focus of the code is to provide information on initial conditions prior to dry storage, such as fission gas inventory and its distribution within the fuel pellet, initial volumes of storage spaces and their locations, radial profile of heat generation within the pellet, etc. Potential degradation mechanisms that may affect sheath integrity of CANDU spent fuel during dry storage are: creep rupture under internal gas pressure, sheath oxidation in air environment, stress corrosion cracking, delayed hydride cracking, and sheath splitting due to UO2 oxidation for a defective fuel. To upgrade the developed code that address all the damage mechanisms, the first step was a review of the available technical information on phenomena relevant to fuel integrity. The second step was an examination of the technical bases of all modules of the in-house code, identify and extend the ranges of all modules to required operating ranges. Further improvements being considered include upgrades of the analysis module to achieve sufficient accuracy in key output parameters. The emphasis in the near future will be on validation of the in-house code according to a rigorous and formal methodology. The developed models provide a platform for research and industrial applications, including the design of fuel behavior experiments and prediction of safe operating margins for CANDU spent fuel.

To estimate the removal efficiency of TRU and rare earth elements in an oxide spent fuel, basic dissolution experiments were performed for the reaction of rare earth elements from the prepared simfuel with chlorination reagents in LiCl-KCl molten salt. Based on the literature survey, NH4Cl, UCl3, and ZrCl4 were selected as chlorination reagent. CeO2 and Gd2O3 powders were mixed with uranium oxide as a representative material of rare earth elements. Simfuel pellets were prepared through molding and sintering processes, and mechanically pulverized to a powder form. The experiments for the reaction of the simfuel powder and chlorination reagents were carried out in a LiCl-KCl molten salt at 500°C. To observe the dissolution behavior of rare earth elements, molten salt samples were collected before and after the reactions, and concentration analysis was performed using ICP. After the reaction completed, the remaining oxide was washed with water and separated from the molten salt, and XRD was used for structural analysis. As a result of salt concentration analysis, the dissolution performance of rare earth elements was confirmed in the reaction experiments of all chlorination reagents. In an experiment using NH4Cl and ZrCl4, the uranium concentration in the molten salt was also measured. In other words, it seemed that not only rare elements but also uranium oxide, which is a main component of simfuel, was dissolved. Therefore, it is thought that the dissolution of rare earth elements is also possible due to the collapse of the uranium oxide structure of the solid powder and the reaction with the oxide of rare earth elements exposed to molten salt. As a result of analyzing the concentration changes of Simfuel before and after each reaction, there was little loss of uranium and rare earth elements (Ce/Gd) in the NH4Cl experiment, but a significant amount of rare earth elements were found to be reduced in the UCl3 experiment, and a large amount of rare earth elements were reduced in the ZrCl4 reaction.

Strontium-90 is a high heat-generating nuclide in spent nuclear fuel. The removal of the nuclide separation is indispensable to reduce the burden of storage and disposal of high-level radioactive waste. Korea Atomic Energy Research Institute has developed the molten salt immersion technique to separate the strontium by the chlorination of the strontium oxide in molten salt. It is needed to separate the salt for the recovery of strontium from the salt solution after the chlorination reaction. In this study, it was investigated on the recovery of the strontium from the salt. Vacuum distillation was used for the separation of strontium from the molten salt. The vapor pressures of the candidate salts were calculated by HSC chemistry and the apparent evaporation rates (AER) were measured at 830°C to evaluate the salts for strontium recovery. The candidate salts were LiCl, KCl, MgCl2, NaCl and CaCl2. The AERs of MgCl2 and NaCl were 1.9 and 1.3 g/cm2-h, respectively. Those two salts can be separated from the strontium compound even though the AER values are much lower than those of LiCl-KCl (~ 8 g/cm2-h). CaCl2 salt was rarely evaporated (AER < 0.03 g/cm2-h) and it is not suitable to use as a strontium recovery salt. Therefore, MgCl2, NaCl, LiCl and KCl can be regarded as candidates for a strontium recovery salt.

The evaluation of the damage ratio of spent nuclear fuel is a very important intermediate variable for dry storage risk assessment, which requires an interdisciplinary and comprehensive investigation. It is known that the pinch load applied to the cladding can leaded to Mode-3 failure and the cladding becomes more vulnerable to this failure mode with the existence of radial hydrides and other forms of mechanical defects. In this study, the failure resistance of Zircaloy-4 cladding against the pinch load is investigated using numerical simulations assuming the existence of radial hydrides. The simulation model is based on the microscopic images of cladding. A pixel-based finite element model was created by separating the Zircaloy-4 and hydride using the image segmentation method. The image segmentation method uses a morphology operation basis, which is a preprocessing method through erosion operation after image expansion to enable normal segmentation by emphasizing pixels corresponding to hydrides. The segmented images are converted into a finite element model by assigning node and element numbers together with corresponding material properties. Using the generated hydride cladding finite element model, several numerical methods are investigated to simulate crack propagation and cladding failure under pinch load. Using extended finite element (XFEM) models the initiation and propagation of a discrete crack along an arbitrary, solution-dependent path can be simulated without the requirement of remeshing. The applicability of fracture mechanical parameters such as stress intensity, J-integral was also investigated.

In accordance with the Enforcement Decree of the Act on Physical Protection and Radiological Emergency, operators of Nuclear Power Plants (NPP)s must conduct full cyber security exercise once a year and partial exercise at least once every half year. Nuclear operators need to conduct exercise on systems with high attack attractiveness in order to respond to the unauthorized removal of nuclear or other radioactive material and sabotage of nuclear facilities. Nuclear facilities identify digital assets that perform SSEP (Safety, Security, and Emergency Preparedness) functions as CDA (Critical Digital Assets), and nuclear operators select exercise target systems from the CDA list and perform the exercise. However, digital assets that have an indirect impact (providing access, support, and protection) from cyber attacks are also identified as CDAs, and these CDAs are relatively less attractive to attack. Therefore, guidelines are needed to select the exercise target system in the case of unauthorized removal of nuclear or other radioactive material and sabotage response exercise. In the case of unauthorized removal of nuclear or other radioactive material, these situations cannot occur with cyber attacks and external factors such as terrorists must be taken into consideration. Therefore, it is necessary to identify the list of CDAs that terrorists can use for cyber attacks among CDAs located in the path of stealing and transporting nuclear material and conduct intensive exercise on these CDAs. A typical example is a security system that can delay detection when terrorists attack facilities. In the case of sabotage exercise, a safety-related system that causes an initiating event by a cyber attack or failure to mitigate an accident in a DBA (Design Basis Accident) situation should be selected as an exercise target. It is difficult for sabotage to occur through a single cyber attack because a nuclear facility has several safety concepts such as redundancy, diversity. Therefore, it can be considered to select an exercise target system under the premise of not only a cyber attack but also a physical attack. In the case of NPPs, it is assumed that LOOP (Loss of Offsite Power) has occurred, and CDA relationships to accident mitigation can be selected as an exercise target. Through exercise on the CDA, which is more associated with unauthorized removal of nuclear or other radioactive material and sabotage of nuclear facilities, it is expected to review the continuity plan and check systematic response capabilities in emergencies caused by cyber attacks.

This study was undertaken to compare meal skipping, snacking, and weight perceptions between students on-campus living alone and off-campus living with parents, in an urban college in the United States. The self-report survey was completed by 219 college students (on-campus=100, off-campus=119) between April and May 2012. Two-thirds (67%) of the respondents skipped at least one meal in the past week, and most participants showed strong desires to lose weight despite their normal/under-weight status. Significant differences between the two groups were obtained for the reason to skip a meal and the type of snack consumed. Compared to on-campus students, significantly higher values were obtained for off-campus students for choosing ‘no time to prepare’ as a meal skipping reason for lunch and dinner, and ‘sweets’ as a preferred snack. In addition to the group comparison, multiple regression results indicate that the body mass index (BMI) positively correlates with meal skipping and snacking frequencies. Younger students and female students were determined to have a higher frequency of meal skipping and morning snacking. Future research is required to study the dietary factors associated with living arrangements, to help college students develop healthy eating habits.