Advanced Spent Fuel Conditioning Process Facility Research Articles

ASNC upgrade for nuclear material accountancy of ACPF

A safeguards neutron coincidence counter for nuclear material accountancy of the Advanced spent-fuel Conditioning Process Facility (ACPF), known as the ACP Safeguards Neutron Counter (ASNC), was upgraded to improve its remote-handling and maintenance capabilities. Based on the results of the previous design study, the neutron counter was completely rebuilt, and various detector parameters for neutron coincidence counting (i.e., high-voltage plateau, efficiency profile, dead time, die-away time, gate length, doubles gate fraction, and stability) were experimentally determined. The measurement data showed good agreement with the MCNP simulation results. To the best of the authors’ knowledge, the ASNC is the only safeguards neutron coincidence counter in the world that is installed and operated in a hot-cell. The final goals to be achieved were (1) to evaluate the uncertainty level of the ASNC in nuclear material accountancy of the process materials of the oxide-reduction process for spent fuels and (2) to evaluate the applicability of the neutron coincidence counting technique within a strong radiation field (e.g., in a hot-cell environment).

Effect of Radiation on the Transmission Rate of Emission Intensity of Optical Fiber Cable Used in a Nuclear Material Facility

The performance and eligibility of the fiber optic laser-induced breakdown spectroscopy (FO-LIBS) instrument will be primarily evaluated at the Advanced Spent Fuel Conditioning Process Facility (ACPF), where spent nuclear fuel is processed in a high-temperature molten salt bath using electrochemical methods. The damage incurred by the optical fiber cable due to radiation should be addressed to ensure the reliability of FO-LIBS measurements. High-level and low-level gamma ray and neutron irradiation experiments were conducted to measure the effect of radiation on the optical transmission rate of the optical fiber cable. Conclusively, we determined the dependence of the transmission rate of the cable on the radiation dose rate as a function of the wavelength.

Crane system with remote actuation mechanism for use in argon compartment in ACPF hot cell

The Advanced spent fuel Conditioning Process Facility (ACPF) at the Korea Atomic Energy Research Institute (KAERI) has recently been successfully renovated. One of the highlights of this renovation project was the installation of a small argon compartment within the atmospheric hot cell of the facility. Even though a crane system was considered necessary for the remote handling of the processing equipment inside the argon compartment, no suitable commercial cranes were available. This was because a limited amount of space had been reserved for the installation of the crane. Moreover, a master-slave manipulator (MSM), the only available means of maintenance of the crane, was unable to reach it in the limited workspace. To address the difficulties in the design of this crane, in this study, a remote actuation mechanism is devised where the mechanical and electrical parts of the crane system are separated, positioned far away from each other, and connected through power transmission shafts. This approach has two main advantages. First, the electrical parts can be placed inside the workspace of the MSM, hence allowing for remote maintenance. Second, the space occupied by the electrical parts and their cables, which are separate from the crane in the proposed design, can be considered and exploited in designing the mechanical parts of the crane. This enables the construction of a short, special crane in order to maximize the workspace. Furthermore, the mechanical parts for the MSM located outside the workspace are designed to possess a high safety margin to ensure durability. An accurate servo-control system is also developed based on absolute positioning measurement. This allows for the safer performance of perform through automatic operation.

Hot cell renovation in the spent fuel conditioning process facility at the Korea Atomic Energy Research Institute

Abstract Background The advanced spent fuel conditioning process facility (ACPF) of the irradiated materials examination facility (IMEF) at the Korea Atomic Energy Research Institute (KAERI) has been renovated to implement a lab scale electrolytic reduction process for pyroprocessing. The interior and exterior structures of the ACPF hot cell have been modified under the current renovation project for the experimentation of the electrolytic reduction process using spent nuclear fuel. The most important aspect of this renovation was the installation of the argon compartment within the hot cell. Method For the design and system implementation of the argon compartment system, a full-scale mock-up test and a three-dimensional (3D) simulation test were conducted in advance. The remodeling and repairing of the process cell (M8a), the maintenance cell (M8b), the isolation room, and their utilities were also planned through this simulation to accommodate the designed argon compartment system. Results and conclusion Based on the considered refurbishment workflow, previous equipment in the M8 cell, including vessels and pipes, were removed and disposed of successfully after a zoning smear survey and decontamination, and new equipment with advanced functions and specifications were installed in the hot cell. Finally, the operating area and isolation room were also refurbished to meet the requirements of the improved hot cell facility.

Hot-Test Results of the Advanced Spent Fuel Conditioning Process Safeguards Neutron Counter for PWR Spent Fuel Rods

A passive neutron coincidence counter for nuclear material measurement of the advanced spent fuel conditioning process (ACP) has been developed by the Korea Atomic Energy Research Institute (KAERI) since 2003 and was deployed in a hot cell of the ACP Facility (ACPF) in 2005. The most dominant neutron source among the spontaneous fission nuclides contained in spent fuel is 244Cm. To obtain the neutron counting rates of the singles, doubles, and triples coincidences of the neutron counter with an increment of the 244Cm mass, a hot test of the neutron counter was performed in 2007 with several spent fuel rod-cuts in the ACPF hot cell. The source term of the spent fuel rod-cuts was obtained using the ORIGEN-ARP burnup simulation code, and a set of preliminary calibration curves of the neutron counter for 244Cm was generated. The calibration curves were also obtained from the results of an MCNPX code simulation, but there was a wide difference of ˜30% in the slope of the double-rate calibration curve between the measurements and the MCNPX results. Chemical analysis results of the spent fuel samples were obtained in September 2008, and it was found that the difference between the measurements and the MCNPX results is due to an error in the declared burnup since the chemical analysis burnups of the samples differ from the declared ones by ˜10%. The expected burnup of each rod-cut was also obtained from the results of self-multiplication correction for the 244Cm mass of the rod-cuts, and the difference between the expected burnup results and the chemical analysis results is <2%. This study shows high performance of the neutron coincidence counter for 244Cm measurements of spent fuel and also shows that the burnup of spent fuel samples can be obtained through a series of ORIGEN-ARP code simulations if it is possible to acquire the measurement data of neutron counting rates for 244Cm of the samples.

Concept and safety studies of an integrated pyroprocess facility

The Korea Atomic Energy Research Institute (KAERI) has been developing pyroprocess facilities for the dry processing research of spent fuel for over 10 years since 1997. A hot cell facility, named the Advanced spent fuel Conditioning Process Facility (ACPF), for the demonstration of a head-end part of pyroprocess was developed in November 2005. An inactive demonstration facility for the integrated pyroprocess, named the PyRoprocess Integrated inactive Demonstration (PRIDE) facility, has been developing since 2007. This facility is equipped with several types of pyroprocess equipment, such as a decladding/voloxidation device, a powder mixing device, electro-reduction equipment, electro-refining equipment, electro-winning equipment, Cd distillation equipment, waste salt regeneration & solidification equipment, and a salt distillation equipment. Safety evaluation and safety related systems are also required to inhibit the release of radioactivity into the environment. Accident evaluations and argon flow characteristics are studied for ensuring the expected safety issues. These conceptual and safety studies will be also used to obtain the basic requirements for design of the Engineering Scale Pyroprocess Facility (ESPF) which is the demonstration facility for feasibility of pyroprocess commercialization.

Advances in the ACP Facility Electrochemical Reduction Process

The Advanced Spent Fuel Conditioning Process (ACP) has been proposed and developed by the Korea Atomic Energy Research Institute (KAERI) to treat oxide spent fuels (SFs) from light water reactors to reduce the volume, heat load, and radiotoxicity of processed SFs. In the ACP, an electrochemical reduction process has been developed, and an electroreducer with a maximum 20 kg/batch scale has been installed in the KAERI ACP facility. In this study, electrochemical reduction runs were carried out with 10 kg/batch of SIMFUEL at 923 K under current controlled conditions.The electrochemical reduction processes adopted LiCl molten salt as the electrolyte, and initially, 3.0 or 4.9 wt% of Li2O was dissolved to increase the oxygen ion activity in this work. A porous MgO basket was used to contain the powder-type test fuels; the basket and fuels along with a metal conductor as the current lead comprise a packed bed reactor where reduction takes place. During the three runs of reduction, the Li2O concentration was decreased with the applied current, and it was found that Ar bubbling in the bulk phase accelerated the depletion rate. Alkali and alkaline earth metal elements from the test fuels had dissolved and accumulated in the molten salt. The reduced metal was recovered after the runs, and sampled products exhibited >90% reduction yields with respect to their positions in the MgO basket. In addition to the experimental study, a three-dimensional model was developed to analyze respective phases in a reactor by using commercial tools. Streamlines of the fluids, the temperature distribution, and the oxygen partial pressure were obtained for the gas phase in motion, and the potential field calculation was carried out to reveal that most of the potential was applied to the cathode side because of the low electrical conductivities of the constituents.

Design and Verification of Shielding for the Advanced Spent Fuel Conditioning Process Facility

An Advanced spent fuel Conditioning Process Facility (ACPF) has recently been constructed by a modification of previously unused cells. ACPF is a hot cell with two rooms located in the basement of the Irradiated Materials Experiment Facility (IMEF) at the Korea Atomic Energy Research Institute. This is for demonstrating the advanced spent fuel conditioning process being proposed in Korea, which is an electrolytic reduction process of spent oxide fuels into a metallic form. The ACPF was designed with a more than 90 cm thick high density concrete shield wall to handle 1.38 PBq (37,430 Ci) of radioactive materials with dose rates lower than 10 muSv h in the operational areas (7,000 zone) and 150 muSv h in the service areas (8,000 zone). In Monte Carlo calculations with a design basis source inventory, the results for the bounding wall showed a maximum of 3 muSv h dose rate at an exterior surface of the ACPF for gamma radiation and 0.76 muSv h for neutrons. All the bounding structures of the ACPF were investigated to check on the shielding performance of the facility to ensure the radiation safety of the facility. A test was performed with a 2.96 TBq (80 Ci) 60Co source unit and the test results were compared with the calculation results. A few failure points were discovered and carefully fixed to meet the design criteria. After fixing the problems, the failure points were rechecked and the safety of the shielding structures was confirmed. In conclusion, it was confirmed that all the investigated parts of the ACPF passed the shielding safety limits by using this program and the ACPF is ready to fulfill its tasks for the advanced spent fuel conditioning process.