High-flux Advanced Neutron Application Reactor Research Articles

Development of a Data-driven Decision Support System for the Efficient Operation of the Research Reactor Secondary System

The High-flux Advanced Neutron Application Reactor (HANARO) is a research reactor in the Republic of Korea. The secondary cooling system of HANARO releases heat into the atmosphere via cooling towers and fans. Because a part of the system is exposed to the external atmosphere, the behavior of the secondary cooling system is coupled with atmospheric conditions. However, no procedure exists to reflect such coupling, and the cooling fans are empirically controlled by the operators. This empirical decision-making may increase the workload and reduce operational efficiency; therefore, the cooling fan operational schemes must be improved. In this study, a decision support system is developed based on two artificial intelligence (AI) models to aid operators’ decision-making in controlling the cooling fans. During model development, data augmentation was applied to alleviate data imbalances. Additionally, a graphical user interface-based decision support system prototype was developed based on the models to provide operators with more comprehensive summaries of the information related to cooling-fan operations and outputs from the AI models. The models demonstrated acceptable performance on the testing data. The prototype system was installed in the main control room of HANARO and evaluated for its usability improvements and feasibility in practical applications.

Developing mini 4[formula omitted] coincidence counter for measuring activity

For measuring activity of radionuclides produced in High-flux Advanced Neutron Application Reactor (HANARO) at the Korea Atomic Energy Research Institute (KAERI), a small size 4πβ–γ coincidence counter was developed. This counter comprises a liquid scintillator for detecting beta-ray and NaI crystal for detecting gamma-ray, each coupled to SiPMs (silicon photomultipliers) that do not require high-voltage devices. The performance of the newly developed detector was validated using 134Cs and 177Lu reference materials.

Thermal-hydraulic safety analysis of radioisotope production in HANARO using MCNP6 and COMSOL multiphysics: A feasibility study

The High-flux Advanced Neutron Application Reactor (HANARO) produces radioisotopes (RIs) (131I, 192Ir, etc.) through neutron irradiation on various RI production targets. Among them, 177Lu and 166Ho are particularly promising owing to their theranostic characteristics that facilitate simultaneous diagnosis and treatment. Prior to neutron irradiation, evaluating the nuclear heating of the RI production target is essential for ensuring the thermal-hydraulic safety of HANARO. In this study, the feasibility of producing 177Lu and 166Ho using irradiation holes of HANARO was investigated in terms of thermal-hydraulic safety. The nuclear heating rates of the RI production target by prompt and delayed radiation were calculated using MCNP6. The calculated nuclear heating rates were used as an input parameter in COMSOL Multiphysics to obtain the temperature distribution in an irradiation hole. The degree of temperature increase of the 177Lu and 166Ho production targets satisfied the safety criteria of HANARO. The nuclear heating rates and temperature distribution obtained through the in silico study are expected to provide valuable insight into the production of 177Lu and 166Ho using HANARO.

Considerations of the Optimized Protective Action Distance to Meet the Korean Protective Action Guides Following Maximum Hypothesis Accidents of Major KAERI Nuclear Facilities

Background: Korea Atomic Energy Research Institute (KAERI) operates several nuclear research facilities licensed by Nuclear Safety and Security Commission (NSSC). The emergency preparedness requirements, GSR Part 7, by International Atomic Energy Agency (IAEA) request protection strategy based on the hazard assessment that is not applied in Korea.Materials and Methods: In developing the protection strategy, it is important to consider an accident scenario and its consequence. KAERI has tried the hazard assessment based on a hypothesis accident scenario for the major nuclear facilities. During the assessment, the safety analysis report of the related facilities was reviewed, the simulation using MELCOR, MACCS2 code was implemented based on a considered accident scenario of each facility, and the international guidance was considered.Results and Discussion: The results of the optimized protective actions were 300 m evacuation and 800 m sheltering for the High-Flux Advanced Neutron Application Reactor (HANARO), the evacuation to radius 50 m, the sheltering 400 m for post-irradiation examination facility (PIEF), 100 m evacuation or sheltering for HANARO fuel fabrication plant (HFFP) facility.Conclusion: The results of the optimized protective actions and its distances for the KAERI facilities for the maximum postulated accidents were considered in establishing the emergency plan and procedures and implementing an emergency exercise for the KAERI facilities.

Development of deep autoencoder-based anomaly detection system for HANARO

The high-flux advanced neutron application reactor (HANARO) is a multi-purpose research reactor at the Korea Atomic Energy Research Institute (KAERI). HANARO has been used in scientific and industrial research and developments. Therefore, stable operation is necessary for national science and industrial prospects. This study proposed an anomaly detection system based on deep learning, that supports the stable operation of HANARO. The proposed system collects multiple sensor data, displays system information, analyzes status, and performs anomaly detection using deep autoencoder. The system comprises communication, visualization, and anomaly-detection modules, and the prototype system is implemented on site in 2021. Finally, an analysis of the historical data and synthetic anomalies was conducted to verify the overall system; simulation results based on the historical data show that 12 cases out of 19 abnormal events can be detected in advance or on time by the deep learning AD model.

CFD Analysis to Suppress Condensate Water Generated in Gas Sampling System of HANARO

The high-flux advanced neutron application reactor (HANARO) is a research reactor with thermal power of 30 MW applied in various research and development using neutrons generated from uranium fission chain reaction. A degasifier tank is installed in the ancillary facility of HANARO. This facility generates gas pollutants produced owing to internal environmental factors. The degasifier tank is designed to maintain the gas contaminants below acceptable levels and is monitored using an analyzer in the gas sampling panel. If condensate water is generated and flows into the analyzer of the gas sampling panel, corrosion occurs inside the analyzer's measurement chamber, which causes failure. Condensate water is generated because of the temperature difference between the degasifier tank and analyzer when the gas flows into the analyzer. A heating system is installed between the degasifier tank and gas sampling panel to suppress condensate water generation and effectively remove the condensate water inside the system. In this study, we investigated the efficiency of the heating system. In addition, the variations in the pipe temperature and the amount of average condensate water were modeled using a wall condensation model based on the changes in the fluid inlet temperature, outside air temperature, and heating cable-setting temperature.

Development of long-term irradiation testing technology at HANARO

As the High Flux Advanced Neutron Application Reactor (HANARO) has been recently required to support new R&D relevant to future nuclear systems requiring a much higher neutron fluence, the development of irradiation capsule technology for long-term irradiation testing was performed in three steps (3, 5, 10 dpa). At first, several design improvements of a standard capsule were suggested based on a failure analysis of the capsule and successfully applied for irradiation testing at HANARO at up to eight reactor operation cycles equivalent to 3 dpa. Based on a schematic stress analysis of the vulnerable parts of the previous capsule, an optimized design of the capsule was made for 5 dpa irradiation. The newly designed capsule was safely out-pile tested up to 450 days, which was equivalent to 5 dpa irradiation in the reactor. The test results were submitted to the Reactor Safety Review Committee of HANARO and irradiation testing for 5 dpa was approved. The capsule was also successfully out-pile tested to evaluate the possibility of irradiation testing for 10 dpa. For a higher neutron fluence exceeding 10 dpa, new capsule technologies, including a new capsule that has a different bottom design and neutron flux boosting capsule, were also suggested.

Tritium Research and Development Status at KAERI

Korea has 26 nuclear power plants (NPPs). Out of these 26 plants, 4 are Canada Deuterium Uranium (CANDU) reactors at the Wolsong nuclear power site. In CANDU reactors, deuterium oxide is used as a moderator/coolant, and tritium is produced whenever a deuterium oxide nucleus captures a neutron. The Wolsong Tritium Removal Facility was designed to remove tritium generated in CANDU reactors. We are introducing tritium environmental protection not only at the Wolsong NPP but also at the High-Flux Advanced Neutron Application Reactor (HANARO) and in high-temperature gas-cooled reactors (HTGRs). We present a tritium behavior analysis code and assess the concentration of tritium in combustible dry active waste. Advanced techniques are introduced to transfer tritium from tritiated water to the gaseous phase. In addition, research on the nuclear fusion tritium storage and delivery system, which is part of the fuel cycle, has been carried out. In this paper, we present the recent progress in the effort to develop tritium systems at the Korea Atomic Energy Research Institute.

In-Core Power Measurement Using SiC Semiconductor Detector

A SiC detector was fabricated and tested in harsh radiation environment of the High Flux Advanced Neutron Application Reactor (HANARO) reactor core at Korea Atomic Energy Research Institute (KAERI). A 4H-SiC with 30 µm thick epitaxial layer was used as the radiation sensor, and the detector was designed to be tolerable against thermal and radiation damages. Alpha response and I-V characteristics of fabricated SiC sensor was measured and detection performance of the SiC detector was evaluated in a neutron field of HANARO ex-core neutron irradiation facility. After preliminary tests, reactor power monitoring using the SiC detector was carried out by inserting it into the HANARO irradiation hole, IP-4. Radiation-induced current of the detector was recorded as reactor power increased up to 10 MWth. Maximum thermal and fast neutron fluxes were 9.4×1012 and 2.5×109 neutrons/cm2/sec, respectively, and total neutron fluence irradiated on the detector was 4.7×1016 neutrons/cm2. The detector showed good linearity of response up to the tested fluence, with R2 = 0.9997. Response speed of SiC detector was compared to that of a Rh self-powered neutron detector (SPND) in terms of signal saturation time. Averaged SiC detector saturation time was 12.8 seconds, approximately 11 times faster that of the Rh SPND.

Estimation of Residual Radioactivity and Radiation Damage in SiC After Neutron Irradiation

In the process of neutron transmutation doping (NTD), Si, C, and impurities in the SiC become radioactive nuclides by neutron capture reaction (n, $\gamma $ ) and several threshold reactions. The radiations emitted from the residual radionuclides constantly damage the SiC until they completely decay. The radiation damage can create many defects in the SiC, and the defects can reduce the electron mobility and distort the band structure. This radiation damage to the SiC should be evaluated in terms of quality management. In order to quantify the sources of radiation damage, time variations of the residual radionuclides’ radioactivity in 5-in cylindrical SiC ingot after neutron irradiation were calculated using the DCHAIN program linked to the particle and heavy ion transport code system (PHITS). In the calculation, it was assumed that the SiC ingot was irradiated in the NTD1 irradiation hole of the High-Flux Advanced Neutron Application Reactor (HANARO) at the Korea Atomic Energy Research Institute (KAERI). The energy spectrum of neutrons in the HANARO NTD1 irradiation hole calculated by using the Monte Carlo N-particle code version 6.1 (MCNP6.1) code was considered as a neutron source for the calculation. Based on the radioactivity data, the total flux and energy spectra of the electrons and gamma-rays in the SiC were calculated to analyze the properties of the radiation sources. Most of the radiations were emitted from the beta decay of 31Si, but they decayed early, and radionuclides with a relatively long half-life, such as 59Fe and 32P, became the major radiation sources. Finally, the radiation damage was calculated in the displacement per atom (DPA) unit. The time variations of the DPA rate and cumulative DPA in the SiC are presented.

Operational Vulnerability Identification Procedure for Nuclear Facilities Using STAMP/STPA

The nuclear facilities are operated to give safety the utmost priority and all possible scenarios that may lead to hazardous states must be evaluated. To date, the probabilistic safety assessment has been used as one of the standard tools for the safety evaluation; however, concerns have been raised about its capability to treat the complex interaction between human operators, digital systems, and diverse plant processes. This paper proposes an operational vulnerability identification procedure based on STAMP/STPA (System Theoretic Accident Model and Process/Systems-Theoretic Process Analysis) which allows us to derive unsafe control action (UCA) leading to the unwanted consequence of a system, such as a spurious reactor trip. The effectiveness of the proposed procedure is demonstrated with the case study of a cold neutron source system installed in High-Flux Advanced Neutron Application Reactor (HANARO). In result, 127 UCAs were derived for 51 control actions regarding spurious trip scenario. The UCAs were reviewed by the HANARO operators and found new scenarios that requires further investigation for reducing the possibility of a spurious trip. The proposed procedure is expected to provide a holistic viewpoint for operational vulnerability identification and further used to suggest recommendations for the safety enhancement of nuclear facilities.

Estimation of nuclear heating by delayed gamma rays from radioactive structural materials of HANARO

Abstract To improve the accuracy and safety of irradiation tests in High flux Advanced Neutron Application ReactOr (HANARO), the nuclear energy deposition rate, which is called nuclear heating, was estimated for an irradiation capsule with an iridium sample in the irradiation hole in order. The gamma rays emitted from the radioisotopes (RIs) of the structural materials such as flow tubes of fuel assemblies and heavy water reflector tank were considered as radiation source. Using the ORIGEN2.1 code, emission rates of delayed gamma rays were calculated in consideration of the activation procedure for 8 years and 2 months of HANARO operation. Calculated emission rates were used as a source term of delayed gamma rays in the MCNP6 code. By using the MCNP code, the nuclear heating rates of the irradiation capsules in the inner core, outer core, and heavy water reflector tank were estimated. Calculated nuclear heating in the inner core, outer core, and heavy water reflector tank were 200–260 mW, 80–100 mW, and 10 mW, respectively.

Atom probe tomography analysis of nanostructure evolution in Ni-Cr-Mo low alloy steel under neutron irradiation

Ni-Cr-Mo low alloy steels are being considered as alternative materials to replace the Mn-Mo-Ni low alloy steels used in reactor pressure vessels in nuclear power plants, because of their higher strength and toughness. However, the neutron irradiation occurring during reactor operation causes degradation of Ni-Cr-Mo low alloy steel. In this study, irradiation-induced clusters in a Ni-Cr-Mo model alloy irradiated in the High-flux advanced neutron application reactor (HANARO) research reactor were investigated via Atom probe tomography (APT). The irradiated specimens showed irradiation-induced hardening and embrittlement. The neutron irradiation caused Si clustering, and these spherical clusters were homogeneously distributed within the matrix. Ni was also clustered at the Si clusters. However, the other elements did not clearly exhibit clustering behavior. Si and Ni atoms were also located at the dislocations. To quantify the nano-sized clusters, a method based on the Density-based spatial clustering of applications with noise (DBSCAN) algorithm was implemented. The total number of clusters was calculated to be ~7 × 10-4 n/nm3 and the average cluster radius was less than 2 nm. The APT approach was demonstrated to be well suited for discovering the irradiation defect structures.

Development of a Low-Temperature Irradiation Capsule for Research Reactor Materials at HANARO

A new capsule design was prepared and tested at the High Flux Advanced Neutron Application Reactor (HANARO) for neutron irradiation of the core materials of research reactors at a low temperature (of <100°C). The capsule was first designed at HANARO to have the coolant flow through the capsule to cool down the irradiation temperature of the specimens. The safety of the newly designed capsule should be fully checked before irradiation testing. Out-pile performance and endurance testing before HANARO irradiation testing was performed using a capsule in the HANARO out-pile test facilities. The new capsule had a much higher coolant flow-induced vibration than a standard capsule, resulting in fatigue failure at the rod tip of the capsule. The lifetime of the rod tip was greatly improved by changing the material from Type 304 stainless steel to Type 316L stainless steel and by changing the welding method from tungsten inert gas welding to electron beam welding. With the optimized design, the capsule was successfully irradiated at low temperatures of <100°C for up to eight cycles (6075 MWd) at HANARO.

Material Irradiation Technology Using Capsules at HANARO

The Korean research program on nuclear technology requires various in-pile tests to evaluate the safety of currently operating nuclear power plants and develop a future nuclear system. HANARO (High-flux Advanced Neutron Application Reactor) provides a peak thermal and fast flux of 5.0 × 1014 n/cm2 · s (E < 0.625 MeV) and 2.1 × 1014 n/cm2 · s (E > 0.821 MeV), respectively, at 30 MW maximum thermal power. A capsule system has been developed for irradiation tests of nuclear materials and fuels at the core region. Extensive efforts have been made to establish the design and manufacturing technology for various capsules and a temperature control system, which should be compatible with HANARO’s characteristics. The capsule system has been actively utilized for various materials and fuel irradiation tests requested by users from research institutes, universities, and industries. Since 1995, more than 10,000 specimens have been irradiated using the developed capsule system. Presently, new irradiation technologies, such as a high-temperature irradiation capsule for a very-high-temperature reactor and a sodium-cooled fast reactor, and a low-temperature irradiation capsule for a research reactor, are being developed. These technologies will be completed with the development of instruments such as a linear variable differential transformer, a micro-electric heater, and a self-powered neutron detector in the near future, and they will be used for the Generation-IV nuclear system in Korea.

Neutron Flux Characterization of Irradiation Holes for Irradiation Test at HANARO

The High flux Advanced Neutron Application ReactOr (HANARO) is a unique research reactor in the Republic of Korea, and has been used for irradiation testing since 1998. To conduct irradiation tests for nuclear materials, the irradiation holes of CT and OR5 have been used due to a high fast-neutron flux. Because the neutron flux must be accurately calculated to evaluate the neutron fluence of irradiated material, it was conducted using MCNP. The neutron flux was measured using fluence monitor wires to verify the calculated result. Some evaluations have been conducted, however, more than 20% errors have frequently occurred at the OR irradiation hole, while a good agreement between the calculated and measured data was shown at the CT irradiation hole.

Visibility evaluation of a neutron grating interferometer operated with a polychromatic thermal neutron beam

Visibility evaluation of neutron gratings for a polychromatic thermal neutron beam was performed for a neutron grating interferometer. Four sets of neutron gratings designed for neutron wavelengths of 2.0Å, 2.7Å, 3.5Å, and 4.4Å were fabricated and tested to find the neutron grating interferometer setup with maximum visibility. The measurements were carried out at the thermal neutron beamline of the Ex-core Neutron irradiation Facility (ENF) of the High-flux Advanced Neutron Application Reactor. The maximum visibility was obtained at the neutron grating set designed for a neutron wavelength of 2.7Å among the four sets, and the visibility was 9.7%. The experimental data can be the basis for an optimization of the neutron grating interferometer at the thermal neutron beamline, and can be further optimized for neutron dark-field imaging with high spatial resolution and a shorter data acquisition time.

Research on Material Irradiation in HANARO

HANARO (High-Flux Advanced Neutron Application Reactor) is a 30MWth multi-purpose research reactor generating a very high neutron flux for scientific and technical applications. Since its initial criticality in Feb. 1995, it has worked as a national neutron source for neutron beam research, RI production and related research, material and fuel irradiation research, and neutron transmutation doping. The installation of a cold neutron source and related beam instrument makes HANARO serve as a regional source for beam research as well. As Korea is developing nuclear power systems and fuels, irradiation research is a main utilization subject in HANARO, and irradiation facilities have been actively utilized for various nuclear fuel and material irradiation tests requested by users from research institutes, universities, and industries. Most of the irradiation tests were related to the R & D relevant to the ageing management and safety evaluation of the present nuclear power reactors. Korea is conducting R & D programs relevant to new nuclear systems including a research reactor, System-integrated Modular Advanced Reactor (SMART), and future nuclear systems such as a very high temperature reactor system (VHTR) and sodium cooled fast reactor system (SFR). To effectively support the R&D for new nuclear systems, advanced irradiation technologies such as high-temperature irradiation, instrumentation, and long-term irradiation are being developed. In addition, research on the irradiation characteristics of super-conductor materials and new chemical materials is being conducted as a part of fundamental research.

A compact spin-exchange optical pumping system for 3He polarization based on a solenoid coil, a VBG laser diode, and a cosine theta RF coil

For use as a neutron spin polarizer or analyzer in the neutron beam lines of the HANARO (High-flux Advanced Neutron Application ReactOr) nuclear research reactor, a 3He polarizer was designed based on both a compact solenoid coil and a VBG (volume Bragg grating) diode laser with a narrow spectral linewidth of 25 GHz. The nuclear magnetic resonance (NMR) signal was measured and analyzed using both a built-in cosine radio-frequency (RF) coil and a pick-up coil. Using a neutron transmission measurement, we estimated the polarization ratio of the 3He cell as 18% for an optical pumping time of 8 hours.

Fusion tritium research facilities in KAERI

Korea Domestic Agency (KODA) is developing a nuclear fusion fuel storage and delivery system (SDS) as one of the Korean procurement packages. Korea Atomic Energy Research Institute (KAERI) is operating the following basic scientific research laboratories for an SDS and tritium supply study: a metal hydride bed preparation laboratory, hydrogen isotope recovery and delivery performance test rig, in-bed calorimetry performance test rig, and tritium shipping container integrity test facility. Furthermore, the development of a test blanket module (TBM) is required to test and validate the design concept of tritium breeding blankets relevant to fusion power plants. KAERI is also operating the following laboratories for the TBM research, such as a tritium extraction performance test rig, High-flux Advanced Neutron Application Reactor (HANARO), and Experimental Loop for Liquid Breeder (ELLI).