[en] The utilization of modular sodium-to-supercritical CO₂ heat exchangers may yield significant improvements for an overall plant energy utilization. The consequences of a failure of the sodium CO₂ heat exchanger boundary, however, would involve the blowdown and intermixing of high-pressure CO₂ in a sodium pool, causing a pressurization which may threaten the structural integrity of the heat exchanger. Available data seems to indicate that the chemical reaction between sodium and CO₂ would likely produce sodium oxides, sodium carbonate, carbon and carbon monoxide. Information on the kinetics of the sodium-CO₂ reaction is virtually non-existent

[en] This report described the experimental apparatus and the operation for the Na-CO₂ reaction experiments, and the analysis results through the experiments on the temperature and pressure of the sodium and gas flow

[en] In the design of sodium_cooled fast reactor (SFR), the integrity of fuel is monitored as part of core monitoring. To perform this function, the fuel failure is real-time monitored and the continuous operation of reactor is determined by the severity of fuel failure. As any fuel failure is detected, then the failed fuel is located and the results are henceforth provided for the operation of failed fuel replacement. Any pin-hole or failure on the fuel clad makes cause of transferring a fission product into the core and then contaminates whole integrated reactor. When a fuel failure occurs, the system designed in this study monitors the integrity of fuel through detecting the fission gases and the delayed neutron radiated from failed fuel. To perform system functions, the system applies two types of detectors. One is a high purity germanium detector (HP-Ge) for monitoring the gamma-ray of fission gases existing in the reactor head and the other is a fission chamber for detecting the delayed neutron within the intermediate heat-exchanger (IHX). In addition a gas analyzer is used to detect and sort the tag gases leaked from each fuel so as to locate the failed fuel. This study describes three methods applied to the design of failed fuel monitoring system and the design concept of an integrated monitoring system based on them. Accordingly this report can be applied to the conceptual and basic design of SFR failed fuel monitoring system to be performed in the near future

[en] Radioactivities of the stack air effluents from the Advance Fuel Science Building (AFSB) at KAERI have been investigated and evaluated. In this AFSB, nuclear fuels for the HANARO research reactor have been fabricated and the advanced nuclear fuels have been studied. A stack air monitoring system has been continuously operating to monitor the stack air effluents from the facility to protect the environment. As the results of the periodical radioactivity measurement and both the gamma and alpha spectrometry for the millipore filters taken from the stack air monitor from January until March 2008, a trace amount of primordial ⁴⁰K and the short-lived decay products of natural borne ²²²Rn and ²²⁰Rn have been detected. However, the radioactivities have rapidly decayed to the level below the Minimum Detectable Activity (MDA) of the counting system. Therefore, it was evaluated that no uranium isotopes have been released to the atmosphere from the stack of the AFSB at KAERI

[en] Scope and Contents of Project. Development of rapid dose reconstruction technology for large-scale radiation accidents and terrorism. Development of quantification technology for neutron / gamma mixed fields. Research results. Development of new radiolabeling material and securing technology for dose restoration. Development of rapid reading technology for exposure to large-scale accident Development of integrated neutron / gamma mixed radiation quantification technology. Proposal for Applications. New radiation marker. Algorithm and program for converting dose of labeling substance into human exposure dose. In-situ dose restoration equipment. Establishment of research network with dose restoration laboratories (speed efficiency through emergency dose distribution). Exposure dose information on tracking vehicle / building interior / suspect portable goods of radiation terrorism. New materialisation material for neutron / gamma simultaneous measurement. Neutron / gamma simultaneous measurement algorithm and measurement system

[en] In the experiments to investigate the characteristics of the free surface fluctuation in a vessel, the experimental correlation was modeled to describe the free surface fluctuation in the upper plenum of a liquid metal reactor within 95% reliability and 2.4% error. The correlation was used to verify the computational model. The new conceptual flowmeters were suggested to measure the sodium flow for the reliability enhancement. The electromagnetic flowmeter with permanent magnet showed a good linearity and repeatability. For reuse of the sodium contaminated component, CO₂ bubbling method was developed. Sodium in 0.3mm crevice specimen was removed completely. The optimum condition for the used sodium treatment was deduced to estimate which reaction is more safe and adequate for operation condition by analyzing the reactivity alleviation condition and the reaction rate with the control of sodium hydroxide concentration A series of tests were carried out to investigate the enlargement rate of the nozzle hole itself and the sodium-water reaction temperature associated with needle-like jets of a high-pressure water/steam into the sodium side of a steam generator. The size of the nozzle hole became larger with an increased duration of the steam injection both for the 2.25Cr-1Mo and M9Cr-1Mo steels by a self-wastage phenomenon. For developing the SWR acoustic leak detection technology, the tool prepared by the LabVIEW was installed with the system, and confirmed the performance of the on-line acoustic leak detection tool using the SWR leak signal acquired in the KAERI facility

[en] Korean government recently published a national regulation on the internal exposure monitoring and dose evaluation (internal dosimetry) based on the most recent ICRP recommendation 60 and subsequent publications, which supercede the former ICRP recommendation 26 and publication 30, on which the internal dosimetry practice in Korea had been based so far. Consequently, this project, according to the demand from both government and nuclear industry, had been launched to develop a user-friendly computer code on internal dosimetry adopting the most up to date ICRP biokinetic and dosimetric model to resolve the difficulties and problems faced to nuclear industry and to develop related technology. The reliability of this code, named as BiDAS, as a result of several benchmark calculations for self assurance appeared to be excellent comparing with the foreign computer code. This computer code is expected to be successfully utilized in nuclear industry and related fields in complying with the national regulation on internal dosimetry program started from late 2003. Reference low level gamma(γ) radiation field for calibration of environmental radiation(γ) monitor and reference neutron field for calibration of n monitoring equipment have been established and characterized. International cross comparison of these reference radiation fields have been performed and radiation response of various radiation monitoring instrument has been tested by using these reference radiation fields. A technology which can directly measure the radiation quality factor and tissue absorbed dose has been established to evaluate the neutron dose in terms of operational quantity in the unknown mixed n-γ radiation field. Spherical and cylindrical TEPC systems have been designed and manufactured and a portable TEPC system to measure the neutron quality and dose in the real work field has been developed and tested in accelerator laboratory

[en] No matter how much the importance is emphasized, the exact assessment of the absorbed doses administered to the patients to treat the various diseases such as lately soaring malignant tumors with the radiotherapy practices is the most important factor. In reality, several over-exposed patients from the radiotherapy practice become very serious social issues. Especially, the development of a technology to exactly assess the high doses and high energies (In general, dose administered to the patients with the radiotherapy practices are very huge doses, and they are about three times higher than the lethal doses) generated by the radiation generators and irradiation equipment is a competing issue to be promptly conducted. Over fifty medical centers in Korea operate the radiation generators and irradiation equipment for the radiotherapy practices. However, neither the legal and regulatory systems to implement a quality assurance program are sufficiently stipulated nor qualified personnel who could run a program to maintain the quality assurance and control of those generators and equipment for the radiotherapy practices in the medical facilities are sufficiently employed. To overcome the above deficiencies, a quality assurance program such as those developed in the technically advanced countries should be developed to exactly assess the doses administered to patients with the radiotherapy practices and develop the necessary procedures to maintain the continuing performance of the machine or equipment for the radiotherapy. The QA program and procedures should induce the fluent calibration of the machine or equipment with quality, and definitely establish the safety of patients in the radiotherapy practices. In this study, a methodology for the verification and evaluation of the radiotherapy doses is developed, and several accurate measurements, evaluations of the doses delivered to patients and verification of the performance of the therapy machine and equipment are conducted. With these conducts, not only the socio-economical losses by the patients from the maladministration of the radiotherapy doses could be greatly reduced but also huge benefit to them from the enhancement of the quality of life, which is more than the monetary value be brought. To achieve these goals, two ultimate objectives are set up and the study is conducted to develop a technology for the evaluation of the high absorbed doses and high energies administered to the patients and the performance test of the radiotherapy machine and equipment and to fabricate the calorimeters or chemical dosimeters for the absolute measurement of the absorbed doses (from gamma rays and high energy x-rays) in the radiotherapy practices, to establish the standards for the evaluation of radiotherapy doses and to verify an internationally acknowledged traceability of the performance of the machine and/or equipment

[en] The liquid sodium which is used as a coolant in LMFBR, may give rise to a serious trouble in the safety aspect of steam generator. The defects in a heat transfer tube, such as pin-hole or tube welding defect, will result in a leakage of high pressure steam into the sodium side and production of hydrogen gas and corrosive sodium compounds which can cause significant damage to the tube wall of steam generator by using exothermic reaction. In significant damage to the tube wall of steam generator by using exothermic reaction. In this case, initial leak size will be enlarged with time and the leak rate developed to large leak through the micro, small, intermediate leaks. Therefore, the analysis of sodium-water reaction phenomena on the micro and small water leaks in the heat transfer tube is very important in the initial leak stage in the aspects of the protection of leak progress and safety evaluation of steam generator. In this study, firstly, the micro and small leaks phenomena, such as reopen size, shape, and time of leak path, self-wastage, corrosion of tube materials, was analyzed from the literature survey and water leakage experiments using the leak specimen. In small water leak experiments, the leak path was plugged by the sodium-water reaction products at the leak path of a specimen, and re-open phenomena were not observed in initial experiments. Other leak experiments, reopen phenomena of self-plugged leak path was observed. Re-open mechanism of sealed path could be explained by the thermal transient and vibration of heat transfer tube. As a result, perfect reopen time of self plugged leak path was observed to be about 130 minutes after water leak initiation. Reopen shape of a specimen was appeared with double layer of circular type, and reopen size of this specimen surface was about 2 mm diameter on sodium side. Also, the corrosion of a specimen initiated from sodium side, the segregation phenomena of Cr in the specimen was found much more than those of other elements, in AES analysis. In small water leakage experiments were carried out using the 2.25Cr-1Mo steel through co-work with IPPE, the following correlation equation about the reopen time between sodium temperature and initial leak rate was obtained, τ = δ·g^-0.83·10⁽3570/T_na-3.34), in 400-500 deg C of liquid sodium atmosphere

[en] Sodium fire is graded 'D' and it is difficult to extinguish sodium fire. In this report, the characteristics of sodium fire and the methods composing the suitable fire extinguishing systems to suppress fire effectively were described