Moon Hee Han

Influence of predictive contamination to agricultural products due to dry and wet processes during an accidental release of radionuclides

Abstract The influence of predictive contamination to agricultural products due to the wet processes as well as dry processes from radioactive air concentration during a nuclear emergency is comprehensively analyzed. The previous dynamic food chain model DYNACON considering Korean agricultural and environmental conditions, in which the initial input parameter was radionuclide concentrations on the ground, is improved so as to evaluate radioactive contamination to agricultural products from either radioactive air concentrations or radionuclide concentrations on the ground. As for the results, wet deposition is a more dominant mechanism than dry deposition in contamination on the ground. While, the contamination levels of agricultural products are strongly dependent on radionuclide and precipitation when the deposition of radionuclides occurs. It means that the contamination levels of agricultural products are determined from which is the more dominant process between deposition on the ground and interception to agricultural plants.

AN INVESTIGATION INTO RADIATION LEVELS ASSOCIATED WITH DISMANTLING THE KOREA RESEARCH REACTOR

We confirmed that the dismantling of two research reactors with thermal power of 2MW th and 100kW th , respectively, reveals no significant difference between the radiation levels of the research reactor site and the surrounding environment far away from it, from the radiation level aspect. Radiation dose and radioactivity were measured at monitoring points around the research reactor site of the Korea Atomic Energy Research Institute (KAERI) in Seoul and comparison points 0.5 km to 3.3 km from the site. To grasp trends in the radiation levels during dismantling from the end of 2002 to the end of 2007, the gamma radiation dose rate, the accumulated dose, and the radioactivity of the strontium, tritium, and gamma isotopes were statistically treated and estimated. The averages of these items between the two groups, the research reactor site and comparison points, were assessed by applying a T-test with a significance level of 0.05. P-values found by using the T-test were from 0.12 to 0.83 where the values were much higher than the significance level. As a result, no difference was observed between the radiation levels at the research reactor site and at the comparison points by this T-test. This study showed that dismantling activity of the Korea Research Reactor of the Seoul site did not expose the public or the environment to harmful levels of radiation.

Quantitative Analysis of Meteorological Conditions for a Comparative Risk Estimation of Nuclear Power Plants in Korea

The meteorological conditions of Korean nuclear power plant sites were analyzed by using the integral parameters developed by Allwine and Whiteman. The method of integral parameters was applied to 76 sites in Korea which are evenly distributed. The integral quantities of stagnation and recirculation were calculated at four nuclear power plant (NPP) sites and these values were analyzed with the distribution of the integral quantities estimated with the results of the 76 sites. The comparative study shows that the meteorological conditions of the four NPP sites in Korea are quite good from the meteorological aspects.

A Predictive Model for a Radioactive Contamination in an Urban Environment and Its Performance Capability to the EMRAS Project

A model, called METRO-K, has been developed for a radiological dose assessment due to a radioactive contamination for the Korean urban environment. The model has been taking part in the Urban Remediation Working Group within the IAEA’s EMRAS project to provide an opportunity to compare the modeling approaches and the predictive results of models that describe the behavior of radionuclide in an urban environment. The modeling approaches of METRO-K and the predictive results that have been carried out as a part of the Working Groups activities are presented and discussed. Contribution of contaminated surfaces to absorbed dose rates revealed a distinct difference for the locations of a receptor.

Development of an Accident Consequence Assessment Code for Evaluating Site Suitability of Light- and Heavy-water Reactors Based on the Korean Technical Standards

Background: Methodologies for a series of radiological consequence assessments show a distinctive difference according to the design principles of the original nuclear suppliers and their technical standards to be imposed. This is due to the uncertainties of the accidental source term, radionuclide behavior in the environment, and subsequent radiological dose. Both types of PWR and PHWR are operated in Korea. However, technical standards for evaluating atmospheric dispersion have been enacted based on the U.S. NRC’s positions regardless of the reactor types. For this reason, it might cause a controversy between the licensor and licensee of a nuclear power plant.

RADIOLOGICAL DOSE ASSESSMENT ACCORDING TO METHODOLOGIES FOR THE EVALUATION OF ACCIDENTAL SOURCE TERMS

The object of this paper is to evaluate the fission product inventories and radiological doses in a non-LOCA event, based on the U.S. NRC’s regulatory methodologies recommended by the TID-14844 and the RG 1.195. For choosing a non-LOCA event, one fuel assembly was assumed to be melted by a channel blockage accident. The Hanul nuclear power reactor unit 6 and the CE 16×16 fuel assembly were selected as the computational models. The burnup cross section library for depletion calculations was produced using the TRITON module in the SCALE6.1 computer code system. Based on the recently licensed values for fuel enrichment and burnup, the source term calculation was performed using the ORIGEN-ARP module. The fission product inventories released into the environment were obtained with the assumptions of the TID-14844 and the RG 1.195. With two kinds of source terms, the radiological doses of public in normal environment reflecting realistic circumstances were evaluated by applying the average condition of meteorology, inhalation rate, and shielding factor. The statistical analysis was first carried out using consecutive three year-meteorological data measured at the Hanul site. The annual-averaged atmospheric dispersion factors were evaluated at the shortest representative distance of 1,000 m, where the residents are actually able to live from the reactor core, according to the methodology recommended by the RG 1.111. The Korean characteristic-inhalation rate and shielding factor of a building were considered for a series of dose calculations.

Predictive Contamination of Animal Products Due to the Inhalation of Air and the Ingestion of Soil of Cattle in an Accidental Release of Radioactive Materials - Focusing on Contaminative Influence of Milk

In an accidental release of radioactive materials to the environment, the contaminative influence of animal products due to the inhalation of air and the ingestion of soil of cattle, both of which are considered as minor contaminative pathways in most radioecological models but may be important ones, was investigated with the improvement of the Korean radioecological model DYNACON. Although mathematical models for both contaminative pathways have been established for considering all animal products and incorporated into the model, investigation was limited to milk. As a result, it was found that both pathways are influential in the contamination of milk during the non-grazing period of dairy cows. Precipitation was an influential factor in milk contamination due to the ingestion of soil, especially for 137Cs. In the case of an accidental release during the grazing period of dairy cows, the contaminative influence due to the inhalation of air was negligible irrespective of the existence of precipitation during an accidental release.

The Radioactivity of 3H in Metals by a High Temperature Furnace and a Liquid Scintillation Counter

The radioactivity of 3 H of the metal samples from the nuclear sites was analyzed by using a commercialized high temperature furnace and a Liquid Scintillation Counter (LSC). The 3 H activity of the sample was measured according to the duration of the high temperature combustion and the oxidation temperature. Basically, the recovery from the furnace was 90% for 3 H and the LSC had a quenching efficiency of approximately 30 %. HNO3 was used as a trapping solution for 3 H and the solution was cocktailed with a scintillator. The activity extracted from the sample was increased till the combustion time elapsed 60 minutes and the increasing rate was reduced continuously thereafter at 600 °C whereas 80% of radioactivity was extracted during the first 15 minutes at 900 °C. Also, the pretreatment for the metal sample, which included a high temperature combustion and trapping, had the time required of at least four hours at 900 °C. Finally, it was suggested that this high temperature combustion method could be applied to analyze the activity of the radioactive metal waste from the nuclear power plants.© 2010 ASME