Combustion/absorption process for the separation of 14C and 3H in radwastes released from nuclear power plants and their analysis.

Radioactivities of 3H and 14C in spent radioactive ion exchange resins and spent radioactive lubricant oils released from nuclear power plants, has been determined using a combustion and sorption method (combustion method). The liquid scintillation counting (LSC) spectra showed that the interference of other radionuclides has not significantly affected the determination of radioactivities of 3H and 14C in the radwaste samples. The chemical structure of 14CO2, which originated from the combustion of radwastes, trapped 14C sorbent has been investigated using Fourier transform infrared spectroscopy (FT-IR). FT-IR study showed interesting results that peaks for uncoupled CO2 and carbonic amide appeared at FT-IR spectra of CO2 high-absorbed 14C sorbents, while the peak for carbamate was only observed at the spectra of CO2 low-absorbed sorbents. During the CO2 sorption in 14C sorbent, temperature and viscosity of the sorbent increased owing to decrease of enthalpy and increase of apparent molecular weight of the sorbent caused by the bonding formation between sorbent molecules.

Analysis and evaluation for consumer goods containing NORM in Korea.

We analyzed the consumer goods containing NORM by ICP-MS and evaluated the external dose. To evaluate the external dose, we assumed the small room model as irradiation scenario and calculated the specific effective dose rate using MCNPX code. The external doses for twenty goods are less than 1 mSv considering the specific effective dose rates and usage quantities. However, some of them have relatively high dose and the activity concentration limits are necessary as a screening tool.

Validation of a procedure for the analysis of 226Ra in naturally occurring radioactive materials using a liquid scintillation counter.

An analytical procedure for detecting 226Ra in naturally occurring radioactive materials (NORMs) using a liquid scintillation counter (LSC) was developed and validated with reference materials (zircon matrix, bauxite matrix, coal fly ash, and phosphogypsum) that represent typical NORMs. The 226Ra was released from samples by a fusion method and was separated using sulfate-coprecipitation. Next, a 222Rn-emanation technique was applied for the determination of 226Ra. The counting efficiency was 238 ± 8% with glass vials. The recovery for the reference materials was 80 ± 11%. The linearity of the method was tested with different masses of zircon matrix reference materials. Using 15 types of real NORMs, including raw materials and by-products, this LSC method was compared with γ-spectrometry, which had already been validated for 226Ra analysis. The correlation coefficient for the results from the LSC method and γ-spectrometry was 0.993 ± 0.058.

Simultaneous Determination of the Depth of an Embedded Source and its Radioactivity in the Medium.

The simultaneous determination of the depth of an embedded source and its radioactivity in the medium at the environmental surveys is a very useful and advisable method for an in-situ gamma-ray measurement with respect to the time and cost constraint. An algorithm for the determination of the source depth and its radioactivity in the medium was developed using the information on the uncollided photon fluences and measured net count rates, which mean not scattered fluences and background subtracted count rate, at the detector positions. Uncollided photon fluences were calculated at several source depths in the medium as well as at detector positions from the Monte Carlo N-Particle (MCNP) simulation. The results were then used to establish a database to output their values according to the source depth in the medium by inputting the photon energy and detector position from the medium. A simple program about the simultaneous determination of two variables was applied to the results on a task to find out the depth and activity of Cs and Cs at in-situ gamma-ray spectrometry. Less than 10% and 15% differences compared with the real values at the source depth and radioactivity, respectively, were achieved using the developed program.

Analytical evaluation of natural radionuclides and their radioactive equilibrium in raw materials and by-products.

An investigation into the distribution of natural radionuclides and radioactive secular equilibrium in raw materials and by-products in a domestic distribution was conducted to deduce the optimum conditions for the analytical evaluation of natural radionuclides for (238)U, (226)Ra, and (232)Th using a gamma-ray spectrometer and inductively coupled plasma mass spectrometer (ICP-MS). The range of the specific activities of natural radionuclides was first evaluated by analyzing (228)Ac and (214)Bi, which are (232)Th and (226)Ra indicators, respectively, in about 100 samples of raw materials and by-products through a gamma-ray spectrometer. From further experiments using several samples selected based on the results of the distribution of natural radionuclides, the validation of their analytical evaluations for the indirect measurements using a gamma-ray spectrometer and direct measurements using ICP-MS was assured by comparing their results. Chemically processed products from the raw materials, such as Zr sand and ceramic balls, were generally shown for the type of bead and particularly analyzed showing a definite disequilibrium with above a 50% difference between (238)U and (226)Ra in the uranium series and (232)Th and (228)Ra in the thorium series.

Design and performance of an automated radionuclide separator: its application on the determination of 99Tc in groundwater.

A modular automated radionuclide separator for (99)Tc (MARS Tc-99) has been developed for the rapid and reproducible separation of technetium in groundwater samples. The control software of MARS Tc-99 was developed in the LabView programming language. An automated radiochemical method for separating (99)Tc was developed and validated by the purification of (99m)Tc tracer solution eluted from a commercial (99)Mo/(99m)Tc generator. The chemical recovery and analytical time for this radiochemical method were found to be 96 ± 2% and 81 min, respectively.

Development of scaling factors for the activated concrete of the KRR-2.

The biological shielding concrete of KRR-2 was activated by a thermal neutron reaction during the operation of the reactor, thus a variety of radionuclides were generated in the concrete. In order to verify the radioactivity for the final disposal of waste and to achieve a more efficient cutting of the concrete, the radioactivity inventories and distributions of the activated concrete were evaluated. The activity of gamma-emitting radionuclides was measured by using an HPGe detector. The beta-emitting radionuclides were measured by an oxidation/combustion method for (3)H and (14)C and a combined method of an extraction chromatography and a liquid scintillation for (55)Fe and (63)Ni. The dominant radioactive nuclides in the activated concrete were (3)H, (14)C, (55)Fe and (60)Co, and the maximum gamma activity was 105Bq/g at the surface around the thermal column. The specific activities of all the nuclides were found to decrease almost linearly on a logarithmic scale along the depth from the inner surface of the concrete. Equations for scaling factors were obtained by a linear regression of logarithms from the radioactivity data of (3)H/(60)Co, (14)C/(60)Co and (55)Fe/(60)Co nuclide pairs of the activated concrete. The scaling factors can be utilized for the estimation of beta radioactivity without the time consuming separation processes of the nuclides.