Jong-Sik Shon

The improvement of the mechanical stability and leachability of bituminized waste form of radioactive ash by addition of reused polyethylene

This study was carried out in order to produce bituminized waste forms, which have dimensional and mechanical stability like cement-based waste forms. This paper reports the effects of adding polyethylene (PE) to the bituminized waste form. The additive used for the experiment was the spent PE generated from agricultural use. The bitumen used in the sample preparation is straight-run distillation bitumen of penetration 60/70 (paving asphalt). The waste used for the experiment was a bottom ash generated from an industrial (inactive) waste incinerator. Bituminized waste forms with PE contents of 5 wt% or more resulted in maintaining dimensional and mechanical stability. The compressive strength and softening point of bituminized waste forms increase in proportion to the amount of additional PE. The leaching test using ANS 16.1 shows that the principal leaching mechanism of elements (Cs, Sr, Co) from bituminized waste forms is diffusion. Furthermore, it is demonstrated that additive PE of 5-10 wt% does not change the leaching mechanism, and bituminized waste forms maintain a high leach resistance.

A PRACTICAL METHOD FOR THE DISPOSAL OF RADIOACTIVE ORGANIC WASTE

Radioactive organic wastes containing acetone, alcohol, and particularly tributyl phosphate (TBP)/dodecane contaminated with uranium are extracted from the PUREX process and the decontamination of related equipment. An evaporation method that utilizes existing DU oxidation apparatuses and ventilation systems and a typical muffle furnace installed with an aspirating system are adopted. A separation method using phosphoric acid especially for the TBP/dodecane waste is also studied and evaluated. The results show that a simple evaporation process is utilizable for wastes containing acetone or alcohol with a lower boiling point. A modified muffle furnace is more appropriate to dispose directly of organic wastes having a higher boiling point, such as TBP/dodecane, without generating a condensed waste solution. It is recommended that, when the uranium concentration of TBP/dodecane waste is much higher than stipulated levels, separation technology should be applied to remove uranium from the mixture. Each type of solvent after separation can then be considered disposable below the regulatory limit in the modified furnace discussed in this study.

Characteristics of the mechanical stability and leachability of waste form with plating sludge by reused polyethylene

Abstract The objective of this study was to investigate the effects of spent polyethylene (PE) addition on the mechanical stability and leachability bituminized waste forms. The waste used for experiments was the actual sludge generated from an industrial plating factory and spent PE generated from an agricultural polyethylene film, respectively. The bitumen used in sample preparation is straight‐run distillation bitumen, a paving asphalt. Bituminized waste forms with PE contents of 5 wt% or more resulted in maintaining dimensional and mechanical stability. The compressive strength and softening point of bituminized waste forms increase in proportion to the amount of spent PE. Moreover, the enhanced mechanical stability is possible to evaluate the bituminized waste forms exactly. The precise leach test cannot be performed because of the deformation of the bituminous specimen. Leach test revealed that the principal leaching mechanism of metals (Zn, Cr, Cu) from bituminized waste forms is diffusion.

Development of the Sampling and Nuclide Analysis Methods for Spent HEPA Filter Wastes

Spent filter wastes of about 2,160 units have been stored in the waste storage facility of the Korea Atomic Energy Research Institute since its operation. These spent filters have generally consisted of a HEPA filter after its filtering of all the contaminants in the gas stream generated during the operation of the HANARO research reactor and the nuclear fuel cycle facilities. At the moment, to secure enough storage space, it is necessary to make a volume reduction of the stored radioactive wastes through a compression treatment or a regulatory clearance. There have been many studies on a treatment and a clearance of the low level radioactive wastes generated from nuclear facilities. These methods are used in view of a reduction of a management cost and disposal cost and the security of free space for a waste storage facility approaching saturation. In order to dispose of the spent filters, it is first necessary to conduct a radionuclide assessment of them. To do that, a sampling procedure should be prepared to obtain a representative sample from a spent filter. As for conducting a nuclide analysis for this representative sample, a corresponding spent filter can be determined as either a regulatory clearance waste or a radioactive waste.Copyright

Development of the Analysis Method for the Radioactivity Concentration Estimation of Soils for a Regulatory Clearance

In this study, for the analysis of a radioactivity concentration of soil, a sampling and an analyzing method were developed. To create homogeneity of the contents for each drum, big particles such as pebbles, rocks and scraps of concrete were removed after pouring the soil into a tray. And then the soil in the tray was mixed thoroughly. A 10 × 10 grid was used to partition the soil into 100 sections. 2 liter of soil was sampled out of 30 randomly pre-selected sections. Only 1 liter of the soil out of 2 liters was used for the γ-spectrometry analysis. The remaining 1 liter of soil was stored for a validation purpose. For a verification of the sampling process, 3 samples were taken from each drum and analyzed. 5 drums were used for the verification. And the results show that this sampling method has about a 9% sampling error. Also, the analysis results of the 865 drums of soil showed that the major nuclides in the soils were Co-60 and Cs-137 while a small amount of Mn-54, Fe-59, I-131, Cs-134 and Eu-152 were detected as γ-emitters. About 73% of the soils had a total radioactivity concentration below 0.1 Bq/g, while the soils with more than 0.4 Bq/g of a radioactivity concentration were only 3%. Based on the guide for the regulatory clearance criteria recommended by the IAEA (International Atomic Energy Agency), about 73% of the soils can be regulatory cleared without any treatment. Also, the remaining soils can be regulatory cleared after a further storage. Only 3% of the soils are considered to be necessary for a decontamination treatment. The results of this study can be applied to the treatment of radioactive soils generated in a large amount during the decommissioning of a nuclear facility.Copyright

Radioactive Analysis of a Spent HEPA Filter Using the Distribution Characteristics of the Captured Radionuclide

To investigate the species and the distribution of the captured nuclides in a HEPA filter, it was dismantled into a metal part and a filter medium part to obtain a filter medium. From the nuclide analysis results for a filter medium part through pre-treatment of it, it was possible to obtain three kinds of typical distributions in view of the distribution of the captured nuclides in the filter medium. When considering these distribution characteristics of the captured radionuclide, the region showing the high concentration of the captured nuclides was the intake or the outlet part of the HEPA filter. On the other side, the middle part generally represented a uniform distribution below the average concentration of the captured nuclides. Therefore, in the event of taking a representative sample of a HEPA filter at the intake and the outlet part, the results of a nuclide analysis for that sample could be estimated as existing in the range from 1.0 to 1.5 times the real concentration of the nuclides captured by a filter medium. As a result, to conduct a radionuclide assessment of a spent HEPA filter without a dismantlement of it, the analysis results for a representative sample taken from both the intake and the outlet part of a spent HEPA filter could be regarded as an average value for the corresponding HEPA filter.

Radiological Dose Assessment for a Regulatory Clearance of the Soil and Concrete Wastes at KAERI

At the KAERI, about 4,800 drums of radioactive contaminated soils and concretes wastes have been stored since their generation in 1988. As these wastes have been stored for more than 18 years, some of them can be regulatory cleared. Before such a regulatory clearance, the radiological characteristics of these wastes should be analyzed first. And based on the analysis result, radiological dose should be estimated to confirm the safety of a disposal of these cleared wastes. In this study, a working procedure for a representative sampling and analysis of the wastes was developed. According to the analysis result, Co-60 and Cs-137 were major radionuclides while some wastes were contaminated with Mn-54, Fe-59, I-131, Cs-134 or Eu-152 of an extremely low concentration. The analysis results show that about 75% of wastes have a radioactivity concentration below 0.1Bq/g and were considered for a clearance. It was assumed that radiation workers are exposed by the inhalation dose and the external dose. The radiological dose was estimated using the RESRAD code for the disposal workers and the management workers as 5.32µSv/yr and 3.13µSv/yr for an individual dose and 1.60E-4 man · Sv/yr and 3.13E-5 man · Sv/yr for a public dose, respectively.

Conditioning Operation by an Encapsulation and Shielding of Spent Sealed Radium Sources

In order to avoid accidents that could result from an improper storage of spent radium sources, it is necessary to condition and store them safely. The program for a safe conditioning of spent radium sources by the IAEA (International Atomic Energy Agency) has been established to assist the developing countries. The main object of this paper is to summarize the technology that was adapted by the IAEA for the conditioning of spent radium sources in the national inventory of Ra-226 sources in member states and the actions performed by the Korean expert team as a part of the IAEA’s project titled as ‘Radium Conditioning in Southeastern Asia’. The whole inventory of the spent radium sources of 8,671.13mCi was safely conditioned by the Korean expert team according to the guidelines under the supervision of the IAEA’s technical officer. The 1,821 sources of spent radium were encapsulated, welded, and conditioned into 18 concrete-shielded drums.Copyright