• Nuclear Engineering and Technology
• /
• v.40 no.6
• /
• pp.497-504
• /
• 2008

In a study of the optimum operational condition for a melting decontamination, the effects of the basicity, slag type and slag composition on the distribution of depleted uranium were investigated for radioactively contaminated metallic wastes of iron-based metals such as stainless steel (SUS 304L) in a direct current graphite arc furnace. Most of the depleted uranium was easily moved into the slag from the radioactive metal waste. The partitioning ratio of the depleted uranium was influenced by the amount of added slag former and the slag basicity. The composition of the slag former used to capture contaminants such as depleted uranium during the melt decontamination process generally consists of silica ($SiO_2$), calcium oxide (CaO) and aluminum oxide ($Al_2O_3$). Furthermore, calcium fluoride ($CaF_2$), magnesium oxide (MgO), and ferric oxide ($Fe_2O_3$) were added to increase the slag fluidity and oxidative potential. The partitioning ratio of the depleted uranium was increased as the amount of slag former was increased. Up to 97% of the depleted uranium was captured between the ingot phase and the slag phase. The partitioning ratio of the uranium was considerably dependent on the basicity and composition of the slag. The optimum condition for the removal of the depleted uranium was a basicity level of about 1.5. The partitioning ratio of uranium was high, exceeding $5.5{\times}10^3$. The slag formers containing calcium fluoride ($CaF_2$) and a high amount of silica proved to be more effective for a melt decontamination of stainless steel wastes contaminated with depleted uranium.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2002.09a
• /
• pp.207-209
• /
• 2002

A fraction of TRIGA contaminated soil whose decontamination is practicable by soil washing was about 34.2 %. It appeared from results of first decontamination experiment that decontamination efficiency using (NH$_4$)$_2$SO$_4$, H$_2$C$_2$O$_4$, and NaOH solution were high. Meanwhile, the most suitable ratio of contaminated soil mass(g) to decontamination solution volume(ml) appeared to be 1:10 according to experiment results. And the most suitable concentration of oxalic acid used as a decontamination solution appeared to be 0.5 M.

• Journal of the Korean institute of surface engineering
• /
• v.40 no.6
• /
• pp.271-278
• /
• 2007

In this study, applicable possibility in chemical decontamination for reactor coolant pump(RCP) was investigated for the various stainless steels. The stainless steel(STS) 304 showed the best electrochemical properties for corrosion current density and the lowest weight loss ratio in chemical decontamination process model 3-3 than other materials. The weightloss quantity in chemical decontamination process model 3-3 presents the lowest value compare to the other chemical decontamination process model 1, 2, 3-1 and 3-2. In the case of SEM observation, the pitting corrosion was generated in both STS 415 and STS 431 with the increasing numbers of cycle. The intergranular corrosion in STS 431 was sporadically observed. The sizes of their pitting corrosion were also increased with increasing cycle numbers.

• Corrosion Science and Technology
• /
• v.10 no.5
• /
• pp.167-174
• /
• 2011

Due to commercialization of nuclear power, most countries have taken interest in decontamination process of nuclear power plant and tried to develop a optimum process. Because open literature of the decontamination process are rare, it is hard to obtain skills on decontamination of foreign country and it is necessarily to develop proper chemical decontamination process system in Korea. In this study, applicable possibility in chemical decontamination for reactor coolant pump (RCP) was investigated for the various stainless steels. The stainless steel (STS) 304 showed the best electrochemical properties for corrosion resistance and the lowest weight loss ratio in chemical decontamination process with immersion type than other materials. However, the pitting corrosion was generated in both STS 415 and STS 431 with the increasing numbers of cycle. The intergranular corrosion in STS 431 was sporadically observed. The sizes of their pitting corrosion also increased with increasing cycle numbers.

• Korean Chemical Engineering Research
• /
• v.43 no.1
• /
• pp.33-38
• /
• 2005

The distribution of vanadium and iron ionic species in the presence of picolinate ligand has been simulated at various conditions with different pH values and compositions in the decontamination waste solution. In spite of variations of metal concentration in the decontamination solution, the shape of distribution diagrams were not changed greatly at both high (the molar ratio of picolinate to vanadium is 6) and low (the molar ratio is 3) LOMI decontamination conditions. However, in the solution of low-picolinate condition the shape of the distribution diagram of iron(II)-picolinate complexes was changed significantly. This phenomenon is attributed to the shortage of relative amount of picolinate ligand to iron existed in the solution, and originated from the difference in stability constants for complexes formed between vanadium(III) and iron(II) species with picolinate ligand. The distribution diagrams obtained in this study can be applied very usefully to the prediction or understanding the reaction phenomena occurred at various conditions in the course of the LOMI waste treatments such as an ion exchange operation.

• Nuclear Engineering and Technology
• /
• v.21 no.4
• /
• pp.321-331
• /
• 1989

A bench scale incineration process for the burnable radwaste has been constructed and operated at KAERI as a self-surpported development of incineration technology. The purposes of operating the process are to get experience in incineration, to analyze the characteristics of combustion and to test the performance of off-gas treatment units. Simulated paper and polyethylene wastes were incinerated. Volume reduction ratio and decontamination factor of the process have been determined to observe the economical efficiency and operational capability of the process. A methodology to estimate the acceptance limit of specific activity to an incineration facility by using a decontamination factor and to calculate the volume reduction ratio of the facility is introduced. The acceptance criteria for different radionuclides in the combustible waste at the bench scale incineration process are suggested using this methodology.

• Journal of the Korean institute of surface engineering
• /
• v.40 no.5
• /
• pp.234-240
• /
• 2007

As a reactor coolant pump (RCP) is operated in the nuclear power system for a long time, so its surface is continuously contaminated by radioactive scales. In order to maintain for RCP internals, a special chemical decontamination process should be used to reduce the radiation from the RCP surface. In this study, applicable possibility in chemical decontamination for RCP was investigated for the various stainless steels. The stainless steel (STS) 304 showed the best electrochemical properties for corrosion resistance and the lowest weight loss ratio in chemical decontamination process model 3-1 than other materials. However, the pitting corrosion was generated in both STS 415 and STS 431 with the increasing numbers of cycle. The intergranular corrosion in STS 415 was sporadically observed. The sizes of their pitting corrosion were also increased with increasing cycle numbers.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.2 no.4
• /
• pp.245-251
• /
• 2004

Soil washing equipment was developed for decontamination of radioactively contaminated soil generated during normal operation or decommissioning and verification experiments were performed. Decontamination effciency above $80{\%}$ was achieved. In case of low radiation level and large particle size, decontamination efficiency was higher. According to the ratio of volume of water to soil quantity, decontamination efficiency was higher in case of high radiation level. Re-decontamination using decontaminated soil was effective in case of small particles. Using soil washing equipment, radioactivity of contaminated soil generated in nuclear power plant can be decreased and volume of soil for disposal can be decreased. And this equipment can be used in decommissioning.

• Membrane Journal
• /
• v.26 no.5
• /
• pp.401-406
• /
• 2016

In this study, we have investigated the removal of the low level radioactive ions of Cs and I in water by the reverse osmosis (RO) process. The two RO modules produced in domestic region and the waste RO module after the cleaning process were selected. Then we compared removal performance of both Cs and I. The experiments are conducted by varying the concentration of feed, the pressure. As a results, it was confirmed that all three modules are higher I decontamination factor than Cs. And particularly, for the cleaned RO module, its decontamination factor of I was 1140. Since the results at low pressure condition were better than that at high pressure conditions, the use of the direct installation of RO modules on the tap water might be possible. In addition, it was confirmed that the waste RO module after cleaning process using EDTA, SBS and NaOH, increased the decontamination performance better than before cleaning, in particular, the recovery ratio after cleaning was 6.3% higher.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.12 no.4 s.27
• /
• pp.253-259
• /
• 2006

This paper investigated on anti-corrosion characteristic in chemical decontamination at extremely severe condition{process model-2) of stainless steels used with reactor coolant pump. The electrochemical properties of stainless steel{STS) 304 with the lapse qf cycle is better than those of STS 415 and STS 431. The STS 304 in process model-1 and process model-2 present the lowest weightloss ratio. The experiment results for STS 304, STS 415, and STS 431 in process model-2 solution, it was ascertained that weightloss ratio of process model-2 solution for process model-1 solution show 2..908, 2.572, and 2.370 times, respectively. The reason suggests that process model-2 is higher concentration of chemical and temperature compare to process model-1.