Wolsong Tritium Removal Facility Research Articles

Tritium Distribution in the Low-Level and Intermediate-Level Wastes of a Korean CANDU Reactor

Korea Hydro & Nuclear Power Company, Ltd., has operated the Wolsong Tritium Removal Facility (WTRF) since 2007 to reduce tritium concentrations in the moderator and coolant of the Wolsong nuclear power plant. As a result of the WTRF operation, the concentration of tritium in the moderator and coolant significantly decreased from 2320 to 9.3 GBq/kg. In particular, the tritium concentrations of the radioactive waste directly affected by radioactivity in the moderator and coolant were reduced by up to 99% during the WTRF operation. For this purpose, a chemical separation and quantification method for tritium separation was developed, and its average recovery yield was 98%.

Tritium Research and Development Status at KAERI

Korea has 26 nuclear power plants (NPPs). Out of these 26 plants, 4 are Canada Deuterium Uranium (CANDU) reactors at the Wolsong nuclear power site. In CANDU reactors, deuterium oxide is used as a moderator/coolant, and tritium is produced whenever a deuterium oxide nucleus captures a neutron. The Wolsong Tritium Removal Facility was designed to remove tritium generated in CANDU reactors. We are introducing tritium environmental protection not only at the Wolsong NPP but also at the High-Flux Advanced Neutron Application Reactor (HANARO) and in high-temperature gas-cooled reactors (HTGRs). We present a tritium behavior analysis code and assess the concentration of tritium in combustible dry active waste. Advanced techniques are introduced to transfer tritium from tritiated water to the gaseous phase. In addition, research on the nuclear fusion tritium storage and delivery system, which is part of the fuel cycle, has been carried out. In this paper, we present the recent progress in the effort to develop tritium systems at the Korea Atomic Energy Research Institute.

Development of Tritium Technologies at KAERI

Tritium is formed by neutrons captured from deuterium. If left to accumulate, tritium oxide will become a hazard to the operating staff and public. The primary purpose of a Tritium Removal Facility (TRF) is to reduce tritium concentration in a heavy water moderator. In Korea, operation of a TRF commenced at the Wolsong Nuclear Power Site on July 26th, 2007. Nowadays, KAERI is developing a Very High Temperature Gas Cooled Reactor (VHTR). We have developed a tritium behavior analysis code for the VHTR. We also developed analytical methods for the measurement of food stuffs. Korea shared in the construction of the ITER fuel cycle plant with the EU, Japan, and the US, and is responsible for the supply of an SDS (Tritium Storage and Delivery System). We present the recent progress in the development of tritium storage technology, and safety features of the related system. KAERI has been developing tritium technologies related to the Wolsong TRF, HANARO, VHTR, and nuclear fusion fuel systems. We thus present details on the recent development progress of these tritium systems.

Tritium Research Activities in KAERI

Korea has twenty nuclear power plants and a nuclear research reactor in operation. Out of the twenty plants, four are CANDU reactors at the Wolsong Nuclear Power Site. In the CANDU reactors, deuterium (heavy water) is used as a moderator and as the primary heat transport from the nuclear fuel. The nuclear research reactor, HANARO, in KAERI (Korea Atomic Energy Research Institute) uses heavy water as a neutron reflector. Tritium is formed by a neutron capture from the deuterium. If left to accumulate, tritium oxide would become a hazard to the operating staff and public. The primary purpose of a Tritium Removal Facility (TRF) is to reduce tritium concentration in a heavy water moderator. Operation of a TRF commenced at the Wolsong Nuclear Power Site on July 26th, 2007. Korea shared in the construction of the ITER fuel cycle plant with the EU, Japan, and US, and is responsible for the supply of an SDS (Tritium Storage and Delivery System). KAERI has been developing tritium technologies related to the Wolsong TRF, HANARO, and nuclear fusion fuel systems. We thus present details on the recent development status of the tritium systems.

Test of a Large-Volume Calorimeter in KEPRI Tritium Laboratory

A tritium assaying and dispensing system has been designed and is being constructed in KEPTL (Korea Electric Power Research Institute, Tritium Laboratory). This facility will be used to supply tritium from WTRF (Wolsong Tritium Removal Facility) to customers for industrial uses, R&D application, ITER operation and other purposes. In order to account the tritium amount loaded in and out this facility, KEPTL purchased a large volume calorimeter from Setaram. This calorimeter is integrated in a dedicated room of the KEPTL in 2008 and the site acceptance tests are completed. The KEPTL calorimeter is a twin cell type and its measuring range is from 0.01 gram of tritium to 60 gram of tritium. The tritium storage beds loaded into the measuring cell of the calorimeter reach a maximum size of 200 mm in diameter and 570 mm in height. The performance test has been successfully completed with a Joule effect cell simulating tritium decay heat. It is demonstrated that the precision of the calorimeter is measured to be less than 0.28% at 50 mW and 0.13% at 10W. Relative error on real tritium test is measured to be 0.06% on 37 TBq of tritium.

Development of nuclear micro-battery with solid tritium source

A micro-battery powered by tritium is being developed to utilize tritium produced from the Wolsong Tritium Removal Facility. The 3D p–n junction device has been designed and fabricated for energy conversion. Titanium tritide is adopted to increase tritium density and safety. Sub micron films or nano-powders of titanium tritide is applied on silicon semiconductor device to reduce the self absorption of beta rays. Until now protium has been used instead of tritium for safety. Hydrogen was absorbed up to atomic ratio of ∼1.3 and ∼1.7 in titanium powders and films, respectively.

Tritium production, recovery and application in Korea

Four CANDU reactors have been operating at the site of Wolsong Nuclear Power Generation in Korea. The Wolsong tritium removal facility was constructed to reduce the tritium levels in heavy water systems. This facility was designed to process 100 kg/h of tritiated heavy water feed and to produce 99% pure T 2. This recovered tritium will be made available for commercial applications. The initial phases on the tritium applications are made to establish the infrastructure and the tritium controls.

Estimation of Tritium and Helium Inventory in the Tritium Handling System in Korea

In Korea, the Wolsong Tritium Removal Facility (WTRF) is under construction to reduce the amount of tritium present in the moderator and coolant of the CANDU type Wolsong nuclear power plants. Recently, a study on the tritium handling system for recovery of the tritium collected from the WTRF was started. Some tritium would enter the steel of the container walls and subsequently decay to helium. This helium can deteriorate the mechanical properties of the material of the tritium handling system. To evaluate the tritium and helium inventory in the stainless steel wall of this system, the time-dependent diffusion equation was developed, solved and the results are presented in this paper. These results were compared to previous work that evaluated the tritium inventory in the stainless steel wall of 50-L tritium containers. Tritium and helium concentration profiles and the corresponding inventories were evaluated with respect to the various parameters such as exposure time, temperature, and partial pressure. After 24 years, the helium inventory in the wall of the tritium handling system exceeds the tritium inventory.

Installation of liquid phase catalytic exchange columns for the Wolsong tritium removal facility

The catalyst loading and installation of liquid phase catalytic exchange (LPCE) columns for the Wolsong tritium removal facility (WTRF) was completed on the 22nd of April 2006. Two LPCE columns are connected in series. The first column has 28 sections, a sump and a separate overhead condenser. The second column has 27 sections, a sump and a humidifier. Each section of the LPCE columns consists of three parts: mass transfer packing bed, separate catalyst bed and liquid distributor. The Sulzer CY packing for the vapor–liquid mass transfer is packed into the inner shell of each section and the wet proofed catalyst for the vapor–gas reaction is loaded into between the inner and outer shell. The liquid distributors are equipped on the Sulzer CY packing of each section. The performance test will be accomplished according to the WTRF construction and commissioning schedule. The WTRF is the first commercial facility applying LPCE process for the tritium removal. The WTRF is expected to remove 7 MCi-tritium per year at least from the Wolsong CANDU6 reactors and will be a main tritium source for the ITER.

The performance of a trickle-bed reactor packed with a Pt/SDBC catalyst mixture for the CECE process

The combined electrolysis and catalytic exchange (CECE) process with a hydrophobic catalyst is a very effective method to remove small quantities of tritium from light or heavy wastewater streams because of its high separation factor and mild operating conditions. A hydrophobic platinum/styrene-divinyl benzene copolymer (Pt/SDBC) catalyst which was developed for the liquid-phase catalytic exchange (LPCE) column of the Wolsong tritium removal facility (WTRF) has been tested in a trickle bed reactor for the design of the CECE process. An experimental apparatus has been built for the testing of the catalyst at various temperatures and gas velocities. The catalyst column was packed with a mixture of a hydrophobic catalyst and a hydrophilic packing (Dixon gauze ring) to improve the liquid distribution and vapor/liquid transfer area. Many tests have been carried out at Korea Atomic Energy Research Institute (KAERI) to measure the activity of the catalyst, K y a (1 s −1), under various operating conditions. K y a increases with the hydrogen flow rates in the range of 0.4–1.6 m s −1 at STP. The height of the catalyst column was determined from these K y a values according to the reaction temperatures and hydrogen flow rates.

Deactivation of Hydrophobic Pt/SDBC Catalyst in the WTRF LPCE Column for Tritium Separation

The styrene divinylbenzene copolymer (SDBC) supported platinum catalyst and the liquid phase catalytic exchange (LPCE) column have been developed to be applicable to the Wolsong tritium removal facility (WTRF) in Korea. The catalyst deactivation subject to both reversible uniform poisoning and permanent loss by impurity poisoning was investigated using a time-on-stream theory and a simplified shell progressive poisoning scenario in special case of higher internal diffusion resistance. Experimental data from fixed bed reactors with the Pt/SDBC catalysts have been used to establish the deactivation model and to estimate key parameters to be used in the WTRF LPCE column design. It was found that an impurity control in the streams would be critical to the WTRF LPCE column operation since the impurity poisoning played a very important role in the overall catalytic exchange reaction. Except for the case of the severe impurity poisoning of the whole catalysts, the LPCE column can be in operation over 10 years without any regeneration of the catalysts.

Deactivation of Hydrophobic Pt/SDBC Catalyst in the WTRF LPCE Column for Tritium Separation

The styrene divinylbenzene copolymer (SDBC) supported platinum catalyst and the liquid phase catalytic exchange (LPCE) column have been developed to be applicable to the Wolsong tritium removal facility (WTRF) in Korea. The catalyst deactivation subject to both reversible uniform poisoning and permanent loss by impurity poisoning was investigated using a time-on-stream theory and a simplified shell progressive poisoning scenario in special case of higher internal diffusion resistance. Experimental data from fixed bed reactors with the Pt/SDBC catalysts have been used to establish the deactivation model and to estimate key parameters to be used in the WTRF LPCE column design. It was found that an impurity control in the streams would be critical to the WTRF LPCE column operation since the impurity poisoning played a very important role in the overall catalytic exchange reaction. Except for the case of the severe impurity poisoning of the whole catalysts, the LPCE column can be in operation over 10 years wi...

Manufacturing process of self-luminous glass tube utilizing tritium gas: Optimization of phosphor coating conditions

Domestic research utilizing tritium will become more attractive when tritium is produced from the Wolsong Tritium Removal Facility (WTRF) in Korea, which will start to operate in late 2005. As starting domestic tritium technology research, this study is focused on the mass production of commercially available self-luminous glass tubes (SLGTs) and the design of a new product by simulation. With a low power microscope, SEM-EDX, ICP (Inductively Coupled Plasma) spectrometer, some commercially available SLGTs have been investigated. The inner side of the glass tubes was coated with greenish ZnS phosphor particles with sizes varying from 4–5 Μm, and Cu and Al as an activator and a co-dopant, respectively. Besides, the coating thickness is different for each product. and the thickness range of the products to be considered is 10–100 μm. With the phosphor, a binder package was also selected to meet optimal coating conditions. Cathodoluminescence (CL) device (energy: 0–10 keV, electron flux: nA) was used to simulate β-ray emitted from tritium. From the CL measurement the optimal conditions were 580–600 °C and 30 minutes. At these conditions the degradation of the phosphor by a heat is minimized. We determined all the coating conditions including the phosphor, binder package, coating thickness, and calcinating temperature for the production of SLGTs. Now we are testing our pilot-scale coating device for a mass production with selected experimental conditions

Assessment of the Environmental Impact of Tritium Release from Wolsong Tritium Removal Facility at the Postulated Accident

In Korea, Wolsong Tritium Removal Facility (WTRF) is scheduled to begin operation in 2005 to reduce the amount of tritium generated in the moderator and coolant. The objective of this study is to evaluate the environmental impact of tritium released from WTRF in the postulated accident. In order to achieve this, a computer code was developed at KAIST (Korea Advanced Institute of Science and Technology). This code can be used to evaluate the individual and public dose with the source term. This source term can represent not only the concentration of tritium that will be stored at the long term tritium storage vault located in the underground of WTRF building but also may be released to the environment from the WTRF online system by variously postulated accidents. To validate this code, calculated results were compared with the previous reference under the same assumption. Even if the most severe postulated accident that the tritium may be released through the fracture of the storage vault was occurred, the result of individual dose at the exclusion area boundary is turned out to be within the radiation dose limit.

Performance of 500kCi Tritium Storage Vessel for WTRF

A prototype TSV (Tritide Storage Vessel) has been manufactured for the long-term storage of tritium of the WTRF (Wolsong Tritium Removal Facility). A performance test was carried out to demonstrate that the TSV could hold a minimum of 500kCi of tritium. This experiment was conducted by a batch type hydriding reaction. Hydrogen gas equivalent to 50kCi of tritium was reacted with the titanium sponge in a batch reaction. Experimental results for 10 batches show that the TSV has enough capacity to store 500kCi of tritium.

Tritium Activities in Korea

ABSTRACTAn overview of the tritium related research and activities presently undertaken in Korea is presented. These activities encompass the Wolsong Tritium Removal Facility (WTRF) in KHNP, isotope separation, storage and biology in KAERI, KEPRI and KAIST. The design status of the WTRF that serves four CANDU reactors is described. It is made up of three parts; liquid phase catalytic exchange (LPCE), cryogenic distillation, and metal hydride storage. Results from the technological R&D of tritium processing for the WTRF and biology are summarized.