Darlington Tritium Removal Facility Research Articles

Tritium Emissions from a Detritiation Facility

Tritium is produced in heavy-water reactors through neutron capture by the deuterium atom. Annual production of tritium in a CANDU reactor is typically 52-74 TBq/MW(e). Some CANDU reactor operators have implemented detritiation technology to reduce both tritium emissions and dose to workers and the public from reactor operations. However, tritium removal facilities also have the potential to emit both elemental tritium and tritiated water vapor during operation. Authorized releases to the environment, in Canada, are governed by Derived Release Limits (DRLs). DRLs represent an estimate of a release that could result in a dose of 1 mSv to an exposed member of the public. For the Darlington Nuclear Generating Station, the DRLs for airborne elemental tritium and tritiated water emissions are ∼15.6 PBq/week and ∼825 TBq/week respectively. The actual tritium emissions from Darlington Tritium Removal Facility (DTRF) are below 0.1% of the DRL for elemental tritium and below 0.2% of the DRL for tritiated water vapor. As part of an ongoing effort to further reduce tritium emissions from the DTRF, we have undertaken a review and assessment of the systems design, operating performance, and tritium control methods in effect at the DTRF on tritium emissions. This paper discusses the results of this study.

Darlington Tritium Removal Facility and Station Upgrading Plant Dynamic Process Simulation

Ontario Power Generation Nuclear (OPGN) has a 4 x 880 MWe CANDU nuclear station at its Darlington Nuclear Division located in Bowmanville. The station has been operating a Tritium Removal Facility (TRF) and a D2O station Upgrading Plant (SUP) since 1989. Both facilities were designed with a Distributed Control System (DCS) and programmable logic controllers (PLC) for process control. This control system was replaced with a DCS only, in 1998. A dynamic plant simulator was developed for the Darlington TRF (DTRF) and the SUP, as part of the computer control system replacement. The simulator was used to test the new software, required to eliminate the PLCs. The simulator is now used for operator training and testing of process control software changes prior to field installation. Dynamic simulation will be essential for the ITER isotope separation system, where the process is more dynamic than the relatively steady-state DTRF process. This paper describes the development and application of the DTRF and SUP dynamic simulator, its benefits, architecture, and the operational experience with the simulator

Tritium Emission Reduction at Darlington Tritium Removal Facility Using a Bubbler System

Ontario Power Generation Nuclear (OPGN) has a 4 x 880 MWe CANDU nuclear station at its Darlington Nuclear Division located in Bowmanville. The station operates a Tritium Removal Facility (TRF) to reduce and maintain low tritium levels in the Moderator and Heat Transport heavy water systems of Ontario’s CANDU fleet by extracting, concentrating, immobilizing and storing as a metal tritide. Minimizing tritium releases to the environment is of paramount importance to ensure that dose to the public is as low as reasonably achievable (ALARA) and to maintain credibility with the Public. Tritium is removed from the Cryogenic Distillation System to the Tritium Immobilization System (TIS) glove box via a transfer line that is protected by a rupture disc and relief valve. An overpressure event in 2003 had caused the rupture disc to blow, resulting in the release of a significant quantity of elemental tritium into the relief valve discharge line, which ties into the contaminated exhaust system.As a result of a few similar events occurring over a number of years of TRF operation, the released elemental tritium would have been converted to tritium oxide in the presence of a stagnant moist air environment in the stainless steel discharge line. A significant amount of tritium oxide hold-up in the discharge line was anticipated. To minimize any further releases to the environment, a Bubbler System was designed to remove and recover the tritium from the discharge line.This paper summarizes the results of several Bubbler recovery runs that were made over a period of a month. Approximately 3500 Ci of tritium oxide and 230 Ci of elemental tritium were removed and collected. The tritium contained in the water produced from the Bubbler system was later safely recovered in the station’s downgraded D2O clean-up and recovery system.

Characterization of Tritiated Hydrocarbon Species and Measurement of Their Concentrations in Air during Vacuum Pump Maintenance

When organic materials are exposed to elemental tritium, the hydrocarbons incorporate the tritium as a result of radiation induced reactions. The use of oil based vacuum pumps in tritium service gives rise to waste oil which contains, in addition to significant amounts of dissolved HT and HTO, a complex mixture of dissolved hydrocarbon species with a wide range of volatilities. The behavior of these species in the human body is not as well understood, and consequently, reliable dosimetry models only exist for the two most common tritiated species, HT and HTO. A quantitative radio-gas chromatography technique was developed to analyse the head space above waste vacuum pump oils. The technique was then applied at the Darlington Tritium Removal Facility (TRF) to assess the tritium exposure to personnel changing the oil from one of the high tritium cold boxes. 7 refs., 2 figs., 2 tabs.

UV/Ozone Treatment to Decontaminate Tritium Contaminated Surfaces

Tritium contamination on surfaces is often encountered during operation and maintenance of equipment at the Darlington Tritium Removal Facility and likely at other tritium handling facilities. The use of efficient decontamination techniques that produce little or no secondary wastes is desirable. At Ontario Hydro Technologies (OHT) we have been developing a process utilizing a combination of ultraviolet (UV) radiation and ozone gas to remove tritium surface contamination from materials often used in tritium service. This paper summarizes the performance of the technique. The results are encouraging because the technique is very effective, simple in terms of equipment requirements and concentrates tritium in an easily managed waste form. 7 refs., 3 figs., 2 tabs.

Tritium Environmental Source Terms for the Effluents of ITER Water Systems

An analysis of the heat transport and water detritiation systems of ITER has been performed in order to determine major pathways for tritium loss and estimate releases during normal operation (operational tritium release). Heavy water escape and tritium release estimates compiled on the basis of operating experiences of typical CANDU PWR and the Darlington Tritium Removal Facility (DTRF) have been appropriately scaled on the basis of water and tritium inventories and tritium concentrations to fit ITER design and operating conditions. The paper estimates the chronic and acute tritium releases to the environment in elemental and oxide forms, via waterborne and airborne pathways of the ITER water systems. The results of the analysis will be used to demonstrate that the ITER design will meet the dose limits for occupational and accidental tritium releases. 5 refs., 5 tabs.

Operating Experience with Tritium Accounting and Analysis Systems in Our Tritium-Handling Facilities

An integral part of the operation of a tritium-handling facility is the need to maintain a tritium accounting system which meets both operational and regulatory requirements. The Darlington Tritium Removal Facility processes heavy water to remove tritium for storage or sale. The Chalk River Tritium Laboratory is a general-purpose experimental facility, handling various quantities and specific activities of tritium in separate systems, including re-packaging of tritium from large metal-getter storage beds to smaller aliquots. Tritium accounting procedures, analytical techniques and operational experience gained to date in the operation of these tritium-handling facilities are described.

The derived emission limit for tritiated hydrogen gas from the Darlington Tritium Removal Facility

The derivation of the emission limit for tritiated hydrogen gas (HT) from Tritium Removal Facility is described using the model CEDM-HT. This compartment model assumes equilibrium between HT in air and tritium oxide (HTO) in the soil resulting from HT oxidation by soil bacteria. Subsequent transfer of this HTO occurs to air and food, resulting in dose to people. The factors taken into account in determining the critical group and the dose and emission limit calculations are described. The consumption of local-grown fruits and root vegetables was found to be potentially the major contributor to adult dose resulting from HT emissions. For young children, milk consumption is also potentially significant.

Development of Organic Tritium Light Technology at Ontario Hydro

Tritium is a by-product of CANDU heavy water reactor operations and is the major contributor to internal dose for plant workers. The Darlington Tritium Removal Facility (DTRF) is decontaminating heavy water by removing tritium and storing it as a metal hydride. In view of the large tritium separation capacity, (24 MCi/a, 888 PBq/a). This paper reports that Ontario Hydro is interested in pursuing markets for the peaceful uses of tritium. One of these peaceful uses is in self-luminous lighting. The state of the art at present is a phosphor coated tube filled with tritium gas. However, safety considerations have restricted the use of these lights to outdoor or essential safety applications. Binding the tritium to a solid non-volatile matrix would increase the safety of tritium lights and allow the use of other phosphors, matrices and construction geometries. Solid, organic based tritium lights were produced using two different polymer matrices. While both these materials produced visible light, the intensity was low and radiolytic damage to the polymers was evident.

Fusion technology experience at Ontario Hydro's Darlington Tritium Removal Facility and heavy water upgraders

Ontario Hydro has nine operating heavy water upgraders and has constructed the world's largest tritium removal facility, with a design removal capacity of 24 MCi/yr. The extensive experience obtained in the construction, commissioning and operation of these facilities is very relevant to systems in the fuel cycle of a DT burning fusion reactor. This paper primarily summarizes the experience obtained during construction, commissioning and early operation of the tritium removal facility. In addition, relevance of experience gained in successfully operating heavy water upgraders is indicated.

Commissioning and First Operating Experience at Darlington Tritium Removal Facility

Ontario Hydro’s Tritium Removal Facility (DTRF) is presently in its early operating phase. The DTRF was built in order to reduce the average dose rate per worker and tritium emissions in all of Ont...

FLOSHEET - A Computer Program for Simulating Hydrogen Isotope Separation Systems

Ontario Hydro has developed a computer program called FLOSHEET for simulation of hydrogen isotope and fusion fuel processing systems. The development of the program was initiated to provide support for the commissioning and operation of the Darlington Tritium Removal Facility (DTRF) at Ontario Hydro’s Nuclear Generating Station A. The program has also proven useful in simulating tritium systems in fusion applications. FLOSHEET has been developed as a general purpose simulator which can be used to simulate many different types of processes and process flowsheets. This paper describes the FLOSHEET process simulator and its application to the DTRF and fusion reactor tritium systems.