A dissertation submitted to the Department of Physics, University of Surrey, in partial fulfilment of the degree of Master of Science in Radiation and Environmental Protection
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- Figure 1 [33]
- Figure 2 Vanguard- Class Nuclear Submarines
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- Problems with Treating Chelated Ion Resins
- F acts About Carbon-14
- H istorical Management of Resins
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Option Study for Resin Treatment and Disposal at Devonport by Nikki Green A dissertation submitted to the Department of Physics, University of Surrey, in partial fulfilment of the degree of Master of Science in Radiation and Environmental Protection Department of Physics Faculty of Electronics & Physical Sciences University of Surrey
© Nikki Green 2009 Abstract Many methods of treating radioactive waste have moved back and forth for years. Some methods are more favourable than others, but cost vast sums of money, and not every country is able to give that type of support. Government backing is very difficult to obtain and the issue of processing waste is also very contentious with the public. Naturally occurring radiation is of constant presence within the atmosphere and the Nuclear Installations Inspectorate (NII), Radioactive Substances Act (RSA) and Environment Agency (EA) all work together to ensure that radioactive releases to the environment are very carefully controlled and do not vastly increase existing levels. Decommissioning strategies are being drawn up all over the world and many countries are very advanced on their plans, favouring, in many cases, deep geological repositories where the waste can be recovered at a later date in order to be processed in a more environmentally acceptable and efficient way. There are however, many other alternative options and this project looks at a few of them. Each nuclear facility has limits on the amount of radioactive waste it is able to process annually. There is a major push towards volume reduction and pressures are being put on the Nuclear Industry to meet ever tighter restrictions. Finding a solution which satisfies all criteria will be no easy task.
P. Jarvis (Supervisor) Babcock Marine (Safety Case Project Manager) A. Harper Babcock Marine (Radioactive Waste Plant Manager) M. Clarke Babcock Marine (Health Physicist) M. Leisvik Babcock Marine (Senior Safety Engineer) R. Collison Babcock Marine (Health Physics Advisor) P. Coleman Babcock Marine (Health Physics Foreman) S.Tucker Babcock Marine (Health Physicist) M.Smith Babcock Marine (NUB Manager) P. Lant Babcock Marine (Business Quality Manager) S. Cadmore Babcock Marine (Senior Design Engineer) Table of Contents
Abbreviations
Aim The aim of this project is to determine a solution for the treatment of resins at Devonport. Objectives
Introduction Her Majesty’s Naval Base (HMNB) Devonport, is one of 3 UK operating bases for the Royal Navy. (The other two are HMNB Clyde and HMNB Portsmouth). It is the largest naval base in Western Europe and is the only nuclear repair and refuelling facility in the Royal Navy. The Devonport dockyard is owned and operated by Babcock International group, Marine Division (BM), who took over ownership in 2007. The Dockyard consists of 14 dry docks, 4 miles of waterfront, 25 tidal berths, 5 basins and an area of 650 acres. Devonport is the base for 7 Trafalgar class nuclear powered hunter killer submarines and the main refitting base for all Royal Navy nuclear submarines. Devonport also serves as headquarters for Flag Officer Sea Training, which is responsible for the training of all the ships of the Navy and Royal Fleet Auxiliary, along with many foreign naval services. [15] The Pressurised Water Reactor used in Nuclear Submarines 
Figure 1 [33] Naval Pressurised water reactors comprise a Primary and Secondary coolant system. The primary system circulates water in a closed loop, under pressure to keep it from boiling. Water passes through the steam generator, losing its heat to generate steam in the secondary system. The water then flows back to the reactor to be heated again. Inside the steam generator, heat energy is transferred across a watertight boundary to the secondary system, which is also a closed loop. The unpressurised water in the secondary system turns to steam when heated. The steam then flows through the secondary system to propel the turbines, turning the propellers, and to the turbine generators which supply electricity. As it cools, it condenses to water and is pumped back to the steam generator. [33] Pressurised Water Reactor (PWR 1) The first British naval reactor, the PWR 1, went critical in 1965. There were 3 sets of cores used; Core 1 2x Valiant Class boats 4x Resolution Class Core 2 3x Churchill Class boats
7x Trafalgar Class boats PWR 2 The latest nuclear reactor design to power the Royal Navy’s submarines. The PWR 2 was developed for the Vanguard Class Trident Missile submarines and is a development of the PWR 1. The first PWR 2 reactor was completed in 1985 with testing beginning in August 1987. The latest design of the PWR 2 is the ‘core-h’, which removes the need for refuelling and eliminates the need for two reactor refits in its service lifetime. The Astute Class submarines will have the full-life core installed initially, whereas HMS Vanguard and her 3 sister boats will be fitted with the new core during refit. The resins used on-board the submarines control the level of radionuclides within the primary circuit water and keep them to specified levels. These resins become contaminated with 3H, 14C and 60Co. After berthing, the submarines discharge their spent resin. The 3H arises in the primary coolant by neutron activation of 6Li released from the on board resin. Li is used for pH control. 3H levels depend on the proportion of 6Li in the resin compared with inert 7Li, as well as the submarine power history. 14C is mainly produced through neutron activation of 17O in the circulating water. A smaller amount of 14C arises from the activation of 14N dissolved in water and 13C in steels. 60Co arises from activation of corrosion products from the primary circuit components posing an external radiation hazard to MoD staff and Dockyard personnel. [9] On-shore arisings from PWR1 systems come from the primary circuit decontamination prior to refuelling. The circuit water is treated using chelating agents, removing into solution a significant fraction of radionuclides that deposit on the internal surfaces of the primary circuit. 60Co is significantly reduced, enabling Dockyard personnel to refit and refuel in levels justified as As Low As Reasonably Practicable (ALARP). At the end of the treatment phase, the circulating water is passed through ion exchange resins within the plant, removing most of the radionuclides that have been brought into solution by the chelating agents, along with those originally in solution. Due to the problems caused by chelating agents, special approval has been granted by the EA for contaminated spent resins to be subjected to a wet oxidation process at Winfrith, the ModulOx process. This process destroys the chelating agents within the resins, and allows the product to be appropriately encapsulated and disposed of. [9] The Primary Circuit resins contain relatively high levels of radionuclides and are chemically contaminated. They require pre-treatment at Winfrith before final disposal at LLWR Drigg. Boronated resins arise from the ACRC plant to ensure solidification of cement. Spent resins arising from the PWR1 and ACRC plant are radioactively contaminated but relatively free of chemical contamination. The most significant chemical compounds comprise the chelating agents used in the PCD processes, PWR1 and PWR2, along with the relatively high levels of boron in the ACRC plants using boron. 
Figure 2 Vanguard- Class Nuclear Submarines The Devonport Nuclear Licensed Site  
N008 Area 
9 Dock 
8 Dock 
Transport Area 
Scrap Pound Figure 3 Ion Exchange Resins Ion Exchange Resins are used for a number of reasons; ~ To limit levels of γ-emitting radionuclides (60Co) within the primary circuit water during submarine operation. ~ To remove radionuclides from effluent produced during decontamination of internal surfaces of submarine primary circuit, undertaken prior to refitting and refuelling. ~ To remove radionuclides from low level effluent prior to discharge from DRDL to the Hamoaze. (The Hamoaze is an estuarine stretch of water at the point where the tidal River Tamar, the River Tavy, and the River Lynher meet, prior to entering Plymouth Sound). The Hamoaze flows past Devonport Dockyard and is owned by the Royal Navy. Reducing radionuclide levels in the primary circuit water reduces radiation doses to Ministry of Defence (MoD) personnel during operation significantly, whereas removing most of the dissolved radionuclides from liquid effluent keeps doses to members of the public from discharges to levels that are As Low As Reasonably Practicable (ALARP). Ion exchange resins are used to remove soluble radioactive materials during the clean-up of liquid effluents. When the capacity of these resins is exhausted, the resins become solid waste. The sources of resin waste at Devonport are as follows;
The resins used by DRDL are a mixed bed which have been used to absorb different metals in both chelated and ion exchanged forms. The spent resin wastes contain significant amounts of 14C, 3H, 55Fe, 60Co, 53Ni and a minor amount of Cs. The chelating agents are a problem as they solubilise and mobilise actinides, such as plutonium, curium or neptunium (which are all fissionable) if they are free and then proceed to migrate through the aqueous environment, which causes an obvious problem in terms of waste disposal. All of the resins used at DRDL are organic in origin and some, especially those used to treat water used in shore-based management of some systems, will contain boron compounds. These can be treated chemically to facilitate the setting of grout currently used as a conditioning method for spent resins prior to disposal. Current Treatment Method for Resins at Devonport 
Figure 4
Figure 4 shows both current and potential future treatment methods. Problems with Treating Chelated Ion Resins Oxidation of carbonaceous material to release 14C to the atmosphere as 14CO2 is necessary in order to reduce the activity levels to Low Level Waste (LLW). It is unclear as to the residence of 14C in the matrix of the material, so all of the organic material must be destroyed. An ash is left behind after oxidisation and although there should not be any 14C left, some activity could remain in metallic form which would need to be encapsulated before final disposal at Low Level Waste Repository (LLWR) (Drigg). There are obvious considerations of secondary waste arisings which need to be planned for. Some processes are more effective at destroying organic material than others and also differ in the amount of further treatment required. F  acts About Carbon-14 Figure 5 [10] [23]
  
  
 
  
 
   
  
  
H  istorical Management of Resins
Waste disposal from Devonport Site has constantly been well below the authorised limits. But, annual volume of Very Low Level Waste (VLLW) disposal from Devonport between 2005 and 2008 has typically been in the order of 75-90% of the authorised limit. A clearance and exemption route for this type of waste would reduce the VLLW arisings by ~60%.[3] Production of all waste streams from all establishments must be reduced and minimised. Waste is managed by the waste hierarchy;
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