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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- RSV Number C-14 Solid C-14 Liquid H-3 Solid
- Appendix 1 Chemical Treatment Processes Cold Wet Oxidation
- Low Temperature Plasma Ashing
- High Temperature Plasma Destruction
- Thermo-Chemical Treatment
- Appendix 2 Long Term Aerial Dose Release Ratios (LADRR)
- Appendix 3 Radionuclide Data and Radiobiological Information
Table 6 Table 6 shows the dose rates calculated by Microshield. The build-up factor is assumed to be within the source and the program is able to re-create the dimensions of the RSV and automatically calculate the dose rate given the activity, which is different for each RSV.
Table 7 Table 7 shows the difference in total radionuclide activity when a HEPA filter is used. HEPA filters remove 99.99% of radionuclide content and so the total radionuclide content for all 20 RSV’s is shown along with the HEPA filter totals. 
Figure 14 Figure 16 is a cost comparison and highlights the fact that maintenance on the resins which are currently stored at Devonport are costing double the amount of money compared with the other two prospective options.
Figure 15
Figure 16 The figures used in this project are current with the resins in storage now, but the activities will change according to half-lives etc. There may be up to a 20% error margin on these resins but this is a best estimate. The figures have been used to calculate the approximate doses that exist and could therefore be scaled accordingly when quantities are known should any additional facilities be put in place. The figures prove that the doses to operators are low and that it would be possible to implement a new plant and still keep operator and public doses to below the limits set by Devonport. Conclusions It is possible to develop a new disposal route which conforms with government policy and regulatory guidance on radioactive waste management. The ModulOx plant so far seems to offer the best solution, and could potentially be sited at both Devonport and Winfrith. This could be the quickest solution to implement out of the 5 options studied. Broadening the treatment process of chelated resins to include high 14C resin waste satisfies management principles concerning waste accumulation on site and the use of existing routes as necessary. There are two major drawbacks which would affect the implementation of a new facility on site. Firstly, an authorisation would need to be sought from the regulators to allow the discharge of increased amounts of 14C. Without this discharge authorisation, the facility cannot be implemented. Secondly, there is no ModulOx plant that DRDL or the MoD can have immediate access to and therefore cannot guarantee long-term access. It may therefore be difficult to achieve the financial support required for a new facility. Table 8 [35] Winfrith already has a prototype plant, authorisations and financial support. According to table 6, this could be the most logical site for ModulOx treatment and conditioning of treated waste for disposal to Drigg. If the‘store, treat and dispose’ method fails for any particular resin watestream, then a back-up plan will need to include the development of a long-term conditioned waste store with an immobilisation plant on the Devonport site. A deep geological repository could be a good option for interim storage until a better, more environmentally safer option can be found. If the repository was never intended to be sealed then it would be easy to recover the waste for further processing and may also have a better effect on the public and could help in convincing them that this was a conceivable way forward.
1 Waste Water Engineering Treatment, Disposal, Reuse. 3rd Ed. 1991. Singapore. Metcalf & Eddy. Mc-Graw-Hill Int. Ed’s Civil Engineering Series. 2 Immobilisation Science Laboratories, University of Sheffield. August 2007. Report prepared by Alstec as part of Rosyth resin treatment. 3 Waste Management Strategy Report, Integrated Waste Strategy for the Devonport Site Environmental Management. May 2009. M. Leisvik 4 Available at: www.world-nuclear.org/sym [Accessed on 3rd June 2009] 5 Devonport Royal Dockyard Limited, Disposal of solid radioactive waste directly (or via Sellafield) to the low level waste repository near Drigg. B. Wright and K. Watterson FP-19-12-000 6 Perry’s Chemical Engineers Handbook. 7th Ed. R.H. Perry and D.W.Green. 1997. USA 7 Division of Nuclear Physics, AMS and Radiating Physics Group. Carbon-14 generated by Nuclear Power Reactors. Investigations including ion exchange resins and environmental samples. A Magnusson. 2005. 8 Environment Agency. Certificate of Authorisation and Introductory Note. Authorisation Reference AN7104/CC3093. Devonport Royal Dockyard Limited. 01-06-2009 9 BPEO Study on Management Options for spent Resins. Serco Assurance, Oxfordshire.June 2005 10 Development and Deployment of the ModulOx process for the destruction of organically contaminated wastes. T.J. Abraham, M. Williams and J. Wilks. WM’05 Conference, Feb.27th- Mar.3rd 2004 11 Design and Operation of Radioactive Waste Incineration Facilities. International Atomic Energy Agency. Vienna. 1992. [online] Accessed at http://www-pub.iaea.org/MTCD/publications/PDF/Pub921e_web.pdf [Accessed on 2nd September 2009]
Available at http://www.defra.gov.uk/ENVIRONMENT/radioactivity/waste [Accessed 8th July 2009]
8-10th September 1999; London. The Deep Geological Repository; an Unavoidable and Ethically Correct Solution. 14 Environmental Health and Safety. Radiation Safety Manual for Laboratory Users. Appendix B: The Characteristics of Common Radioisotopes [online] Princeton University. Available at:http://web.princeton.edu/sites/ehs/radmanual/radman_app_b.htm#h3 [accessed 28th July 2009]
Available at:http://en.wikipedia.org/wiki/HMNB_Devonport [Accessed 27th July 2009]
Nuclear Utilities Building Facilities Plant Safety Case. Issue 2. 01-09-2006. 17 SLG-PSC-420 Core Pond Water Treatment Plant Safety Case. Issue 2. 15-11-1996. 18 SLG-PSC-510 Effluent Receipt and Transfer Safety Case. 12-03-1998. 19 SLG-PSC-610 Reactor Systems and Processes Plant Safety Case, Volume 1, Active Jet Vacs. Issue 2. 01-05-1997. 20 TD-PSC-680 Movement of Radioactive and Contaminated Items on Licensed Site. Issue 1. 01-07-2003. 21 SLG-MNC-1100F Nuclear Transfers Pre-Operational Safety Report in Support of the Vanguard Class. Issue3 01-05-2002. 22 SLG-PSC-310 MODIX Decontamination Plant Safety Case. Issue 4. 01-01-2003. 23 Argonne National Laboratory, EVS. August 2009. [Online] Available at: http://www.ead.anl.gov/pub/doc/carbon14.pdf [Accessed on 11th August 2009]
Available at: http://www.ead.anl.gov/pub/doc/Cobalt.pdf [Accessed on 11th August 2009]
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[Accessed 11th August 2009] 28 Atoms, Radiation and Radiation Protection. 3rd Ed. Turner. Wiley-VCH. 2007 29 World Nuclear Association. Radiation and Life. [Online] Available at: http://www.world-nuclear.org/education/ral.htm [Accessed on 20-08-2009]
Available at http://www.navaltechnology.com/projects/vanguard [Accessed on 20-08-2009]
[Accessed on 20-08-2009] 33 Rolls- Royce PWR Available at: http://en.wikipedia.org/wiki/Rolls-Royce_PWR [Accessed 20-08-2009]
[Accessed on 21-08-2009] 35 Management of Spent Radioactive Ion Exchange Resin arising from SSN and TSSBN Reactor Plant Decontamination and On-Board Primary Coolant Treatment at Devonport Royal Dockyard –Phase 2 Report –Option and Strategy Selection. AEA Technology M.A. Twissell, December 2002
This is a mild process which is conducted at ambient temperatures and used extensively in the pulp and paper industry. It uses soluble oxidants such as hydrogen peroxide, combined with a catalyst to remove low molecular weight material, such as sugar acids and phenols. There is emphasis to use oxygen based oxidants to avoid problems with formation of haloform compounds. This process only converts soluble organic compounds rather than totally oxidising. Ion exchange resins have resistant polystyrene resin at ambient temperatures, so this process will only destroy chelating agents. Low Temperature Plasma Ashing This process operates at low pressure and temperature in an oxygenated environment where the oxygenated plasma generated is induced by a radio frequency electro-magnetic field or microwaves. The organic material is destroyed but the downside of the process is that radioactive material remains in the ash, so a second treatment process may be necessary if the activity level does not constitute LLW. A positive side though is that the volatile components remain in the ash. Finland is experimenting with this process and has built a half-scale plant. High Temperature Plasma Destruction This process operates at elevated temperatures where an electric arc is generated in an inert gas atmosphere, usually temperatures are in excess of 5000’C. Careful selection of the additives and atmosphere means that conditions can be created in which most organic material is readily oxidised and dioxins are not created. This process has the capacity to operate as either a batch process or a continuous process, but the latter only if the molten product is tapped off and the feed controlled. The final product is normally a glass with addition of glass-forming materials such as silicate. The process has been designed to handle mixed organic-containing materials. As with some of the previous processes, gas output needs scrubbing as high temperatures volatilise a wide range of materials. It must be noted that some high temperature processes are not suited to handle wastes with large amounts of organic materials due to the pre-treatment process needed in order to reduce the organic component to manageable proportions. Molten Salt Oxidation This is a flameless oxidation process in which waste is added to a bath of molten salts and held at 600-900’C. The salts are nitrates which result in the complete oxidation of organic material and all inorganic materials are retained in the molten salt. This process is only able to occur on a small scale and there has been only a small amount of experimental work carried out on this process to date. Thermo-Chemical Treatment This is a thermal desorption process, where a powdered reactive metal fuel interacts with waste, which usually contains water. The process involves the formation of hydrogen and burning it in the presence of oxygen, which combusts the waste leaving an ash. Gas emission in this process is reduced because any reactive gases combine with the metal powder to form salts. Melting This is an induction heating process where temperatures of 1500’C and above are achieved. This is used for the melting of radioactive iron and steel. The process is being developed for other applications. There is no guarantee that C-14 levels will be reduced to levels acceptable for LLWR Drigg. Vitrification Waste material is melted with glass-forming additives to form a solid waste glass. Different melters are used, including induction-heated cold crucibles or Joule heated ceramic crucibles. Pre-treatment is normally required, usually pyrolysis, for high organic-containing materials in order to remove the carbonaceous material. This process is used for HLW, where a pre-treated calcine is introduced to a mixture containing a glass frit. The process of fusing HLW and ILW with glass-forming components (by electrode Joule heating to between 1400’C and 1800’C) has been further developed and is now being applied to LLW streams. Toxic heavy metals and radionuclides are retained in the glass residue whilst organic material is vaporised off as CO2 and H2O.
This process mixes hot sulphuric acid and nitric acids together at a temperature of ~300’C. The sulphuric acid carbonises the organic material and the nitric acid acts as an oxidant converting the carbon formed into CO2.Inorganic wastes are converted to sulphates which can be removed by filtration or dissolved from waste and treated either by cementation or by vitrification. Many of these processes are designed for smaller waste volumes and would not be substantial enough to be used on a large industrial scale. DRDL have a predicted volume of 450m3 of radioactive waste which needs treating and disposing of in the next years. One very strong contender though is incineration, the next option to be studied. Appendix 2 Long Term Aerial Dose Release Ratios (LADRR)
This method assumes that specific activity of the radionuclide element in air will be identical to that in the food –stuff at equilibrilium. (Remember that the calculations are not straight forward as the stable element concentration in air depends on the current vapour pressure of water in air, which in turn depends on many environmental parameters). External Doses
DCFEXT(I) NRPB-DL10 dose concentration factor (Sv Bq m-2) FRACIN Fraction of time spent indoors (0.9) SPERY Seconds per year
GROUND_SHIELDING GROUND SHIELDING Attenuation for deposition Gamma dose due to being indoors, set at 0. TOTAL DOSE
DEP_DOSE(i) Deposited Gamma dose to discharge of 1 TBq-1 of radionuclide(I) (Sv yr-1) FOOD CHAIN
INGDOSE(J,I,K) Dose due to foodstuff,k, contaminated by radionuclide(I) released at a rate of 1TBq yr-1 by age group J (Sv yr-1) FOODIN(J,K) Food intake rate for foodstuff K by age group J (Kg yr-1) DCFING(J,I) Dose conversion factor for ingestion of food contaminated by radionuclide (I) by age group J (Sv Bq -1) TRNFAC(K,I) Transfer parameter to foodstuff K for radionuclide I (BQ Kg-1 food per Bqm-2 s-1deposit for one year) FOOD_MULTI(K) Factor for local food consumption (set at x0.1) RDEC(I) Radioactive decay constant of radionuclide (I) (s-1) TCONS(K) Average time to consumption of foodstuff K from harvesting (d) SPERD Seconds per day INHALATION DOSE
INHDOSE(J,I) Inhalation dose for age group J due to aerial release of 1TBq of radionuclide(i) (Sv yr-1) BREATH(J) Breathing rate of age group J (m3 d-1) DCFINH(J,I) Dose conversion factor for inhalation by age group J of radionuclide I (Sv yr-1) NUCREL (I) Annual release of isotope I (1 TBq yr-1) RESUSP Resuspension factor (1.01 consistent with results ascribed in NRPB) DPERY Days per yr OCCUPANCY Occupancy factor for time spent at location in question (0.9) UNIT Converts from 1TBq yr-1 to Bq s-1 (1TBq yr-1 =3.171E04 Bq s-1)
So…. LADRR’s are the sum of the above pathways.
LADRR(j,i) Committed Effective Dose for age group J due to discharge of 1 TBq yr-1 of isotope I (Sv yr-1)
CED(J) Committed Effective Dose for age group J (Sv yr-1) ANNREL(I) Annual release of isotope (I) (TBq yr-1) Example; 0.2TBq yr-1 60Co from a stack of 20m effective height and 100TBq yr-1 of 51Cr from a stack of 1m effective height, the limiting age group dose can be calculated as follows: Dose Release Ratios
2.67E-04 Adult 2.68E-04 Child 2.60E-04 Infant 51Cr 1.79E-07 Adult 2.47E-07 Child 2.55E-07 Infant Multiply each LADRR by the respective release.
2.67E-04*0.2=5.34E-05 Sv yr-1 (and child/infant) 51Cr 1.79E-07*100=1.79E-05 Sv yr-1 (and child/infant) Add doses for each group together, taking most limiting age group as the critical group. 60Co 51Cr 5.34E-05 1.79E-05 7.13E-05 5.36E-05 2.47E-05 7.83E-05** 5.20E-05 2.55E-05 7.75E-05 Appendix 3 Radionuclide Data and Radiobiological Information
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