Magnox wastes

MCB MCC MINEQL MOX MSWI p,-SXRF MW Microwave burn-out Materials Characterization Center Mineral equilibria (computer program) Mixed-oxide (fuel) Municipal solid waste incinerator Synchrotron-based X-ray microfluorescence Magnox waste glass (British Nuclear Fuel Public Ltd. Company)... 

RADIONUCLIDE RECORDING LEVELS AND PRIORITISATION OF CHEMICAL / RADIOCHEMICAL ANALYSES OF MAGNOX WASTES FOR NIREX COMPLIANCE... 

Table 2 15 Radionuclides potentially difficult to measure directly in Magnox Wastes...

Plutonium-242 and Americium-243 Pu-242 and Am-243 are produced in fuel by multiple nuclear reactions. They therefore appear in items contaminated by fuel. They were found to exceed the GQ limit in HNA and HPA MCI and HPA SPF waste (high uncertainty). In addition in IX resins at HPA and HNA, Am-243 was above the GQ. Neither of these radionuclides are currently analysed in Magnox wastes because they are used as yield tracers in other analyses. To measure these two radionuclides, it is possible to simply repeat the current analyses for Pu and Am with and without tracers. No development work should be required. It has been possible to use these isotopes as tracers because the amount present (in terms of activity) is very low. FISPIN predicts the following radioisotope ratios in fresh waste Am-241 to Am-234 of 111 to 1 and Pu-239/-240 to Pu-242 of 2,500 to 1. At these activity levels, it may be more accurate to estimate the activities rather than measure them. 

The introduction of NIREX GQs for packaging and disposal of ILW has resulted in the need to analyse or calculate the specific activities of radionuclides that had not been important historically. This paper identifies those nuclides that are likely to exceed the GQ in a range of Magnox waste streams and considers whether adequate procedures exist for all. For those... 

Extension of the Tc-99 analysis method from environmental samples at Sellafield to Magnox wastes contaminated with fission and activation products, for example IX resin, is required and failing this a new analysis method is beneficial. 

Beryllium-10 Be-10 is an activation product of Be-9. It was identified in several mobile and solid waste streams but exceeded the GQ only in fuel channel components (FCC) at HNA due to the natural Be content of the Zr D-bar fuel component. Laboratories within Magnox Electric do not currently analyse waste for Be-10 therefore the Best Estimate activity in the Nirex... 

From the 86 streams selected as representative of Magnox reactor operational solid and mobile intermediate level wastes, 49 radionuclides were identified which are subject to detailed determination under UK Nirex requirements for radioactive ILW packages. 

Magnox Reactor waste streams include a wide range of materials such as ion exchange (IX) resins, sludge, Magnox fuel element debris (FED), reactor graphite and carbon and stainless steels. Some wastes will exhibit heterogeneity and for many construction materials such as steels there will be radionuclides present which are neutron activation products of trace impurities and were un-quantified at the time of manufacture. 

The potential for a radioactive material to cause harm is generally highest when stored in its un-treated state. Many of the wastes associated with Magnox power stations have been stored for many decades and there is the possibility that the hazard represented by a waste... 

Of particular relevance is the inherent hazard represented by the radioactive inventory of the waste and is the summed product of the activity (Bq) of each radionuclide present and its corresponding Specific Instantaneous Toxic Potential (SITP). This can be adjusted for decay for longer timescales and it is usual to employ the full radionuclide inventory for waste streams as sampled and quantified by Magnox Electric Ltd and reported in the U.K. Radioactive Waste Inventory. ... 

Magnox cladding, which has been removed mechanically from spent fuel rods at the start of reprocessing operations, is contaminated with small pieces of fuel and will require treatment before disposal to the environment. At present, this waste is stored under water (to eliminate any fire risk) in large concrete silos and processes are now under development for the conditioning of this waste to make it suitable for disposal. The favored processing route comprises the following operations ... 

WOOLLAM, P.B. and PUGH, I.G. Neutron Induced Activation, Waste Disposal and Radiation Levels for the Reactor Island Structure of a Decommissioned Magnox Power Station. IAEA-SM-234/10. 

Other plants of the Magnox type which were addressed at the TCM included the Vandellos 1 nuclear power plant in Spain and the Tokai 1 unit in Japan. Defuelling of the Vandellos reactor was completed in 1994 with subsequent dismantlement of the spent fuel ponds achieved early this year. Currently, nearly all of the radwaste generated during the operation and the waste (primarily graphite fuel support sleeves) from three silos at Vandellos have been extracted and packaged. 

By deriving the inventory of chlorine-36 in Magnox (and other GCR decornrnissiorimg wastes) the effect on disposal risks has been established. It should be noted that it is unlikely packages will be able to retain their integrity for long periods comparable to the half-life of chlorine-36, hence risk is primarily ameliorated by a combination of dilution and long return times from a potential repository. 

This work was supported under the UK H.SE Co-ordinated Programme on Waste and Decommissioning (IMC Ref. WD/GNSR/5004) and is published by permission of the members of the Industry- Management Committee (British Nuclear Fuels pic. Magnox Electric pic. Nuclear Electric Ltd and Scottish Nuclear Ltd). 

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