EA1202: Monitoring unusual pathways for the transfer of radioactivity from the Sellafield site into the environment.

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1 RSC Conference 2012 EA1202: Monitoring unusual pathways for the transfer of radioactivity from the Sellafield site into the environment. Choon Yee Tan MSc Environmental Assessment and Management September 2012 Project Sponsor: Environment Agency Project Supervisor: Mike Wood

2 Contents Background Aim and Objectives Methodology Results and Discussion Conclusion and Recommendations Questions

3 Background - Site Overview Sellafield Gaseous Discharge Liquid Discharge Seascale Doses to Public Unusual Pathways

4 Aim To determine whether the existing monitoring programmes for monitoring unusual pathways are fit for purpose. Objectives a) To identify gaps in current unusual pathways monitoring and needs for improvements. b) A case study assessment of the unusual assurance monitoring results post the Seascale/Sellafield pigeon contamination incident.

5 Case Study Background Since 1999, the EA has maintained surveillance monitoring on road drain gully pots at Seascale village. Gully pots act as contaminant indicators through collection of wash off from the catchment area. Gully Pot Sediment Am-241 Gully Pot Sediment Cs-137 In 2010, elevated concentrations were noted at one site (Seascale SS 233).

6 Case Study - Specific Objectives To determine the distribution of radionuclide concentration in 13 gully pot sediments in Seascale. the particle size distribution of gully pot sediments in Seascale. the organic content of gully pot sediments in Seascale. the activity ratio of radionuclides in gully pot sediments at Seascale and Sellafield. the activity ratio of radionuclides in seawater particulate at Seascale and Sellafield.

7 Case Study - Specific Objectives To compare the activity ratio of radionuclides difference in 5 gully pot sediments at Seascale over 13 years. the mean activity ratio of radionuclides difference in gully pot sediments and seawater particulate at Seascale over 13 years.

8 Case Study - Specific Objectives To correlate the influence of sediment particle size on radionuclide concentration in gully pot sediment in Seascale. the influence of organic matter content on radionuclide concentration in gully pot sediment in Seascale. the influence of rainfall intensity on radionuclide concentration in gully pot sediment in Seascale.

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10 Project Methodology Phase 1 Phase 2 Phase 3 Phase 4 Desk based study Case study sampling and analysis Statistical analysis and interpretation Assessment of findings Primary Data 13 gully pots sediments were collected Gamma ray Organic matter content Particle size distribution Secondary Data Monitoring results since gully pots sediments (EA) 4 gully pots sediments (SL) Seawater particulate (EA) Seawater particulate (SL) Rainfall records (SL)

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12 Marked decrease compared to the findings in Spread of higher Cs was within the radius of bird sanctuary extending few meters to the south. Variable particle size distribution, similar trend in SS208, SS204, SS206 and SS207. Distribution of variable organic matter content in gully pot sediments. No significant correlation between radionuclide concentrations with both the variables.

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14 Correlation between rainfall intensity and radionuclide concentrations The statistical analysis showed slight correlation (R 2 = ) of radionuclide concentrations with rainfall amounts in the month proceeding to the sediment sampling, in comparison to the yearly rainfall. This indicates rainfall events have influence on sediment deposition and subsequent movement of radionuclides in the gully pot (Napier, 2006). Depending on the design and efficiency of the gully pot, aliquots of the more contaminated gully pots might be transferred to a less contaminated gully pot (Memon & Butler, 2002). It is also recognised that significance of statistical correlation was less than expected may have related to the size of the variable set being studied i.e. 13 data sets from 1999 to 2011.

15 Activity Ratio Pu-238/Pu-239, SS 231 SS 232 SS 209 SS 204 SS 233 Pu-238/Pu-239, Intertidal sediment (SL discharge) Compost heap, Bird s feathers Sweeping, droppings Global fallout Year

16 1.98 Activity Ratio Am-241/Cs-137 Seawater particulate SS 231 SS 232 SS 209 SS 204 SS 233 Am-241/Cs Bird s feathers Sweepings Airborne particulate SL perimeter Year

17 Conclusion Various factors influence the spatial pattern and distribution of radionuclides. Activity ratios in SS204 and SS233 have been constant, closely associated with the legacy issue. No feral pigeon activity was observed at the Bird Sanctuary during site visits. Two major setbacks: Lack of information on the drainage system configuration at Seascale village Lack of effective record keeping for gully pots cleaning However, by a comparison of the results over the past 13 years, it has been possible to assure that there has not been a recurrence of contamination caused by avian pathways within the environment at Seascale.

18 Recommendations Topographical survey be carried out to understand surface runoff behaviour in Seascale village and inform the gully pot monitoring assurance programme. Depending on the issue under report Sediments collected from the gully pots cleaning regime is bulked together and monitored as a whole. Installation of custom made sampler at gully pots of interest to provide an estimate of materials and better information on build up and residence time. Further consideration for assessing encounter probabilities for contaminant transport in terrestrial environment, particularly through non-food exposure route.

19 References Memon, F. A. & Butler, D. (2002). Identification and modelling of dry weather processes in gully pots. Water Research. Vol. 36, pp Napier, B. A. (2006). Alternative conceptual models for assessing food chain pathways in biosphere models. Pacific Northwest National Laboratory Retrieved from

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