Trawsfynydd, 2018
Total Page:16
File Type:pdf, Size:1020Kb
Cefas contract report C7325 Radiological Habits Survey: Trawsfynydd, 2018 Environment Report RL 06/19 This page has been intentionally left blank Environment Report RL 06/19 Radiological Habits Survey: Trawsfynydd, 2018 B.J. Greenhill, F.J. Clyne and K.J. Moore 2019 The work described in this report was carried out under contract to the Environment Agency, the Food Standards Agency, Natural Resources Wales and the Office for Nuclear Regulation. Cefas contract C7325 FSA Project FS131008 Cefas Document Control Radiological Habits Survey: Trawsfynydd, 2018 Environment Agency, Food Standards Agency, Natural Resources Wales Submitted to: and Office for Nuclear Regulation Date submitted: 03/05/2019 Project Manager: Victoria Ly Report compiled by: Billy Greenhill Quality control by: Fiona Clyne Approved by & date: Kins Leonard 25/03/2019 Version: Final Version Control History Author Date Comment Version Sent to EA, FSA, Billy Greenhill 30/12/2018 NRW and ONR for Draft 1 comment Revised and sent to Billy Greenhill 19/02/2019 FSA, EA, NRW and Draft 2 ONR for comment Revised and sent to Billy Greenhill 04/03/2019 FSA, EA, NRW and Draft 3 ONR for comment All amendments Billy Greenhill 03/05/2019 Final completed. This report should be cited as: Greenhill, B.J., Clyne, F.J. and Moore, K.M., 2019. Radiological Habits Survey: Trawsfynydd, 2018. RL 06/19. Cefas, Lowestoft A copy can be obtained by downloading from the Cefas website: www.cefas.co.uk © Crown copyright, 2019 Page 2 of 66 Radiological Habits Survey: Trawsfynydd, 2018 CONTENTS KEY POINTS .......................................................................................................................................... 7 SUMMARY .............................................................................................................................................. 9 1 INTRODUCTION ........................................................................................................................... 15 1.1 Regulatory framework ........................................................................................................... 15 1.2 Radiological protection framework ........................................................................................ 16 2 THE SURVEY ............................................................................................................................... 18 2.1 Site activity ............................................................................................................................ 18 2.2 Survey objectives .................................................................................................................. 18 2.3 Survey areas ......................................................................................................................... 19 Figure 1. The Trawsfynydd aquatic survey area .......................................................................... 20 Figure 2. The Trawsfynydd terrestrial and direct radiation survey areas ..................................... 21 2.4 Conduct of the survey ........................................................................................................... 22 3 METHODS FOR DATA ANALYSIS ............................................................................................. 24 3.1 Data recording and presentation ........................................................................................... 24 3.2 Data conversion .................................................................................................................... 24 3.3 Rounding and grouping of data ............................................................................................. 25 Table A. Names of age groups and range of ages within each age group ................................... 25 3.4 Approaches for the identification of high rates ...................................................................... 26 3.5 Profiles of habits survey data for use in total dose assessments ......................................... 27 3.6 Data quality ........................................................................................................................... 27 4 AQUATIC RADIATION PATHWAYS ........................................................................................... 29 4.1 Aquatic survey area .............................................................................................................. 29 Figure 3. Maentwrog Dam ............................................................................................................. 30 Figure 4. Looking towards the northern shore ............................................................................... 31 Figure 5. Club Bay ......................................................................................................................... 31 Figure 6. Boat angler on Lake Trawsfynydd ................................................................................. 32 Figure 7. The footbridge from Trawsfynydd Village across the lake ............................................ 33 Figure 8. South of the footbridge ................................................................................................... 34 Figure 9. Looking along the western shore .................................................................................. 34 Figure 10. From Maentwrog Dam looking along the River Prysor ............................................... 35 Figure 11. Waterfall on the River Prysor........................................................................................ 36 4.2 Commercial fisheries ............................................................................................................. 36 4.3 Angling .................................................................................................................................. 36 4.4 Wildfowling ............................................................................................................................ 37 4.5 Other pathways ..................................................................................................................... 37 4.6 Food consumption data ......................................................................................................... 37 Table B. Summary of adults’ consumption rates of foods from the aquatic survey area .............. 38 Table C. Summary of children’s consumption rates of foods from the aquatic survey area ......... 38 4.7 Lake shore and river bank occupancy .................................................................................. 38 Table D. Summary of adults’ lake shore and river bank occupancy rates ................................... 39 Table E. Summary of children’s and infants’ lake shore and river bank occupancy rates ........... 39 4.8 Gamma dose rate measurements......................................................................................... 39 Table F. Summary of gamma dose rate measurements taken over lake shore and river bank substrates ...................................................................................................................................... 40 4.9 Commercial handling of fishing gear and sediment .............................................................. 40 4.10 Water based activities ........................................................................................................... 40 5 TERRESTRIAL RADIATION PATHWAYS .................................................................................. 42 5.1 Terrestrial survey area .......................................................................................................... 42 5.2 Destination of food originating from the terrestrial survey area ............................................ 43 5.3 The potential transfer of contamination off-site by wildlife .................................................... 43 Page 3 of 66 CONTENTS 5.4 Food consumption data ......................................................................................................... 43 Table G. Summary of adults’ consumption rates of foods from the terrestrial survey area .......... 44 Table H. Summary of children’s and infants’ consumption rates of foods from the terrestrial survey area .................................................................................................................................... 45 6 DIRECT RADIATION PATHWAYS .............................................................................................. 46 6.1 Direct radiation survey area .................................................................................................. 46 6.2 Residential activities .............................................................................................................. 46 6.3 Leisure activities .................................................................................................................... 47 6.4 Commercial activities ............................................................................................................ 47 6.5 Occupancy rates ................................................................................................................... 47 Table I. Summary of direct radiation occupancy rates ................................................................. 48 6.6 Gamma dose rate measurements......................................................................................... 48 Table J. Summary of gamma dose