THE IMPACT OF LIQUID RADIOACTIVE WASTE DISCHARGES FROM TO THE IN RECENT YEARS.

B. D. Smith, G. J. Hunt and W. C. Camplin

CEFAS, Lowestoft Laboratory, Pakefield Road, Lowestoft, NR33 0HT,

Abstract. This paper describes the trends in liquid radioactive waste discharges from British Nuclear Fuels plc (BNFL) Sellafield and in concentrations in local marine environmental media. The 10-year period 1993 to 2002 is covered during which time discharges commenced from the Thermal Oxide Reprocessing Plant (THORP), which reprocesses oxide fuels and from the Enhanced Actinide Removal Plant (EARP), which treats current and historic liquid wastes, particularly to remove transuranic radionuclides. Radionuclides examined in detail include 3H, 14C, 99Tc, 129I, 137Cs, 239 + 240Pu and 241Am. The paper considers the relationship between discharges and environmental concentrations, and relates concentrations to changes in recent discharge patterns, the effects of historic discharges and environmental influences. In view of the interest in 99Tc, more data are included than for the other radionuclides. The effects of environmental concentrations in terms of radiological significance to the potentially critical group of fish and shellfish consumers local to Sellafield are also presented. Doses have varied during the period, partly because of changed radionuclide concentrations in seafoods, but also as a result of the changing patterns in the amounts of seafood eaten by the group. The paper examines these factors. The influence of the OSPAR Radioactive Substances strategy on future discharges and impacts is also discussed.

1. Introduction

Since the 1950s, British Nuclear Fuels plc (BNFL) and its predecessors have operated nuclear plants at Sellafield in west , UK. Primarily, the site undertakes reprocessing of irradiated nuclear fuel from Magnox and oxide fuel reactors in the UK and abroad. Associated storage of fuel elements in cooling ponds is undertaken prior to reprocessing. The site also includes the Calder Hall nuclear power plant which, until its closure in March 2003, has generated nuclear power since 1956. In more recent times, BNFL has also begun manufacturing mixed oxide fuels, and has increasingly turned its attention to decommissioning redundant plant and facilities, including the Windscale Advanced Gas- cooled Reactor (WAGR).

Operations on site generate liquid radioactive wastes which are discharged into the Irish Sea, some of the streams being treated to reduce their radioactive content. These plants include the Site Ion Exchange Effluent Plant (SIXEP), which treats fuel storage pond water, and the Enhanced Actinide Removal Plant (EARP) which treats routine and decay-stored waste streams mainly from the older, Magnox reprocessing plant. The adjacent United Kingdom Atomic Energy Authority (UKAEA) research facilities also discharges minor quantities of liquid wastes via the BNFL site.

Under UK legislation, discharges to the environment have to be authorised, and in the period considered by this paper (1993 to 2002), several authorisations have been in force. Discharges in 1993 were covered by a variation in January 1990 to an authorisation granted in 1986 under the Radioactive Substances Act 1960. Discharges in 1994 to 1999 were covered by an authorisation which came into effect in January 1994 under the Radioactive Substances Act 1993. This authorisation took account of the start up of EARP and the Thermal Oxide Reprocessing Plant (THORP), and included consideration of the commissioning periods for these new plants. More details have been published [1]. Both the 1990 variation and the 1994 revision were issued by the Ministry of Agriculture, Fisheries and Food (MAFF) and Her Majesty’s Inspectorate of Pollution (HMIP). Increased 99Tc discharges to the Irish Sea followed the commencement of EARP operations and this attracted

© British Crown Copyright, 2004

1 particular attention both nationally and internationally. As a consequence, the Environment Agency (EA) issued a variation which reduced the 99Tc limit applicable from January 2000. Under the Environment Act 1995, the EA, which subsumed HMIP, had become the sole authorising body for radioactive waste discharge authorisations in . At the same time, MAFF became a Statutory Consultee, though in 2000 this responsibility passed to the Food Standards Agency (FSA) under the Food Standards Act 1999. Table I shows the annual limits in these authorisations in simplified form.

Table I. Authorised annual liquid discharge limits for BNFL Sellafield.

1990 Variation 1994 Revision 2000 Variation Radionuclide Limit Limit (in Limit (after 1994) Limit (TBq y-1) 1994) (TBq y-1) (TBq y-1) (TBq y-1) 3H 3500 31000 31000 30000 14C 4 20.8 20.8 20.8 60Co 8 13 13 13 90Sr 35 30 48 48 95Zr/95Nb 180 50 9 9 99Tc 10 200 200 90 106Ru 170 75 63 63 129I 0.4 2 2 2 134Cs 10 6.6 6.6 6.6 137Cs 110 75 75 75 144Ce 22 10 8 8 Pu-alpha 7 4 0.7 0.7 241Pu 170 150 27 27 241Am 3 1.3 0.3 0.3 total alpha 10 4.7 1 1 total beta 500 400 400 400

NB Limits for 3H and 129I from 1994 onwards are upper values. Actual limits within a year are related to reprocessing throughput in THORP.

2. Changes in discharges from 1993 to 2002

The trends in discharges of selected radionuclides from 1993 - 2002 are shown as the histograms in Figures 1-10. Discharges of 3H (Figure 1) and 129I (Figure 5) have gradually increased in the period due to commissioning of THORP. Thus far, the increases in 3H have not been as great as envisaged by BNFL when the 1994 authorisation was set. Carbon-14 discharges (Figure 2) increased from 1994, as expected, with the re-routing from a gaseous waste stream into a liquid one. Increases were greater in the mid-1990s than late-1990s, but discharges were at 13 TBq y-1 by 2002 compared with 2 TBq y-1 prior to the diversion. Discharges of 99Tc (Figures 3 – 4) have increased due to processing of stored wastes through EARP, reaching a peak of 192 TBq y-1 in 1995, substantially above the pre-EARP level of less than 10 TBq y-1. Though subsequently lower, discharges in 2002 were close to the authorised annual limit of 90 TBq. Discharges of 137Cs (Figure 6) decreased over the period, partly due to EARP, but also because of improved performance of the site ion-exchange effluent plant (SIXEP) which treats effluents from fuel element storage ponds. Typically, discharges were less than 10 TBq y- 1 compared with up to 5000 TBq in the 1970s. Discharges of 239Pu + 240Pu (Figure 7) and 241Am (Figure 8) decreased by at least an order of magnitude as a result of EARP operations. Some small increases in discharges of 239Pu + 240Pu are apparent in 2001 – 2002.

3. Concentrations in marine biota

On behalf of FSA (and previously MAFF), CEFAS carries out an extensive programme for monitoring radioactivity due to Sellafield in the marine environment. This programme is regularly reviewed to allow for changes in discharges, environmental conditions and the habits of critical groups. Monitoring results are published annually, for example [2] and [3], as well as more frequently on the FSA’s web site (www.foodstandards.gov.uk). Selected results from near Sellafield are presented with the discharge data in figures 1-10. Examples have been chosen for species which are of radiological significance to the critical group of fish and shellfish consumers. Sampling and analytical uncertainties are described in the annual reports, but for the purposes of this paper, the concentration data have representative ±10% error bars.

Figure 1 presents annual mean concentrations of 3H in plaice (Pleuronectes platessa) from Ravenglass, about 10 km south of the site. Analyses of 3H in marine biota around Sellafield have begun in recent years and there are insufficient data to suggest trends. However, comparison with 3H in seawater around Sellafield suggests that some bioaccumulation is taking place.

Figure 2 presents annual mean concentrations of 14C in plaice and cod (Gadus morhua) from the small ‘Sellafield Offshore Area’ about 5km south of the discharge pipeline outlet. A natural background component of 26 Bq kg-1, typical of levels in these species away from anthropogenic sources, has been subtracted. Concentrations reflect discharges though there appears to be a residual effect of discharges following reductions during the late-1990s.

In view of the interest in 99Tc, Figures 3 and 4 show concentrations in winkles (Littorina littorea) and lobsters (Homarus gammarus) around Sellafield. Winkles were collected from Ravenglass and Nethertown. Lobsters were obtained from landings at Ravenglass and from the ‘Sellafield Coastal Area’ (SCA). The latter extends 11km offshore between Head (about 15 km north of the site) and Selker (about 15 km south of the site), though samples were obtained predominantly from the north of this area. Concentrations reflect discharge patterns and there is a lag between peak concentrations and the peak discharge in 1995. It is interesting to note that Ravenglass lobsters show lower concentrations than SCA lobsters, whereas Drigg winkles show higher concentrations than Nethertown winkles.

Data for 129I in the seaweed Fucus vesiculosus from St Bees are shown in Figure 5, and concentrations reflect increasing discharges over the period. This seaweed is not eaten but it can be used as a fertiliser. It also provides a useful indicator species since it concentrates the levels due to the low discharges.

Figure 6 presents annual mean concentrations of 137Cs in plaice and cod from the ‘Sellafield Offshore Area’. There appears to be a close correlation between concentrations and discharges, both showing the same reductions over the period. However, this correlation needs some caution since it is known that there is a significant contribution due to remobilisation of 137Cs from historic discharges adsorbed on sediments [4].

Figures 7 and 8 present concentrations of 239Pu + 240Pu and 241Am in winkles from Nethertown. Despite large decreases in discharges of 239Pu + 240Pu, there is only a small reduction in concentrations, with a small increase in 2001 – 2002 in both discharges and concentrations. A similar pattern is apparent for 241Am except for the lack of discharge increases. The observations are consistent with the known adsorption of transuranic radionuclides on sediments and the effect on concentrations near Sellafield of higher discharges in the 1970s and 1980s. Concentrations of 241Am are also influenced by ingrowth from past discharges of 241Pu [5].

4. Radiological significance

Radiation doses to members of the public from Sellafield discharges are kept under close review. Potential critical pathways are high-rate consumption of local fish and shellfish, and external exposure through occupancy of intertidal areas during, for example, angling and bait digging. The dose to the critical group (i.e. the most exposed) depends upon the habits of the people comprising the group and upon the radioactivity concentrations or external dose rates. Habits are reviewed annually, and the data

3 for the most exposed local group (members of the Sellafield fishing community) used in dose assessments are summarised in Table II. Data have been taken from the relevant annual reports, for example [2] and [3].

Table II. Summary of Sellafield habits data

Year Fish consumption Crustacean consumption Mollusc consumption External occupancy

rate, Species rate, species rate, species rate, location kg y -1 kg y -1 kg y -1 h y -1 1993 28 plaice & cod 15 crabs & lobsters 7.8 winkles & other molluscs 1994 26 plaice & cod 12 crabs & lobsters .7 winkles & other molluscs 1995 26 plaice & cod 8.6 Crabs & lobsters 12 winkles & other (75%:25%) molluscs 1996 25 plaice & cod 12 crabs & lobsters 12 winkles & other (60%:40%) molluscs (60%:40%) 1997 37 plaice & cod 17 crabs, lobsters & 4.2 winkles & other (25%:75%) nephrops molluscs (50%:40%:10%) (40%:60%) 1998 45 plaice & cod 28 crabs & lobsters 15 winkles & other 1100 over sand & (50%:50%) (85%:15%) molluscs mollusc beds (30%:70%) 1999 43 plaice & cod 24 crabs & lobsters 25 winkles & other 1000 over sand & (50%:50%) (80%:20%) molluscs mollusc beds (50%:50%) 2000 31 cod & other 20 crabs, lobsters & 17 winkles & other 1000 over sand & fish nephrops molluscs mollusc beds (40%:60%) (40%:40%:20%) (50%:50%) 2001 31 cod & other 20 crabs, lobsters & 17 winkles & other 1000 over sand & fish nephrops molluscs mollusc beds (40%:60%) (40%:40%:20%) (50%:50%) 2002 51 cod & other 16 crabs, lobsters & 29 winkles & 1200 over sand & fish nephrops mussels mollusc beds (40%:60%) (50%:30%:20%) (60%:40%)

Figure 9 shows effective doses [6] for 1993 - 2002 with the contributions from different radionuclides while Figure 10 shows the contributions of the different pathways. Total doses have remained well within the 1mSv dose limit. Variations in doses have been due to changes in habits rates as well as changes in radioactivity concentrations. Throughout the period, doses have been largely due to the actinides (241Am and plutonium isotopes) with increased contributions due to 99Tc. As shown earlier, most of the actinide concentrations are due to Sellafield discharges in the 1970s and 1980s rather than current ones. Contributions from other radionuclides have been low, with doses due to 3H and 129I too small to show separately on Figure 9.

The main pathway contributing to doses throughout the period, apart from 1997, has been consumption of molluscs, with more than half of the doses. In 1997, the main pathway was consumption of crustaceans, and this has been the next most important pathway for much of the remaining period. Since 1998, doses from external pathways have also contributed significantly to the overall doses to the critical group. By contrast, doses from consumption of fish have been relatively small. Since consumption rates for fish have been much higher than for either crustaceans or molluscs during the period, the low doses are indicative of the much lower concentrations of radiologically significant radionuclides in fish.

5. Future trends

In 1998, the UK became party to the OSPAR Radioactive Substances strategy which, inter alia, requires discharges to be reduced by 2020 such that they result in ‘close to zero’ additional concentrations in the marine environment above historic levels [7]. The OSPAR Commission is working to define ‘historic levels’ and ‘close to zero’. In 2002, Defra published the UK Strategy for Radioactive Discharges 2001 – 2020 which provides details of intended discharge reductions, including those from Sellafield [8]. Furthermore, the EA have been reviewing, with a wide public consultation, the discharge authorisations for Sellafield, which would entail reductions [9]. As a result of these factors, discharges from Sellafield to the Irish Sea, particularly the radiologically significant ones, will be further reduced in future. However, as demonstrated above, doses to the local population are predominantly due to discharges from the 1970s and 1980s, apart from those for 99Tc. It would appear that discharge reductions for radionuclides other than 99Tc will not significantly affect doses, any dose reductions being dependant on the future environmental behaviour of historic discharges. Continued monitoring will enable the situation to be kept under review.

6. References

1. Smith, B.D., Hunt, G.J., Porter, I.T. and Tipping, J. Revision of Sellafield’s Authorisation for Liquid Radioactive Waste Discharges: A Brief Account of Technical Experience. Proc. Regional. Congr. Int. Rad. Prot. Ass. Portsmouth. 233-238. Nuclear Technology Publishing, Ashford (1994). 2. Camplin, W.C. Radioactivity in Surface and Coastal Waters of the British Isles, 1993. Aquat. Environ. Monit. Rep. No. 42. MAFF, Direct. Fish. Res., Lowestoft (1994). 3. Environment Agency, Environment and Heritage Service, Food Standards Agency and Scottish Environment Protection Agency. Radioactivity in Food and the Environment, 2002. RIFE-8. EA, EHS, FSA and SEPA, Warrington, Belfast, London and Stirling (2003). 4. Hunt, G.J. and Kershaw, P.J. Remobilisation of Artificial Radionuclides from the Sediment of the Irish Sea. J. Radiol. Prot. 10(2): 147-151 (1990). 5. Hunt, G.J. and Smith, B.D. The radiological impact of actinides discharged to the Irish Sea. J. Environ. Rad. 44: 389 - 403 (1999). 6. International Commission on Radiological Protection. 1990 Recommendations of the International Commission on Radiological Protection. Annals ICRP 21(1-3), Pergamon Press, Oxford (1991). 7. OSPAR. SINTRA Statement. Summary Record OSPAR 98/14/1, Annex 45. OSPAR, London, (1998). 8. Department for Environment, Food and Rural Affairs, Department of the Environment, Northern Ireland, National Assembley for Wales and Scottish Executive. UK Strategy for Radioactive Discharges 2001-2020. Defra, London, (2002). 9. Environment Agency. Proposed Decision for the Future Regulation of Disposals from British Nuclear Fuels plc Sellafield. EA, Warrington (2002).

5 3500 Discharge 250 Ravenglass plaice 3000 200 2500

150 2000

1500 100 Discharge,TBq/y

1000 Concentration, Bq/kg (wet) 50 500

0 0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

FIG. 1. Sellafield 3H discharges and concentrations in Ravenglass plaice.

15 Discharge 150 Sellafield Offshore Area cod/plaice

10 100

Discharge, TBq/y 5 50 Concentration, Bq/kg (wet)

0 0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

FIG. 2. Sellafield 14C discharges and concentrations in Sellafield Offshore Area cod/plaice. 200 Discharge 4000 Nethertown winkle Drigg winkle 150 3000

100 2000 Discharge, TBq/y

50 1000 Concentration, Bq/kg (wet)

0 0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

FIG. 3. Sellafield 99Tc discharges and concentrations in Nethertown and Drigg winkles.

Discharge 200 20000 Sellafield Coastal Area lobster Ravenglass lobster 150 15000

100 10000 Discharge, TBq/y

50 5000 Concentration, Bq/kg (wet)

0 0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

FIG. 4. Sellafield 99Tc discharges and concentrations in Sellafield Coastal Area and Ravenglass lobsters.

7 Discharge 1.0 10 St Bees Fucus vesiculosus

0.5 5 Discharge, TBq/y Concentration, Bq/kg (wet)

0.0 0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

FIG. 5. Sellafield 129I discharges and concentrations in St Bees Fucus vesiculosus.

25 25 Discharge Sellafield Offshore Area cod/plaice 20 20

15 15

10 10 Discharge, TBq/y Concentration, Bq/kg (wet)

5 5

0 0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

FIG.6. Sellafield 137Cs discharges and concentrations in Sellafield Offshore Area cod/plaice. 1 50 Discharge Nethertown winkles

0.5 25 Discharge, TBq/y Concentration, Bq/kg (wet)

0 0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

FIG. 7. Sellafield 239Pu + 240Pu discharges and concentrations in Nethertown winkles.

1 100

Discharge Nethertown winkles

0.5 50 Discharge, TBq/y Concentration, Bq/kg (wet)

0 0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

FIG. 8. Sellafield 241Au discharges and concentrations in Nethertown winkles.

9 0.25 External C-14 Tc-99 0.20 Cs-137 Pu isotopes

0.15 Am-241 Others mSv/year 0.10

0.05

0.00 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

FIG. 9. Effective doses by radionuclide to high rate fish and shellfish consumers near Sellafield.

0.25

External

0.20 Fish Crustaceans Molluscs 0.15 mSv/year 0.10

0.05

0.00 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

FIG. 10. Effective doses by pathway to high rate fish and shellfish consumers near Sellafield.