NE Atlantic discharges15 August 2011
European countries signed up to the OSPAR Convention are committed to achieve ‘good environmental status’ of the Atlantic Ocean. This includes reducing radioactive discharges to levels where the additional concentrations above historic levels are close to zero by 2020. The most recent report finds the nuclear industry making progress, but improvements are still required. By Penny Hitchin
The OSPAR Quality Status Report 2010 (QSR 10), a detailed report based on 10 years of monitoring and assessment of the North-East Atlantic, was published in September 2010. One significant area covered by the report is an assessment of radioactive discharges between 1988 and 2008.
The OSPAR Convention for the Protection of the Marine Environment of the North-East Atlantic is concerned with preventing pollution and dumping in the Atlantic Ocean. The Convention covers about 13.5 million km2 of the North-East Atlantic and its adjacent seas. It is an international legal instrument covering the protection of the marine environment. OSPAR is ratified by Belgium, Denmark, Finland, France, Germany, Iceland, Ireland, Luxembourg, Netherlands, Norway, Portugal, Sweden, Switzerland and the United Kingdom and approved by the European Community and Spain.
OSPAR combines and updates the 1972 Oslo Convention on dumping waste at sea with the 1974 Paris Convention on land-based sources of marine pollution. One of its six strategies concerns radioactive substances; its objective is that by 2020 discharges, emissions and losses of radioactive substances will be reduced to levels such that additional concentrations above historic levels are close to zero.
The report draws several conclusions about sources of radioactive discharges into the NE Atlantic:
- Ninety-two operational and decommissioning nuclear installations in OSPAR countries directly or indirectly discharged radionuclides to the North East Atlantic area over the ten years. These include nuclear power plants, fuel fabrication and enrichment plants, fuel reprocessing plants and research and development facilities. Fuel reprocessing plants and fabrication and enrichment plants account for 98% of discharges of radionuclides from the nuclear sector. Radionuclides used as indicators of discharges from this sector are caesium-137, technetium-99, plutonium-239, plutonium-240 and tritium. Inputs of radionuclides to the sea are associated with liquid discharges and to a lesser extent with solid wastes and emissions to air.
- The offshore oil and gas industry is the largest non-nuclear source of radioactive discharges. Radionuclides come from produced water (water extracted from the reservoir with the oil and gas) and from descaling the insides of pipes. Less importantly, radioactive substances (e.g. tritium) may be used as tracers. The naturally occurring radionuclides in produced water include lead-210, polonium-210 and radium-226 and -228.
- Radioactive discharges from the medical sector come mainly from the use of radioactive iodine-131, but its short half-life and discharge via sewers means that negligible levels reach the sea.
- Atmospheric nuclear weapons testing, fallout from the 1986 Chernobyl accident, former nuclear waste disposal sites and sunken nuclear submarines have contributed to levels of radioactive nuclides in the sea.
- Waste from the phosphate fertiliser industry was a significant source of naturally occurring radionuclides to the marine environment until the early 1990s. All discharges from this industry ceased by 2005, but past discharges are still present.
The nuclear sector accounts for most of the input of beta-emitting radionuclides to the OSPAR area. For some radionuclides such as tritium, reduction technologies at an industrial scale are not currently available. On the effects of discharges, the OSPAR report concludes:
- Total beta-activity discharges (excluding tritium) from the nuclear sector, notably discharges of Tc-99, have fallen. Related concentrations in seawater and biota have decreased in a number of monitoring areas.
- The effect of discharges and concentrations of radioactive substances from the nuclear sector on the quality of the OSPAR area, and doses and impacts on humans and biota are considered low.
- In the North Sea area, elevated concentrations of some radionuclides are mainly due to the transport of these radionuclides by ocean currents.
- There is insufficient data to show whether the objective of the Radioactive Substances Strategy for 2020—reduction of discharges, emissions and losses of radioactive substances to levels close to zero—will be met.
- Abatement-at-source based on a precautionary approach and the principle of prevention, and application of best available technique (BAT) must continue to be used and developed to minimise the impact of radioactive discharges.
OSPAR’s work to prevent and reduce pollution from radioactive substances focused on the nuclear sector and the application of BAT to minimise pollution of the marine environment by radioactive discharges. Examples include treatment systems for converting radionuclides in effluents into solid waste for disposal. Low-level radioactive discharges into the environment are usually unavoidable; these are regulated through licences from the authorities. Reports to OSPAR indicate that the use of BAT is stipulated in national legislation and regulations, and that management systems are in place to minimise radioactive discharges from the nuclear sector.
OSPAR has established common tools and methods for monitoring and reporting discharges from nuclear installations, as well as baselines against which to monitor progress in reducing the amount of radioactive substances discharged by the nuclear sector. Statistical methods to evaluate progress towards achieving the objectives of the Radioactive Substances Strategy have also been identified for discharges from the nuclear sector.
OSPAR has not developed BAT for reducing discharges of radionuclides from the non-nuclear sector, but started collecting data on annual discharges from non-nuclear sources in 2005.
OSPAR has collected data on annual discharges of indicator radionuclides from the nuclear sector since 1990 and from non-nuclear sources since 2005. For the nuclear sector, the period between 1995 and 2001 has been agreed as the baseline period against which progress towards the objective of the Radioactive Substances Strategy is evaluated.
Annual discharges from nuclear installations show that of the assessed radionuclides the beta-emitter tritium accounts for most discharges, numerically several magnitudes greater than the total alpha activity and total beta activity from other radionuclides discharged from the nuclear sector. Tritium discharges mainly relate to nuclear reprocessing plants. Although they appear high in terms of activity, tritium discharges have very low radiotoxicity to humans and biota. There is no current technology capable of removing tritium from industrial radioactive waste streams.
Average discharges from the nuclear industries in the period 2002–2006 relative to the 1995–2001 baseline period show that there has been a statistically significant decrease of 38% in total beta activity discharges (excluding tritium), but no statistically significant change in total alpha activity discharges.
OSPAR analysed 1990-2008 discharge figures. Key findings include:
- Discharges of radioactive substances, measured as total alpha and total beta activity and excluding tritium, from nuclear installations decreased over the period 1990 – 2008
- Discharges of tritium peaked in 2004
- Total alpha activity discharged from all nuclear installations over the 18-year period decreased
- Discharges of alpha activity are at their lowest level, which is 6% of the peak value in 1993
- There was a three-fold decrease in alpha discharges from the fuel fabrication sub-sector, in particular from the UK Springfields site
- Compared to 2007, La Hague reprocessing plant alpha discharges decreased by 18%; Sellafield reprocessing plant alpha discharges increased slightly (by 1.6 %)
- Since 2004, downward trends for discharges of tritium have been re-established
- Despite a 32% decrease of discharges of tritium from La Hague, it still contributed more than 70% of the total tritium discharges
- Sellafield, which registered an increase of 24% in tritium discharges, contributed 7% of all total tritium discharges
- Discharges of tritium from nuclear power stations dropped during 2008 (largely due to AGR reactors being offline), but still contributed 20% to overall tritium discharges
- Total beta discharges (excluding tritium) from all nuclear installations was the lowest recorded by OSPAR since the collection of data
- Decline in activity at Springfields meant that reprocessing now accounted for 76% of the total beta discharges overall.
- Compared with 2007, there was a 42% reduction in Sellafield discharges and a 52% reduction in Tc-99 discharges, which now represent only 17% of total beta discharges from the site as a whole
- Total beta discharges (excluding tritium) arising from decommissioning were insignificant.
Both the Cap de la Hague and Sellafield nuclear fuel reprocessing facilities are located in the northwest of their respective countries, France and the UK. Reprocessing of spent nuclear fuel leads to the production of waste streams with particular radiological fingerprints. The La Hague facility in Normandy reprocesses PWR and BWR fuel; Sellafield in West Cumbria reprocesses Magnox, AGR and LWR fuel.
After treatment, liquid effluents from La Hague are filtered and monitored and released into the English Channel by pipeline, into the Raz Blanchard current. In 2003, French nuclear regulators tightened limitations on levels of releases of liquid and gaseous chemical effluents. The limits were modified again in 2007 so that now La Hague annual authorization for liquid effluents is 18,500 TBq of tritium, 2.6 TBq of iodine, 42 TBq of carbon-14, 11 TBq of strontium-90, 8 TBq of caesium-137, 0.5 TBq of caesium-134, 15 TBq of ruthenium-106, 1.4 TBq of cobalt-60, 60 TBq of other beta and gamma emitters, and 0.14 TBq of alpha emitters.
Liquid effluents are classified as ‘V’ if beta activity apart from tritium is less than 1.85 MBq per litre and if alpha is less than 3.7 kBq per litre. Other radioactive effluent is classified as ‘A.’ In 2008, La Hague released into the sea 98,928 m3 of ‘V’ effluent and 1607 m3 of ‘A’ effluent. It also discharged 574,850 m3 of effluent from rainwater and underground drainage networks.
In 2008, fuel fabrication plants in the OSPAR region operated in Gronau and Hanau, Germany; Almelo, Netherlands; Juzbando, Spain; and Capenhurst and Springfields, UK.
Sellafield technetium abatement
One operation carried out at Sellafield on the north-west coast of England is the reprocessing of spent Magnox fuel. The process produces liquid waste containing radionuclides. In the 1960s and 70s the waste was stored for several years while some decay took place before being discharged by pipeline into the Irish Sea.
Public concern over these radioactive discharges contributed to a change in policy; from 1981 the waste was retained in storage tanks. Between 1981 and 1994, the waste was stored in tanks on the Sellafield site awaiting construction of a new £168 million waste treatment plant, the Enhanced Actinide Removal Plant (EARP). The new plant, which started operating in 1994, was built to remove actinides and some key fission products including americium and caesium. It was not designed to remove Tc-99, which remained present in the discharge stream. As a result, in 1994 when EARP started treating the backlog of waste, Tc-99 discharges and concentrations in the marine environment increased.
In response to strong protests from countries with Atlantic borders, notably from Ireland and Norway, as well as OSPAR, the UK regulators reduced Sellafield’s Tc-99 discharge limit from 200 to 90 TBq/yr, from January 2000, leading to redoubled efforts to find abatement techniques.
Sellafield site operators BNFL undertook a Best Practicable Environmental Option (BPEO) study with regard to Tc-99 in December 2000, concluding in favour of discharge to sea. However, the Norwegian government and NGOs continued to press the UK to stop the discharges, which were reaching the country’s coast, where it was found to be prevalent in shellfish and seaweed.
In 2003, British Nuclear Fuels Limited conducted laboratory-scale testing of a new TPP process. The method consists of adding tetraphenylphosphoniumbromide (TPP) to the liquid waste and then filtering the water out. The residue could then be mixed into the vitrification stream and stored as medium-level solid radioactive waste. Following a successful trial, the technology was implemented.
The first diversion of Medium Active Concentrate (MAC) from Magnox reprocessing to the high level waste stores on the Sellafield site took place in 2003. Tc-99 is now diverted to the vitrification plant for immobilisation, rather than discharged into the sea.
In April 2006 UK regulators reduced the Sellafield Tc-99 discharge limit to 10 TBq/yr. Actual discharges were below 5 TBq in 2007. By the end of 2007 all the stored technetium-bearing waste had been treated and associated discharges of Tc-99 from this main source at Sellafield ended.
Before the development of the technetium abatement technique, Magnox reprocessing had to be completed by 2012 to meet the government’s OSPAR commitments. The operational life of the remaining Magnox generators has subsequently been extended (Oldbury to 2011 and Wylfa to 2012), and the Magnox reprocessing schedule is now scheduled for completion in 2016. Vitrification of the Magnox MAC concentrates will be completed by the 2020 deadline.
In February 2011 environmental group CORE (Cumbrians Opposed to a Radioactive Environment) published a report saying that the rate of discharge from planned reprocessing operations at Sellafield will breach OSPAR commitments. CORE believes that a range of technical issues currently restricting Sellafield operations—particularly the lack of capacity to treat the highly radioactive liquid wastes produced by reprocessing—could see reprocessing extended beyond its scheduled end-date of 2020. CORE is critical of the decision to extend Magnox generation beyond the dates agreed under the earlier plan which would have seen Magnox reprocessing completed by 2012. The site owner, UK government agency the Nuclear Decommissioning Authority, says that based on current plans, the UK will meet its 2020 OSPAR obligation. However, if it does not, then a contingency plan will be required, which could mean agreeing to miss the OSPAR deadline.
CORE spokesman Martin Forwood said: “Radioactive discharges to the Irish Sea, including plutonium, are dominated by those from Sellafield’s two reprocessing plants B205 and the Thermal Oxide Reprocessing Plant (THORP), particularly the former. The accepted correlation between annual reprocessing rates and subsequent radioactive discharge levels is amply demonstrated by the recent reduction in discharges from the site following several years of unusually low reprocessing rates. This recent reduction however will be completely reversed by NDA plans that include the reprocessing of some 4700 tonnes of spent fuel from the UK’s Magnox reactors in B205 in the next six years, requiring a rate more than double that achieved over the last five years.”
Tables2008 discharges (TBq/yr) from nuclear fuel reprocessing plants