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Progress for the nuclear sector

OSPAR has identified indicator radionuclides for discharges from each of the sectors against which progress towards the objective of the OSPAR Radioactive Substances Strategy is being assessed Table 6.1. This was achieved by establishing the composition of discharges from the various sectors and the significance of the radiation dose of the radionuclides involved. OSPAR has collected data on annual discharges of indicator radionuclides from the nuclear sector since 1990 and from non-nuclear sources since 2005. The data for the nuclear and non-nuclear sectors differ widely with respect to temporal period and quantity. 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. Mean values of discharges of the individual indicator radionuclides in the baseline period have been established. There are too few reported data to develop a baseline for assessing trends in discharges from the non-nuclear sector. As well as the individual indicator radio­nuclides, total α-activity and total β-activity (excluding tritium) are used to indicate discharges of radioactive substances across sectors as a whole.

Discharges of some radionuclides from the nuclear sector have decreased

Annual discharges from nuclear installations show that of the assessed radionuclides the β-emitter tritium accounts for most discharges, numerically several magnitudes more than the total α-activity and total β-activity from other radionuclides discharged from the nuclear sector Figure 6.2. 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 currently no 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 β-activity discharges (excluding tritium), but no statistically significant change in total α-activity discharges Figure 6.3.

France and the UK have demonstrated through their reports on implementing OSPAR Recommendation 91/4 that BAT has been applied to minimise radionuclide discharges from their reprocessing plants. For example, the French authorities required the operators of the La Hague facility to achieve further reductions in discharges when they reviewed discharge authorisations. Since 2002, the nuclear fuel reprocessing plant at Sellafield (UK) has achieved reductions in discharges of 99Tc, a radionuclide to which both the 1998 and 2003 OSPAR Ministerial Meetings drew special attention. Discharges of 99Tc are expected to fall further and be maintained at low levels.

Figure 6.2 Annual discharges of total β-activity...

Figure 6.3 Average discharges of total α-activity...

Box 6.1 Drastic reduction in technetium discharges from Sellafield

The reduction of 99Tc discharges from the nuclear fuel reprocessing plant at Sellafield (UK) shows how OSPAR measures have helped to address a site-specific source of radioactive discharges. At Sellafield, reprocessing of spent nuclear fuel produces liquid waste containing 99Tc and other radionuclides. The waste was initially discharged to the Irish Sea after several years of decay storage. Following public concern over these discharges, the waste was retained in storage tanks after 1981. The Enhanced Actinide Removal Plant (EARP) was built at Sellafield to treat the waste, but was not designed to remove 99Tc. As a result, when EARP started treating the backlog of waste in 1994, 99Tc discharges and concentrations in the marine environment increased.

In response to concerns expressed by some OSPAR countries, in particular Ireland and Norway, and the joint statement by OSPAR Ministers for a reduction of 99Tc discharges, the UK reduced Sellafield’s 99Tc discharge limit from 200 to 90 TBq/yr, from 1 January 2000, and reviewed potential abatement techniques for 99Tc. The solution implemented in 2003 for new arisings of waste was vitrification and storage on land, but this technology was unsuitable for the residual stored waste. Research by Norway showed that doses to critical groups in the UK from 99Tc discharges to sea were higher than via disposal on land. This finding supported the development of a method involving precipitation of 99Tc and then storage on land.

A full-scale trial of the technique was launched, during which discharges from waste treatment were suspended. The trial was a success and the technology was implemented, allowing the UK to reduce the 99Tc discharge limit to 10 TBq/yr in April 2006. Actual discharges were below 5 TBq in 2007. By the end of 2007 all the stored technetium-bearing waste (medium-active concentrate) had been treated and associated discharges of 99Tc from this main source at Sellafield ended.

Towards the Radioactive Substances Strategy objectives

Nuclear and non-nuclear sectors contribute in different ways

The activity concentrations of naturally occurring radionuclides discharged from the offshore oil and gas industry are very low, both in produced water and in scale from pipes. However, the volumes of produced water are very large which results in substantial discharges of radionuclides. Annual discharges of total α-activity from the offshore oil and gas industry ranged from 6.4 TBq in 2005 to 7.4 TBq in 2007, while annual discharges of total β-activity (excluding tritium) were lower ranging from 4.3 TBq in 2005 to 4.9 TBq in 2007. These are best estimates calculated from the radioactivity of individual indicator radionuclides, rather than from measurements of total α-activity and total β-activity.

A comparison of the estimated radioactivity discharged in 2007 from the offshore oil and gas industry and that measured in discharges from the nuclear sector provides an indication of the relative magnitudes of the radioactivity discharged Figure 6.4. On the basis of these data, the offshore oil and gas industry is the dominant source of total α-activity, whereas the nuclear sector is the dominant source of total β-activity. For tritium, discharges from the nuclear sector are far higher than those from its use as a tracer in the Norwegian oil and gas industry.

Radionuclides used in the medical sector (e.g. 131I and 99mTc) are either short-lived or estimated to make a very small contribution to marine radioactivity at the regional level. The total activity of 131I discharged by nine OSPAR countries in 2007 was estimated at 20 TBq. In 2007, the sum of the 99Tc discharged from the decay of the medical product 99mTc for the five OSPAR countries that reported data was only 1MBq. OSPAR will no longer require reporting data on 99Tc from medical uses.

Figure 6.4 Comparison of activity discharges from the offshore oil...