Environmental radioactivity measurements in the United Kingdom

Environment International, Vol. 10, pp. 137-141, 1984

0160-4120/84 $3.00 + .00 Copyright © 1984 Pergamon Press Ltd.

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ENVIRONMENTAL RADIOACTIVITY MEASUREMENTS IN THE UNITED KINGDOM P. Christmas National Physical Laboratory, Teddington, Middlesex, TWl 10LW, United Kingdom (Received 9 December 1983; Accepted 9 April 1984) An account is given of current work in the field of radioactivity measurements in the marine and terrestrial environments of the United Kingdom. Reference is made to the increasing need for quality assurance and to the role of measurement standards and traceability.

Introduction Concern for environmental radioactivity in the United Kingdom dates largely from the end of World War II. At that time there was a general resumption and expansion of established industrial, research, and medical activities involving radioactive substances and, more important, the creation of large, new atomic energy and radionuclide production programs. Most notable were the decisions to establish the Atomic Energy Research Establishment (AERE) at Harwell and the Radiochemical Centre (now Amersham International Plc) at Amersham. The need to protect both man and the environment from these new activities was recognized at an early date: the Atomic Energy Act 1946 was the first U.K. legislation relating to atomic energy, and since then a wealth of additional legislation has come into being (Sim and Ritchie, 1983). The legal requirements are intended primarily to protect the individual; many of these guidelines, especially those involving the operation of nuclear installations and the disposal of radioactive waste, embody clear requirements for environmental monitoring. The growing concern with environmental radioactivity was underlined by the publication in 1976 of the so-called "Flowers Report" (Royal Commission on Environmental Pollution, 1976), which dealt primarily with the impact of the U.K. civil nuclear power program. A concise summary of environmental radioactivity monitoring in the United Kingdom has already been presented (Knight and Goodier, 1980). The present work aims to provide further insights into current activities in the various establishments concerned with radioactivity in the environment; it will also comment

briefly upon quality assurance, traceability, and the role of the national standards laboratory. During recent months there have been two meetings in the United Kingdom primarily concerned with aspects of environmental radioactivity, and the following remarks are in large measure based upon the proceedings of these meetings (Richards et al., 1983; Glover et al., 1983).

Current Measurement Programs All nuclear sites in the United Kingdom must be licensed, and site operators are required to perform environmental monitoring in order to meet the conditions of their authorization. The most notable among these operators are British Nuclear Fuels Ltd. (BNFL), the Central Electricity Generating Board (CEGB), the United Kingdom Atomic Energy Authority (UKAEA), and Amersham International Plc (AI). Although a new organization, the Nuclear Industry Radioactive Waste Executive (NIREX) has recently been established by the nuclear industry to deal specifically with radioactive waste storage and disposal in the United Kingdom, under the Radioactive Substances Act 1960, the power to authorize the disposal or accumulation of such waste remains under strict government control. In England and Wales such authorization is vested in the Secretary of State for the Environment; responsibility to ensure compliance with the conditions of authorization is shared by the Department of the Environment (DOE) and the Ministry of Agriculture, Fisheries and Food (MAFF). There are similar arrangements for other parts of the United Kingdom. 137

138 Within DOE, matters relating to the control of radioactivity are in the hands of the Radiochemical Inspectorate (RI). The necessary monitoring programs are performed largely by MAFF through its own laboratories, although DOE also arranges for some measurements to be made under contract by other government organisations or within the private sector. While the site operators, notably CEGB and BNFL, carry out their own extensive monitoring programmes (Heap and Short, 1983; BNFL, 1983; Short, 1984), a number of government bodies are concerned with a wider range of environmental radioactivity monitoring around licensed sites and elsewhere. Among the most active of these bodies, in addition to MAFF, are the UKAEA and the National Radiological Protection Board (NRPB). The next section will review some of the current activities of these organizations. Similar work is carried out by site operators and in universities and elsewhere.

Environmental Monitoring within the Atomic Energy Authority Within the Authority the greatest concentration of relevant effort is within the Environmental and Medical Sciences (EMS) Division of AERE, Harwell; the EMS Division is concerned with many aspects of environmental radioactivity monitoring (Cox et al., 1982). A program of fallout sampling in air and rain water has been in operation for some 25 years; it serves to monitor the levels of radioactivity resulting from nuclear test explosions and other sources. This work involves sampling of 9°Sr and '37Cs at seven stations in the United Kingdom and 19 others around the world, and has been complemented by in vivo measurements of 'aTCs" Other EMS programs are concerned with depth profiling for cesium, plutonium, and americium in peat, as well as the measurement of radioactivity in the vicinity of nuclear installations such as the Sellafield, Cumbria, works of BNFL and the Dounreay Nuclear Power Development Establishment (UKAEA) in Scotland. The latter measurements involve both actinides and fission products. Of particular note have been studies of sea-toland transfer of radionuclides, which have provided evidence for mechanisms by which surf-zone sea-spray is enriched in actinides relative to their concentration in the bulk sea water; these mechanisms themselves have also been examined. Note may also be taken of EMS studies of the migration of plutonium and americium though soil and the uptake of cesium and plutonium by grass and other crops. Measurements of uranium, thorium, and radium in coal samples have been made, largely in order to provide base data for the estimation of the radiological dose to the general public which may result from the use of fossil fuels.

P. Christmas In relation to the above work, research within the EMS Division and elsewhere at Harwell is concerned with the development of analytical techniques of improved sensitivity, including radiochemistry and o~-ray and y-ray spectrometry; for the latter, increasing use is being made of computer methods for data recording and analysis (Glover et al., 1983).

Environmental Monitoring by the National Radiological Protection Board The National Radiological Protection Board was established by the Radiological Protection Act 1970; the Board is responsible for performing research and development and providing information, advice, and services to those with responsibilities for radiological protection. Much of the work of NRPB is supported wholly or in part by other government organisations such as DOE, MAFF, and the Health and Safety Executive (HSE); substantial funding is also provided by the Commission of the European Communities (CEC). A large part of the work of the Board (NRPB, 1982) is concerned with environmental monitoring, environmental pathways to man, bodily uptake, metabolism and elimination of radioactivity, and the related dosimetry. A major objective is the reliable prediction of the consequences of accidental releases of radioactivity from nuclear installations, in relation both to transfer through the environment and to the ultimate hazard to man. Particular importance is attached to the environmental and biological behavior of transuranic elements, notably plutonium, americium, and curium, resulting from nuclear weapons testing and worldwide nuclear power programs; the NRPB staff has contributed to a recent international effort on this subject (NEA, 1981). Other recent work has included an investigation of the uptake of 239÷24°pu, 241Am, 9°Sr, and '37Cs by potatoes grown in soil containing Cumbrian estuarine sediment. The Board has also carried out the analytical work involved in a MAFF study of the levels of artificial radioactivity in a range of crops produced in West Cumbria, sampling soil and grass, milk, and cattle and sheep tissue; this study embraced radionuclides both deposited from releases to the atmosphere and discharged to the sea and subsequently deposited upon sea-washed pastures. NRPB continues regularly to monitor radioactivity in milk, a task previously carried out by the Letcombe Laboratory of the Agricultural Research Council. With regard to natural radioactivity, an on-going study seeks to quantify the radiation levels in buildings due to 222Rn decay products arising from uranium in various constructional materials and, more particularly, from the ground upon which the buildings stand. Measurements in the field are being augmented by a postal survey of some 2000 homes in the United Kingdom. This work will provide data upon which to base advice

Radioactivitymeasurementsin the UnitedKingdom on whether the United Kingdom should move toward control limits for radon exposure similar to those being considered in some other countries (O'Riordan et al., 1983). A number of articles available to the public contain uranium and thorium and their daughters; recent work at NRPB has studied the possible radiological hazards arising from collected geological specimens and incandescent gas mantles. Other work at NRPB has concerned the hazards from radon decay products in mines; this work has been carried out on behalf of the Mines and Quarries Executive of the HSE. U.K. statutory requirements to control exposure to this source of radiation are currently being drafted, taking account of NRPB recommendations. A recent survey has examined the radiological consequences of the emission of natural radioactivity from coal-fired power stations. Measurements, primarily of ~l°Pb, were made on liver samples from cattle grazed on pastures close to the CEGB power station at Didcot; the results were compared with similar measurements on material from an undisturbed rural site. This work is complementary to that being carried out by the UKAEA, discussed above. A substantial research and development effort is directed towards the improvement of instrumentation and measurement techniques. Recent advances in this area have included enhanced methods of radiochemical analysis and, for example, a sensitive method for the determination of ~29I by neutron activation analysis. There has also been development of calibration procedures for in vivo measurement of low-energy photon emitters.

Environmental Monitoring by the Ministry of Agriculture, Fisheries and Food The responsibilities of MAFF in relation to the Radioactivity Substances Act 1960 (discussed above), are vested in the Atomic Energy Unit of the Food Sciences Division and are enacted largely by the MAFF laboratories. There is concern for both the terrestrial and aquatic environments. In relation to the former, for example, the MAFF Central Veterinary Laboratory, Weybridge, carries out routine measurements of milk samples. The greater part of the environmental monitoring within MAFF is, however, concerned with the impact of radioactive discharges directly or indirectly into the sea (Hunt, 1982). An extensive monitoring program (Hunt, 1982) is carried out by the Fisheries Radiobiological Laboratory (FRL), part of the Directorate of Fisheries Research, Lowestoft. The purpose of this program is to verify the satisfactory control of liquid radioactive waste discharges to the marine environment from U.K. nuclear facilities and to ensure that public radiation exposure is within nationally accepted limits. The program is independent of similar programs carried out by the

139 operators of the facilities as a condition of their authorization to discharge radioactive waste. FRL also performs monitoring on behalf of DOE, the Welsh Ofrice, the Scottish Office, the Department of the Environment for Northern Ireland, the Channel Islands States, and the Republic of Ireland. The Channel Islands monitoring program is important in providing surveillance of the effects of radioactive liquid discharges from the French nuclear fuel reprocessing plant at Cap de la Haque. The measurement techniques employed by FRL include the determination of total ~-ray activity using thin sources with a '°K standard and -r-ray spectrometry with both NaI and Ge(Li) detectors. Pure B-ray emitters such as 9°Sr and 99Tc are separated chemically prior to counting. Transuranic nuclides are chemically separated and analyzed by o~-ray,spectrometry using silicon surface barrier detectors. Within FRL, as elsewhere, the conversions from measured activity to estimated dose to the public are based largely upon recommendations of the International Commission on Radiological Protection (ICRP) (ICRP, 1979-1982), although use has been made of revised uptake factors for transuranics in man recently published by the NRPB (Harrison, 1982). Results are quoted in terms of effective dose equivalent as a percentage of the ICRP-recommended dose limit of 5 mSv yr-1 for members of the public (ICRP, 1977). In the vicinity of a given nuclear facility, consideration must in general be given to the radiation exposure of the public from both internal and external sources. The former will involve measurements of radioactivity in fish and shellfish (occasionally also seaweed) and the study of their consumption, in order to identify possible critical groups among the local population. External exposure estimates, on the other hand, are based upon the results of measurements of intertidal areas with portable -y-ray dosimeters together with data upon occupancy of such areas. The British Committee on Radiation Units and Measurements (BCRU) has examined in detail the problems of the measurement of environmental ~,-ray dose rate (Spiers et al., 1981). Recent work at FRL has included, in addition to the above, the determination of radium and radon isotopes in marine environmental samples (Richards et al., 1983; Glover et al., 1983). These radionuclides are of interest as oceanographic tracers and in the study of sedimentation rate (21°Pb dating), mixing ratios, and bioturbation in sediments. The study of the transfer within the marine biological environment of radium, originating from the sea bed, may also provide a perspective against which to assess the significance, for marine organisms, of exposure arising from the disposal of radioactive waste into the sea. Also studied (Glover et al., 1983) have been the applications of yield tracers for the determination of et-ray-emitting actinides, such as the use of 2aSNp for the determination of neptunium.

140

The Impact of Environmental Radioactivity on Offshore Oil & Gas Production A recent meeting on offshore radioactivity (Oyez, 1983) was concerned not only with the potential hazards associated with the use of sealed sources for -y-ray radiography and other purposes but also with problems arising from geological radioactivity. It has been found, for example, that hydrocarbon production facilities in the North Sea are becoming contaminated by ~38U daughters leached from black shales by chloride-bearing brines. 2~2Rn is thereby released into the gas or oil deposits, and its daughters are deposited within scale which forms in the pipework of the production facility. The levels of radioactivity so far detected in the active scale are low; nevertheless, they may constitute a hazard during descaling operations. Consideration must be given to the need to avoid the generation of airborne dust and to prevent the ingestion or inhalation of active material. The accumulated scale may require treatment as radioactive waste. [While there are no specific regulations concerning radioactive substances on the U.K. continental shelf, the handling of active scale may be deemed to be covered by, for example, the Radioactive Substances Act of 1960 and the Health and Safety at Work Act of 1974 (Sim and Ritchie, 1983)]. It has been suggested that the tradition of offshore descaling may give way to the use of onshore facilities in which the descaling operations themselves and the associated controis could be more easily effected. Radon in North Sea gas contributes to the radon concentration in buildings where gas is used as a fuel; however, the activity concentrations have been estimated to be low (O'Riordan et al., 1983), on a par with those arising from domestic water supplies.

Quality Assurance, Standards, and Traceability The need for quality assurance in low-level radioactivity measurements was underlined by Fry and O'Riordan in a paper presented at the recent Harwell Meeting (Glover et al., 1983), in which attention was drawn to the need for well-designed programs with clear objectives, incorporating measurements of appropriate sensitivity. Other papers presented at the same meeting emphasized the growing requirements, for example, for natural matrix standards and for various types of u-ray standards both for assay purposes and for checking the performance of detector and data-processing systems. Reference was also made to the need for large-area radioactivity standards to provide reference radiations for the calibration of instruments used for routine monitoring of s-ray and/~-ray surface contamination; attention was also drawn to the increasing importance of reliable nuclear data. An important aspect of quality assurance is the verification of measurement procedures through intercomparisons, particularly at the international level. At

P. Christmas

Harwell (Glover et al., 1983), reference was made to the Geochemical Ocean Sections Study (GEOSECS) and to intercomparisons organized by the International Atomic Energy Agency (IAEA) and the International Committee for Radionuclide Metrology (ICRM). A current U.K. contribution in this area involved distribution of a Z2STh/~32U spike solution prepared at AERE, Harwell. As pointed out previously (Knight and Goodier, 1980), the majority of calibrations of radioactivity measurement systems are achieved by reference to commercially available standard solutions. Such standards are generally of high quality and their calibrations are often related in a demonstrable manner to the national standards provided for the United Kingdom by the National Physical Laboratory (NPL). However, as noted by the present author (Glover et al., 1983), this relationship is not generally of itself sufficient to guarantee traceability of the end-of-the-line measurements. The preparation of working standards for environmental measurements may involve radiochemistry, large dilution factors and complex source preparation procedures, together with an increasing reliance upon automated equipment. The achievement of measurement traceability requires not only the use of appropriate standards but also, and equally important, strict adherence to specified procedures. The importance of traceability in radiation protection is emphasized in the United Kingdom at the present time by new legislation being prepared by the Health and Safety Commission (HSC, established under the Health and Safety at Work Act of 1974 and embodying the HSE) to comply with CEC Directives. In its Consultative Document (HSC, 1982) the Commission pays close attention to the manner in which compliance with its regulations is to be ensured and breaks new ground in seeking to introduce explicitly the concept of traceability into U.K. law. Provision is made for formal approval of personal dosimetry laboratories and test houses for monitoring instruments. In meeting the proposed HSC requirement that "measurements made in the course of type testing, preuse testing and routine testing of calibration should make use of radiation standards which are traceable to national standards," a role is foreseen for the British Calibration Service (BCS). BCS, part of NPL, operates by accrediting laboratories for particular calibration procedures; it is already active across a wide spectrum of nonradiological metrology, and approval criteria have been written for several categories of radiological calibration. The customer may benefit from the traceability incorporated into BCS certificates and from reciprocity between national calibration services; mutual recognition of certificates already exists, for example, between BCS and its counterparts in Italy and the Federal Republic of Germany. NPL welcomes the HSC initiatives in respect of

Radioactivity measurements in the United Kingdom

traceability and the proposal to involve BCS in radiological protection. It is foreseen that BCS accreditation criteria will involve regular measurement assurance programs. It also appears inevitable that, within the United Kingdom, producers, users, and measurers of radioactivity at all levels will become increasingly involved in such programs, in which NPL may expect to play an important part through its Division of Radiation Science and Acoustics. a Recent events in the United Kingdom and elsewhere have shown that environmental radioactivity measurements may be subject to retrospective scrutiny and that the results of such measurements may achieve new significance as further insights are sought, or gained, into the effects upon man of low levels of radioactivity. Quality assurance, incorporating traceability, has an essential role in ensuring confidence in measurement data and in risk estimates based upon those data. It is hoped that such quality assurance will ultimately secure general acceptance of nuclear power programs and other beneficial applications of nuclear science and technology. Acknowledgement--The author is indebted to I. W. Goodier for his

comments upon the draft of this paper.

References British Nuclear Fuels Ltd. (1983) Annual report on radioactive discharges and monitoring of the environment during 1982. Report, BNFL, London. Cox, R. A., Carter, T., Gibson, J. A. B., Morgan, A., Salmon, L., and Taylor, M. (1982) Environmental and Medical Sciences Division progress report 1981. United Kingdom Atomic Energy Authority Report AERE PR EMS 9, Her Majesty's Stationery Ofrice, London. Glover, K. M., Ivanovich, M., and Lally, A. E. (10, 13 May 1983) International Committee for Radionuclide Metrology seminar on alpha particle spectrometry and low level measurement. United Kingdom Atomic Energy Authority Report AERE-R10900, Harwell. Glover, K. M., Ivanovich, M., and Lally, A. E. (1984) Proceedings second seminar on alpha-particle spectroscopy and low-level measurement. Nucl. Instrum. Methods 223, 181-628.

aNote added in proof: Amersham International Pie has recently applied for BCS accreditation in respect to a range of radionuclide standards.

141 Harrison, J. D. (1982) Gut uptake factors for plutonium, americium and curium. NRPB report R129, Her Majesty's Stationery Office, London. Health and Safety Commission (1982) The Ionizing Radiations Regulations 198-. HSC Consultative Document, Her Majesty's Stationery Office, London. Heap, G. F. and Short, A. (1983) Report on radioactive discharges, associated environmental monitoring and personal radiation doses resulting from operation of CEGB nuclear sites during 1982. Report HS/R 182/83, Central Electricity Generating Board, London. Hunt, G. J. 0982) Radioactivity in surface and coastal waters of the British Isles, 1980. Aquatic Environment Monitoring Report No. 8, MAFF Directorate of Fisheries Research, Lowestoft. International Commission on Radiological Protection (1977) Recommendations of the International Commission on Radiological Protection. ICRP publ. 26, Pergamon Press, Oxford. International Commission on Radiological Protection (1979-1982) Limits for intakes of radionuclides by workers. ICRP publ. 30, Pergamon Press. Oxford. Knight, A. and Goodier, I. (1980) Environmental monitoring in the United Kingdom. Environ. Int. 3, 427-428. National Radiological Protection Board (1982) Research and development report 1979-1981. National Radiological Protection Board Report NRPB/R&D4, Her Majesty's Stationery Office, London. Nuclear Energy Agency (1981) The environmental and biological behaviour of plutonium and some other transuranium elements. Report by an NEA group of experts, NEA/OECD, Paris. O'Riordan, M. C., James, A. C., Rae, S., and Wrixon, A. D. (1983) Human exposure to radon decay products inside dwellings in the United Kingdom. National Radiological Protection Board report NRPB-R152, Her Majesty's Stationery Office, London. Oyez (15 April 1983) Offshore Radioactivity-Contamination and Sources. Conference, organized by Oyez International Ltd., London. Richards, L. A., Bates, T. H., Crook. M. A., Dutton, J. W. R., Eakins, J. D., and Ware, A. 08, 19 April 1983) Fourth Symposium on the Determination of Radionuclides in Environmental and Biological Materials. Department of Industry, Laboratory of the Government Chemist, London. Royal Commission on Environmental Pollution (1976) Nuclear power and the environment. Sixth Report, Command 6618, Her Majesty's Stationery Office, London. Short, A. (1984) Environmental monitoring around nuclear sites, J. Soc. Radio/. Protect., (in press). Sim, D. F. and Ritchie, K. J. S. 0983) Summary of the law relating to atomic energy and radioactive substances. United Kingdom Atomic Energy Authority, London. Spiers, F. W., Gibson, J. A. B., and Thompson, I. M. G. (1981) A guide to the measurement of environmental gamma-ray dose rate. A report prepared on behalf of the British Committee on Radiation Units and Measurements. National Physical Laboratory, Teddington.