Notes

7.1 This section deals with general environmental monitoring for radioactivity, and the routine monitoring of radioactive waste disposals from nuclear sites.

Disposals from Nuclear Sites and Environmental Monitoring for Discharges

7.2 Tables 7.1 to 7.3 show radioactive waste disposals from nuclear sites in Scotland. Until 1 April 1996, responsibility for the control of radioactive waste disposal rested with the Chief Inspector of HM Industrial Pollution Inspectorate, but from that date the functions of the Chief Inspector were transferred to the new Scottish Environment Protection Agency. Disposal is prohibited except in accordance with an authorisation. Authorisations are granted only after the operator's proposals have been examined to ensure that radioactive waste is not being produced unnecessarily and that there is a justifiable need to dispose.

A certificate is issued containing limitations and conditions designed to achieve compliance with relevant national and international standards including the dose limits for members of the public recommended by the International Commission on Radiological Protection. The certificates contain the requirement that records be kept of radioactive discharges and that the techniques employed for measuring the radioactivity of discharges are subject to the agreement of the Chief Inspector (now SEPA). In addition, samples of waste are collected and analysed by external laboratories to provide independent checks on the operator's results. The Scottish Office Agriculture, Environment and Fisheries Department (SOAEFD) statistical bulletin Radioactive Waste Disposals from Nuclear Sites in Scotland: 1991 to 1995 (Env/1996/3) and the joint Ministry of Agriculture, Fisheries and Food and Scottish Environment Protection Agency report Radioactivity in Food and the Environment, 1996 gives further details.

7.3 Tables 7.4 to 7.6 deal with the regular programme of monitoring, undertaken by operators as a condition of authorisation, to check the environmental effects of disposals from nuclear sites. As mentioned in paragraph 7.2 above, HM Industrial Pollution Inspectorate (HMIPI) ceased to exist with effect from 1 April 1996 when the statutory functions of the Chief Inspector were transferred to the newly formed Scottish Environment Protection Agency (SEPA). From that date, SEPA became the body responsible for the regulation of the safe keeping, use and disposal of radioactive sources and waste under the provisions of the Radioactive Substance Act (1993). It also has the wider responsibity of protecting human health and environmental quality.

SEPA also carries out a monitoring programme to determine levels of radioactivity in the environment around nuclear licenced sites, and to determine the exposure of the general population. Information from local habit surveys is combined with data from this monitoring programme to help in assessing the dose to the most exposed individuals (critical groups) and for comparison with national and international standards including dose limits for members of the public. More detail is contained in the SOAEFD statistical bulletin Environmental Monitoring for Radioactvity in Scotland , 1991-1995 (Env/1996/6), and the report Radioactivity, in food and the Environment 1996 (RIFE-2), jointly published by SEPA and the Ministry of Agriculture Fisheries and Food (MAFF).

Exposure to Natural Radiation in Dwellings

7.4 Radiation of natural origin is responsible for most of the exposure to the population. According to the latest review by the National Radiological Protection Board (NRPB), some 85 per cent of the annual dose in the United Kingdom arises from natural sources, the main components of which are cosmic rays, terrestrial gamma rays, the short-lived decay products of radon and long-lived radionuclides in the body from diet. The situation is similar for Scotland (chart 7.1). The short-lived decay products of radon-222, often called radon daughters, are the most important source and account for almost half of the overall dose from natural radiation, they also cause the highest doses to individual people. In 1990, NRPB recommended to

Government that the Action Level for radon in homes should be 200 becquerels per cubic metre of air (bqm^-3) and suggested a comprehensive control strategy based on the concept of Radon Affected Areas. These are specified as areas where one per cent or more of homes exceed the Action Level. The Government accepted this advice and continued the work it had already begun on radon. The Scottish Office Environment Department (now SODD) commissioned the NRPB to carry out surveys of radon levels in Scottish dwellings.

7.5 A survey to review the available data on radon in homes in Scotland from work undertaken by NRPB (Radon in Dwellings in Scotland : 1996 Review, NRPB M569) was published in October 1996. Previously, NRPB advised SODD that parts of the districts of Caithness, Sutherland, Gordon and Kincardine and Deeside qualified as Radon Affected Areas and published contoured maps showing the percentage of homes above the Action Level (map 7.2) (Radon Affected Areas: Scotland Doc. NRPB 4, No 4, 1-8). Subsequently, arrangements have been made by SODD for home owners within the Radon Affected Areas to qualify for free radon measurements from NRPB, and to continue the radon mapping programme (map 7.1 and chart 7.2).

7.6 A survey of indoor gamma-ray dose rates was also undertaken by NRPB in homes in Scotland. The gamma-ray dose rate was found to be relatively low and fairly constant across the country and action to control exposure was not considered necessary. Further details are given in Natural Radiation Exposure in UK Dwellings. (NRPB R190 - May 1988).

General Environmental Monitoring

7.7 Gamma radiation levels outdoors in Great Britain were measured by NRPB staff. The intention was to make at least one measurement in every readily accessible 10km square of the Ordnance Survey Grid and over 3,100 measurements were made covering 90 per cent of the 2,400 or so 10km grid squares in Great Britain. To achieve total coverage, the missing values were infilled using special mathematical techniques. In general, the gamma-ray dose rate varies within a 10km grid square and individual measurements are of limited value. A smoothing routine was therefore used to produce a more representative value for each square. Map 7.3 uses the infilled data and thus emphasises local detail while map 7.4 uses infilled doubly-smoothed data revealing general underlying patterns. Greater detail is given in Gamma-radiation Levels Outdoors in Great Britain (NRPB R191- February 1989).

7.8 As part of the National Response Plan, introduced by the Government in 1987 to deal with the possible effects on the UK of nuclear incidents abroad such as that at Chernobyl, a network known as the Radioactive Incident Monitoring Network (RIMNET) was established to detect any unusual rise in radioactivity. The network is operated by the Department of the Environment. At present there are 27 RIMNET sites in Scotland and chart 7.3 summarises the monthly mean gamma dose rates at each site. Detailed results are published by the Department of the Environment, Transport and the Regions, in a series of statistical bulletins.

7.9 Programmes of general environmental monitoring are undertaken by the National Environmental Technology Centre (NetCen) of AEA Technology plc, at their Culham Laboratory and NRPB. The AEA Technology sampling points at Lerwick and Eskdalemuir (charts 7.4 to 7.6) are part of an international network of sites for monitoring radionuclides in air and rainwater. At the two Scottish sites, air is sampled continuously at 1m above the ground by passing quantities of air through filter papers. Rainwater samples are collected by funnels mounted over polythene bottles, and laboratory analysis of samples, is performed by gamma ray spectrometry. More information is contained in the AEA Technology series of reports Radioactive Fallout in Air and Rain.

7.10 The NRPB operates an environmental surveillance programme in order to assess the intake of artificially produced radionuclides in the UK population. In Scotland, the programme includes the analysis of airborne dust and rainwater in Glasgow, and of samples of milk from a number of depots throughout the country. For the milk analysis, account is taken of the quantity of milk handled by each depot. Samples from 3 months are bulked to provide a quarterly sample which is analysed for strontium 90, caesium 137 and calcium (chart 7.7). Laboratory analysis is performed by radiochemical methods. Further details are contained in the NRPB series of reports entitled Environmental Radioactivity Surveillance Programme.

7.11 Following the Chernobyl accident in April 1986, extensive monitoring surveys of its effect in Scotland were undertaken by the Scottish Office. Full details of Chernobyl monitoring in Scotland are given in two statistical bulletins Chernobyl Accident, Monitoring for Radioactivity in Scotland published by SODD April 1988 and SOAEFD in August 1990.