Radiation Science and the Law: Experience in Relation to Childhood Leukemia in the vicinity of Sellafield, UK.

During 1983, a television documentary revealed the existence of an elevated incidence of leukemia in young people living in the village of Seascale, the community nearest to the nuclear fuel reprocessing site operated by British Nuclear Fuels plc (BNFL) at Sellafield in Cumbria. The programme not surprisingly alleged that the excess of leukemias could be linked to operations at the Sellafield site, and in particular to emissions of radioactivity from the site into the environment. 

At that time the study of the incidence of rare diseases such as leukemia in small population groups, and the apparent `clustering' effects which appear when incidence statistics are broken down in this way, was highly controversial. Although these controversies are not entirely resolved a series of scientific inquiries and advisory committees set up by the UK Government concluded that the incidence of leukemia in young people resident in Seascale has been elevated over the entire period from 1963 to 1992, with 8 cases of leukemia and non Hodgkin's lymphoma being recorded against 0.65 cases which would be expected in a population of that size on the basis of national incidence statistics. 

As a direct consequence of the television documentary, a major programme of scientific investigation was instigated, in part through scientific inquiries and advisory committees established by the UK Government and in part through BNFL and the UK nuclear industry as a whole, who saw the issue as posing a major challenge to public credibility in the safety of their operations. The scientific investigations touched upon a wide range of issues including: 

• The epidemiology of childhood leukemia in Seascale, in the vicinity of other nuclear sites and also more generally;
• The history of discharges to the environment from the Sellafield site, pathways of radiation exposure and the `reconstruction' of consequent radiation doses to young people living in Seascale;
• The radiation exposure of employees at the Sellafield site, in relation to the hypothesis that occupational radiation exposure of the parents could pass predisposition to leukemia through the germline to their children;
• Fundamental studies of radiobiology linked to low dose radiation exposure and the above possible causative mechanisms;
• Studies of other possible causative mechanisms of childhood leukemia which might explain the observed elevated incidence in Seascale.

The results of the scientific investigations and debates were therefore tested not only by the process of scientific peer review but also by the legal process and cross examination in Court. In both civil cases the Courts found in favour of BNFL and in 1996 the UK Committee on the Medical Aspects of Radioactivity in the Environment (COMARE) concluded, after review of all the available scientific evidence: 

"We have investigated possible causes ... and conclude that: 
On current knowledge, environmental radiation exposure from authorised or unplanned releases could not account for the excess. Much work has been done to reduce the uncertainties in the previous assessment although some uncertainties do still remain. 
On current knowledge occupational exposure to radiation is very unlikely to account for the excess. Although there are uncertainties regarding internal radiation exposures it is not clear how these could affect the population of Seascale and not the other residents of small towns and villages nearby where workers from the Sellafield site also live. 
Other possible hypotheses regarding chemicals and infectious aetiology have been considered. We conclude that environmental exposure to chemicals is unlikely to offer an explanation although admittedly the data are sparse. We do, however, believe that a mechanism involving infection may probably be a factor affecting the risk of leukemia and NHL in young people in Seascale."

• Understanding the entire history of site operations, including exposure of employees and emissions to the environment, is of great importance.
• Maintenance of good records - and successful recovery and interpretation of historical data - are a essential part of the management of historical liabilities.
• Whilst dose limits and associated standards are an appropriate basis for operational management of safety issues, it is always necessary to understand and keep under review the underpinning science, and to be continually both aware and critical of the many assumptions which underpin dose and risk assessment.

Assessment of the Dose from Contaminated Surfaces via Various Exposure Pathways

Various studies have been undertaken in the past to derive working levels for surface contamination by relating these to the dose received via various pathways. Dose assessments were, however, based on rather crude and conservative assumptions or experiments and mainly related to some of the most radiotoxic nuclides like Pu-239. 

For the present study realistic exposure scenarios for exposure to surfaces contaminated with natural radioactivity were considered. It covered both occupational exposure conditions inside metallurgical plants at mines and public exposure conditions to contamination released from mines. 

Resuspension for typical metallurgical plants, scrap handling facilities and transfer factors for contamination from surfaces to hands were verified through experiments while both beta and gamma doses from contaminated surfaces were calculated using Monte Carlo methods and derived or empirical formulas. 

The results indicated that derived working levels (DWL's) for surface contamination are plant and material specific. If determined in this way, considerable relaxation of area classification in terms of surface contamination as per requirements in document LG-1029 should in most cases be possible. Some relaxation for the release of contaminated equipment and egress of persons from controlled areas should also be possible. 

Considering an unconditional excempt dose of 10mSv/a, present unconditional release levels seem, however, to be realistic.
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Assessment of Radiological Dose Due to Incremental Radioactivity Increases in Cleared Former Mine Land

Historical mining activities resulted in the radioactive contamination of acres of land with enhanced natural radionuclides, e.g. land covered by slimes dams and sand dumps. In many cases there will be considerable economic advantage in the redevelopment of such land, after removal of the mining residues. The Nuclear Energy Act specifies a limit to the radio-nuclide content of the soil, below which the site is accepted as radiologically safe. Should the limit content value be exceeded, the site must be cleared to a lower level, considered to be representative of the background content level of the site, or, it must be proven that doses resulting from the residual activity will not be unacceptable high. 

The methods used to survey a given site and the sampling and analysis procedures will be discussed. Special modeling approaches were developed and used for the radon intrusion and external pathways. The ingestion pathway was assessed directly from dose conversion factors, taking the future land use scenarios into account. The effects of removal of soil from certain limited areas only, and in limited amounts, were modeled and optimised. 

The results show that, after removing limited amounts of material, doses on the site will be within the public dose limits stipulated in the Act if the site is used for industrial purposes. Certain areas of the site may be suitable for residential purposes.
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Radiation Doses to South African Underground Mine Workers

This paper provides a summary of the latest available data relating to underground radiation hazards at licensed mines. The data that will be presented should cover approximately 80% of the total underground workforce. 
These hazard assessments have relied largely on area monitoring with exposures measured within given areas being assigned to workers within those areas. The estimation of area exposure levels was based on the summation of the contributions from radon progeny, gamma radiation, and long-lived alpha radiation from potential dust inhalation. 

A frequency distribution of the data will be presented. The distribution will be tested for log-normality using accepted tests. 

A comparison of the data will be made with data from the following published works; 

1. Working Group on the Implications of the 1990 Recommendations of the International Commission on Radiological Protection (ICRP WG) Final Report.The Uranium Institute, November 1993
2. The Impact on the South African Gold Mining Industry of the Implementation of the 1990 ICRP Recommendations to Underground Operations.Chamber of Mines, September 1993
3. Combined Impact of Post-1990 ICRP Recommendations on Radiological Control Requirements Within the South African Mining Industry.Dr G P de Beer Atomic Energy Corporation of SA Ltd

Validation of the Electret Radon Monitor as an Underground Radon Dosimeter

It is common knowledge that some South African gold mines have elevated radon levels. Where these levels are of concern, and may have an effect on the health of the worker, it is necessary to measure the radon dose to the workers in the mine. 

There are at present only two types of personal radon dosimeter available that is able to measure radon namely the track etch detector and the electret ion chamber. The former has been accredited by the Council for Nuclear Safety for use underground in local mines. This study was undertaken to validate the electret ion chamber as provided Radelect of the U.S.A. 

As moisture and mud may present a problem, a special pouch made from Gortex was designed to carry the dosimeter in whilst underground. This material breaths whilst it is waterproof. The material was evaluated in a radon chamber with a NIST radon standard and found to be perfectly transparent to radon. 

Five electrets and five track etch detectors were issued to six workers. The work area, because it is an area with a particularly high radon concentration, has been well characterized through radon measurements wit a ML 98 Radon Spectrometer over a period of a year. In addition to the personal radon monitors each worker was further issued with Alpha Prism Radon Monitors. These monitors because they are so heavy, were only issued on a basis of one day per week 

The results of these measurements will be presented. From these measurements it may be concluded that the electret radon monitor is a suitable personal radon monitor for use underground.
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Radiation Dosimetry Services at BNFL's Sellafield Site, United Kingdom

BNFL operates two nuclear fuel reprocessing plants, four magnox nuclear reactors, a mixed oxide fuel fabrication facility, a complex of plants for the management of liquid and solid radioactive wastes, various research and development facilities and is engaging in decommissioning of redundant facilities, at its Sellafield Site located in the north west of England, adjacent to the Irish Sea and the English Lake District National Park. There are typically 7000 BNFL employees and 5000 Contractors employees working on site. 

Radiation dosimetry services, for the assessment and recording of radiation dose to workers arising from external sources of ionising radiation "external dose", and from radioactive materials taken into the body "internal dose", have been organised and run by a Site-based team for 45 years. This service is currently the largest and most comprehensive operating in the United Kingdom. 

In addition to producing information for purposes of complying with the law, the past ten years has seen a growth in other, but no less compelling, reasons why it is necessary for BNFL to be able to provide information and advice in response to: 

• requests from employees and members of the public for facts and understandable explanations;
• enquiries relating to alleged radiation linked disease in individuals;
• requests for information required to support independent scientific research into the health of workers and children.

Discussion of the Results Obtained from the Analysis of Ra and U in Water Performed by Different Laboratories

In 1997 an inter-comparison study was initiated by the CNS to assess the accuracy and the sensitivity of the analytical techniques used by radio-analytical laboratories. These studies related to the assessment of uranium and radium in water using different techniques. Five laboratories took part in the radium in water study and six laboratories took part in the uranium in water study. Evaluation of the results revealed certain anomalies which required resolution. 

This paper will report on the nature of the anomalies and the adequacy of the techniques (including the procedures) used with reference to environmental dose assessment in the mining industry and other fields.
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