Summaries of articles

2002-2005 · 2006

JRP volume 26, issue 2 (June 2006)
 

Cancer consequences of the Chernobyl accident: 20 years on
E Cardis et al (127--140)
26 April 2006 marked the 20th anniversary of the Chernobyl accident. On this occasion, the World Health Organization (WHO), within the UN Chernobyl Forum initiative, convened an Expert Group to evaluate the health impacts of Chernobyl. This paper summarises the findings relating to cancer. A dramatic increase in the incidence of thyroid cancer has been observed among those exposed to radioactive iodines in childhood and adolescence in the most contaminated territories.  Iodine deficiency may have increased the risk of developing thyroid cancer following exposure to radioactive iodines, while prolonged stable iodine supplementation in the years after exposure may reduce this risk. Although increases in rates of other cancers have been reported, much of these increases appear to be due to other factors, including improvements in registration, reporting and diagnosis. Studies are few, however, and have methodological limitations. Further, because most radiation-related solid cancers continue to occur decades after exposure and because only 20 years have passed since the accident, it is too early to evaluate the full radiological impact of the accident. Apart from the large increase in thyroid cancer incidence in young people, there are at present no clearly demonstrated radiation-related increases in cancer risk. This should not, however, be interpreted to mean that no increase has in fact occurred: based on the experience of other populations exposed to ionising radiation, a small increase in the relative risk of cancer is expected, even at the low to moderate doses received. Although it is expected that epidemiological studies will have difficulty identifying such a risk, it may nevertheless translate into a substantial number of radiation-related cancer cases in the future, given the very large number of individuals exposed.

Fission, critical mass and safety - a historical review
G Meggitt (141--159)
The paper is a historical review of the discovery of nuclear fission, the evolution of the concept of critical mass and how it has been determined. The development of calculational methods - starting with those used in the Manhatten Project - and their relationships to experimental determinations are traced. The increasing power of computers has radically changed what can be done and the use of criticality codes in ensuring nuclear safety is
outlined to the present day.

Comparison of a generic biosphere model with site specific models for the BIOMOSA project
Q Chen et al (161--187)
This paper outlines the development and application of a generic biosphere tool BIOGEM (BIOsphere GEneric Model) as part of the BIOMOSA project (BIOsphere Models for Safety Assessment of radioactive waste disposal). The model was applied to five typical locations in the EU and a comparison between BIOGEM and five site-specific biosphere models was carried out. The results were estimates of the annual effective individual doses to the critical groups and the ranking of the importance of the exposure pathways for each of the sites. Uncertainty in the results was also estimated by means of stochastic calculations based on variation of the site-specific parameter values. In general there was an acceptable agreement between the BIOGEM results and the results from the site-specific models for both the deterministic and stochastic calculations.
 

Collective dose – practical ways to estimate a dose matrix
J Simmonds et al (189--198)
This paper is an initial attempt to provide a breakdown of collective doses by geographic region and time, and to give an idea of associated individual doses for routine discharges to atmosphere. The results show that it is important to distinguish between the different population groups for up to a few hundred years following the discharge. However, beyond this time the main contribution is from global circulation and this distinction is less important. The majority of the collective dose was delivered at low levels of individual doses, less than 10^-5 Sv y^-1.

Public exposure to radio waves near GSM microcell and picocell base stations
T G Cooper et al (199--211)
Masts and rooftop mounted radio transmitters have spread throughout the environment wherever people use mobile phones. Sometimes concern is expressed about exposure to the radio waves, and key elements of any risk assessment are measured exposure levels. Data have been published for exposures near to such macrocell base station transmitters, but not for exposures near microcell and picocell base stations, which are less visually obvious but have their antennas deployed nearer to ground level. This project reports the results from visits to 20 randomly chosen microcell and picocell transmitter sites and finds exposures comfortably within accepted guideline levels, even when people are standing directly beneath the antennas. Nevertheless, exposures can be higher than with macrocells because people can approach nearer to the antennas.

Towards establishment of the national reference dose levels from CT examinations in Tanzania
J E Ngaile et al (213--225)
The study was carried out to assess the radiation dose levels from CT examinations in Tanzania according to reference dose quantities recommended by the EC guidelines. The reference dose levels (RDLs) from five common CT examinations obtained from eight hospitals were estimated from measurements of CT dose index (CTDI) in standard phantoms using typical exposure parameters. Wide variations of mean CTDIw and dose-length product (DLP) values per examination were observed among hospitals. These variations were mainly attributed to the variations of CT scanning protocols and scanner types. The mean CTDIw values per examination for almost all hospitals were below proposed RDLs, while the mean DLP values per examination were almost all above the proposed RDLs for all except one hospital. These were influenced by large scan length used in Tanzanian hospitals. Further investigations on optimisation of scanning protocols are needed in order to achieve the required level of dose for establishment of the national RDLs.

Hormone melatonin against radiation induced damage in mouse cerebellum
R Sisodia et al (227--234)
This study with the hormone melatonin supplemented orally in Swiss albino mice confirms the antioxidative properties of melatonin resulting in its prophylactic property against radiation induced biochemical and cellular alterations in cerebellum, with special reference to Purkinje cells. The findings support the idea that melatonin may be used as an anti-irradiation drug due to its potent free radical scavenging and antioxidative efficacy.
 

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JRP volume 26, issue 1 (March 2006)
 

Case-control study of leukaemia incidence along the Techa River
E Ostroumova et al (17--32)
Radioactive materials released in liquid effluents from the Mayak nuclear weapons facility (in the Southern Urals, Russia) during the period 1949--56 caused exposure to people living along the Techa River. A case-control study nested within the Extended Techa River Cohort was conducted to determine whether the risk of leukaemia incidence increased with protracted exposure to ionising radiation, considering also non-radiation risk factors. The study included 83 leukaemia cases and 415 controls. The leukaemia risk associated with a 1 Gy increase of total, external, and internal red bone marrow dose was increased by factors of 3.5, 5.8 and 3.3, respectively. A history of solid tumour incidence was associated with a 2.5-fold increase in leukaemia risk.

Events at Sellafield from 1950 to 2000 with an off-site impact
G A M Webb et al (33--49)
The Sellafield nuclear installation, formerly Windscale and Calder Works, in Cumbria, England, started operations in 1950. This paper reports the results of a review from then up to 2000 of all events that had, or could have had, radiological implications for members of the general public. A complete list of events is given that would now be assessed as INES Level 3 or above (that is a `very small release’ or greater) on the basis of off-site impact. Of these 21 events, 15 have been rated in the lowest category (Level 3). The last such event occurred in 1984. Some of these events have been fully documented in the public domain, but a number have been identified that had not previously been fully reported.

Thyroid cancer among Ukrainians and Belarusians who were children or adolescents at the time of the Chernobyl accident
P Jacob et al (51--67)
The study explores thyroid cancer incidences after the Chernobyl accident associated with radiation and with other factors (baseline incidence). In most of the Ukrainian regions with high doses, and in Belarusian regions, the baseline cancer incidence was found to be a factor of 2.3 to 4.0 larger than in other regions of Ukraine. Due to an improved surveillance the thyroid cancer baseline incidence increased from 1988 to 1999 by a factor of two to three. The baseline cases contributed about 70% to the total thyroid cancer incidence in Ukraine, and about 40% in Belarus.

What kind of distribution of doses between individuals is ethically acceptable?
P Wikman-Svahn et al (69--84)
What weight should be given to individual doses in relation to collective or aggregated doses and what makes one distribution of individual doses better than another? Which principles should be used for making such judgements, and are there any rational or ethical grounds for choosing among alternative principles? This paper introduces a mathematical framework in which such assessments can be made precisely in terms of comparisons between alternative distributions of individual doses. Principles from radiation protection and from parallel discussions in moral philosophy and welfare economics are defined using this framework and then analysed on the basis of their formal properties.

Radon in Irish schools
H Synnott et al (85--96)
Indoor radon contributes over 60% of the radiation dose to the Irish public and it can be linked to nearly 200 lung cancer deaths each year in Ireland, approximately 13% of all lung cancers. The national survey of radon in Irish dwellings found a significant proportion of homes in certain areas had elevated radon concentrations. Concern was expressed that schools could also have high radon concentrations, and the Irish Department of Education and Science commissioned a radon survey in all schools and arranged for remedial work to be carried out where elevated radon concentrations were found.  This paper presents the methodology and results of this survey.

Neutron fluence measurements using thermoluminescence dosimeter TLD-600
F Torkzadeh and F Manouchehri (97--103)
Thermoluminescence dosimeter TLD-600 chips were used in this work on thermal neutron fluence measurements. The number of induced 3H nuclei in TLD-600 after thermal neutron irradiation was determined. The thermoluminescence intensity due to the absorbed energy of tritium decay betas was used for the calculation of the number of ³H nuclei, which is proportional to the neutron fluence. The damage effect due to the high neutron dose has been reduced by a 24 h special thermal treatment. The long half-life of tritium made an accurate and convenient measurement of neutron fluence possible.

RADCONTAB 1.0: a look-up tables tool for radiological assessment of contaminated land on Nuclear Licensed sites
S M Willans and H G Richards (105--110)
A simple electronic spreadsheet  `look-up tables’ tool has been developed to provide a consistent basis for performing radiological assessments of contaminated land on UK Nuclear Licensed sites. The specification and design of the tool has been subject to open consultation and peer review. The tool with accompanying guide is now freely available on the internet.