Radiation Protection Dosimetry - recent issues

EURADOS intercomparison 2006 to harmonise European early warning dosimetry systems

Dombrowski, H., Neumaier, S., Thompson, I. M. G., Wissmann, F. — 2009-06-30

In 2006, the European Radiation Dosimetry (EURADOS) Working Group on Environmental Radiation Monitoring (WG3) organised a third European intercomparison of dosimetry systems operated in national early warning networks. Similar to the intercomparisons in 1999 and 2002, the main aim of this exercise was to support the process of harmonisation of area monitoring in Europe by providing the network operators with basic information on the calibration and performance of their dosimetry systems. In order to characterise these systems, their following basic parameters were investigated: the response to terrestrial and cosmic radiation, the detectors' inherent background, the response at low dose rates, the energy dependence of the response as well as the sensitivity of the detector systems to small changes of the dose rate in a natural environmental radiation field. In the 2006 EURADOS intercomparison, scientists from seven countries participated to study the characteristics of 11 detector systems. All results are presented in terms of the operational quantity ambient dose equivalent, H*(10). The advent of this quantity has caused the development of new detector systems for area monitoring. Some of these new systems participated in a EURADOS intercomparison for the first time. The results are consistently presented together with uncertainties so that statistical effects can be distinguished from real detector features, which improves the interpretation of the results. By using the results of this intercomparison, some detectors were re-calibrated. The achievable improvements concerning harmonisation in dose-rate measurements in the natural environment are discussed.

Monte Carlo estimation of photoneutrons contamination from high-energy X-ray medical accelerators in treatment room and maze: a simplified model

2009-06-30

Despite all advantages associated with high-energy radiotherapy to improve therapeutic gain, the production of photoneutron via interaction of high-energy photons with high atomic number (Z) materials increases undesired dose to the patient and staff. Owing to the limitation and complication of experimental neutron dosimetry in mixed beam environment, including photon and neutron, the Monte Carlo (MC) simulation is a gold standard method for calculation of photoneutron contaminations. On the other hand, the complexity of treatment head makes the MC simulation more difficult and time-consuming. In this study, the possibility of using a simplified MC model for the simulation of treatment head has been investigated using MCNP4C general purpose MC code. As a part of comparative assessment strategy, the fluence, average energy and dose equivalent of photoneutrons were estimated and compared with other studies for several fields and energies at different points in treatment room and maze. The mean energy of photoneutrons was 0.17, 0.19 and 0.2 MeV at the patient plan for 10, 15 and 18 MeV, respectively. The calculated values differed, respectively, by a factor of 1.4, 0.7 and 0.61 compared with the reported measured data for 10, 15 and 18 MeV. Our simulation results in the maze showed that the neutron dose equivalent is attenuated by a factor of 10 for every 4.6 m of maze length while the related factor from Kersey analytical method is 5 m. The neutron dose equivalent was 4.1 mSv Gy^–1 at the isocentre and decreased to 0.79 mSv Gy^–1 at a distance of 100 cm away from the isocentre for 40 x 40 cm². There is good agreement between the data calculated using simplified model in this study and measurements. Considering the reported high uncertainties (up to 50%) in experimental neutron dosimetry, it can be concluded that the simplified model can be used as a useful tool for estimation of photoneutron contamination associated with high-energy photon radiotherapy.

Organ dose conversion coefficients for external photon irradiation using the Chinese voxel phantom (CVP)

Li, J., Qiu, R., Zhang, Z., Liu, L., Zeng, Z., Bi, L., Li, W. — 2009-06-30

A set of conversion coefficients from kerma free-in-air to the organ absorbed dose are presented for external monoenergetic photon beams from 10 keV to 10 MeV based on a whole-body, Chinese adult male voxel phantom. This computational phantom, called the Chinese voxel phantom (CVP), including totally 23 organs, was developed from magnetic resonance imaging of a young healthy Chinese man at a resolution of 2 x 2 mm. Compared with the ICRP Reference Man, more than half of the organs or tissues in the CVP show mass differences of more than 20. Monte Carlo simulations with MCNP code were carried out to calculate the organ dose conversion coefficients. Irradiation conditions include anterior–posterior, posterior–anterior (PA), right-lateral, left-lateral, rotational and isotropic geometries. Organ dose conversion coefficients from this study are compared with the data from the Asian voxel phantoms Visible Chinese Human and KORMAN. These data sets agree with each other within 10% for photon energy >5 MeV. However, discrepancies of 34–63% were observed for organs of the alimentary tract, such as the oesophagus and stomach, those of the urinary system, such as the bladder wall and thyroid, especially at low photon energy range and PA geometry. These results suggest that the anatomical variation within the Chinese population, as represented by these adult male voxel phantoms, can lead to uncertainties when a standard phantom is used for the entire population.

Study of environmental radioactivity in Palestine by in situ gamma-ray spectroscopy

Lahham, A., Al-Masri, H., Judeh, A. — 2009-06-30

This work presents qualitative and quantitative evaluation of environmental radioactivity in the central and southern areas of the West Bank, Palestine. For this purpose, the technology of in situ gamma-ray spectroscopy is used with a scintillation of 7.6 x 7.6 cm NaI(Tl) crystal connected to multichannel analyzer InSpector 2000 from Canberra instruments and laptop computer. Gamma-ray spectra were collected using the detector placed 1 m above the ground surface. Calibration of the detection system for in situ measurements of gamma-emitting radionuclides in open terrain is performed theoretically using Monte Carlo techniques. Measurements are conducted in 18 locations in 3 regions across the West Bank. The vast majority of identified radionuclides are naturally occurring gamma-emitting sources (the decay products of ²³⁸U, ²³²Th and ⁴⁰K). The only identified anthropogenic radionuclide is ¹³⁷Cs. Activity concentrations of ⁴⁰K, ²³⁸U, ²³²Th as well as the total outdoor gamma dose rate from these radionuclides were determined from the gamma-ray spectra. The highest activity concentrations of the three primordial radionuclides were 203 Bq kg^–1 for ⁴⁰K, 32 Bq kg^–1 for ²³⁸U and 30 Bq kg^–1 for ²³²Th. The total outdoor gamma dose rate calculated for the whole study area at 1 m above ground ranged from 6 to 30 nGy h^–1 with a mean of 18 ± 7 nGy h^–1, which represents about 30% of the world average value.

Mass attenuation coefficients of natural Rhizophora spp. wood for X-rays in the 15.77-25.27 keV range

Shakhreet, B. Z., Bauk, S., Tajuddin, A. A., Shukri, A. — 2009-06-30

The mass attenuation coefficients (µ/) of Rhizophora spp. were determined for photons in the energy range of 15.77–25.27 keV. This was carried out by studying the attenuation of X-ray fluorescent photons from zirconium, molybdenum, palladium, silver, indium and tin targets. The results were compared with theoretical values for average breast tissues in young-age, middle-age and old-age groups calculated using photon cross section database (XCOM), the well-known code for calculating attenuation coefficients and interaction cross-sections. The measured mass attenuation coefficients were found to be very close to the calculated XCOM values in breasts of young-age group.

Radioactivity in drilled and dug well drinking water of Ogun state Southwestern Nigeria and consequent dose estimates

Ajayi, O. S., Achuka, J. — 2009-06-30

Activity concentrations of ⁴⁰K, ²²⁶Ra, ²²⁸Ac and ²³⁵U were measured in 11 dug and 9 drilled well water samples from 3 large cities in Ogun state, Southwestern Nigeria, consumed by the population living in the cities. The measurement was done using co-axial type high-purity germanium (HPGe) detector (Canberra Industries Inc.). The measured activity concentrations in the water samples ranged from 1.74 ± 1.83 to 4.69 ± 0.17 Bq l^–1; 2.89 ± 0.62 to 7.79 ± 7.22 Bq l^–1; 0.35 ± 0.07 to 1.17 ± 0.40 Bq l^–1 and 0.18 ± 0.05 to 4.77 ± 0.34 Bq l^–1 for ⁴⁰K, ²²⁶Ra, ²²⁸Ac and ²³⁵U, respectively. Total annual effective dose rates from the ingestion of these radionuclides in the untreated wells were estimated using measured activity concentrations in the radionuclides and their ingested dose conversion factors. Estimated annual effective dose rates ranged from 0.04 to 6.82; 0.01 to 1.36 and 0.01 to 1.49 mSv y^–1 for age groups <1, 2–7 and ≥17 y, respectively. Committed dose for age group ≥17 y ranged from 8.8 x 10^–4 to 8.9 x 10^–2 Sv. The calculated annual effective dose values due to the ingestion of ²²⁶Ra in the Awujale, Ake, Saboab, Alagbon, Alapora and Totoro samples exceeded International Commission on Radiological Protection limit of 1.0 mSv y^–1 for individual public exposure. These wells are recommended for treatment that would remove radium from their waters.

Radiation exposure from radioactive iodine 131I in and surrounding the patients' room

Abu-Khaled, Y. S., Sandouqa, A. S., Haddadin, I. M. — 2009-06-30

The purpose of this study is to measure the environmental radiation exposure in and surrounding the room of patients treated with ¹³¹I. Absorbed dose rates were measured using thermoluminescence dosemeters, type TLD-200 (CaF₂:Dy), in a continuous monitoring programme. It is found that the estimated annual shallow and deep dose rates are 226 and 175 mGy at the patient bed; 94 and 72 mGy in the bathroom; and 12 and 10 mGy at the visitor chair, respectively. The annual absorbed dose in the corridor is almost at the background level. It is found that the annual doses at the patient bed and in bathroom were above the limit for radiation workers, whereas the dose rate at the visitor chair was within the accepted limit for radiation workers and above the limit for the public.

Preface

Chen, J., Kramer, G. H., Richardson, R. B., Wilkinson, D. — 2009-06-29

Issues, considerations and recommendations on emergency preparedness for vulnerable population groups

Chen, J., Wilkinson, D., Richardson, R. B., Waruszynski, B. — 2009-06-29

The Workshop on Emergency Preparedness for Vulnerable Population Groups was held on 2 and 3 March 2009 in Ottawa, ON, Canada. The purpose of the workshop was to enhance communications within the emergency community response network and to identify the needs and gaps of emergency preparedness against chemical, biological, radiological, nuclear and explosives events for vulnerable population groups. The workshop was organised to enable extensive round-table discussions and provide a summary of key issues, considerations and recommendations for emergency response planners.

Dealing with at-risk populations in radiological/nuclear emergencies

Wilkinson, D. — 2009-06-29

In a mass casualty event, there will be at-risk populations that will require unique triage, treatment and consequence management to minimise immediate and long-term health effects. This statement is particularly true for radiological/nuclear (R/N) disasters where individuals exhibit a broad range of physiological responses to radiation exposure. For example, immunocompromised individuals will experience more detrimental radiation health effects; however, it is not always possible to definitively identify these individuals at the time of triage. Immediate and long-term consequence management for these individuals may require unique and potentially limited resources. Thus, at the time of an R/N event, it is crucial to assist community planners by: (a) rapidly identifying at-risk individuals who may have been exposed; (b) determining the dose and individual-specific health risks associated with radiation exposure; (c) identifying additional resources needed to deal with unique, population-specific requirements; and (d) developing treatment strategies in keeping with the rules of ‘supply and demand’. A comprehensive approach to identifying issues relevant to the R/N emergency preparedness for dealing with at-risk populations will be discussed with the aim of defining future research objectives.

Lead toxicity, vulnerable subpopulations and emergency preparedness

Healey, N. — 2009-06-29

This paper reviews some evidence of the toxic effects of lead (Pb) in the context of vulnerable subpopulations and emergency preparedness. Pb is ubiquitous in the environment and is used in many building materials. Environmental Pb concentrations and body burdens of Pb have been shown to increase following disasters. Pb is a systemic toxicant with no known beneficial biological function and, for several endpoints, no identified threshold of toxicity. The fetus, children, pregnant and elderly are particularly susceptible to some of the toxic effects of Pb. Pb exposures in infancy have been shown in vivo to produce an equal degree of neurobehavioural impairment as exposures of much longer duration at equivalent doses during adolescence. Evidence from animal bioassays indicates that the carcinogenic potency of perinatal Pb exposure may be about 3-fold higher than adult lifetime exposure at an equivalent dose. Animal assays show up to a 12-fold difference between fetal, neonatal and adult life stages in sensitivity to the immunological effects of Pb. Pb exposure is associated with increased risk of cardiovascular and cerebrovascular morbidity and mortality—health endpoints for which the elderly are at increased risk. Finally, endogenous and exogenous variables, such as psychological and physiological stress, dietary deficiencies and concomitant exposure to other chemical, biological and radiological hazards, can also potentially modify or potentiate the toxic effects of Pb. Because of the potential for concurrent influence of these modifying variables in a post-disaster environment, emergency response planners are encouraged to consider disaster victims and responders, as a whole, as a potentially vulnerable subpopulation.

A methodology for improving throughput using portal monitors

2009-06-29

The National Internal Radiation Assessment Section (NIRAS), which operates the Canadian National Calibration Reference Centre for Bioassay and In Vivo Monitoring, has field deployable equipment for emergency response. A substantial part of this tool kit is a set of portal monitors that can be used to quickly screen people into the ‘uncontaminated’ and the ‘contaminated’. The former term refers to a person who has <60 kBq (empirical practical detection limit) of activation/fission products and the latter group is contaminated by that amount or more. Recent field work has shown that one type of the NIRAS's portal monitors can be alarmed at significant distances if the level of contamination is high enough. The other types, which do not initiate a count until either an infra-red beam is broken or a proximity detector is activated, do not alarm but their background will be raised and this causes other problems. This paper proposes a method of group monitoring to help speed up the process of screening a large number of potentially contaminated persons using portal monitors. In short, the group of potentially contaminated persons will be kept isolated from the portal stations. Depending on a real-time estimate of the percentage of contaminated persons in the crowd, groups of persons will be selected for screening. The hypergeometric distribution has been used to decide on the sampling group size with an expectation that 90% of the time no contaminated person will be present in the group. Once removed from the main waiting area, the group will be pre-screened and then, depending on the result, sent to the appropriate portal. It is anticipated that this will greatly speed up processing as it substantially reduces the transit time. Transits times have also been estimated in addition to the number of personnel required to run all of NIRAS‘s field deployable equipment.

Emergency preparedness of Research Center for Radiation Medicine and its hospital to admit and treat the patients with signs of acute radiation sickness

Belyi, D. A., Khomenko, V. I., Bebeshko, V. G. — 2009-06-29

After the Chernobyl accident, the Research Center for Radiation Medicine (RCRM) was established in Kiev (Ukraine). Its main task was to maintain a high level of emergency preparedness and be ready to examine and treat patients who suffer as a result of hypothetical radiation accident. Based on the previous experience, this institution's specialists worked out new diagnostic criteria and drug treatment schemata for acute radiation sickness, created a database on 75 patients with this diagnosis and improved educational programmes for medical students and physicians working in the field of radiation medicine. RCRM collaborates fruitfully with western partners through the joint research projects and connects with the World Health Organization's Radiation Emergency Medical Preparedness and Assistance Network centre. Collaboration with Kiev Center for Bone Marrow Transplantation allows RCRM to use aseptic wards having highly filtered air for the treatment of most severely irradiated patients.

Polonium-210: lessons learned from the contamination of individual Canadians

2009-06-29

This paper describes the radioactive poisoning episode in London in 2006 and the Health Canada response to locate and test any Canadians who might have been contaminated by this event. The search strategies and testing methods are explained and the results given. The lessons learned are summarised and implications for vulnerable populations are discussed. The greatest public health impact was probably the generation of fear and concern, especially among those prone to health-related anxiety disorders. The groups of individuals at risk were effectively managed by a single point of contact system combined with rapid triage and counselling that was provided to everyone to address their individual concerns.

Factors that elevate the internal radionuclide and chemical retention, dose and health risks to infants and children in a radiological-nuclear emergency

Richardson, R. B. — 2009-06-29

The factors that influence the dose and risk to vulnerable population groups from exposure and internal uptake of chemicals are examined and, in particular, the radionuclides released in chemical, biological, radiological, nuclear and explosive events. The paper seeks to identify the areas that would benefit from further research. The intake and body burdens of carbon and calcium were assessed as surrogates for contaminants that either act like or bind to hydrocarbons (e.g. tritium and ¹⁴C) or bone-seeking radionuclides (e.g. ⁹⁰Sr and ²³⁹Pu). The shortest turnover times for such materials in the whole body were evaluated for the newborn: 11 d and 0.5 y for carbon and calcium, respectively. However, their biokinetic behaviour is complicated by a particularly high percentage of the gut-absorbed dietary intake of carbon (~16%) and calcium (~100%) that is incorporated into the soft tissue and skeleton of the growing neonate. The International Commission on Radiological Protection dose coefficients (Sv Bq^–1) were examined for 14 radionuclides, including 9 of concern because of their potential use in radiological dispersal devices. The dose coefficients for a 3-month-old are greater than those for adults (2–56 times more for ingestion and 2–12 times for inhalation). The age-dependent dose and exposure assessment of contaminant intakes would improve by accounting for gender and growth where it is currently neglected. Health risk is evaluated as the product of the exposure and hazard factors, the latter being about 10-fold greater in infants than in adults. The exposure factor is also approximately 10-fold higher for ingestion by infants than by adults, and unity for inhalation varying with the contaminant. Qualitative and quantitative physiological and epidemiological evidence supports infants being more vulnerable to cancer and neurological deficit than older children.

On the need for a radiation accident registry in Canada

Chen, J., Moir, D. — 2009-06-29

To be able to respond effectively to any radiological or nuclear emergency, a radiation accident registry is a valuable asset. This type of registry is able to assist responders in preparing for and managing situations during the event and in providing effective follow-up on the long-term health effects of persons exposed. It is especially important to register radiation-exposed people in vulnerable population groups, such as children and pregnant women, to ensure proper long-term health care and protection. As part of its national system of emergency preparedness for response to radiological or nuclear events, Canada needs to develop a plan for a radiation accident registry. Apart from radiation dose information, this registry should also contain a sub-database of available medical facilities and necessary supplies as well as professionals specialising in radiation treatment and protection. Following the establishment of the registry, it should routinely be tested in training exercises to ensure its readiness for implementation whenever the need might arise.

Therapeutic product disposition in at-risk populations

Foster, B. C. — 2009-06-29

In an emergency situation, such as a chemical, biological, radionuclide, nuclear or explosion (CBRNE) event, all patient populations are at increased risk of serious adverse events. Therapeutic product (TP) safety and efficacy depend on the disposition of the product through absorption, distribution, metabolism and excretion. The ability of a patient to benefit from or merely tolerate a TP can be modified by many factors, including but not limited to culture, diet, disease, environmental contaminants, genetic predisposition, stress and socioeconomic status and recent life experiences. Metabolism is considered to have the greatest effect on safety and efficacy, as chemicals not metabolised can accumulate to toxic levels. Inter-individual variances in most drug metabolism enzymes may range up to greater than 1000-fold. The fetus, neonates, infants, individuals with hormonal change, infection or prior exposure to licit or illicit products and the elderly are more susceptible to increased risk of serious adverse health effects. The critically ill are the most at risk. The at-risk populations for a serious adverse event are dependent then on the CBRNE event, their physical and cognitive states and the inter-individual intrinsic and extrinsic factors that affect TP disposition.

Populations at risk--paediatrics

Kollek, D., Karwowska, A. — 2009-06-29

Disasters affect all segments of the population. Many subsets of the general adult population have specific needs and vulnerabilities. One group with specific needs and which is always at high risk in disasters is children. The physiological, anatomical, developmental and psychological requirements in children differ from those of adults. Disaster planning must recognise and adapt to this. For the past 3 years, the Centre of Excellence in Emergency Preparedness (CEEP) has been developing a document that will outline specific paediatric issues in disasters and provide general (and, where possible, specific) guidelines for Canadian health-care providers and disaster planners. This paper discusses special issues of emergency preparedness for children and reviews the content of the document being developed at CEEP.

Putting the puzzle together: reducing vulnerability through people-focused planning

Hutton, D. — 2009-06-29

Supporting and integrating vulnerable persons into emergency management has emerged as an increasing priority in emergency management in Canada. Events such as the 2003 European heat wave and Hurricane Katrina have shown that disasters almost always have the harshest affects on the frail elderly, people with disabilities, the disadvantaged and the least able. While it is neither possible—nor the role of emergency management—to eliminate or reduce many factors that make people vulnerable to hazards, it is important that emergency managers work closely with communities to not only identify risks and vulnerabilities, but also to build on the resources and capacities that enable people to effectively prepare for, respond to and recover from threats of all types. To this end, emergency management must take into account the level of capacities and resources that a community has to prepare for emergencies and disasters, in addition to people's vulnerabilities to extreme events. To be successful, people must be viewed not as a part of the problem to be solved or managed during an emergency, but rather a part of the solution to building more resilient and disaster-resistant societies. This requires ‘people-focused’ planning methodologies that move beyond planning for to planning with all segments of society, including the most vulnerable and marginalised groups that are more readily overlooked. This not only begins to ensure that emergency planning and response capacities can effectively address the diverse needs of all people, but is also an important step to empowering the most vulnerable to prepare themselves for emergencies and other critical events.

Support for families coping with stroke or dementia: special considerations for emergency management

O'Sullivan, T. L. — 2009-06-29

Public resilience, an important determinant of effective disaster management, is dynamic, and families coping with debilitating illnesses, such as stroke or dementia, experience unique vulnerabilities as a result of their caregiving responsibilities. When social networks cannot sustain care, family caregivers turn to formal respite programmes for support. This has tremendous implications on demands for respite services in any disaster response. With an ageing population, the demands for family caregiving are increasing, and more people face the challenges of balancing work and family responsibilities. This includes members of the response community who have family members who need assistance with daily living. Without support, many responders may struggle to fulfil their professional roles, creating a threat to response capacity. Preparedness interventions should focus on building resilience and encourage families to explore possibilities for respite care as well as other standard strategies to ensure self-sufficiency in the early phases of a disaster.

When ageing and disasters collide: lessons from 16 international case studies

Powell, S., Plouffe, L., Gorr, P. — 2009-06-29

Sixteen case studies examined the impact of various natural disasters and conflict-related emergencies on older people, the strengths and gaps in emergency planning, response and recovery, and the contributions older people made to their families and communities. Case examples were chosen from both developed and developing countries. Older persons suffered disproportionate impacts in several cases. Regardless of the country's level of prosperity, those most affected tended to be economically disadvantaged, disabled or frail, women, socially isolated, or caregivers of family members. Emergency responders were often not aware of distinct needs or abilities of older persons and not equipped to respond appropriately. The best emergency practices recognised and included specific needs within mainstream efforts and integrated older persons in community planning, response and recovery activities. This paper presents the ‘lessons learned’ from these case studies and makes the case for greater attention to this segment of the population in emergency management.

Emergency preparedness for higher risk populations: psychosocial considerations

Lemyre, L., Gibson, S., Zlepnig, J., Meyer-Macleod, R., Boutette, P. — 2009-06-29

This paper was meant to be on ‘vulnerable populations’, as some population sub-groups do require special care, special planning and special integration of needs. However, the issue should be reframed in terms of groups at higher risks. The text explains how (1) there are contextual vulnerabilities, in (a) higher susceptibility, i.e. higher exposure to risk, (b) higher sensitivity, i.e. higher damage or higher brittleness, and (c) weaknesses and gaps in the emergency system; (2) that these higher susceptibility, sensitivity and system weaknesses involve important psychosocial considerations, which may stem from socio-demographic status or ripple effects in the community; and finally, (3) that addressing those ‘soft spots’ using the phrase ‘vulnerable populations’ can be misleading and disserving because it disempowers, stigmatises and deters one from a more thorough analysis.

WORKSHOP ON EMERGENCY PREPAREDNESS FOR VULNERABLE POPULATION GROUPS

2009-06-29

Activities of ISO/TC82/SC2 'Radiation protection', Subcommittee 2 of ISO Technical Committee 85

Ambrosi, P., Swinth, K. L. — 2009-05-22

Simultaneous 222Rn and 220Rn measurements in Winnipeg, Canada

Chen, J., Schroth, E., MacKinlay, E., Fife, I., Sorimachi, A., Tokonami, S. — 2009-05-22

Naturally occurring isotopes of radon in indoor air are identified as the second leading cause of lung cancer after tobacco smoking. Winnipeg had the highest radon (²²²Rn) concentration among 18 Canadian cities surveyed in the past. There is great interest to know the current radon as well as thoron (²²⁰Rn) concentrations in Winnipeg homes. Therefore, radon–thoron discrimination detectors were deployed in 117 houses for a period of 3 months. The results confirmed that thoron is present at detectable levels in about half of the Winnipeg homes and radon remains significantly higher than the national average. In this study, radon concentrations ranged from 20 to 483 Bq m^–3 with a geometric mean of 112 Bq m^–3 and a geometric standard deviation of 2.07. It is estimated that 20% of Winnipeg homes could have radon concentrations above the Canadian indoor radon guideline of 200 Bq m^–3. This conclusion is similar to the previous estimation made 20 y ago. Thoron concentrations were below the detection limit in 60 homes. Among the homes with detectable thoron concentrations, the values varied from 5 to 297 Bq m^–3, the geometric mean and standard deviation were 21 Bq m^–3 and 2.53, respectively.

Determination of human absorbed dose of 67GA-DTPA-ACTH based on distribution data in rats

Shanehsazzadeh, S., Jalilian, A. R., Sadeghi, H. R., Allahverdi, M. — 2009-05-22

The absorbed radiation dose to human organs has been estimated, following intravenous administration of ⁶⁷Ga-labelled adrenocorticotrophic hormone (ACTH) using distribution data from injected normal rats. Four rats were sacrificed at exact time intervals and the percentage of injected dose per gram of each organ was measured by direct counting from rat data. The Medical Internal Radiation Dose formulation was applied to extrapolate from rat to human and to project the absorbed radiation dose for various organs in a human. From rat data, it is estimated that a 185-MBq injection of ⁶⁷Ga-diethylenetriaminepentaacetic acid-ACTH into a human might result in an estimated absorbed dose of 2.22 mGy to the whole body; the highest absorbed dose was in the bladder wall with 82.1 mGy and the organs that received the next highest doses were the lungs 31.8, liver 22.6 and spleen 8.72 mGy. These results suggest that it should be possible to perform early imaging of the lung anomalies.

Characterisation of nasal swab samples by alpha spectrometry

Fukutsu, K., Yamada, Y., Akashi, M. — 2009-05-22

A positive nasal swab taken at a radiation emergency, when properly collected and analysed, is a good indication of a potential inhalation intake. It may be expected to be a useful method for early dose assessment in cases of accidental inhalation of an alpha emitter. To improve the first estimation of intake activity, the quality of a nasal swab measurement was experimentally investigated. Alpha spectrometry was used to examine the experimental nasal swab samples involved with a plutonium solution or particles. Also, a numerical simulation analysis on the alpha spectrum using advanced alpha-spectrometric simulation was made to characterise the experimental results. It was observed that the alpha energy spectrum had a quite different shape among samples, and it was characterised by the type of contaminant. This could be the second advantage of using alpha spectrometry in addition to nuclide identification. The absorption of alpha radiation within the experimental nasal swab sample was different between the types of contaminants. For a quantitative discussion, the absorption for a swab sample must be determined for each type of contaminant. This new finding could be very useful for first responders. A nasal swab sample measured using an alpha spectrometer will give more useful information during the first response of an emergency.

Estimating 241Am activity in the body: comparison of direct measurements and radiochemical analyses

Lynch, T. P., Tolmachev, S. Y., James, A. C. — 2009-05-22

The assessment of dose and ultimately the health risk from intakes of radioactive materials begins with estimating the amount actually taken into the body. An accurate estimate provides the basis to best assess the distribution in the body, the resulting dose and ultimately the health risk. This study continues the time-honoured practice of evaluating the accuracy of results obtained using in vivo measurement methods and techniques. Results from the radiochemical analyses of the ²⁴¹Am activity content of tissues and organs from four donors to the United States Transuranium and Uranium Registries (USTUR) were compared with the results from direct measurements of radioactive material in the body performed in vivo and post-mortem. Two were whole-body donations and two were partial-body donations. The ²⁴¹Am lung activity estimates ranged from 1 to 30 Bq in the four cases. The ²⁴¹Am activity in the lungs determined from the direct measurements were within 40% of the radiochemistry results in three cases and within a factor of 2 for the other case. However, in one case the post-mortem direct measurement estimate was a factor of 10 higher than the radiochemistry result for lung activity, most probably due to underestimating the skeletal contribution to the measured count rate over the lungs. The direct measurement estimates of liver activity ranged from 2 to 60 Bq and were consistently lower than the radiochemistry results. The skeleton was the organ with the highest deposition of ²⁴¹Am activity in all four cases. The skeletal activity estimates ranged from 30 to 300 Bq. The skeletal activity obtained from measurements over the forehead were within 20% of the radiochemistry results in three cases and differed by 78% in the other case. The results from this study suggest that the measurement methods, data analysis methods and calibration techniques used at the In Vivo Radiobioassay and Research Facility can be used to quantify the activity in the lungs, skeleton and liver when ²⁴¹Am activity is present in all three organs. The adjustment method used to account for the contribution from activity in other organs improved the agreement between the direct measurement results and the radiochemistry results for activity in the lungs and skeleton. The method appeared to overestimate the contribution from the other organs to the liver activity measurements, although the low activity levels complicated the analysis. The unadjusted liver activity estimates from the direct measurements were generally in better agreement with the radiochemistry results than the adjusted liver activity. The data from this study indicates that the results from the in vivo measurement techniques provide reasonable estimates of radioactive material in the lungs and skeleton under the most challenging conditions where there is ²⁴¹Am activity in multiple organs. The data analysis from additional USTUR cases with both direct measurement results and radiochemistry results is in progress to further evaluate how best to account for the contributions from ²⁴¹Am activity in multiple organs and to better understand the uncertainty associated with the adjusted activity.

Dosimetric evaluation of lithium carbonate (Li2CO3) as a dosemeter for gamma-radiation dose measurements

Popoca, R., Urena-Nunez, F. — 2009-05-22

This work reports the possibility of using lithium carbonate as a dosimetric material for gamma-radiation measurements. Carboxi-radical ions, CO₂^– and CO₃^–, arise from the gamma irradiation of Li₂CO₃, and these radical ions can be quantified by electron paramagnetic resonance (EPR) spectrometry. The EPR-signal response of gamma-irradiated lithium carbonate has been investigated to determine some dosimetric characteristics such as: peak-to-peak signal intensity versus gamma dose received, zero-dose response, signal fading, signal repeatability, batch homogeneity, dose rate effect and stability at different environmental conditions. Using the conventional peak-to-peak method of stable ion radicals, it is concluded that lithium carbonate could be used as a gamma dosemeter in the range of 3–100 Gy.

Canadian national internal dosimetry performance testing programme: results of the pilot programme

Kramer, G. H. — 2009-05-22

This paper describes the design and construction of a new performance testing programme that was implemented in Canada in 2008. The Canadian Regulator (Canadian Nuclear Safety Commission) had determined that their licensees, in addition to participating in the existing in vivo and in vitro performance tests, needed to demonstrate their ability in interpreting bioassay results to obtain intakes and resulting doses. The new programme is administered by the Canadian National Calibration Reference Center for Bioassay and In Vivo Monitoring (NCRC). Currently, the NCRC carries out the performance testing for the in vitro and in vivo. At the time of writing, the first round has been completed and the results for ³H and ^natU exposures were very consistent, while the committed effective dose from ¹³⁷Cs intake varied by a factor of two.

Air contamination analysis during emergency medical treatment

Yamada, Y., Fukutsu, K., Yuuki, M., Akashi, M. — 2009-05-22

After radiological emergencies, patients contaminated with radioactivity are taken to radiation emergency hospitals for treatment. Numerical simulations using the computer software ‘Flow Designer^®’ were made in order to evaluate indoor air contamination caused by the breathing out of contaminated air. The National Institute of Radiological Sciences facility was used for the numerical evaluation. Results indicate that the dispersion of contaminated air depends on the characteristics of the contaminants, and that the dispersion range was limited and localised. Only medical staff standing in a special position near the patient was exposed to almost un-diluted contaminated air. Highly contaminated air was evacuated with a local exhaust pump system. Room air quality was monitored using a continuous air sampling system, but it was found that the sampling point was not representative for the purpose of radiation protection. From the air-flow analysis, some problems that affect radiological safety were revealed and valuable information and measures for preventing secondary contamination were determined.

Uncertainty in HPGe detector calibrations for in situ gamma-ray spectrometry

Boson, J., Johansson, L., Rameback, H., Agren, G. — 2009-05-22

Semi-empirical methods are often used for efficiency calibrations of in situ gamma-ray spectrometry measurements with high-purity germanium detectors. The intrinsic detector efficiency is experimentally determined for different photon energies and angles of incidence, and a suitable expression for the efficiency is fitted to empirical data. In this work, the combined standard uncertainty of such an efficiency function for two detectors was assessed. The uncertainties in individual efficiency measurements were found to be about 1.9 and 3.1% (with a coverage factor k = 1, i.e. with a confidence interval of about 68%) for the two detectors. The main contributions to these uncertainties were found to originate from uncertainties in source-to-detector distance, source activity and full-energy peak count rate. The standard uncertainties of the fitted functions were found to be somewhat higher than the uncertainty of individual data points, i.e. 5.2 and 8.1% (k = 1). With the introduction of a new expression for the detector efficiency, these uncertainties were reduced to 3.7 and 4.2%, i.e. with up to a factor of two. Note that this work only addresses the uncertainty in the determination of intrinsic detector efficiency.