Internal dose assessment in radiation accidents

Although numerous models have been developed for occupational and medical internal dosimetry, they may not be applicable to an accident situation. Published dose coefficients relate effective dose to intake, but if acute deterministic effects are possible, effective dose is not a useful parameter. Consequently, dose rates to the organs of interest need to be computed from first principles. Standard bioassay methods may be used to assess body contents, but, again, the standard models for bioassay interpretation may not be applicable because of the circumstances of the accident and the prompt initiation of decorporation therapy. Examples of modifications to the standard methodologies include adjustment of biological half-times under therapy, such as in the Goiania accident, and the same effect, complicated by continued input from contaminated wounds, in the Hanford 241Am accident.     

Dosimetric performance requirements for the routine dose assessment of external radiation

Dosimetric performance requirements must take the following into consideration: general radiation protection requirements established by the International Commission on Radiological Protection (ICRP), workplace conditions prevailing during (routine) work, and technical requirements set by international or national bodies. For performance tests the general requirements on the precision of dose measurements can be represented by the 'trumpet curves'. For photon radiation several measurements of the workplace conditions are reported. The main conclusions drawn from these measurements are the following: the photon energy range from 20 keV to 2 MeV, or even 7 MeV, is of importance for individual monitoring. The range of directions of radiation incidence on the dosemeter is very large, nearly the frontal hemisphere or even rotating, and almost all spectra are broad with respect to energy. In view of the great variety of workplace conditions, the scope of most of the technical requirements is not sufficiently great. No technical requirement is at present fully in accordance with the general principles of an uncertainty analysis.     

Improvements in extremity dose assessment for ionising radiation medical applications

This study aims at testing the INTE ring dosemeter based on MCP-Ns and TLD-100 detectors on users from the field of medical applications, namely radiopharmacists, personnel at a cyclotron facility with corresponding FDG synthesis cells, interventional radiology technologists and radiologists. These users were chosen due to the fact that they have a significantly high risk of exposure to their hands. Following previous results, MCP-Ns TL thin material was used for radiology measurements, whereas TLD-100 was preferred for other applications. The dosemeters were tested to make sure that they were waterproof and that they could be sterilised properly prior to use. Results confirm the need to implement finger dosimetry, mainly for interventional radiologists as finger dose can be >50 times higher than whole-body dose and 3 times higher than wrist dose.     

Evaluation of occupational exposures to natural radiation in the Czech Republic

The Czech approach to limit the occupational exposures to natural radiation is based on the rules given by the Atomic Act and by the Decree of the State Office for Nuclear Safety (SONS) on radiation protection. Workplaces with potential risk of increased exposure to natural sources are specified explicitly. A new method to perform the above-mentioned measurements and to determine the effective doses of workers was proposed in 2005 and accepted by the SONS in 2007. The first experience illustrates its applicability.     

Effective dose assessment for workers in caves in the Czech Republic: experiments with passive radon detectors

The new RAMARN system for radon volume activity measurement was developed in 2003 and has been in use since then. RAMARN system consists of a plastic chamber that is conically cylindrical in shape and about 0.5 l in volume; a bare Kodak LR 115 is located on the bottom of this diffusion chamber. The size was chosen to avoid the influence of deposited decay products of radon. Kodak has a spectrometric character-the tracks are visualized only for alphas with energies between 1 and 3 MeV that touch the foil; thus the effective volume has a lens shape. The response therefore corresponds to diffused radon and half of (218)Po born by radon gas decay. The experiments described below were conducted as one part of a routine methodology control, focused on classifying worker irradiation from natural ionizing radiation sources in show caves and in caves used for speleotherapy.     

Three Mile Island epidemiologic radiation dose assessment revisited: 25 years after the accident

Over the past 25 years, public health concerns following the Three Mile Island (TMI) accident prompted several epidemiologic investigations in the vicinity of TMI. One of these studies is ongoing. This commentary suggests that the major source of radiation exposure to the population has been ignored as a potential confounding factor or effect modifying factor in previous and ongoing TMI epidemiologic studies that explore whether or not TMI accidental plant radiation releases caused an increase in lung cancer in the community around TMI. The commentary also documents the observation that the counties around TMI have the highest regional radon potential in the United States and concludes that radon progeny exposure should be included as part of the overall radiation dose assessment in future studies of radiation-induced lung cancer resulting from the TMI accident.     

Triage, monitoring and dose assessment for people exposed to ionising radiation following a malevolent act

The part played by individual monitoring within the context of the overall response to incidents involving the malevolent use of radiation or radioactive material is discussed. The main objectives of an individual monitoring programme are outlined, and types of malevolent use scenario briefly described. Some major challenges facing those with responsibilities for planning the monitoring response to such an incident are identified and discussed. These include the need for rapid selection and prioritisation of people for individual monitoring by means of an effective triage system; the need for rapid initiation of individual monitoring; problems associated with monitoring large numbers of people; the particular difficulties associated with incidents involving pure-beta and alpha-emitting radionuclides; the need for techniques that can provide retrospective estimates of external radiation exposures rapidly and the need for rapid interpretation of contamination monitoring data. The paper concludes with a brief review of assistance networks and relevant international projects planned or currently underway.     

Preliminary assessment of the dose to the interventional radiologist in fluoro-CT-guided procedures

A preliminary assessment of the occupational dose to the intervention radiologist received in fluoroscopy computerised tomography (CT) used to guide the collection of lung and bone biopsies is presented. The main aim of this work was to evaluate the capability of the reading system as well as of the available whole-body (WB) and extremity dosemeters used in routine monthly monitoring periods to measure per procedure dose values. The intervention radiologist was allocated 10 WB detectors (LiF: Mg, Ti, TLD-100) placed at chest and abdomen levels above and below the lead apron, and at both right and left arms, knees and feet. A special glove was developed with casings for the insertion of 11 extremity detectors (LiF:Mg, Cu, P, TLD-100H) for the identification of the most highly exposed fingers. The H(p)(10) dose values received above the lead apron (ranged 0.20-0.02 mSv) depend mainly on the duration of the examination and on the placement of physician relative to the beam, while values below the apron are relatively low. The left arm seems to receive a higher dose value. H(p)(0.07) values to the hand (ranged 36.30-0.06 mSv) show that the index, middle and ring fingers are the most highly exposed. In this study, the wrist dose was negligible compared with the finger dose. These results are preliminary and further studies are needed to better characterise the dose assessment in CT fluoroscopy.     

Numerical system utilising a Monte Carlo calculation method for accurate dose assessment in radiation accidents

A system utilising radiation transport codes has been developed to derive accurate dose distributions in a human body for radiological accidents. A suitable model is quite essential for a numerical analysis. Therefore, two tools were developed to setup a 'problem-dependent' input file, defining a radiation source and an exposed person to simulate the radiation transport in an accident with the Monte Carlo calculation codes-MCNP and MCNPX. Necessary resources are defined by a dialogue method with a generally used personal computer for both the tools. The tools prepare human body and source models described in the input file format of the employed Monte Carlo codes. The tools were validated for dose assessment in comparison with a past criticality accident and a hypothesized exposure.     

Effectiveness of strategic environmental assessment in the Czech Republic

The widespread application of SEA over the last 15 years in the Czech Republic has allowed for a gradual accommodation of SEA procedural steps into the standard bureaucratic routine of public authorities. In this paper, we discuss results of a small-scale survey among Czech SEA practitioners focusing on issues related to the effectiveness and efficiency of the SEA. The results suggest a moderate progress driven primarily by the accumulation of practical experience among both SEA consultants and the planners, and there is certainly no shortage of examples where SEA positively affected a plan. On the other hand, continuation of many negative general environmental trends (e.g. excessive conversion of virgin land for development, continuation of environmentally harmful agriculture and forestry policies, etc.) seem to conform the notion that the SEA, as currently practiced, in the Czech Republic fails to deliver to its full potential.     

韩国升级再造设计的个案分析及设计价值

利用废弃材料二次创作而成的升级再造产品要获得市场的认可,需要寻找废弃材料与消费者期望间的连接点。目的 对韩国升级再造设计品牌进行案例分析及产品价值的解读,以探讨废旧材料转化为新商品的可能性,为废弃材料的价值再创造以及升级再造产品获得市场认可提供可借鉴的思路。方法 以文献研究法,研究升级再造设计的含义及社会意义;以案例分析法,从材料、功能、外观三个维度对升级再造产品进行设计分析,总结升级再造产品的设计特征;从产品设计价值的相关理论对升级再造产品的价值进行归纳与总结。结论 投入足够的设计创意后,由废弃材料设计和制作而成的升级再造产品也能同时获得功能性和美观性;环保价值是该类产品最具代表性的特征与价值;具备功能、审美、环保价值因素的升级再造产品更容易获得消费市场的认可,使升级再造产品能持续性地生产和消费成为可能。     

Accurate dose assessment system for an exposed person utilising radiation transport calculation codes in emergency response to a radiological accident

A system has been developed to assess radiation dose distributioninside the body of exposed persons in a radiological accidentby utilising radiation transport calculation codes—MCNPand MCNPX. The system consists mainly of two parts, pre-processorand post-processor of the radiation transport calculation. Programsfor the pre-processor are used to set up a ‘problem-dependent’input file, which defines the accident condition and dosimetricquantities to be estimated. The program developed for the post-processorpart can effectively indicate dose information based upon theoutput file of the code. All of the programs in the dosimetrysystem can be executed with a generally used personal computerand accurately give the dose profile to an exposed person ina radiological accident without complicated procedures. An experimentusing a physical phantom was carried out to verify the availabilityof the dosimetry system with the developed programs in a gammaray irradiation field.     

Patient dose measurements in diagnostic radiology procedures in Korea

This study is the first nationwide investigation aimed at estimating the patient dose for radiographic examinations in Korea including gastrointestinal studies, computed tomography and mammography. The survey data from 161 hospitals and the dose data from 32 hospitals were analysed. The third quartile entrance surface dose, dose area product (DAP), weighted CT dose index (CTDIw) and mean glandular dose (MGD) were reported. All the estimated doses were less than the stated International Atomic Energy Agency (IAEA) reference levels for radiographic examinations. However, DAPs for the fluoroscopic examinations had higher dose values than the IAEA reference levels. In addition, the CTDIw and MGD were lower than the IAEA reference levels.     

Measurement of radiation dose in dental radiology

Patient dose audit is an important tool for quality control and it is important to have a well-defined and easy to use method for dose measurements. In dental radiology, the most commonly used dose parameters for the setting of diagnostic reference levels (DRLs) are the entrance surface air kerma (ESAK) for intraoral examinations and dose width product (DWP) for panoramic examinations. DWP is the air kerma at the front side of the secondary collimator integrated over the collimator width and an exposure cycle. ESAK or DWP is usually measured in the absence of the patient but with the same settings of tube voltage (kV), tube current (mA) and exposure time as with the patient present. Neither of these methods is easy to use, and, in addition, DWP is not a risk related quantity. A better method of monitoring patient dose would be to use a dose area product (DAP) meter for all types of dental examinations. In this study, measurements with a DAP meter are reported for intraoral and panoramic examinations. The DWP is also measured with a pencil ionisation chamber and the product of DWP and the height H (DWP x H) of the secondary collimator (measured using film) was compared to DAP. The results show that it is feasible to measure DAP using a DAP meter for both intraoral and panoramic examinations. The DAP is therefore recommended for the setting of DRLs.     

Radon dose calculation methodology for underground workers in the Czech Republic

The project focused on classifying the level of irradiation from natural ionising radiation sources for workers in publicly accessible caves and in caves used for speleotherapy, with applicability to other underground workplace. A correct and accurate procedure (and calculation) is defined for determining the effective dose that workers are exposed to in caves, based on the results of integral measurements of radon volume activity and on the length of time spent by workers in the caves. A review was made of various approaches for evaluating lung irradiation found in the literature. Experimental measurements of cave atmosphere characteristics (continuous measurement of radon volume activity, continuous and integral measurements of radon decay products, interior climatic parameters and aerosol spectra) were the main sources for the methodology.     

Measurement of natural radioactivity and dose rate assessment of terrestrial gamma radiation in the soil of southern Punjab, Pakistan

Activity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs in soil samples collected from the most populous area of southern Punjab of Pakistan have been measured by gamma-ray spectrometry. The measured activity concentrations for these radionuclides are compared with the reported data from different other countries and it is found that measured activity concentrations are comparable with the worldwide measured average values reported by the UNSCEAR. Subsequently assessed radiological effects show that the mean radium equivalent activity (Ra(eq)) is 96.7 +/- 15.2 Bq kg(-1) and air absorbed dose rate (D) is 46.1 +/- 7.3 nGy h(-1). The values of internal and external radiation hazard indices are found to be less than unity. The annual effective radiation dose is calculated to be 0.28 +/- 0.05 mSv, which is well below the limit of 1.0 mSv y(-1) recommended by the International Commission on Radiological Protection, for the general public.     

Retrospective dose assessment: the measurement of the dose in quartz in dating and accident dosimetry

In retrospective dosimetry using luminescence it is never possible to obtain a sample of the unaltered phosphor as it was at somc time in the past and before radiation exposure. This prevents direct calibration using conventional personnel dosimetry techniques, and so measurement protocols must be devised which allow accurate estimation of the dose using only the exposed phosphor. This has led to the use of complex protocols, requiring many tens of notionally identical subsamples, to obtain one estimate of the unknown dose. More recently, considerable effort has gone into devising protocols which provide an estimate of the unknown dose from only one subsample. These avoid the need to assume homogeneity in the sample. These protocols also allow faster measurement, which for the first time makes it practical to obtain multiple estimates of the unknown dose and thus externally calculated random errors. This paper discusses the development of single-aliquot protocols, with particular reference to those devised for use with quartz, and finally reviews some of their applications in the retrospective assessment of dose.     

Evaluation of indoor gamma radiation dose in dwellings

The use of materials containing naturally occurring radionuclides for house construction may enhance the natural radiation background to which some population groups are exposed. External exposure results from gamma emitter radionuclides existing in the walls, floor and ceiling. Mathematical models can be used to predict external dose rates inside a room, provided the compartment geometry and the radionuclide concentration activities are known. This paper presents a methodology and a computer code for theoretical evaluation of indoor external gamma doses in the air. The room was modelled as three pairs of rectangular slabs of finite thickness. Doses were evaluated by applying a photon transport model, taking into account self-absorption and radiation build-up. Calculations were performed for 40K, 226Ra and 232Th, considering concrete walls. The results obtained show good agreement with those reported in the literature. Dose conversion factors are presented in a practical manner, ready to use for radiological impact screening.