Permissible Dose Limit Research Articles

Exposure to ionizing radiation of medical staff performing vascular and interventional radiology procedures.

Vascular and interventional radiology procedures are characterized by high exposure of personnel to ionizing radiation. This study assessed the exposure of medical personnel to ionizing radiation during vascular radiology and mechanical thrombectomy procedures. During vascular radiology procedures, the exposure of 4 groups of workers participating in the procedures was analyzed, i.e., the main operating physician, an assistant physician, a sterile nurse, and a nurse. Measurements of exposure to ionizing radiation were performed using thermoluminescent dosimetry. The registered effective dose during 1 treatment in individual groups is, respectively: mean (M) ± standard deviation (SD) 75±15 μSv, 24±5 μSv, 13±3 μSv, and 8±2 μSv. During mechanical thrombectomy, the operating physician receives an effective dose of M±SD 9±2 μSv. The equivalent doses for the lenses for the operating physician and the doctor assisting during vascular radiology procedures are M±SD 1419±285 μSv and 987±198 μSv, respectively, and for the hands, including the left and right hands, M±SD 4605±930 μSv, 1420±284 μSv, 1898±380 μSv, 1371±274 μSv. If the principles of optimizing radiological protection are not applied during vascular radiology procedures, the permissible dose limits and operational limits equivalent to doses to lenses and hands may be exceeded. Exposure during vascular radiology procedures is comparable to exposure during nuclear medicine procedures in terms of the use of glucose labeled with radioactive fluorine. Int J Occup Med Environ Health. 2024;37(4).

Methodology for shielding design and evaluation for container scanners.

There has been an increase in the use of high energy photon beam for container scanners in many countries for multi purposes such as detecting high atomic number materials which might be nuclear materials, drugs, high explosive materials and other contrabands etc. High energy photon beams generally 6 and 9 MV can be used for scanning such materials. However, it is important to ensure that radiation level beyond the container scanner installation is within the permissible dose limit specified by the national competent authority for the protection of public and radiation workers. In this paper, challenges in the biological shielding during the installation of high energy X-ray system for scanning vehicles containing suspected materials are discussed. The purpose of the present study is to develop a methodology for shielding design and evaluation for container scanner installations. The basic concept pertaining to shielding evaluation of radiotherapy installations provided in National Council on Radiation Protection and Measurements (NCRP)/International Atomic Energy Agency (IAEA) reports are referred, and appropriately used to calculate optimized shielding thicknesses requirements for container scanner installation. Workload is estimated based on number of containers scanned, machine ON time and dose rate at 1m. The shielding evaluation includes use of beam stopper in the primary beam, scattering by heterogeneous metallic scrap materials or any other suspected materials contained in the vehicle and their impact on the thickness of shielding walls. A model lay out plan to be used for installation of container scanner is developed. A methodology for shielding evaluation for various protective walls and ceiling of this model is also discussed. The study provides basic requirement for designing a structural room for installing 9MV container scanner from radiological safety view point.

Radiation dose assessment for nuclear medicine workers in Riyadh, Saudi Arabia

Nuclear medicine (NM) is an essential radiology department in healthcare facilities. In NM procedures, radioactive isotopes are administered intravenously or orally to assess the molecular, metabolic, physiologic, anatomical and pathologic states of the body for diagnostic therapy and research applications. The annual dosimetric records of 269 nuclear medicine technologists (NMTs) and 132 nuclear medicine nurses (NMNs) from 2016 to 2021 are collected in four major medical centres. Personal radiation doses in NM departments are monitored on a quarterly basis using thermoluminescent dosimeters (TLDs). The TLDs used have an approximate tissue equivalence of 8.14 and a density of around 2.64 g cm−3. TLDs are read using WinREMS software and a Harshaw 6600 plus reader. In this study, only Hp (10), which estimates the effective dose, is included in the analysis. The result showed that the NMTs and NMNs’ overall mean effective dose during the study period were 1.06 ± 0.60 mSv (0.06–3.26 mSv) and 0.92 ± 0.70 mSv (0.01–5.52 mSv), respectively. The result of our study found lower values of annual mean effective doses compared to previous studies conducted in Saudi Arabia. The dosimetric records show that the mean effective dose among both workers were below the permissible dose limits, which suggest a safe work environment in term of radiation protection practices.

Measurement of Radium and Radon Exhalation Rate in Marble Samples used in Al-Bayda City Market-Libya

The aim of the present study is to measure the activity concentrations of 226Ra, 222Rn, the mass exhalation rate of 222Rn, and the annual effective dose of radon in marble samples collected from Al-Bayda city local market –Libya. Samples were measured by using a low-background NaI (Tl) detector. The average activity concentrations of 226Ra and 222Rn were 72.57 Bq.kg-1 and 597.85 Bq.m-3.The radon exhalation rate in marble samples vary from 0.05-0.30 Bq.kg-1.S-1 with an average of 0.13 Bq.kg-1.S-1. The annual effective dose of radon was calculated in samples under investigation. For most samples, the values were lower than the maximum permissible dose limits. It can be concluded that marble samples under investigation do not pose any radiological hazard to the dwellers of buildings used in their construction.

A coverage path planning approach for autonomous radiation mapping with a mobile robot

In nuclear and radiation-related industries, it is crucial to ensure that the radiation dose exposure to the radiation worker is maintained below the permissible dose limit. A radiation map is a useful tool for visualizing the radiation distribution across the work area and for coordinating activities involving the hotspots (high radiation areas). The goal of this work was to design and implement a coverage path planning approach for autonomous radiation mapping carried out by a mobile robot. Given a 2D occupancy map, a method to generate uniformly distributed sampling points was proposed. The geometry of the region of interest, the radiation detector module, and the radiation measurement parameters were considered in formulating the sampling positions. Next, the coverage path planning planner integrates the nearest neighbor and depth-first search algorithms to create a continuous path that enables the robot to visit all the sampling points. The K-means clustering algorithm is added for systematic coverage of a large number of sampling points. The clustering provides options to partition the region of interest into smaller spaces, where the robot would perform the mapping cluster by cluster. Finally, the method of building the radiation map from the acquired data was also presented. The approach was implemented in ROS using a commercial mobile robot equipped with a Geiger–Muller detector. The performance and reliability of the proposed approach were evaluated with a series of simulations and real-world experiments. The results showed that the robot is able to perform autonomous radiation mapping at various target areas. The accuracy of the generated radiation map and the hotspots classifications were also compared and evaluated with conventional manual measurements. Overall, the theoretical frameworks and experiments have provided convincing results in the automation of hazardous work and subsequently toward improving the occupational safety of radiation workers.

Chromosome Damage in Relation to Recent Radiation Exposure and Radiation Quality in Nuclear Power Plant Workers.

Ionizing radiation is a well-known carcinogen that causes genomic instability. However, the biological and carcinogenetic effects of occupational radiation exposure at low doses have not been extensively studied. The aim of this study was to assess chromosomal instability in power plant workers exposed to occupational radiation at low doses in South Korea. Chromosomal aberrations in the lymphocytes of 201 nuclear power plant workers and 59 sex-matched controls were measured. Chromosomal aberrations in the lymphocytes of 201 nuclear power plant workers (mean age: 41.4 ± 10.0 years) and 59 sex-matched controls (mean age: 47.2 ± 6.0 years) were measured. A total of 500 metaphases for each subject were scored randomly. The means of recent 1.5-year, recent 5.5-year, and cumulative exposed radiation doses among workers were 8.22 ± 7.0 mSv, 30.7 ± 22.0 mSv, and 158.8 ± 86.1 mSv, respectively. The frequency of chromosome-type and chromatid-type aberrations was significantly higher in workers than that in the control group (p < 0.001), and the frequency of chromosome-type aberrations among workers increased in a radiation dose-dependent manner (τ = 0.16, p = 0.005). Poisson regression analyses revealed that chromosome-type aberrations were significantly associated with recent 1.5-year dose after adjusting for confounding variables such as age, smoking, and alcohol intake, even when only the exposed worker was considered. Frequency of multi-aberrant cells (two or more chromosome aberrations within a cell) increased according to cumulative neutron exposure. Our study demonstrates that chromosome damage can be induced in nuclear power plant workers occupationally exposed to ionizing radiation at low doses below the occupational permissible dose limit. Furthermore, an increase in multi-aberrant cells may provide evidence for chronic neutron exposure in nuclear power plant workers. This study was performed to obtain baseline data for a surveillance program of workers occupationally exposed to ionizing radiation long-term.

Comparative optimization of Be/Zr(BH4)4 and Be/Be(BH4)2 as 252Cf source shielding assemblies: Effect on landmine detection by neutron backscattering technique

Monte Carlo simulations were used to model a portable Neutron backscattering (NBT) sensor suitable for detecting plastic anti-personnel mines (APMs) buried in dry and moist soils. The model consists of a 100 MBq 252Cf source encapsulated in a neutron reflector/shield assembly and centered between two 3He detectors. Multi-parameter optimization was performed to investigate the efficiency of Be/Zr(BH4)4 and Be/Be(BH4)2 assemblies in terms of increasing the signal-to-background (S/B) ratio and reducing the total dose equivalent rate. The MCNP results showed that 2 cm Be/3 cm Zr(BH4)4 and 2 cm Be/3 cm Be(BH4)2 are the optimal configurations. However, due to portability requirements and abundance of Be, the 252Cf-2 cm Be/3 cm Be(BH4)2 NBT model was selected to scan the center of APM buried 3 cm deep in dry and moist soils. The selected NBT model has positively identified the APM with a S/B ratio of 886 for dry soils of 1 wt% hydrogen content and with S/B ratios of 615, 398, 86, and 12 for the moist soils containing 4, 6, 10, and 14 wt% hydrogen, respectively. The total dose equivalent rate reached 0.0031 mSv/h, suggesting a work load of 8 h/day for 806 days within the permissible annual dose limit of 20 mSv.

Study on Occupational Radiation Exposure at Different Hospitals in Nepal using ThermoluminescenceDosimetry

The clinical efficacy of using ionizing radiation in diagnosis and treatment of diseases has been revolu­tionized, benefitting humankind and, at the same time, imposing deleterious health effects, if not han­dled carefully. Personnel dosimetry has emerged as an essential tool to monitor occupational radiation exposure. The present study intends to reveal and describe the scenario of occupationally exposed staff by assessing an individual’s dose in radiological facilities at different hospitals in Nepal. Thermo luminescent Dosimetry (TLD) has been used for assessing individual doses. Altogether eight hospitals were chosen from different locations of Nepal. TLD badges were worn by the radiation workers on their chest level while working with the radiological equipment for about three to ten months during their routine work. Later the badges were read out in the TLD badge reader system available at Nepal Academy of Science and Technology (NAST) to obtain the exposed doses. CaSO4: Dy was used as TL phosphor. Exposed doses for health personnel during their routine work were founding the range of (2.21 to 16.17) 0.01 mSv per year, which was low compared to the permissible dose limit of 20 mSv per year set up by International Commission on Radiological Protection(ICRP). Although the exposed dose rates in the monitored hospitals are below the recommended dose limits, it should be made as low as possible based on the ALARA principle.

Comparative Analysis of Emitted Magnetic Fields from Liquid Crystal Display (LCD) and Light Emitting Diode (LED) System

This paper present the Comparative analysis of emitted magnetic fields from Liquid Crystal Display(LCD) and that of Light Emitting Diode (LED) system. A total of eighteen Liquid Crystal Display and Light Emitting Diode Monitors from different manufacturers were used. The magnetic field was measured using a trifield guass meter. The trifield guass meter was placed perpendicularly to the monitors at 5cm steps from the monitor up to 70cm and the magnetic field from each monitor was recorded in milligauss. The result showed that the magnetic field of the liquid crystal display monitors is almost 2 times greater than that of the light-emitting diode monitors. The obtained results were compared with international occupational and general public recommended exposure limit and The result was found to be below the permissible dose limit according to the IEEE( Institute of Electrical and Electronics Engineering) standard. Although there is minimal evidence of the health risk associated with the use of Visual Display Units (VDUs) and it is inconclusive.”

Measurement of the radiation level dose to patient from fluoroscopy device during cardiac catheterization

Fluoroscopy is a type of medical imaging that shows a continuous X-ray image on a screen, it is used in a wide range of examination and procedures for diagnosis such as in cardiac catheterization. Fluoroscopy can result in relatively high radiation doses, especially for complex interventional procedures that it needed to monitor radiation to reduce exposure. The purpose of this study is to determine the radiation doses for patients during cardiac catheterization exam and compare it with the permissible dose limits. The main parameters which are studied in this work are the time of exposure dose rate, x-ray techniques (milliamper. second), tube voltage (kilovolt) and Dose Area Product (DAP). Twenty-seven patients were included and absorbed doses were measured and distributed according to Fluoroscopy (Fluo) time, mAs and Dose Area Product (DPA). It was found that the absorbed dose received by the patients has a linear relationship with the Fluoroscopy time, mAs and DAP. Exposure dose rates were measured and compared with the maximum permissible dose (100 mGy/min), the estimated patient dose rate varied from (12-81.6) mGy/min) for 24 patients as a permissible dose in the safe side, and 3 patients exposed to higher values of the exposure dose rates ) over permissible dose) range (107.4-108) mGy/min

LEVELS OF EXPOSURE TO IONIZING RADIATION AMONG THE PERSONNEL ENGAGED IN CYCLOTRON OPERATION AND THE PERSONNEL ENGAGED IN THE PRODUCTION OF RADIOPHARMACEUTICALS, BASED ON RADIATION MONITORING SYSTEM.

This paper aims to determine the levels of exposure to neutron and photon radiation among the personnel engaged in cyclotron operation and the personnel engaged in the production of radiopharmaceuticals, with the use of the environmental radiation monitoring system (RMS) installed in the positron emission tomography laboratory. The annual exposures of employees operating the cyclotron measured with the use of the RMS system are: 1.39 ± 0.16 mSv in case of photon radiation and 2.61 ± 0.14 mSv in case of neutron radiation. In the case of employees in the radiopharmaceuticals’ production zone, the annual exposures measured by means of the RMS system are 0.15 ± 0.03 mSv in case of photon radiation and 0.11 ± 0.01 mSv in case of neutron radiation. The exposure levels among the personnel engaged in cyclotron operation and the personnel engaged in the production of radiopharmaceuticals are below the permissible radiation dose limits.

Radiation Shielding for Helical Tomotherapy Vault Design.

Purpose:The purpose of the present study is to carry out radiation shielding calculations to find out adequate thicknesses of protective barriers such as walls and ceiling based on minimum space required to house helical tomotherapy unit. This study also aim to derive expression for use factor and estimation of patient workload for tomotherapy facility for optimizing radiation shielding requirements.Materials and Methods:The basic definitions and formulae given in NCRP/IAEA reports were referred and modified for tomotherapy machine to calculate optimized shielding thicknesses requirements. Workload is estimated based on observations of patient treatments on tomotherapy machine and analysis of their treatment plan data. A mathematical expression is derived for calculating use factor in terms of beam divergence angle at source corresponding to field length, angle of source rotation about isocenter, and distance of primary barrier from isocenter. Radiation shielding requirement of protective barriers such as walls and ceiling of helical tomotherapy vault is calculated based on minimum room dimensions as specified by the manufacturer, permissible dose limit (s), and values of optimizing parameters such as workload, use factor etc. for tomotherapy machine.Results:Using derived mathematical expression for use factor in this study, it was found that value of use factor varies with distance of primary barrier from isocenter and its value was found to be 0.093 for given minimum room dimensions. Radiation shielding requirements for protective barriers (walls/ceiling, etc.) were arrived and reported in this paper.Conclusions:A typical helical tomotherapy vault design is proposed based on the calculated shielding thicknesses of protective barriers. Further, it is also concluded that tomotherapy machine can be installed in a vault designed for 6 MV conventional linear accelerator with minor modification.

Radionulide analyses of ingested water from some estuaries within the coastal area of Akwa Ibom State, Nigeria

Radionuclide analyses of ingested water from three selected estuaries within the coastal areas of Akwa Ibom State, Nigeria have been carried out. Fifteen water samples collected at strategic points from the estuaries were pre-treated and each placed on the sodium iodide NaI (Tl) -model 802 detector for 3600 s to obtain the gamma radiation count rate. The activity concentrations and other radiological risk parameters were computed. The effective dose rate of radiation due to ingested water (E.D.I.W.) ranged between 0.25 and 1.86 mSv yr−1, the effective equivalent dose rate due to absorbed radiation in air (Deq) ranged between 0.0065 and 0.0369 mSv yr−1 and the total equivalent dose rate of radiation ranged between 0.257 and 1.87 mSv yr−1. The E.D.I.W exceeded the International Commission on Radiological Protection (ICRP) permissible limit of 0.1 mSv yr−1 set for ingested radionuclides from food. Most surveyed points had their total equivalent dose rate of radiation greater than the ICRP permissible dose limit of 1 mSv yr−1 for radiation exposure from all internal and external sources. The annual gonadal dose equivalent ranged between 0.008 and 0.041 mSv yr−1 and are below the world average value of 0.3 mSv yr−1. The excess lifetime cancer risk ranged between 0.7 × 10−3 and 5.07 × 10−3 and are above the world average value of 0.29 × 10−3. The elevation of most of the radiation risk parameters over the standard limits shows that oil production activities may have raised the background radiation levels of the area. This research also revealed that computing only the Deq and neglecting the E.D.I.W would mean under estimating the radiation doses received by an impacted person by 97.4%–98.3%. Water consumed from these sources could enhance the radionuclide content and the percentage probabilities of developing cancer by impacted persons.

The Realpolitik of Nuclear Risk: When Political Expediency Trumps Technical Democracy

In recent years, a growing number of researchers in science and technology studies have begun to examine the relationship between science and politics. Specifically, they focus on citizen participation in highly technical policy problems and explore the possibility of a technical democracy that avoids pitfalls of technocracy. This focus, however, downplays a possibly more serious obstacle to technical democracy than technocracy, namely, realpolitik. Based on ethnographic and textual data on citizen–government interactions in the aftermath of the Fukushima Daiichi Nuclear Disaster, we first show how citizens mobilised radiation detectors and counter-experts to force the Japanese government to admit scientific uncertainty about the permissible dose limit. We then explain why this successful mobilisation nonetheless had only a small impact on evacuation and compensation policies in terms of the pre-disaster structure of Japanese politics: the dominance of commission-based policy-making allowed the bureaucratic government to play realpolitik in the face of scientific uncertainty to expediently pursue its own interest, circumventing both democratic deliberation and technical rigour.

Brain CT에서 발생하는 선속경화현상 감소방안에 관한 연구

본 연구는 Brain CT검사 시 영상에서 발생하는 선속경화현상의 원인과 감소방법을 알아보기 위하여 선속경화현상에 영향을 미치는 관전압, 관전류, 단면두께, 갠트리 각도, 기준선에 변화를 주었다. 사용한 장비로는 Somatom Sensation 16장비로 Bone opaque head phantom을 이용 영상영향인자에 변화를 주어 스캔하였고 획득한 영상 데이터를 이용하여, CT값 분석을 이용한 정량적 분석과 CT영상평가표를 이용한 정성적 평가를 시행하였다. 정량적 분석결과 관전압은 140kVp일 때 <TEX>$31.56{\pm}2.89HU$</TEX>로 측정되었고, 관전류의 경우 150mA에서 <TEX>$-3.87{\pm}0.12HU$</TEX>, 절편두께는 3mm에서 <TEX>$2.29{\pm}0.78HU$</TEX>로 측정되었으며 갠트리 각도에서 IOML이 <TEX>$13.31{\pm}1.03HU$</TEX>로 선속경화현상이 가장 적었다. 정성적 분석결과 대부분의 평가자들이 140kVp, 150mA, 3mm, IOML 또는 OML에서 스캔한 영상을 선속경화현상이 적게 발생한 영상으로 평가하였으며 모든 조건에서 변화 인자와 비교 시 통계학적으로 유의한 차이가 있었다.(P<0.05) 따라서, 임상적용 시 허용선량한도 범위 내에서 관전압은 높여주고 관전류는 영상 화질 저하에 영향을 미치지 않는 범위 내에서 낮게 설정하며, 절편두께는 해상도 저하를 고려하여 얇은 절편두께를 사용하고, 갠트리 각도는 IOML 또는 OML을 이용한다면 선속경화현상에 의해 발생되어지는 인공물을 최소화시켜 영상 판독자와 환자에게 보다 정확한 양질의 영상을 제공할 수 있을 것으로 사료된다. This study aim is occur in brain CT cause of beam hardening effect and reducing method, We will scan Bone opaque bead phantom on variation of image on the influence factor with equipment called 'Samatom Senation 16' with following listed herein : tube voltage, tube current, slice thickness, gantry angle, base line which affect beam-hardening effect. After that we are going to start Quantitative Analysis resulted in previous scanning and Qualitative Assessment with CT image sheet evaluation. result of quantitative analysis 140kVp <TEX>$31.56{\pm}2.89HU$</TEX> on tube voltage, 150mA <TEX>$-3.87{\pm}0.12HU$</TEX> on tube current, 3mm on slice thickness, and <TEX>$13.31{\pm}1.03HU$</TEX> IOML on gantry angle which was the least beam-hardening effect. Like Qualitative Analysis, we went through Qualitative Assessment and most of valuers got a result of 140kVp on tube voltage, 150mA on tube current, 3mm on slice thickness. As before valuers evaluated gantry angle that scanned image from IOML or OML was the least beam-hardening effect occured. There are meaningful differences when we compare all theses factors statistically(P<0.05). therefore We consider that Minimizing artifact that caused by beam-hardening effect can provide better quality of image to deciphers and patients. if we rise tube voltage in permissible dose limit, set tube current in a limit that does not effect to image quality, use slice thickness too thin enough to harm resolution, use IOML or OML on gantry angle.

Radiological performance of hot water layer system in open pool type reactor

The paper presents the calculated dose rate carried out by using MicroShield code to show the importance of hot water layer system (HWL) in 22MW open pool type reactor from the radiation protection safety point of view. The paper presents the dose rate profiles over the pool surface in normal and abnormal operations of HWL system. The results show that, in case of losing the hot water layer effect, the radiation dose rate profiles over the pool surface will increase from values lower than the worker permissible dose limits to values very higher than the permissible dose limits.

SU‐E‐T‐270: Optimized Shielding Calculations for Medical Linear Accelerators (LINACs)

The purpose of radiation shielding is to reduce the effective equivalent dose from a medical linear accelerator (LINAC) to a point outside the room to a level determined by individual state/international regulations. The study was performed to design LINAC's room for newly planned radiotherapy centers. Optimized shielding calculations were performed for LINACs having maximum photon energy of 20 MV based on NCRP 151. The maximum permissible dose limits were kept 0.04 mSv/week and 0.002 mSv/week for controlled and uncontrolled areas respectively by following ALARA principle. The planned LINAC's room was compared to the already constructed (non-optimized) LINAC's room to evaluate the shielding costs and the other facilities those are directly related to the room design. In the evaluation process it was noted that the non-optimized room size (i.e., 610 × 610 cm2 or 20 feet × 20 feet) is not suitable for total body irradiation (TBI) although the machine installed inside was having not only the facility of TBI but the license was acquired. By keeping this point in view, the optimized INAC's room size was kept 762 × 762 cm 2. Although, the area of the optimized rooms was greater than the non-planned room (i.e., 762 × 762 cm 2 instead of 610 × 610 cm 2), the shielding cost for the optimized LINAC's rooms was reduced by 15%. When optimized shielding calculations were re-performed for non-optimized shielding room (i.e., keeping room size, occupancy factors, workload etc. same), it was found that the shielding cost may be lower to 41 %. In conclusion, non- optimized LINAC's room can not only put extra financial burden on the hospital but also can cause of some serious issues related to providing health care facilities for patients.

Relative radiological risks derived from different TENORM wastes in Malaysia

In Malaysia technologically enhanced naturally occurring radioactive materials (TENORM) wastes are mainly the product of the oil and gas industry and mineral processing. Among these TENORM wastes are tin tailing, tin slag, gypsum and oil sludge. Mineral processing and oil and gas industries produce large volume of TENORM wastes that has become a radiological concern to the authorities. A study was carried out to assess the radiological risk related to workers working at these disposal sites and landfills as well as to the members of the public should these areas be developed for future land use. Radiological risk was assessed based on the magnitude of radiation hazard, effective dose rates and excess cancer risks. Effective dose rates and excess cancer risks were estimated using RESRAD 6.4 computer code. All data on the activity concentrations of NORM in wastes and sludges used in this study were obtained from the Atomic Energy Licensing Board, Malaysia, and they were collected over a period of between 5 and 10 y. Results obtained showed that there was a wide range in the total activity concentrations (TAC) of nuclides in the TENORM wastes. With the exception of tin slag and tin tailing-based TENORM wastes, all other TENORM wastes have TAC values comparable to that of Malaysia's soil. Occupational Effective Dose Rates estimated in all landfill areas were lower than the 20 mSv y(-1) permissible dose limit. The average Excess Cancer Risk Coefficient was estimated to be 2.77×10(-3) risk per mSv. The effective dose rates for residents living on gypsum and oil sludge-based TENORM wastes landfills were estimated to be lower than the permissible dose limit for members of the public, and was also comparable to that of the average Malaysia's ordinary soils. The average excess cancer risk coefficient was estimated to be 3.19×10(-3) risk per mSv. Results obtained suggest that gypsum and oil sludge-based TENORM wastes should be exempted from any radiological regulatory control and should be considered radiologically safe for future land use.

Radiometric survey of teletherapy treatment rooms in Brazil

The Brazilian national regulatory authority, National Commission of Nuclear Energy, requires that dose rates in the vicinity of teletherapy treatment rooms do not exceed the permissible limits for workers as well as members of the public, depending on the place considered. At the end of 2005, the Brazilian national regulatory authority reduced the permissible dose limit for controlled areas from 1000 to 400 microSv week(-1). Therefore, the aim of this work is to verify the adequacy of structural shielding to this new limit for telecobalt units that had their sources changed and clinic linear accelerators (ALs) installed before the end of 2005. Considering the ALs, measurements of dose rates in controlled areas did not exceed the new permissible limit, excepting for a single case. In the case of (60)Co units, a similar situation is observed for controlled areas, although several non-conformities to the limit of uncontrolled area could be observed.

Beta radiation exposure of staff during and after therapies with 90Y-labelled substances

Radioimmunotherapies (RITs) and peptide receptor radiotherapies (PRRTs) with (90)Y-labelled compounds offer promising prospects for tumor treatment in nuclear medicine. However, when preparing and performing these therapies, which require manipulations of high activities of (90)Y (>1 GBq), technicians and physicians may receive high exposures, mainly to the skin of the hands. Even non-occupationally exposed persons, such as caregivers and family members, receive external exposures in the initial period after therapy, arising from the (90)Y in the patient. The local skin doses of the individual staff members, measured during RITs and PRRTs with thermoluminescence detectors fixed with tapes to the fingers, vary considerably. The exposure of staff can exceed the annual permissible dose limit of 500 mSv if radiation protection standards are low. Thus, adequate safety measures are needed. Measurements of the dose rate around patients, made using survey meters with sufficient response to beta particles, indicate that the exposure of caregivers and family members is considerably higher than previously assumed, and was dominated by primary beta radiation instead of bremsstrahlung. Nevertheless, under normal circumstances, the annual dose limits for the public (effective dose: 1 mSv, skin dose: 50 mSv) will be complied with.