Society and Nuclear Energy: What Is the Role for Radiological Protection?

ABSTRACT: The harm that society expects from ionizing radiation does not match experience. Evidently there is some basic error in this assumption. A reconsideration based on scientific principles shows how simple misunderstandings have exaggerated dangers. The consequences for society are far-reaching. The immediate impact of ionizing radiation on living tissue is destructive. However, this oxidative damage is similar to that produced during normal metabolic activity where the subsequent biological reaction is not only protective but also stimulates enhanced protection. This adaptation means that the response to oxidative damage depends on past experience. Similarly, social reaction to a radiological accident depends on the regulations and attitudes generated by the perception of previous instances. These shape whether nuclear technology and ionizing radiation are viewed as beneficial or as matters to avoid. Evidence of the spurious damage to society caused by such persistent fear in the second half of the 20 th century suggests that these laws and attitudes should be rebased on evidence. The three stages of radiological impact-the initial physical damage, the subsequent biological response, and the personal and social reaction-call on quite different logic and understanding. When these are confused, they lead to regulations and public policy decisions that are often inept, dangerous, and expensive. One example is when the mathematical rigor of physics, appropriate to the immediate impact, is misapplied to the adaptive behavior of biology. Another, the tortured historical reputation of nuclear technology, is misinterpreted as justifying a radiological protection policy of extreme caution.Specialized education and closed groups of experts tend to lock in interdisciplinary misperceptions. In the case of nuclear technology, the resulting lack of independent political confidence endangers the adoption of nuclear power as the replacement for fossil fuels. In the long term, nuclear energy is the only viable source of large-scale primary energy, but this requires a re-working of public understanding.

Replace the Linear No-threshold Model with a Risk-informed Targeted Approach to Radiation Protection.

ABSTRACT: The linear no-threshold (LNT) model may be useful as a simple basis for developing radiation protection regulations and standards, but it bears little resemblance to scientific reality and is probably overly conservative at low doses and low dose rates. This paper is an appeal for a broader view of radiation protection that involves more than just optimization of radiation dose. It is suggested that the LNT model should be replaced with a risk-informed, targeted approach to limitation of overall risks, which include radiation and other types of risks and accidents/incidents. The focus should be on protection of the individual. Limitation of overall risk does not necessarily always equate to minimization of individual or collective doses, but in some cases it might. Instead, risk assessment (hazards analysis) should be performed for each facility/and or specific job or operation (straightforward for specialized work such as radiography), and this should guide how limited resources are used to protect workers and the public. A graded approach could be used to prioritize the most significant risks and identify exposure scenarios that are unlikely or non-existent. The dose limits would then represent an acceptable level of risk, below which no further reduction in dose would be needed. Less resources should be spent on ALARA and tracking small individual and collective doses. Present dose limits are thought to be conservative and should suffice in general. Two exceptions are possibly the need for a lower (lifetime) dose limit for lens of the eye for astronauts and raising the public limit to 5 mSv y -1 from 1 mSv y -1 . This would harmonize the public limit with the current limit for the embryo fetus of the declared pregnant worker. Eight case studies are presented that emphasize how diverse and complex radiation risks can be, and in some cases, chemical and industrial risks outweigh radiation risks. More focus is needed on prevention of accidents and incidents involving a variety of types of risks. A targeted approach is needed, and commitments should be complied with until they are changed or exemptions are granted. No criticism of regulators or nuclear industry personnel is intended here. Protection of workers and the public is everyone's goal. The question is how best to accomplish that.

Phantom study of a self-shielded X-ray bone age assessment instrument against scattered radiation in children.

Hand-wrist radiography is the most common and accurate method for evaluating children's bone age. To reduce the scattered radiation of radiosensitive organs in bone age assessment, we designed a small X-ray instrument with radioprotection function by adding metal enclosure for X-ray shielding. We used a phantom operator to compare the scattered radiation doses received by sensitive organs under three different protection scenarios (proposed instrument, radiation personal protective equipment, no protection). The proposed instrument showed greater reduction in the mean dose of a single exposure compared with radiation personal protective equipment especially on the left side which was proximal to the X-ray machine (≥80.0% in eye and thyroid, ≥99.9% in breast and gonad). The proposed instrument provides a new pathway towards more convenient and efficient radioprotection.

Characterizing imaging radiation risk in a population of 8918 patients with recurrent imaging for a better effective dose.

An updated extension of effective dose was recently introduced, namely relative effective dose ( E r ), incorporating age and sex factors. In this study we extended E r application to a population of about 9000 patients who underwent multiple CT imaging exams, and we compared it with other commonly used radiation protection metrics in terms of their correlation with radiation risk. Using Monte Carlo methods, E r , dose-length-product based effective dose ( E DLP ), organ-dose based effective dose ( E OD ), and organ-dose based risk index ( RI ) were calculated for each patient. Each metric's dependency to RI was assessed in terms of its sensitivity and specificity. E r showed the best sensitivity, specificity, and agreement with RI (R2 = 0.97); while E DLP yielded the lowest specificity and, along with E OD , the lowest sensitivity. Compared to other metrics, E r provided a closer representation of patient and group risk also incorporating age and sex factors within the established framework of effective dose.

Factors Affecting Gonadal Shielding Use Among Technologists in California.

PURPOSE: To assess the patient gonadal shielding practices of radiologic technologists in the state of California. METHODS: A survey invitation was sent via email to registered radiologic technologists in California to collect data to determine whether there were significant associations between gonadal shielding practices and various categorical variables, including patient sex, patient age, body part, availability of gonadal shielding protocols, availability of gonadal shields, and supervisor encouragement. RESULTS: There was a significant association between gonadal shielding protocol availability and supervisor encouragement of using gonadal shielding (P = .005) and between gonadal shielding availability and supervisor encouragement of using gonadal shielding (P < .001). Contrary to other studies in the literature, there was a significant difference between patient sex and the likelihood of gonadal shielding use, with participants indicating that they shield girls and women more often than they shield boys and men (P < .001). DISCUSSION: There was a sex-based difference in the frequency of gonadal shielding usage among the sample in this study. Also, supervisors providing accessible protocols and encouraging gonadal shielding can increase technologists' use of gonadal shielding. CONCLUSION: Gonadal shielding is the current Code of Federal Regulations standard, although most professional and scientific organizations support discontinuing shielding during abdominal and pelvic radiography examinations. Shielding of these areas is more likely to occur with the availability of gonadal shielding, supervisory encouragement, protocols mandating shielding, and state regulations.

Radioprotection issues in uraniferous minerals collections with reference to an actual case.

Our work investigated the radioprotection implications associated with the possession of a collection of uraniferous minerals. Considering different scenarios, we developed (and applied to an actual collection) specific formulas for radiation doses evaluation. We discussed the shielding necessary to reduce the gamma irradiation down to the required values. A mathematical model was developed to estimate the minimum air flow rate to reduce the radon air concentration below the reference values. The radiation risks associated to the handling of single specimens was also addressed, including hand skin irradiation and shielding capabilities of surgical lead gloves. Finally, we discussed the radiation risks associated to the exhibition of a single specimen. The results, compared to the safety standards of the EU Directive 13/59, show that the exhibition of uraniferous samples with activity of a few MBq do not need specific radioprotection requirements nor for the involved personnel nor for visitors.

Radiation shielding assessment for interventional radiology personnel: Geant4 dosimetry of lead-free compositions.

The inherent biological hazards associated with ionizing radiation necessitate the implementation of effective shielding measures, particularly in medical applications. Interventional radiology, in particular, poses a unique challenge as it often exposes medical personnel to prolonged periods of high x-ray doses. Historically, lead and lead-based compounds have been the primary materials employed for shielding against photons. However, the drawbacks of lead, including its substantial weight causing personnel's inflexibility and its toxicity, have raised concerns regarding its long-term impact on both human health and the environment. Barium tantalate has emerged as a promising alternative, due to its unique attenuation properties against low-energy x-rays, specifically targeting the weak absorption area of lead. In the present study, we employ the Geant4 Monte Carlo simulation tool to investigate various formulations of barium tantalate doped with rare earth elements. The aim is to identify the optimal composition for shielding x-rays in the context of interventional radiology. To achieve this, we employ a reference x-ray spectrum typical of interventional radiology procedures, with energies extending up to 90 keV, within a carefully designed simulation setup. Our primary performance indicator is the reduction in air kerma transmission. Furthermore, we assess the absorbed doses to critical organs at risk within a standard human body phantom protected by the shield. Our results demonstrate that specific concentrations of the examined rare earth impurities can enhance the shielding performance of barium tantalate. To mitigate x-ray exposure in interventional radiology, our analysis reveals that the most effective shielding performance is achieved when using barium tantalate compositions containing 15% Erbium or 10% Samarium by weight. These findings suggest the possibility of developing lead-free shielding solutions or apron for interventional radiology personnel, offering a remarkable reduction in weight (exceeding 30%) while maintaining shielding performance at levels comparable to traditional lead-based materials.

Directional vector visualization of scattered rays in mobile c-arm fluoroscopy.

Previous radiation protection-measure studies for medical staff who perform X-ray fluoroscopy have employed simulations to investigate the use of protective plates and their shielding effectiveness. Incorporating directional information enables users to gain a clearer understanding of how to position protective plates effectively. Therefore, in this study, we propose the visualization of the directional vectors of scattered rays. X-ray fluoroscopy was performed; the particle and heavy-ion transport code system was used in Monte Carlo simulations to reproduce the behavior of scattered rays in an X-ray room by reproducing a C-arm X-ray fluoroscopy system. Using the calculated results of the scattered-ray behavior, the vectors of photons scattered from the phantom were visualized in three dimensions. A model of the physician was placed on the directional vectors and dose distribution maps to confirm the direction of the scattered rays toward the physician when the protective plate was in place. Simulation accuracy was confirmed by measuring the ambient dose equivalent and comparing the measured and calculated values (agreed within 10%). The directional vectors of the scattered rays radiated outward from the phantom, confirming a large amount of backscatter radiation. The use of a protective plate between the patient and the physician's head part increased the shielding effect, thereby enhancing radiation protection for the physicians compared to cases without the protective plate. The use of directional vectors and the surrounding dose-equivalent distribution of this method can elucidate the appropriate use of radiation protection plates.

On methods for radiometric surveying in radiotherapy bunkers.

Radiometric surveys in radiotherapy bunkers have been carried out in Brazil for many years, both by the same radiotherapy facility for verification of shielding as by the regulatory agency for licensing and control purposes. In recent years, the Intensity Modulated Radiation Therapy (IMRT) technique has been gradually incorporated into many facilities. Therefore, it has been necessary to consider the increased leakage component that has an important impact on the secondary walls. For that, a radiometric survey method has been used that considers an increased 'time of beam-on' for the secondary walls. In this work we discuss two methods of doing this: the first considers that this 'time of beam-on' affects the sum of the two components, leakage and scattered. In another method it is considered that only the leakage component is affected by this extended 'time of beam-on'. We compare the methods and show that for secondary walls withU= 1 the first method overestimates dose rates by important percentages and for secondary walls withU< 1 it can both overestimate or underestimate the dose rates, depending on the parameters of the project. An optimized procedure is proposed, according to the use factor (U) of the secondary wall to be measured.

More May Not be Better: Enhanced Spacecraft Shielding May Exacerbate Cognitive Decrements by Increasing Pion Exposures during Deep Space Exploration.

The pervasiveness of deep space radiation remains a confounding factor for the transit of humans through our solar system. Spacecraft shielding both protects astronauts but also contributes to absorbed dose through galactic cosmic ray interactions that produce secondary particles. The resultant biological effects drop to a minimum for aluminum shielding around 20 g/cm2 but increase with additional shielding. The present work evaluates for the first time, the impact of secondary pions on central nervous system functionality. The fractional pion dose emanating from thicker shielded spacecraft regions could contribute up to 10% of the total absorbed radiation dose. New results from the Paul Scherrer Institute have revealed that low dose exposures to 150 MeV positive and negative pions, akin to a Mars mission, result in significant, long-lasting cognitive impairments. These surprising findings emphasize the need to carefully evaluate shielding configurations to optimize safe exposure limits for astronauts during deep space travel.

Assessment of Radiation Doses to the General Public around Nuclear Power Plants Based on Representative Person Concept.

ABSTRACT: The International Commission on Radiological Protection recommended that the representative person concept should be used in radiation dose assessment of the general public to specify exposed individuals. The objective of this study is to assess radiation doses of the residents around nuclear power plants (NPPs) in relation to the introduction of the representative person concept. Critical group candidates and representative agro-livestock product producing areas were selected around a NPP site by considering radioactive effluents and regional meteorological data, geographical information, etc. A total of five exposure scenarios, including adult (non-fishery, fishery, and commuter), 10-y-old, and 1-y-old groups, were selected for the dose assessment. Generally, radiation doses were higher for 1-y-old, 10-y-old, and adult groups, in that sequence. There was no significant difference among the radiation doses by occupation in adult groups. Radiation dose results calculated by applying the representative person concept and dose assessment method currently used in Korea were compared. Application of the representative person concept results in lower radiation dose by 68.2% due to consideration of actual residential and agro-livestock product producing areas for the radiation dose assessment, by 13.3% due to the application method of habit data for dose calculation, and by 33.3% due to representative value of the dose results. Finally, considering all the factors above, radiation dose calculated by the current dose assessment method was 8.16 × 10 -2 mSv y -1 , while that calculated using the representative person concept was 1.40 × 10 -2 mSv y - 1 (82.8% lower). The results of this study can be used as reference data when introducing the representative person concept to the regulatory systems in Korea.

Assessment of dosimetric approaches in evaluating radiation exposure for interventional cardiologists in Sri Lanka.

Interventional cardiologists face significant radiation exposure during interventional cardiology procedures. Therefore, this study focuses on assessing radiation exposure among interventional cardiologists during their procedures. Specifically, it aims to determine the effectiveness of both single and double dosimeter methods in estimating annual occupational radiation doses. This research holds pioneering significance as it represents the very first study undertaken in Sri Lanka. Thirteen interventional cardiologists performed 486 interventional cardiology procedures over three months in three different healthcare institutes. Active Hp(10) dosimeters were placed to measure radiation exposure. Effective doses were calculated using single and double dosimetric algorithms. Annual occupational doses were assessed on an operator basis. Statistical analyses were conducted to assess algorithmic differences and dose variations using the Kruskal-Wallis test and linear regression. The highest annual occupational dose for each dosimetric algorithm received as 2.00 ± 0.24 mSv, 2.29 ± 0.48 mSv, 3.35 ± 0.71 mSv, and 2.64 ± 0.42 mSv, respectively, and remained below the recommended safety limit of 20 mSv/year. The Kruskal-Wallis test revealed no significant differences in the effective doses among double dosimetric algorithms, as well as between single and double dosimetric algorithms (p > 0.05). Linear regression showed strong correlations among various algorithms, demonstrating consistency. The findings of this study hold significant effects on interventional cardiology practice in Sri Lanka, enhancing radiation safety and monitoring.

Orthopaedic surgeons' knowledge and practice of radiation safety when using fluoroscopy during procedures: A narrative review.

OBJECTIVES: The fluoroscopy environment poses a potential occupational radiation exposure risk to theatre personnel. Risks can be mitigated with effective application of radiation protection knowledge and methods. This review aimed to determine the link between orthopaedic surgeon's knowledge and the use of appropriate safety methods when using fluoroscopy. KEY FINDINGS: A keyword search of three databases discovered six articles, totalling 2209 orthopaedic surgeons, who completed surveys to assess knowledge on various aspects of radiation safety and training. Participants had varying levels of experience. Moreover 1981 participants always wore a lead gown (89 %), while only 1052 participants wore thyroid protection (47 %). 449 participants (20 %) received some form of training. CONCLUSION: Although surveys asked a range of questions it appeared that there was low knowledge of the ALARP principles. Usage of protective equipment is a legal requirement and thus was observed throughout, however, there were a number of incidences of disregarding some protective measures. Although there appeared to be limited knowledge surrounding radiation protection measures and lack of training provided, no clear link was demonstrated between compliance with protective methods and knowledge of the risks. IMPLICATIONS FOR PRACTICE: Formal and continuous training should be provided for the enhancement of knowledge to ensure the safety of all staff and help prevent the long-term effects of ionising radiation when using fluoroscopy.

A new proposed procedure for calibrating personal dosemeters for X and gamma radiations, based on Hp(30)water.

Recently, a new operational quantity Hp(30)water has been proposed to replace Hp(10). This paper describes a new proposed procedure for calibrating personal dosemeters, for X and gamma radiations, in terms of this new quantity Hp(30)water. Compared to the current procedure based on Hp(10), the proposed procedure requires fewer steps and it is easier to implement. Indeed, this new procedure is based on the direct measurement of the quantity of interest, unlike the current one that necessitates the measurement of an intermediate quantity, the air kerma and then the use of conversion coefficients. Some of the advantages of the proposed procedure, such as no need of conversion coefficients to determine the value of the quantity of interest, and no need of additional material to ensure the conditions of electronic equilibrium of the secondary electrons, are highlighted. The feasibility of the proposed procedure is verified. The fluence-to-Hp(30)water conversion coefficients are measured for Cs-137 and Co-60 radiation qualities, and are found in good agreement with those available in the literature.

Moon, Mars and Minds: Evaluating Parkinson's disease mortality among U.S. radiation workers and veterans in the million person study of low-dose effects.

BACKGROUND: Radiation is one of the most important stressors related to missions in space beyond Earth's orbit. Epidemiologic studies of exposed workers have reported elevated rates of Parkinson's disease. The importance of cognitive dysfunction related to low-dose rate radiation in humans is not defined. A meta-analysis was conducted of six cohorts in the Million Person Study (MPS) of low-dose health effects to learn whether there is consistent evidence that Parkinson's disease is associated with radiation dose to brain. MATERIALS AND METHODS: The MPS evaluates all causes of death among U.S. radiation workers and veterans, including Parkinson's disease. Systematic and consistent methods are applied to study all categories of workers including medical radiation workers, industrial radiographers, nuclear power plant workers, atomic veterans, and Manhattan Projects workers at the Los Alamos National Laboratory and at Rocky Flats. Consistent methods for all cohorts are used to estimate organ-specific doses and to obtain vital status and cause of death. RESULTS: The meta-analysis include 6 cohorts within the MPS, consisting of 517,608 workers and 17,219,001 person-years of observation. The mean dose to brain ranged from 6.9 to 47.6 mGy and the maximum dose from 0.76 to 2.7 Gy. Five of the 6 cohorts revealed positive associations with Parkinson's disease. The overall summary estimate from the meta-analysis was statistically significant based on 1573 deaths due to Parkinson's disease. The summary excess relative risk at 100 mGy was 0.17 (95% CI: 0.05; 0.29). CONCLUSIONS: Parkinson's disease was positively associated with radiation in the MPS cohorts indicating the need for careful evaluation as to causality in other studies, delineation of possible mechanisms, and assessing possible implications for space travel as well as radiation protection guidance for terrestrial workers.

Limiting Exposure to Scattered Radiation From a CT System Installed in a Two-Sided Deployable ISO-Shelter.

INTRODUCTION: Diagnostic radiology in the deployed military environment (in-theater diagnostic radiology) was greatly improved in the early 1990s with the addition of CT systems installed in military-grade one-sided expandable ISO-shelters. These shelters were provided with limited radiation shielding by several flexible lead curtains covering only a small portion of the shelter walls, necessitating placement of deployed CT systems at substantial distances from the field medical facility to limit exposures to personnel from secondary radiation. The newest generation deployable CT system is housed in a two-sided ISO-shelter with radiation shielding applied to the shelter walls. To ensure compliance with military and national standards for protection against ionizing radiation, we developed a simple method to calculate safe distances based on workload, frequencies of the various CT exams performed, and occupancy of controlled and uncontrolled areas. MATERIALS AND METHODS: Calculation of radiation air kerma rates outside a two-sided CT ISO-shelter was developed using guidance from the National Council on Radiation Protection and Measurements Report No. 147. The simplified formula included measured radiation transmission factors for the ISO-shelter wall and installed shielding, occupancy factors, fraction of all CT exams that covered the chest, abdomen, and/or pelvis, total number of CT exams per week, and shielding design goals for controlled and uncontrolled areas. The formula was modified subsequently to account for whole-body CT exams expected during armed conflict. RESULTS: Calculated safe distances revealed that the shielded two-sided CT ISO-shelter can be positioned much closer to the surgical shelters of the field medical unit than the previously unshielded one-sided CT ISO-shelter. Tables of safe distances for controlled and uncontrolled areas for the two medical support environments of disaster relief/peacekeeping and combat are provided. For example, for a controlled area at 100% occupancy when 300 CT exams per week are performed and 50% of those exams are of the chest, abdomen, and/or pelvis, the safe distance between the nearest surgical shelter and the shielded CT ISO-shelter is 2.1 m. By comparison, the safe distance for an unshielded CT ISO-shelter is 8.5 m under the same conditions. For lower occupancy factors and lower weekly workload, safe distances from the nearest surgical shelter are often negligible. CONCLUSIONS: The shielding in the new deployable CT ISO-shelter substantially reduces the distance between it and the surgical shelters of the field medical unit necessary to ensure radiation safety. Safe distances depend on several factors including workload, types and frequencies of CT exams, occupancy factors, and classification of the area around the ISO-shelter, i.e., controlled and uncontrolled.

A proposal for the performance evaluation of 0.5 mm lead aprons used in nuclear medicine.

The lead apron plays a crucial role in radiation protection and is extensively used in medical institutions. Periodic performance evaluations, involving visual inspections and transmission imaging, are conducted annually. This research aims to propose a performance evaluation method for 0.5 mm lead aprons used in nuclear medicine departments. The experiments were conducted using transmission imaging and source-based evaluation methods, involving two lead aprons with <1 year of use and two other aprons used for over 10 years. The experimental results indicate that using 50 kVp for transmission imaging is appropriate to detect cracks in the lead aprons. Additionally, in the case of lead aprons used for >10 years, the measured attenuation rate was found to be ~3-5% lower, depending on the measurement method. Consequently, a performance evaluation, including crack detection and actual attenuation rate measurements, should be carried out for lead aprons used long-term to ensure efficacy of radiation protection.

Exploring Past to Present Shielding Guidelines.

PURPOSE: To explore the data and supporting evidence for the 2019 statement by the American Association of Physicists in Medicine (AAPM) that recommends limits to the routine use of fetal and gonadal shielding in medical imaging. METHODS: Three researchers searched 5 online databases, selecting articles from scholarly journals and radiology trade publications. Search results were filtered to include literature published from January 1, 2016, to August 9, 2022, to ensure relevance and provide historical background for the 2019 AAPM statement. RESULTS: The use of patient shielding during medical imaging did not reduce dose, and in certain instances, increased dose received by patients during computed tomography, fluoroscopy, or dental imaging. The use of shielding interfered with technology designed to reduce patient dose, including automatic exposure control and dose modulation. Research showed that errors in shield placement were common and that shields can act as sources of infection or carriers of harmful lead dust. DISCUSSION: In each article reviewed, a compelling case was made for discontinuing routine patient shielding during radiographic procedures. Serious opposition to the discontinuation of the shielding practice was not found. Opportunities exist for further study into technologists' and the public's understanding of the effects of radiation and technologists' compliance with new shielding policies. CONCLUSION: The challenges with properly using shielding, paired with recent technological advancements and a new understanding of radiation protection, have negated the need for contact shielding. This legacy practice can be discontinued in clinical settings, and educational materials for technologists and students should be updated to reflect these changes.

Comparing benefit and detriment from medical diagnostic radiation exposure using disability-adjusted life years: towards quantitative justification.

Justification of medical radiation exposure is one of the main elements of radiation protection for patients. For a medical exposure to proceed, the benefit from the procedure must have been determined to be greater than the detriment. It is rare, however, that justification can be stated quantitatively as a ratio of benefit to detriment, or as a net benefit, and this is particularly true for medical diagnostic exposures associated with non-fatal diseases where survival statistics do not apply. The concept of the disability-adjusted life year (DALY) is well established as a measure of disease severity in public health, and there have been calls to revise the international system of radiation protection dosimetry to employ the DALY as a measure of radiation detriment. This paper looks at possible routes to quantify the benefit and detriment aspects of justification based on initial published results for the use of the DALY as a measure of radiation detriment, together with established values of DALY for a range of diseases. Although spreadsheet-style solutions for the calculation of a justification factor based on statistical life tables can be devised, these will be shown to have some limitations. A justification factor based on the rate of change of benefit divided by the rate of change of detriment following medical exposure is proposed. This factor is simple to calculate, is age independent, can apply to non-fatal diseases and is argued to have logical and ethical advantages for the explanation of the relative benefits and detriments of radiological procedures to patients.