Radiation Safety of Gamma, Electron and X Ray Irradiation Facilities Specific Safety Guide, IAEA Safety Standards Series SSG-8 94 pp.; 8 figures; Language: English, Date Published: 2010

This Safety Guide provides recommendations on how to meet the requirements of the Basic Safety Standards with regard to irradiation facilities. It gives practical information on the safe design and operation of gamma, electron and X ray irradiators in accordance with these requirements, and discusses the beneficial applications of ionizing irradiation and how to avoid potential radiation hazards at industrial irradiators, including contamination arising from damaged radioactive sources. The Safety Guide is intended for use by the designers and operating organizations of these facilities and also by regulatory bodies. 

Contents: 1. Introduction; 2. Justification of practices; 3. Types of irradiator; 4. Principal elements of practices; 5. Individual monitoring of workers; 6. Workplace monitoring; 7. Control over radioactive sources; 8. Irradiator design; 9. Testing and maintenance of equipment; 10. Transport, loading and unloading of radioactive sources; 11. Emergency preparedness and response (Source: www.iaea.org).

Recommended dosage for iodine prophylaxis following nuclear accidents

As per the WHO guidelines (1999) for stable Iodine Prophylaxis, the recommended adult dose is 100 mg of iodine (130 mg of KI) for persons above 12 years. 

Children (3-12 y) - 50 mg of iodine (65 mg of KI)

Infants (1m to 3 months) - 25 mg (32 mg of KI)

Neonates (birth to 1 month) - 12. 5 mg (16 mg of KI)

To obtain full effectiveness of stable iodine for thyroidal blocking, it has to be administered shortly before exposure or as soon after as possible.This protective action is taken to prevent deterministic effects (Hypothyroidism) in the thyroid from the high levels (several Gy) of radiation dose to the thyroid from the uptake of radioiodines (mainly I-131, I-132 & I-133), released from the nuclear accidents, and to reduce the risk of stochastic effect - induction of thyroid cancer. 

Intakes can take place through ingestion/inhalation routes. The best estimate of excess absolute cancer risk is 4.4 × 10 to the power -4 per Gray per year for persons exposed before the age of 15, and virtually no risk is observed for exposure after the age of 40. 

The mass of thyroid varies with the age. Indian data (Source: Asian Reference Man Data, IAEA-TECDOC-1005) show variation from 1.5 gm (newborn), 8 gm (10 years) to 19 gm (male adults). Lower the mass, higher is the dose received for a given uptake and hence greater is the cancer risk.  

There is a greater need to protect the thyroid gland of the pregnant woman since the iodine uptake can be increased as compared to other adults. As much as 1/4 of the iodine taken by the mother may be secreted in the milk within 24 h. Newborn infants are quite likely the critical group of concern when deciding on the implementation of stable iodine prophylaxis. 

A generic intervention level of 100 mGy avertable dose is recommended for all age groups. However, the recommended intervention level for childhood exposure is 10 mGy avertable dose to the thyroid.

(Source: WHO Guidelines for Iodine Prophylaxis following Nuclear Accidents - Update 1999)

IAEA Publication: Storage of Spent Nuclear Fuel, IAEA Safety Standards Series SSG-15 Subject Classification: Radioactive waste management, STI/PUB/1503, 110 pp. Language: English, Date Published: 2012.

This Safety Guide provides recommendations and guidance on the storage of spent nuclear fuel.It covers all types of storage facilities and all types of spent fuel from nuclear power plants and research reactors. It takes into consideration the longer storage periods that have become necessary owing to delays in the development of disposal facilities and the decrease in reprocessing activities. It also considers developments associated with nuclear fuel, such as higher enrichment, mixed oxide fuels and higher burnup. Guidance is provided on all stages in the lifetime of a spent fuel storage facility, from planning through siting and design to operation and decommissioning, and in particular retrieval of spent fuel. 

Contents: 1. Introduction; 2. Protection of human health and the environment; 3. Roles and responsibilities; 4. Management system; 5. Safety case and safety assessment; 6. General safety considerations for storage of spent fuel. Appendix I: Specific safety considerations for wet or dry storage of spent fuel; Appendix II: Conditions for specific types of fuel and additional considerations; Annex: I: Short term and long term storage; Annex II: Operational and safety considerations for wet and dry spent fuel storage facilities; Annex III: Examples of sections in operating procedures for a spent fuel storage facility; Annex IV: Related publications in the IAEA Safety Standards Series; Annex V: Site conditions, processes and events for consideration in a safety assessment (external natural phenomena); Annex VI: Site conditions, processes and events for consideration in a safety assessment (external human induced phenomena); Annex VII:Postulated initiating events for consideration in a safety assessment (internal phenomena). Source: www.iaea.org.

IAEA publication: Evaluation of Seismic Safety for Existing Nuclear Installations Safety Guide, IAEA Safety Standards Series NS-G-2.13 84 pp, Language: English, Date Published: 2009

This Safety Guide provides recommendations regarding the criteria and methodologies to be used for seismic safety evaluation of existing nuclear installations, including installations whose purpose and associated radiological risks have changed, installations where longer term operation is under consideration and installations where comprehensive seismic safety reassessments have become necessary. 

Two methodologies are discussed in detail: deterministic seismic margin assessment (SMA) and seismic probabilistic safety assessment (SPSA). 

Contents: 1. Introduction; 2. Recommendations on formulation of the programme for seismic safety evaluation; 3. Data collection and investigations; 4. Assessment of seismic hazards; 5. Methodologies for the evaluation of seismic safety; 6. Nuclear installations other than power plants; 7. Considerations in upgrading; 8. Management system for seismic safety evaluation; Annex: Methodologies for seismic safety evaluation (Source: www.iaea.org).

Radiological Protection in Cardiology, ICRP Publication 120

Cardiac nuclear medicine, cardiac computed tomography (CT), interventional cardiology procedures, and electrophysiology procedures are increasingly used in medicine and form the major share of patient radiation exposure. Some of the percutaneous coronary interventions and cardiac electrophysiology procedures are associated with high radiation doses. These medical procedures can result in patient skin doses that are high enough to cause radiation injury and an increased risk of cancer. 

The Commission provided recommendations for radiological protection during fluoroscopically guided interventions in Publication 85, for radiological protection in CT in Publications 87 and 102, and for training in radiological protection in Publication 113. This report is focused specifically on cardiology, and brings together information relevant to cardiology from the Commission’s published documents. The material and recommendations in the current document have been updated to reflect the most recent recommendations of the Commission. 

This document provides guidance to assist the cardiologist with justification procedures and optimization of protection in cardiac CT studies, cardiac nuclear medicine studies, and fluoroscopically guided cardiac interventions. It includes discussions of the biological effects of radiation, principles of radiological protection, protection of staff during fluoroscopically guided interventions, radiological protection training, and establishment of a quality assurance programme for cardiac imaging and intervention (Source: www.icrp.org).

Future of Diagnostic Medicine

It is estimated that 10 million people receive diagnostic, therapeutic or interventional medical radiation procedures every day. The number of occupationally exposed workers is much higher in medicine than in any other professional field.

Now for the first time in history, several countries are experiencing population doses from medical uses of radiation that exceed those from natural background radiation and exposure from other artificial sources. Thus, there is a strong need to protect patients and medical staff from accidental and unnecessary exposure.

Medical experts from about 90 countries and 17 international organizations are gathering during 3-7 December, 2012 in Bonn, Germany, at the IAEA's “International Conference on Radiation Protection in Medicine - Setting the Scene for the Next Decade” to discuss the pressing issue of overexposure to ionizing radiation, the threat posed to patients and health workers, and ways to handle and reverse the problem. The conference is intended to come out with a detailed plan of action for the reduction of medical radiation exposure (source: www.iaea.org).

Dose limit for the eyes reduced

The prevailing belief in radiation protection fraternity has been that human radiation-related cataract occurs only after relatively high doses and the ICRP guidelines on minimal doses for cataract induction in humans are given in the table for single exposure and protracted exposure scenarios.

Table: ICRP Guidelines on Minimal Lens Doses for Cataract Induction

End point	Brief exposure (Sv)	Protracted exposure (Sv)	Annual dose (Sv)
Detectable opacities	0.5 to 2	5	>0.1
Visual impairment	5	>8	>0.15

Epidemiological studies among Chernobyl clean-up workers, Atom - bomb survivors in Japan, astronauts, residents of contaminated buildings, radiological technicians and recent surveys of staff in interventional rooms indicate that there is an increased incidence of lens opacities at doses below 1 Gy.

The IAEA studies on radiation induced cataract among cardiologists and support staff in cardiac catheterization laboratories, published in “Radiation Research” received wider attention since it pointed towards possibility of opacities in the lens of the eyes below the currently specified threshold by International Commission of Radiological Protection (ICRP). However, there are issues such as difficulty in accurate dose estimation in eyes of medical staff as hardly any data is available that can be used to correlate with lens opacities. Only rough estimations based on work load and typical factors used in the procedures performed by staff could be made. In contrast, there is much better dosimetry in A-Bomb survivors and much longer follow up period.

Based on the overwhelming data, the ICRP released a statement in 2011 recommending a change in the threshold dose for the eye lens and dose limits for eye for occupationally exposed persons.

According to this statement, the threshold in absorbed dose for the lens of the eye is now considered to be 0.5 Gy. Further, for occupational exposure in planned exposure situations the Commission now recommends an equivalent dose limit for the lens of the eye of 20 mSv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv.

The Commission continues to recommend that optimisation of protection be applied in all exposure situations and for all categories of exposure. With the recent evidence, the Commission further emphasises that protection should be optimised not only for whole body exposures, but also for exposures to specific tissues, particularly the lens of the eye, and to the heart and the cerebrovascular system.

The implementation of the limit amongst the occupational workers in nuclear and radiological facilities is operationally difficult in view of the fact that there is hardly any reliable and recorded dosimetric data available. To begin with, however, some rough assessment of the exposure to eyes can still be made using whole-body exposure data.