Dispersion of radioactive releases. Health consequences of releases. The general approach to the safety of the plant and of the site.
Defence in depth. Quality assurance. Safety analysis: Deterministic safety analysis; Probabilistic safety analysis. Safety analysis review. Classification of plant components. Notes on some plant components: The reactor pressure vessel; Piping; Valves; Containers. Resistance of plants to earthquakes. Resistance of plants to tornadoes. Resistance to external impacts. Nuclear safety criteria: General characteristics; The U. Nuclear safety research. Underground location of nuclear power plants.
Underground nuclear tests. Effects of nuclear explosions. Radioactive waste. Safety of fusion reactors.
Safety of specific plants and of other activities. Nuclear plants on satellites. Erroneous beliefs in nuclear safety. When can we say that a particular plant is safe? The limits of nuclear safety: the residual risk. Appendices: The Chernobyl accident; Calculation of the accident pressure in a containment; Table of safety criteria; Dose calculations; Simplified thermal analysis of an insufficiently refrigerated core; Excerpts from EUR Criteria; Notes of fracture mechanics; U.
Nuclear Safety by Gianni Petrangeli provides a comprehensive overview of the methods and data needed to evaluate the safety of a nuclear plant, examining potential dangers from earthquakes, tornadoes, external impacts, human factors, and more along with analyses of major accidents. The radioactive liquid wastes generated in a NPP are segregated, filtered and conditioned as per procedure and after adequate dilution to comply with the limits of discharges, disposed to the environment water body.
The activity discharged is monitored at the point of discharge and accounted on a daily basis. The AERB has prescribed limits on the annual volume and activity of discharge, daily discharges and activity concentration from each NPP, which are site specific. The radioactive solid wastes are disposed off in brick-lined earthen trenches, Re-enforced cement concrete RCC vaults or tile holes, depending on the radioactivity content and the radiation levels. The discharge of radioactive waste from a NPP is governed by the Atomic Energy safe disposal of radioactive wastes Rules, , which is issued under the Atomic Energy Act, It is mandatory for a NPP to obtain authorization under the above rules from the competent authority for disposal of radioactive wastes.
Derived limits corresponding to the dose apportioned for different radionuclides are established taking into account the site-specific parameters. Authorized limits are set at a much lower value than derived limits to achieve effluent releases ALARA. The releases from NPPs have been only a fraction of release limits specified. The basic objective of the environmental monitoring and surveillance program is to assess the radiological impact under all states of the NPP and demonstrate compliance with the radiation exposure limits set for the members of the public by the AERB.
This is achieved by carrying out a radiological surveillance of the environment by professionals of the ESLs.
They provide the regulatory body with periodic reports on radiological conditions of the NPPs and the results of environmental surveillance. Extensive surveys are carried out around each nuclear power station to collect data on the dietary intake. During the preoperational phase, the annual intake of cereals, pulses, vegetables, fish, meat, eggs and milk are established by direct survey.
Elaborate studies of the topography of the site, land use pattern and population distributions are carried out systematically during the preoperational phase. Also, a detailed epidemiological survey of the population is carried out in the preoperational phase. This is carried out by a neutral agency like the Tata Memorial Hospital or any closely located University Medical College. Along with the topographical and dietary studies, the ESL also carries out the work of establishing the preoperational background radiation levels.
Extensive micrometeorological data such as wind speed and wind direction, temperature and rain fall are collected for a few years to identify the worst sector and critical population. The samples for analysis are selected on the basis of potential pathways of exposure. The program undergoes modification based on experience.
Generally, more samples are collected near the vicinity of the plant and from locations where population clusters exist, and the sampling frequency reduces with the distance. Areas up to a distance of 30 km are covered under the environmental survey program. Although the main emphasis is on samples that are relevant directly to the estimation of the dose, such as drinking water, edible food items, air, etc.
From the radioactivity level in the environmental matrices, intake parameters and dose conversion factors, the population dose is estimated. ESLs are accredited laboratories that take part in inter comparison studies conducted by the International Atomic Energy Agency. NPPs are designed, constructed, commissioned and operated in conformity with existing stringent nuclear safety standards. These standards ensure an adequate margin of safety so that NPPs can be operated without undue radiological risks to the plant personnel and members of the public.
Notwithstanding these safety standards, it is necessary to develop, as a measure of abundant caution and in conformity with international practices, emergency response plans so that any eventuality, howsoever unlikely, with a potential to result in undue radiological risk to plant personnel and public, is handled effectively.
The preparedness and response to emergencies are important responsibilities of the operating organization.
Safety of nuclear power plants / Courses / BNEN - SCK•CEN
All NPPs have established and documented emergency procedures by having an on-site emergency preparedness plan. Similarly, the plan with respect to off-site emergency is made available with the district authority. The role, responsibilities and action plans for various agencies required to act during an emergency are detailed in these plans. The NDMA has the responsibility for laying down policies, plans and guidelines for disaster management for ensuring timely and effective response to any disaster. In line with the above national plan, a state plan and district plans are drawn up by the respective authorities constituted for the purpose.
Specific requirements with respect to emergency preparedness in NPPs have been formulated by the AERB in the various regulations, as given in references. In India, a NPP is generally sited in a relatively low-population zone, with the basic objective of limiting the dose-received members of the public and population as a whole under normal and accident conditions to ALARA levels. In order to achieve the above objective, the area around the NPP is divided into the following zones:.
An exclusion zone of 1. The dose limits to a member of the public, under normal operating conditions and under design basis accident conditions specified, are applied at the boundary of this exclusion zone. With the help of administrative measures, efforts are made to establish a sterilized zone up to a 5-km radius around the plant. This is the annulus around the exclusion zone, which has the potential for extensive contamination in case of a severe accident.
Development activities within this area are controlled so as to check an uncontrolled increase in the population. In this area, only natural growth of the population is permitted.
This is the zone defined around the plant up to a km radius and provides for the basic geographical framework for decision making on implementing measures as part of a graded response in the event of an off-site emergency. The EPZ is examined in great detail while drawing up an offsite emergency plan and arranging logistics for the same. The entire EPZ is divided into 16 equal sectors. The objective is to optimize the emergency response mechanism and to provide the maximum attention and relief to the regions most affected during an offsite emergency.
The emergency measures consist of emergency actions in respect of notification, alerting personnel, assessment of situation, corrective actions, mitigation, protection and control of contamination. These are detailed in the emergency response manual. Any emergency situation will be promptly notified to the concerned personnel as per the notification plan.
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The message conveyed in the notification is required to be clear and concise. Indicating, recording and annunciating instruments provided in the main control room, radiation surveys, environmental surveys, meteorological data and status of plant are utilized to assess the situation and to predict the projected doses.
These assessment actions enable planning timely corrective and protective actions. These actions are taken to correct plant abnormal situations and to bring the plant under control. The types of corrective actions are decided by the situations prevailing at that point of time. These actions are taken to mitigate the consequences of a radiological event and to protect site personnel, members of the public and livestock from radiation.
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