Nuclear energy plays a key role in the country’s energy mix and is being developed alongside other energy sources in an optimal way. As a clean, environmentally friendly, and reliable base load power source available 24/7, it holds significant potential to ensure long-term energy security for the country in a sustainable manner.

The largest part of a nuclear power plant’s life cycle span is often the operational phase section. India owns twenty-two reactors in use, and the aggregate net capability of these reactors is 6780 MWe.] Of these, 18 are Pressurized Heavy Water Reactors {PHWRs) and four are Light Water Reactors {LWRs). [The Pressurised Heavy Water Reactors or PHWRs are fueled by Natural Uranium, the Light Water Reactors or LWRs are fueled by Low Enriched Uranium.] Also, there are eight reactor units under construction; the 500 MW PFBR, being built by BHAVINI is also at different stages of construction with 6000 MW capacity in total. At present, four reactors with a capacity of 2800 MW are under construction, and work has begun on five more reactors with a combined capacity of 3900 MW. Upon the progressive completion of these projects, the total capacity will increase to 13,480 MW.

Nuclear Power Plants Growth Over The Years

India has always embarked on a mission of attaining self reliance in advanced technology since it won independence in 1947. With atomic energy being a metaphor for scientific progress in the post war period it is not surprising that a country with memories of colonial domination setting science as one of its metrics to reassert her newly won independence would set about capturing this new frontier.

But the subject of atomic energy was not entirely unfamiliar to Indians by the time of independence. Inspiring India’s development of nuclear technology was Homi Bhabha – a man who founded Tata Institute of Fundamental research TIFR in 1945 to cover fields of science including nuclear science for the purpose of power generation in the newly developing post colonial India. Prime Minister Jawaharlal Nehru, India’s first, was, like Bhabha, convinced that the key to economic growth relied on soaring electricity generation. Pursuing idealistic goals like others of that era who assumed that atomic energy has potential to deliver cheap electricity to the people, Nehru formed AE Commission (AEC) in 1948 to outline the strategies for the country’s atomic programme, and to monitor the institutions associated with atomic energy. The actual emergence of a large-scale nuclear research center was envisaged in 1949 when the Council of Scientific and Industrial Research, a government body that assesses and coordinates the growth of scientific and technological businesses in India, chose TIFR as the focal organization for the large-scale nuclear research projects.

The nuclear establishment of India had grand claims on this front. Homi Bhabha in 1954 predicted that nuclear power would produce 8000 MegaWatt electricity by the year 1980. Yet, after almost seventy years of its installation, India’s installed Nuclear capacity is 7425 MW and contributes only 3 % of the total electricity generation in the country. 

A need to build indigenous reactors designed, or quality control issues with their components (usually discovered after construction) have caused lengthy delays in the nuclear power program. Such delays along with mitigation costs have resulted in even higher costs. This said, operational efficiency of Indian nuclear plants has been jeopardized by challenges such as secure supplies of reliable fuel. This was causing the Department of Atomic energy (DAE) not to provide electricity cheaper than other sources over a period of time. Therefore, despite the rhetorical homage paid to nuclear power by Indian governments, they largely failed to invest heavily in its most important sector.

Safety Measures

Bhabha Homi Jehangir, one of the key proponents of India’s nuclear programme urged the necessity of a good environmental management plan. This culminated in the creation of ESLs at each NPP site in the 1960s in order to provide rapid response units for the assessment of the environmental dose consequent from routine NPP operations. While it is recognized that nuclear power plants release some radioactivity into the environment through various pathways and forms, these discharges are carefully controlled through planned dilution and dispersion programs that adhere to stringent radiological and environmental regulations. Environmental Survey Laboratories (ESLs) play a key role by establishing site-specific baseline radiological values (Puranik, 2012) and assessing the environmental and radiological impact both before (Gautam et al., 2021) and after a nuclear power plant (NPP) is operational (Hegde et al., 2004). Systematic environmental sampling is conducted within a 30 km radius of each NPP reactor, analyzing radioactivity in air, water, soil, vegetation, and food to measure the impact of NPP activities. This impact is quantified by calculating the effective radiation dose to the public.

To ensure safe operation, ESLs periodically compare the assessed radiation doses with the regulatory public dose limit of 1 mSv/year (1000 μSv/y) above natural background levels, as set by the Atomic Energy Regulatory Board (AERB) in India (AERB, n.d.). The regulator employs a dose apportionment method, dividing the public dose limit among existing and planned facilities at the site, considering atmospheric, aquatic, and terrestrial pathways as well as specific radionuclides. A portion of the dose limit is reserved for future expansions, and these apportioned doses are converted into annual discharge limits and concentration limits for various radionuclides using standard environmental models. Additionally, daily dose limits and release rate limits for specific activity are imposed to ensure safe operation. This multi-tiered system of regulating radioactive discharges ensures that the public radiation dose remains within the apportioned limit and that releases are kept ‘As Low as Reasonably Achievable’ (ALARA) (International Atomic Energy Agency, 2010a, International Atomic Energy Agency, 2010b).

 The Civil Liability for Nuclear Damage Act, addressing third-party liability, was passed by both houses of parliament in August 2010. This legislation was framed and debated against the backdrop of the 1984 Bhopal disaster, one of the world’s worst industrial accidents, which raised national awareness about industrial safety. Under the 2010 Act, responsibility for any nuclear accident is placed on the operator, in line with international standards. The total liability is capped at 300 million Special Drawing Rights (SDR), approximately US$ 450 million, or a higher amount that the Central Government may specify. The operator’s liability is limited to Rs 1500 crore (15 billion rupees, or roughly US$ 285 million), beyond which the Central Government assumes responsibility.

However, the Act includes a provision for legal recourse. After the operator (or their insurers) has paid compensation, clause 17(b) allows the operator to seek compensation from the supplier for up to 80 years after the plant becomes operational, if an Indian court determines that the nuclear incident resulted from an action by the supplier or their employee. This includes the supply of equipment or materials with patent or latent defects, or the provision of substandard services.

Radiation Detection Technologies

Every country operating nuclear power plants has a dedicated nuclear safety inspectorate that works closely with the International Atomic Energy Agency (IAEA). While nuclear power plants are designed for safe operation and to manage malfunctions or accidents securely, no industrial activity can be considered completely without risk.

Hazard recognition and quantification of nuclear radiation is complicated because radiation is impersonal and inapprehensible with human senses. Every radiation monitor has a radiation sensitive detector and a means for registering the response of the detector to radiation including pulse energy and the intensity distribution. These devices involve a wide dynamic range micro-channel plate (MCP) has a simple construction designed to detect radiation within the 6-100 nm range. The detector is designed to cover a full spectrum of radiation intensity, from spontaneous emission to the saturation level of a SASE FEL.

Radiation detectors produce measurable physical effects, such as ionization, in response to radiation. The ion pairs generated can be collected to create an electrical signal corresponding to the radiation’s intensity. Some detectors emit light pulses in response to radiation, and by counting these pulses, the radiation’s intensity can be determined. Others store the effects of ionizing radiation over time, allowing the data to be retrieved later. These devices, in one way or another, respond to the energy deposited by the radiation. Instruments can be designed to indicate either the rate at which radiation is received or the total radiation exposure over a specific period. The following are the media generally used for radiation detection.

• Gasses (e.g. Ion chamber, Proportional counter, GM counter)
• Scintillators [ Na I (Tl), Anthracene, etc.]
• Solid state detectors [Semiconductors, Thermo-luminescent dosimeters etc.]
• Photographic emulsions [Film]

The selection of the detector depends on a variety of factors such as type, energy, and the level of intensity of radiation to be detected in addition to other factors such as cost, size, availability, electronics needed etc. Therefore, an understanding of different types of detectors and their characteristics is an important prerequisite for their selection and optimum use in a given situation.

Principle of Gas-Filled Detectors

The most common radiation detectors are gas-filled detectors, which operate on the principle that radiation passing through air or a specific gas causes ionization of the air or gas molecules. The ion pairs produced are collected and measured as either current or pulses. These detectors typically have a cylindrical shape with two electrodes: a central electrode (the anode) and an outer sheath (the cathode), separated by an insulator.

When a voltage is applied across the electrodes, positive ions are attracted to the cathode, while negative ions move toward the anode. The collection of these charges creates a small current across the detector. By connecting a sensitive current meter between the anode and cathode, this small current can be measured and displayed as a signal. The more radiation that enters the chamber, the higher the current displayed by the instrument. When measuring the number of ion pairs collected at different applied voltages, six distinct regions of response can be observed.

Radiation Monitoring Instruments

Radiation hazard evaluation is essential to ensure proper safety measures are adopted to control radiation exposure. In applications such as nucleonic gauges and well-logging equipment, the radioactive sources are sealed and encapsulated, eliminating the risk of internal exposure unless the source capsule is ruptured during use. However, external radiation hazards are easier to estimate, and numerous devices are available on the market for this purpose, designed by various manufacturers.

From a practical perspective, radiation monitoring devices can be classified into two main categories: area monitoring devices and personnel monitoring devices.

1. Area Monitoring Devices
   These devices are used to assess the radiation levels in a specific area, measuring either radiation intensity or exposure rates. The most commonly used instruments for area monitoring include:
   • Geiger-Müller (GM) Counters: These detect and measure ionizing radiation, giving a quick indication of radiation levels.
   • Ionization Chambers: These measure radiation by detecting the ionization of air or gas within the chamber, providing accurate readings of exposure rates.
   • Proportional Counters: These detect radiation by measuring ionization events in a gas-filled chamber, providing precise data on radiation intensity.
2. Area monitoring devices are essential for ensuring that radiation levels remain within safe limits, especially in controlled environments such as nuclear facilities, laboratories, and industrial settings where radiation sources are used.
3. Personnel Monitoring Devices
   These devices are used to monitor the radiation exposure of individual workers over a specific period. Personnel monitoring is crucial in ensuring that occupational radiation doses stay below regulatory limits. Commonly used personnel monitoring devices include:
   • Pocket Dosimeters: Small, portable devices that measure and display accumulated radiation exposure in real time, allowing workers to track their dose throughout the day.
   • Personnel Dose Monitoring Badges: These badges, often loaded with photo-sensitive film or Thermo-Luminescent Dosimeters (TLD), are worn by workers to record the cumulative radiation dose over a specified period, typically weeks or months.
   • Thermo-Luminescent Dosimeters (TLDs): These devices use materials that store energy when exposed to radiation. When heated, the energy is released as light, which can be measured to determine the radiation dose received by the wearer.

Personnel dosimeters provide valuable data about long-term exposure, allowing safety officers to track individual radiation doses and ensure compliance with safety standards. This helps in preventing overexposure, minimizing the risk of radiation-induced health problems, and maintaining a safe working environment.

Thus, nuclear power plants remain an indispensable component of India’s overall energy portfolio since they help ensure the country’s energy security and advance the cause of sustainable energy. However, ensuring the safety of these plants is paramount. Radioactive detectors are essential in maintaining this safety by continuously monitoring radiation levels, both in the environment and for personnel. These detectors help detect any potential radiation leaks or hazards, enabling quick responses to minimize risks, protect public health, and ensure that the plants operate within regulatory safety limits.