Atomic Energy Regulatory Board Research Articles

Radiological safety and environmental monitoring aspects of mining and processing of uranium ore at Jaduguda, India

Low-grade uranium ore is mined and processed in India since the early 1970s. To adhere to the regulatory compliance monitoring of external gamma level, radon and long-lived alpha activity of ore dust is carried out in uranium mines. Apart from this, surface contamination is also monitored in radiologically important areas of ore processing plant. Exposure of occupational workers is evaluated based on the results of area and personal monitoring. Monitoring of radon and external gamma level is carried out in the vicinity of tailings pond and away. Samples from surface water, groundwater and soil are collected from the environment adjoining the facilities. Results reveal that the exposure of occupational workers is well below the annual average dose limit of 20 mSv as prescribed by the Atomic Energy Regulatory Board (AERB). Results further reflect that the discharges of process waste at tailings pond have not modified the pre-existing radiological status of the environment.

Regulatory practices for nuclear power plants in India

The Atomic Energy Regulatory Board (AERB) is the national authority for ensuring that the use of ionizing radiation and nuclear energy does not cause any undue risk to the health of workers, members of the public and to the environment. AERB is responsible for the stipulation and enforcement of rules and regulations pertaining to nuclear and radiological safety. This paper describes the regulatory process followed by AERB for ensuring the safety of nuclear power plants (NPPs) during their construction as well as operation. This regulatory process has been continuously evolving to cater to the new developments in reactor technology. Some of the recent initiatives taken by AERB in this direction are briefly described. Today, AERB faces new challenges like simultaneous review of a large number of new projects of diverse designs, a fast growing nuclear power program and functioning of operating plants in a competitive environment. This paper delineates how AERB is gearing up to meet these challenges in an effective manner.

Electronics in nuclear power programme of India—An overview

This paper presents an overview of state-of-the art developments in electronics for nuclear power programme of India. Indigenous activities in instrumentation and control (I&C) in the areas of detector development, nuclear instrumentation, monitoring and control electronics and special sensors paved the way to self-reliance in nuclear industry. Notable among the recent I&C systems developed for 540 MWe reactors are Liquid Zone Control System (LZCS), flux mapping system and advance reactor regulating system. In a nuclear plant, apart from ensuring functional requirements, design of electronics needs to meet high level of reliability, safety and security standards. Therefore, a lot of importance is attached to activities such as design review, testing, operation, maintenance and qualifications of I&C systems. Induction of computer based I&C systems mandated a rigorous verification process commensurate with the safety class of the system as specified in Atomic Energy Regulatory Board (AERB) safety guides. Software reliability is assured by following strict development life cycle combined with zero-defect policy and is verified through verification and validation (V&V) process. Development of new techniques in data transmissions with optical fibres as transmission medium and wireless networks in control systems is being pursued. With new I&C systems, efforts were made to utilize the same hardware and software platforms for various plant applications, i.e., for standardization. Thrust was given to use Field Programmable Gate Arrays (FPGA) and Application Specific Integrated Circuits (ASIC) in order to improve the reliability of system by reducing component count. It has become imperative to develop modern contemporary solutions like ASICs, HMCs, System on Chip (SOC) and detector mounted electronics and towards that various ASICs and HMCs have been developed in-house to meet the challenges.

UNCERTAINTY AND SENSITIVITY ANALYSIS OF TMI-2 ACCIDENT SCENARIO USING SIMULATION BASED TECHNIQUES

The Three Mile Island Unit 2 (TMI-2) accident has been studied extensively, as part of both post-accident technical assessment and follow-up computer code calculations. The models used in computer codes for severe accidents have improved significantly over the years due to better understanding. It was decided to reanalyze the severe accident scenario using current state of the art codes and methodologies. This reanalysis was adopted as a part of the joint standard problem exercise for the Atomic Energy Regulatory Board (AERB) - United States Regulatory Commission (USNRC) bilateral safety meet. The accident scenario was divided into four phases for analysis viz., Phase 1 covers from the accident initiation to the shutdown of the last Reactor Coolant Pumps (RCPs) (0 to 100 min), Phase 2 covers initial fuel heat up and core degradation (100 to 174 min), Phase 3 is the period of recovery of the core water level by operating the reactor coolant pump, and the core reheat that followed (174 to 200 min) and Phase 4 covers refilling of the core by high pressure injection (200 to 300 min). The base case analysis was carried out for all four phases. The majority of the predicted parameters are in good agreement with the observed data. However, some parameters have significant deviations compared to the observed data. These discrepancies have arisen from uncertainties in boundary conditions, such as makeup flow, flow during the RCP 2B transient (Phase 3), models used in the code, the adopted nodalisation schemes, etc. In view of this, uncertainty and sensitivity analyses are carried out using simulation based techniques. The paper deals with uncertainty and sensitivity analyses carried out for the first three phases of the accident scenario.

Occurrence of uranium in groundwater of a shallow granitic aquifer and its suitability for domestic use in southern India

Groundwater used for domestic purpose without proper treatment should be free from chemical and biological contaminants. This study was carried out to assess the groundwater quality with respect to uranium in a part of Nalgonda district, Andhra Pradesh, India. Groundwater was regularly monitored for uranium concentration by collection of samples once every two months from March 2008 to November 2009 from 44 wells. The concentration of uranium in groundwater ranged from 0.2 to 118.4 ppb. Groundwater is unsuitable for domestic use in 2 % of this area based on the limit of 60 ppb prescribed by the Atomic Energy Regulatory Board of India. However, due the wide variation in limit suggested by different organizations and countries, the no-observed-adverse-effect level and lowest-observed-adverse-effect level (in mg/kg day) was used to understand the dosage of uranium that reaches the people through drinking water pathway. This level varied from 0 to 0.02 mg/kg day and 0 to 0.08 mg/kg day based on an uncertainty factor of 10 and 50 respectively for the mean uranium concentration in groundwater in each well. With an uncertainty factor of 50, 5 groundwater samples had uranium above 0.06 mg/kg day which is the lowest-observed-adverse-effect level. This study showed that with the presence of present level of uranium concentration in groundwater of this area there is no major threat to humans through the drinking water pathway.

Quality control of 125I-brachytherapy seeds

An indigenous technology for the production of 125I brachytherapy sources has been developed for the management of intraocular cancer. This indigenous method of producing 125I seeds represents a new paradigm, and a thorough quality evaluation of the seeds in accordance with Atomic Energy Regulatory Board (AERB) of India was carried to ensure their safety during therapy. In this current work, we describe an overview of our experience, the efforts made in establishing enviable quality analysis of 125I seeds to ensure their safety in episcleral plaque brachytherapy.

Instantaneous exposure to nuclear medicine staff involved in PET–CT imaging in developing countries: experience from a tertiary care centre in India

To assess the radiation exposure to nuclear medicine staff at a positron emission tomography-computed tomography (PET-CT) centre with high patient throughput. This prospective study included 70 adult patients who underwent 18F-fluorodeoxyglucose (FDG) PET-CT for their clinical indications. The patients' actual injected FDG activity was calculated by subtracting the syringe activity (post-injection) from the loaded syringe activity (pre-injection). The instantaneous exposure to nuclear medicine staff involved in PET-CT imaging was measured. The instantaneous dose rate of the physicians was recorded during FDG injection and that of the technologist was recorded during the patient's positioning, respectively, at 1.0-m distance from the anterior chest using a calibrated portable gamma-ray survey meter. The average FDG activity injected in adult patients was 308.5 MBq (range 173.1-438.8 MBq). The instantaneous exposure to the nuclear medicine (NM) physician during the injection time was 31 μSv/h (14-60 μSv/h). The instantaneous exposure to the NM technologist during positioning was 18 (10-34) μSv/h. With an average of 10 patients per day, the quarterly dose to physicians was 628 μSv and to technologists 182 μSv for 300 patients. The extrapolated annual dose was 2.5 mSv for physicians and 0.7 mSv for technologists, respectively. Instantaneous exposure of nuclear medicine staff involved in PET-CT imaging at a busy tertiary care centre is within permissible limits of the International Commission on Radiological Protection (ICRP-103) (total <100 mSv over 5 years and not >50 mSv in a single year) and atomic energy regulatory board (total <100 mSv over 5 years and not >30 mSv in a single year).

Radiation surveillance in and around cyclotron facility

The cyclotron is the most widely used particle accelerator for producing medically important radio nuclides. Many medical centers in India have installed compact medical cyclotrons for on-site production of short-lived positron-emitting radio nuclides such as 18F, 13N, and 11C. A mandatory requirement for cyclotron installation is radiation control permit from Atomic Energy Regulatory Board. Cyclotron radiation survey is an integral part of the overall radiation safety in the cyclotron facility. Radiation surveillance in and around a newly installed cyclotron was performed using ionization chamber counter and Geiger Muller counter before, during and after operating the cyclotron. The readings were recorded at various locations where a high radiation field was expected. The results were recorded, tabulated and analyzed. The highest exposure level (0.93 μSv) was found at the back wall of the radiochemistry lab facing the cyclotron vault. Reason for the high exposure of 0.93 μSv/h: Synthesis of 18F-Fluoro-Deoxy-Glucose (18F-FDG) was going in the synthesis module and activity (18F) was present in the synthesis module when reading was taken. All other values were found to be below the recommended levels of exposure.

SU-E-T-562: MAGAT Gel and EBT2 Film Based Dosimetry for Evaluating Source Plugging Based Treatment Plan in Gamma Knife Stereotactic Radiosurgery

Purpose: Aim of this work is to show the procedure to assess the overall accuracy associated with Gammaknife treatment planning using source plugging which is used to create dose falloff in the junction between a target and a critical structure Methods: The MAGAT polymergel contained in a head size glass container simulated the entire treatment process of Gamma knife radiosurgery. The 3D‐dose distribution recorded in the gel dosimeter was read using 1.5 Tesla MRI scanner (Siemens, Sonata). Scanning protocol was CPMG pulse sequence with 8 equidistant echoes, TR = 7 s, echo step = 14 ms, pixel size = 1 mm × 1 mm. Interleave acquisition mode was used to obtain 40 2‐mm thick slices. Using calibration relationship between absorbed dose and spin‐spin relaxation rate (R2), we converted R2 images to dose images. The dose comparison was accomplished using an in‐house MATLAB‐based program. Results: Calibrations indicated that the dose response of current polymergel was non‐linear for doses higher than 12 Gy. The isodose overlay of measured and computed dose distribution on transverse planes showed very good agreement. We are able to demonstrate a mean dose difference of 3 % between gel measured and Treatment Planning system (TPS) calculated dose. Since there is no 3D “gold standard” to compare our results, a filmdosimetry with Gafchromic ® EBT2 film was performed to compare the results with calculated TPS dose. The isodose comparison and gamma index analysis of film measurement agreed very closely but was restricted to 2D plane. Conclusions: In summary, verification of Gammaplan calculated dose on account of shield is not part of acceptance testing of Leksell Gamma Knife. Through this study we performed a true comprehensive comparison between 3D dose distributions measured with a polymergel dosimeter and LGP calculations for plans using plugging. Research sponsored by Atomic Energy Regulatory Board, India through Project No ‐ N‐964

Risk Assessment for Natural Uranium in Subsurface Water of Punjab State, India

ABSTRACT Traces of uranium were measured by laser fluorimeter in 235 subsurface water samples collected from four districts of Punjab state in India. The concentration of U in water samples ranged between <2–644 μg/L with a mean value of 73.1 μg/L. The radiological risk was observed to be in the range of 5.55 × 10−6–1.78 × 10−3 with a mean value of 2.03 × 10−4, which is around 22% more than the maximum acceptable level (l.67 × 10−4) as per guidelines of India's Atomic Energy Regulatory Board. The mean of chemical toxicity risk, expressed as life time average daily dose (LADD) was worked out to be 5.56 μg/kg/day with a range of 0.15–48 μg/kg/day by considering a bodyweight of 51.5 ± 8.5 kg, water ingestion rate of 4.05 L/d, and life expectancy of 63.7 yrs for an adult Indian reference man and compared with the reference dose (4.53 μg/kg/day). The average exposure level of U was comparatively high and the chemical toxicity was expected to be more. The mean of hazard quotient (LADD/ RfD) for all four districts was found to be greater than 1, indicating that groundwater may not be suitable for consumption from a chemical toxicity point of view.

Radiation safety concerns and diagnostic reference levels for computed tomography scanners in Tamil Nadu.

Radiation safety in computed tomography (CT) scanners is of concern due its widespread use in the field of radiological imaging. This study intends to evaluate radiation doses imparted to patients undergoing thorax, abdomen and pelvic CT examinations and formulate regional diagnostic reference levels (DRL) in Tamil Nadu, South India. In-site CT dose measurement was performed in 127 CT scanners in Tamil Nadu for a period of 2 years as a part of the Atomic Energy Regulatory Board (AERB)-funded project. Out of the 127 CT scanners,13 were conventional; 53 single-slice helical scanners (SSHS); 44 multislice CT (MSCT) scanners; and 17 refurbished scanners. CT dose index (CTDI) was measured using a 32-cm polymethyl methacrylate (PMMA)-body phantom in each CT scanner. Dose length product (DLP) for different anatomical regions was generated using CTDI values. The regional DRLs for thorax, abdomen and pelvis examinations were 557, 521 and 294 mGy cm, respectively. The mean effective dose was estimated using the DLP values and was found to be 8.04, 6.69 and 4.79 mSv for thorax, abdomen and pelvic CT examinations, respectively. The establishment of DRLs in this study is the first step towards optimization of CT doses in the Indian context.

Neutron and gamma dose measurement in the working area of a research reactor using passive dosimeters

Radiation dose measurement at selected locations around the experimental facilities of a research reactor was carried out. Passive dosimeters based on CR-39 and CaSO 4 :Dy Teflon disc and 6 LiF:Mg,Ti and 7 LiF:Mg,Ti based neutron and gamma dosimeters were used in the study for the measurement of ambient dose equivalent (H*(10)). Measured neutron and gamma dose equivalent rates were found to be within the stipulated limit as per the guidelines of Atomic Energy Regulatory Board (the regulatory authority of India) for the radiation workers.

Radiation survey of first Hi-Art II Tomotherapy vault design in India

A vault as per government-regulation compliance with adequate shielding needs was designed and constructed for Hi-Art II Tomotherapy machine being the first in India. Radiation measurements around this Tomotherapy treatment vault were carried out to check the shielding adequacy of the source housing and the vault. It was mandatory to get this un-conventional machine “Type Approved” by Atomic Energy Regulatory Board (AERB) in India. The aim of this paper was to report on the radiation levels measured during the radiation survey carried out for this machine. The radiation levels in and around the vault were measured for stationary as well as rotational treatment procedures with the largest open field size (5 cm × 40 cm) at the isocenter with and without scattering medium. The survey was performed at three locations near each wall surrounding the vault as well. The leakage radiation from the source housing was measured both in the patient plane outside the treatment field and one meter distance from the source outside the patient plane. The radiation levels both for stationary as well as rotational procedures were within 1 mR/h. No significance difference was observed in the radiation levels measured for rotational procedures with and without scattering medium. The leakage radiation in the patient plane was found to be 0.04% (Tolerance 0.2%), while the head leakage was 0.007% (Tolerance 0.5%) of the dose rate at the isocenter. The treatment delivery with Tomotherapy does play safe radiation levels around the installation layout and also passes the leakage criteria as well.

Harnessing the Atom: Strengthening the Regulatory Board for Nuclear Safety in India Based on the Canadian Experience

Ending months of uncertainty and political drama, the present Indian Government headed by Prime Minister Manmohan Singh won a confidence vote on the floor of the Parliament of India paving the way forward for the historic 123 Agreement with the United States. Once operational, this Agreement could end India’s nuclear apartheid making civilian nuclear commerce with members of the Nuclear Suppliers Group a reality. While energy-hungry India needs enormous power to fuel its surging economy, this also raises serious concerns about nuclear safety. With several cases of near misses and accidents, India’s track record on nuclear safety is suspect. However, not much is known about the true state of affairs, primarily because the civilian and weapons programme are intertwined and the Indian nuclear establishment functions in an atmosphere of absolute secrecy. Given the high population densities, the consequences of a nuclear accident could be catastrophic. This article argues that the 123 Agreement provides India with the opportunity to re-engineer the working of its nuclear establishment in order to ensure greater safety, transparency and accountability. It uses the Canadian experience to offer some suggestions to remodel the Atomic Energy Regulatory Board, India’s watch dog on nuclear safety.

SU‐GG‐I‐69: An Attempt to Establish Regional Diagnostic Reference Levels for CT Scanners in India

Purpose: To establish regional diagnostic reference levels for CT scanners from a survey in Tamil Nadu, South India. Method and Materials: A regional survey of 71 CT scanners in a few districts in Tamil Nadu was done over a period of one year as a part of an ongoing Atomic Energy Regulatory Board (AERB) funded project. The survey included dissemination of necessary data involving exposure parameters and radiation doses used routinely in each centre. Dose estimation in CT scanners was performed using a 32 cm CT dose index (CTDI) acrylic body phantom and a 10cc pencil ion chamber. Weighted CTDI (CTDIw) and effective doses were calculated using observed CTDI values. An attempt to establish regional diagnostic reference levels was made by adopting results from a local dose reference level obtained from the host institution where the study was conducted. Results: Out of the 71 CT scanners surveyed, 24 were conventional, 29 spiral and 18 multidetectors. The mean CTDIw values for biphasic abdominal CT using corresponding routine institutional protocols would be 14.55 mGy, 12.6 mGy and 17.18 mGy for conventional, spiral and multidetector CT scanners respectively. The third quartile values of effective dose for biphasic abdominal CT from the regional dose survey would be 17.15 mSv (range: 5.36 mSv – 46.81 mSv), 14.83 mSv (range: 3.68 mSv – 25.63 mSv) and 20.37 mSv (range: 4.31 mSv – 47.08 mSv) for conventional, spiral and multidetector CT scanners respectively. Conclusion: Regional diagnostic reference levels for body CT examinations could be established from prior knowledge of the local reference levels obtained. The wide variation of dose levels observed from various centres could contribute extensively to the population dose in the region in concern.

Historical, regulatory and safety aspects of nuclear energy in India

Jawaharlal Nehru, former Prime Minister of India and Homi J. Bhabha interacted closely to set up the Atomic Energy Commission in 1948. The Indian parliament replaced the Atomic Energy Act, 1948 with the Atomic Energy Act, 1962 (AEA 1962) and promulgated appropriate rules. The Department of Atomic Energy (DAE) was set up in 1954. The Indian Cabinet established, through a resolution, a new Atomic Energy Commission, with administrative and financial powers of the Government of India to carry out DAE's work. DAE set up the Atomic Energy Regulatory Board (AERB) and delegated to it the responsibility to enforce certain safety and regulatory functions under the AEA 1962. Besides AERB's review mechanisms and some enforcement actions, the paper describes two court cases; one related to the import of Irish butter oil allegedly contaminated with Chernobyl fallout and the other on the diseases in the villages near the Jaduguda uranium mine.

Regulatory practices for nuclear power plants in India

Atomic Energy Regulatory Board (AERB) is the national authority to ensure that the use of ionizing radiation and nuclear energy in India does not cause undue risk to the health of workers and members of the public, and the environment. AERB fulfills its mission by stipulating and enforcing rules and regulations concerned with nuclear and radiological safety. This paper describes the regulatory authorization process of AERB as applicable to nuclear power plants (NPPs) during their construction as well as operating phases. The safety review process during construction is presented as case studies. Some current issues related to operating plants are also described. Two typical examples of safety upgradations made in old generation nuclear plants are given. The regulatory process in India is continuously evolving to cater to the new developments. Some of the recent initiatives taken by AERB in that direction are briefly described. Today AERB faces new challenges like simultaneous review of a large number of new projects of diverse designs, a fast growing nuclear power program and functioning of operating plants in a competitive environment. This paper delineates how AERB is gearing up itself to meet these challenges in an effective manner.

Tarapur Atomic Power Station Units-1 and 2: Design features, operating experience and license renewal

Tarapur Atomic Power Station (TAPS), a twin-unit BWR station is the oldest NPP in India. These units are operating for the last 30 years with impressive operation performance indicators and in this period their operating license was periodically extended by the Atomic Energy Regulatory Board. Certain modifications and improvements have been made in these units based on operating experiences and to further improve the safety standards. Testing of surveillance samples of the reactor vessel material confirmed that the vessel could operate well beyond 60 Effective Full Power Years (EFPYs), whereas till 2003, these units have completed 18 EFPYs. In order to extend the operating license of these units a fresh comprehensive review involving review of plant operating performance, ageing management and design basis and safety analysis was carried out. These units were reviewed against the current safety practices and based on this review some recommendations are made to bring the safety levels of these vintage units on par with the recently authorized plants. This paper gives a general description and describes the operating experience of TAPS. Also, safety review of TAPS carried out for license renewal is covered.

The VVERs at KudanKulam

A Nuclear Power Project is being set-up at KudanKulam in the state of Tamil Nadu, India in collaboration with the Russian Federation. The project comprises of two units each of 1000 MWe VVER type reactor. The design of the plant and supply of all the major equipment is in the scope of the Russian Federation while development of infrastructure and project construction is in Indian scope of works. The VVER (Version V-412) reactor that is under construction at KudanKulam site is an advanced PWR, which incorporates all the features of a modern PWR as per the current Russian, Western and IAEA standards. The KudanKulam site in the southern Indian state of Tamil Nadu was one among the several sites evaluated by the Site Selection Committee, which cleared KudanKulam site for setting up an installed capacity up to 6000 MWe. The design, construction and operation of the plant meets the regulatory and licensing requirements of Russian regulatory body “RTN” as also India's Atomic Energy Regulatory Board. The supply of the equipment from the Russian Federation is on schedule and the project construction work by various Indian agencies is also ahead of schedule. The two units of KudanKulam Nuclear Power Project (KKNPP) are scheduled to achieve first criticality in the year 2007–2008. The paper discusses various design features, project construction and management aspects.

Design aspects of safety critical instrumentation of nuclear installations

Safety critical instrumentation systems ensure safe shutdown/configuration of the nuclear installation when process status exceeds the safety threshold limits. Design requirements for safety critical instrumentation such as functional and electrical independence, fail-safe design, and architecture to ensure the specified unsafe failure rate and safe failure rate, human machine interface (HMI), etc., are explained with examples. Different fault tolerant architectures like 1/2, 2/2, 2/3 hot stand-by are compared for safety critical instrumentation. For embedded systems, software quality assurance is detailed both during design phase and O&M phase. Different software development models such as waterfall model and spiral model are explained with examples. The error distribution in embedded system is detailed. The usage of formal method is outlined to reduce the specification error. The guidelines for coding of application software are outlined. The interface problems of safety critical instrumentation with sensors, actuators, other computer systems, etc., are detailed with examples. Testability and maintainability shall be taken into account during design phase. Online diagnostics for safety critical instrumentation is detailed with examples. Salient details of design guides from Atomic Energy Regulatory Board, International Atomic Energy Agency and standards from IEEE, BIS are given towards the design of safety critical instrumentation systems.