Ex BARC, Ex IAEA & Consultant to AERB
Dr. M R. Iyer after his post graduation from Kerala University joined the then AEET (BARC) in 1958 and has been associated with the radiation protection programs in BARC in various capacities culminating in being the Head of the Radiation Safety Systems Division. He was Instrumentation Specialist in the Department of Safeguards in the IAEA and an accredited Safeguards Inspector during 1994 to 1999. He got this PhD degree in Nuclear physics in 1971. He was a guiding teacher for PhD of the Bombay University and guided about 15 students for their doctoral degrees. He was Chairman of the AERB safety committees for accelerators for 15 years till recently. He is currently a member of the Advisory committee on radiation and nuclear safety of AERB. He served as a member of the Expert Group formed by Government of India to allay the fears of the public about the Kudankulam Nuclear Power Station in 2011. He is also a free lance writer on scientific matters and has just completed the Birth centenary Memoir Compendium on Dr. Ganguly for publication by IARP at its 2018 January conference.
Title: Radiation Physics - Yesterday, Today and Tomorrow
The subject of Radiation Physics owes its origin to Dr A K Ganguly whose centenary year has just started. The term Radiation Physics and the birth of the Indian Society of Radiation Physics in 1976 are some of the outstanding monuments of the far sightedness of Dr Ganguly. Dr Gopinath who was party to this development remembers that it was due to Dr Ganguly’s incessant encouragement and guidance that the Indian Society for Radiation Physics took its birth in 1976 at Mysore. The exercise was so successful that it led to the formation of International Radiation Physics Society in 1985 at Ferrara, Italy. IRPS has held 10 conferences, every three years, since then in various cities in the world. Thanks to his foresight and initiative Radiation Physics stands out today as a vibrant and active discipline
One of the topics which was the subject of investigation in Radiation Physics after consolidation of research under this topic was on radiation transport theory in which Dr Gopinath and his school in BARC and IGCAR have contributed significantly. Analytical methods for solving the anisotropy in radiation scattering were developed which led to development of internationally accepted ASFIT (Anisotropic Source-Flux Iteration Technique) methodology and code. Outside BARC, several universities had strong programmes in the study of basic interactions of radiation with matter. Besides Institutes like IIT Powai in Bombay, INMAS in Delhi and Bose Institute in Calcutta also had active programmes in the subject. The first National Symposium on Radiation Physics at BARC in 1970, inaugurated by Dr. Ramanna brought together almost all the groups in the country working in different areas of Radiation Physics and helped establishing its identity as an independent discipline. Subsequent periodic national conferences on Radiation Physics have recorded several significant developments. These are too many to be recounted in a short talk.
Monte Carlo methods were being developed by Dr P K Sarkar and several others like Prasad in BARC. A variance reduction technique developed by them which reduced the statistical uncertainty in Monte Carlo methodology was a landmark development. It was interesting to see two schools one developing analytical methods and another Monte Carlo methods claiming advantages flourishing side by side. Dr Ganguly, who himself had used Monte Carlo methods in developing “Ganguly Magee theory” in Radiation Chemistry in Notre Dame University in USA in 1956, nurtured these groups as complementary to each other.
Then came some developments in the experimental Radiation Physics which perfected methods for neutron spectrum measurements and convolution of neutron spectrum by using pulse shape discrimination in plastic scintillators of varying sizes based on the range of Compton scattered electrons. And Monte Carlo methods were found useful in this. The sky shine problem due to air scattering of gamma photons which was dealt with theoretically and experimentally led to many practical applications. Today some of the exciting work that is being done is on the possibility of using measured prompt gamma emissions from polyethylene to estimate neutron ambient dose equivalent. For an entirely different application in Safeguards, I was fortunate to be participating in developing a novel method in using self-induced short range x rays for bulk Pu estimation during my stint in IAEA.
Several pioneering developments in the field of physics of thermo luminescence and applications took place in BARC during the last century. So were the development of SSNTD in detectors and use of electrets for radiation monitoring.
Fission product and fission physics was another area which became part of radiation physics. The decay characteristics of fission products at short times of 1 msec to 1 second were experimentally investigated in those days. This led to several practical applications such as quick and precise enrichment analysis in uranium samples. This was followed by the study on fission asymmetry and a model based on systematics of stability of nuclides and Order Disorder phenomenon was developed by Dr. Ganguly and myself (1971) and it explained many fission parameters successfully. One of the notable characteristic of this model was that it envisaged an earlier polarisation of protons in the fissioning nucleus into two halves along with the neutrons corresponding to its stability. This left behind a certain amount of “balance neutrons” which was found to have remarkable correlation with fission asymmetry. It is worth pursuing studies to explain this observation using many body problem.
What lies ahead? There are several exciting problems in Physics that comes under the subject of Radiation Physics today which are worth pursuing. Some of these indicated in the talk are on high-energy photon dose measurements, new concepts of detectors, neutrino measurements and investigations, and development of nano detectors employing nano capacitors. On the environmental aspects of radioactivity some of the unsolved problems include investigation on the source of thorium deposits in the West coast of India on which many Universities in the region have extensive programs and working currently. It might be a good idea to form an inter university brain stroming forum to identify and plan Radiation Physics research for the next 5 years. In these days of applied sciences taking precedence over basic research, Universities have a great role in sustaining basic sciences. I have been floating a suggestion for forming a consortium of universities to install a Cyclotron for radiation physics investigations which can sustain itself by parallely using it for production of PET isotopes required for medical applications.