Thursday, December 23, 2010

50 years of CIRUS: some unforgettable memories


Published: December 23, 2010 01:41 IST | Updated: December 23, 2010 01:57 IST December 23, 2010
50 years of CIRUS: some unforgettable memories
K.S. PARTHASARATHY 


OLD WARHORSE: Research Reactor CIRUS at the Bhabha Atomic Research Centre at Trombay. Photo: V.V. Krishnan
On December 18, the scientists and engineers in the Department of Atomic Energy (DAE) celebrated the Golden Jubilee of CIRUS and the Silver jubilee of DHRUVA. The organizers invited everyone who was associated with the two research reactors. It was an emotional homecoming for many, especially for those who retired decades ago.
The 40 MW research reactor attained criticality on 10{+t}{+h} July 1960. It was constructed under Canadian assistance. India and Canada shared the cost of about $14.14 million. CIRUS, the workhorse of BARC is a symbol of the advanced developments in nuclear science, engineering and technology in India.
Dr Bhabha chose this heavy water moderated, uranium metal fuelled reactor as it would be a powerful tool for research. Also Dr W.B. Lewis, the eminent scientist who led the designers of the reactor was close to him in his Cambridge days.
Veterans recalled the teething problems they faced, the ways in which they solved them and their unforgettable memories. The 188-page commemorative booklet which describes them is a lucidly written, technical document, an A to Z cookbook on research reactor operation and maintenance!
Priceless experience
The reactor operation and maintenance group acquired priceless experience by studying the failure data of components such as valves.
Floating materials, mainly plastic waste and seeds and leaves from ever expanding mangroves, clogged the travelling water screens in the sea water inlet system; silt accumulation in the gland vent ports damaged the pumps. Scientists addressed these issues promptly.
“ In a hurry to start the reactor early, Bombay municipal water was charged to the high head storage tank ( ball tank) and was used in the re-circulating coolant water circuit” Shri S.M. Sundaram, former Director, Reactor Operation and Maintenance Group (ROMG) recalled. The total dissolved solids (TDS) such as silica in water got deposited on the fuel cladding, reducing coolant flow and damaging many of them at higher power level.
The Canadians did not face such a problem in their reactor; they used fresh water from Ottawa River. Sundaram and his team purified water using ion exchangers and solved the problem.
He remembered that then he worked against the orders from their superiors. Bhabha tacitly supported them. “…he said that there may be rare occasions when one may need to disregard the orders of his superior, for a good cause”.
By October 1963, they could raise the power level to 40 MW.. “ever since, CIRUS has been the workhorse of Indian atomic research programme”, Shri N. Veeraraghavan, former Associate Director, ROMG recalled.
He remembered that Dr Bhabha addressed a meeting in the indoor games room in the Old Yacht Club Building, which was attended by CIR project related scientific community sometime end of 1959 or early 1960.
“Bhabha expressed full confidence in the ability of Indian engineers in the production of indigenous, pure natural uranium and its fabrication into fuel rods for the initial loading of the CIRUS reactor”, Shri Veeraraghavan said .
Very bold commitment
“ As I see it today, this was a very bold commitment at that time, which ended happily for all, especially the chemical and metallurgical engineering staff that really worked hard and met the commitment with the loading of indigenous uranium fuel for the first “criticality” of CIRUS reactor,” he added
Most of the members of the newly recruited scientific and engineering staff for CIR operations sent for training to Canada during 1956-1957 came from very conservative backgrounds. They were from different regions of the country and spoke different languages. Most of them were strict vegetarians.
Dr M.R. Srinivasan, former Chairman, Atomic Energy Commission (AEC), delivered a few lectures to them. Bhabha asked him to take them to the Taj Hotel so that they would learn to use knife and fork before going to Canada for further training!
Dr P.K. Iyengar, former Chairman, AEC, recalled that the training school programme which Bhabha spearheaded helped national integration; it brought people from different parts of the country together.
Heartbroken
“I am truly heartbroken to learn that this old workhorse will be put to sleep at the end of this year for reasons that are anything but technical” the words of Shri S.K. Sharma, former Director, Reactor Group, truly reflected those of many others present.
“But then those are the ways of the world that we live in,” he consoled everyone.
In his inaugural address Dr R.K. Sinha, Director, BARC, stated that the CIRUS reactor provided research and development inputs to the nuclear power programme in the country.
It provided a platform to train engineers and technologists in the area of reactor management.
“This is an occasion to reflect on the past and to pay our gratitude to our elders” Dr Srikumar Banerjee, Chairman, AEC, said while addressing the gathering.
K.S. PARTHASARATHY, Raja Ramanna Fellow, DAE
(ksparth@yahoo.co.uk)

Thursday, December 02, 2010

CT: cancer risks for the elderly

Online edition of India's National Newspaper
Thursday, Dec 02, 2010
The study showed cancer incidence from CT scans was less threatening


— photo: K. Murali Kumar

The focus: The study estimates cancer risk to persons above 65.
In a paper presented at the 96 {+t} {+h} Scientific Assembly and Annual Meeting of the Radiological Society of North America, Dr Aabed Meer and co-workers at the Stanford University at Palo Alto, California, have claimed that the risk of developing radiation-induced cancer from computer tomography (CT) may be lower than previously thought.
It is the first time in many years that a scientific study showed that the impact of CT on the incidence of cancer was less threatening! But the RSNA paper does not state that CT scans are risk free. The paper has not undergone any peer-reviewing as it was presented at the RSNA meeting, and not published in a peer-reviewed journal.
The study has certain other limitations. It estimates cancer risk to persons above 65 years. The views of learned bodies and professional associations on the study are yet to be published.
This study is statistically respectable as it included 10 million records of patients from 1998 to 2005. Based on Medicare database, they analyzed the distribution of CT scans, determined the radiation doses associated with them and estimated the associated cancer risk in a population of older adults. Medicare is a social insurance program administered by U.S.government, providing health insurance coverage to people who are aged 65 and over, or who meet other special criteria (Wikipedia).
The researchers included the data from two study groups; 5, 2767,230 records from 1998 through 2001 and 5,555,345 records from 2002 through 2005. They analyzed the number and types of CT scans that each patient received to find out the percentage of patients exposed to “low” radiation doses of 50 mSv to 100 mSv and “high” radiation doses in excess of 100 mSv (Sv is a unit of biologically significant dose and it involves the absorption of one joule per kg of radiation energy; mSv is a thousandth of a Sv).
They calculated the number of cancers that may be induced by using standard cancer risk models.
CT scans of the head numbered 25 per cent of the examinations in the first group and 30 per cent in the second. They found out that abdominal CT exposed patients to the greatest proportion (nearly 40 per cent) of doses in each group. The second and third largest sources of radiation were imaging of pelvis and chest
From 1998 to 2001, 42 per cent of the patients underwent CT scans; the corresponding percentage for 2002 to 2005 was 49. The researchers also found that the percentage of patients exposed to radiation doses in both the low and high ranges nearly doubled from the first group to the second. This was consistent with the increasing use of high speed CT in patient diagnosis and management.
They estimated the cancer incidence associated with exposure to radiation from CT to be 0.02 percent and 0.04 percent of the two groups respectively. The authors found a significantly lower risk of developing cancer from CT than the previous estimates of 1.5 per cent to 2 per cent of the population.
The study which gave higher numbers refers to a paper published by Drs David Brenner and Eric Hall, researchers in the Columbia University Medical Centre, New York in the New England Journal of Medicine (November 29, 2007)
This paper became very controversial. The American College of Radiology, the Radiological Society of North America and the Association of Physicists in Medicine reacted to the paper with predictable alacrity. These associations argued that the conclusions of the paper may scare away patients from clinically needed CTs.
The NEJM study got extensive media coverage as it focused attention on the overuse of CT. It was then estimated that one million children and 20 million adults in the USA undergo unnecessary CT scan procedures annually.
Medical radiation procedures must be carried out only if they are justified. Physicians must ensure that radiation doses are As Low As Reasonably Achievable (ALARA) without compromising clinical needs.
K.S. PARTHASARATHY
RAJA RAMANNA FELLOW DEPARTMENT OF ATOMIC ENERGY
( ksparth@yahoo.co.uk)