Designed for safety

Published : Jun 03, 2011 00:00 IST

Ratan Kumar Sinha: The events at Fukushima have been carefully analysed by NPCIL. - V.V. KRISHNAN

Ratan Kumar Sinha: The events at Fukushima have been carefully analysed by NPCIL. - V.V. KRISHNAN

Interview with R.K. Sinha, Director, Bhabha Atomic Research Centre.

IN the context of the accident at the Fukushima-Daiichi nuclear power plant consequent to the earthquake and tsunami in Japan, the doubts raised about the safety of the French company Areva's EPR-1650 nuclear reactor to be built at Jaitapur in Maharashtra, and the issues raised about the disposal of wastes from nuclear power reactors, Frontline met Ratan Kumar Sinha, the Director of the Bhabha Atomic Research Centre (BARC), Trombay.

Ratan Sinha was earlier Director of the Reactor Design & Development Group and the Manufacturing & Automation Group at BARC. He guided the programmes for the new advanced reactors that will use thorium as fuel. These reactors include the Advanced Heavy Water Reactor (AHWR), which will generate most of its power from thorium and has several innovative passive safety features, and the Compact High Temperature Reactor (CHTR), which will demonstrate the technologies needed to set up transportable nuclear power reactors that can be deployed in remote areas. He spearheaded the development of several remote inspection technologies to replace the coolant channels in the Pressurised Heavy Water Reactors.

This has enabled the safe operation and extended the life of seven PHWRs, including the two at the Madras Atomic Power Station at Kalpakkam, about 60 kilometres from Chennai. He designed, developed and installed the coolant channels and other internal components of the world-class Dhruva (100 MWt) research reactor at Trombay. He has guided the development of technologies that will enable, in a large-scale deployment scenario, the setting up of advanced nuclear power plants close to population centres.

Ratan Sinha graduated in mechanical engineering from Patna University in 1972, standing first in the university. After completing the prestigious one-year course of the BARC Training School, he joined BARC's Reactor Engineering Division in 1973.

Excerpts from the interview:

BARC is one of the biggest R&D organisations of its kind in the world and focussed on a wide variety of subjects, including nuclear power, agriculture, desalination, electronics, supercomputers, robotics, fuel reprocessing, nuclear waste management, and fuel fabrication. What will BARC's thrust area be under your leadership?

The Bhabha Atomic Research Centre is the backbone of the self-reliance acquired by the Indian nuclear power programme over the past several decades. My priority is to maintain this strength in the future even in the presence of international cooperation, the doors for which are getting opened now. In the area of nuclear fuel cycle particularly, we have acquired tremendous capability. This capability should be brought to perfection in order to be available on a large and commercial scale to support our commercial Fast Breeder Reactor programme, which is receiving high priority today.

You said that building the nuclear fuel capability to support a commercial Fast Breeder Reactor programme would be given high priority. In a conversation with me, former BARC Director A.N. Prasad said he feared research in BARC would take a back seat because India was going to import 36 reactors. Former Atomic Energy Regulatory Board (AERB) Chairman A. Gopalakrishnan also said the same thing.

Our priority is absolutely the same. It is clear that for a large country like India, the total demand for nuclear electricity is very large, of the order of 400,000 MWe to 600,000 MWe. What we are talking of today is importing 40,000 MWe of Light Water Reactors [LWRs]. Even the fuel from these LWRs along with our first generation PHWRs will be reprocessed to multiply the capacity fast enough with the help of Fast Breeder Reactors, and subsequently using thorium.

Now, nowhere in the world is a Fast Breeder Reactor being built using plutonium as fuel [as we are doing in India]. Nowhere in the world have mainly thorium-based reactors been developed to the extent we have done ourselves.

Our priorities are extremely well defined and sharply focussed. The world is not in a position to help us multiply our capability significantly. The initial import of water-cooled reactors will certainly help us build a higher capacity in the near term. However, it will be impossible to reach the level of deployment needed by our country without the benefit of multiplication with Fast Breeder Reactor technology and thorium technology in which India is perhaps the best equipped country today. Our R&D is one of the most advanced in these areas, and we will continue to work in these domains to make these technologies available on a commercial level. Importing reactors in no way affects the programme already chalked out. It is an additionality.

India is going to build 700 MWe LWRs indigenously. Consequent to the tsunami and the accident at the Fukushima-Daiichi nuclear power plant in Japan, which had LWRs, what are the lessons that have been learnt in building LWRs in particular or any nuclear power plant in general?

The events at Fukushima have been carefully analysed by Nuclear Power Corporation of India Limited [NPCIL] in the context of our existing and future nuclear power plants. We have confirmed that on account of the specific seismic and tsunamigenic conditions of our region and also the stringent rejection criteria followed in our country, the site selection procedure followed in our country is already very conservative.

Further, the designs of all the reactors in our country and those being built or under proposal to be constructed later incorporate the passive heat decay removal system in some measure, along with availability of a significantly sized inventory of water to serve as a heat sink in a station blackout scenario. Even so, on the basis of a detailed examination of existing design provisions, the task forces of NPCIL have thoroughly reviewed the associated issues and have identified certain areas of improvement and back-fits that will take these reactors to still higher levels of safety.

The LWR technology is already well proven and the current generation [of LWRs] has incorporated all the lessons of the past events. We see no reason why the Fukushima event should significantly alter the acceptability of LWRs or any other nuclear power plants in the country.

I visited the waste management facilities at Tarapur and BARC recently. Managing nuclear waste will be a big problem when the 36 LWRs are imported and when India builds its own 700 MWe PHWRs, Fast Breeder Reactors and thorium-based reactors. All this will mean that more land will be required to store the increasing volume of radioactive waste. How do you plan to tackle the problem of permanently disposing of this waste?

Let me clarify. One gram of uranium-235, when it is fissioned completely, will produce as much as 1 MW of thermal power for one full day. So the energy in a small quantity of nuclear fuel is tremendous. As a corollary, the waste produced for the same amount of energy is extremely small. To give you an example, the two 540 MWe PHWRs at Tarapur will produce nuclear waste in the form of spent fuel, which will be taken up for reprocessing to remove plutonium and uranium and other valuable radioisotopes, leaving behind high-level waste that will be vitrified.

This vitrified waste is placed in small cylindrical containers. To keep these in interim storage condition, we have built the Solid Storage Surveillance Facility at Tarapur. That facility has an area equivalent to one-fourth of a football ground. That area is sufficient to store vitrified waste from two 540 MWe reactors during their full life. So it is easy to manage a facility of this size in controlled conditions for several decades.

First, it will be necessary to keep this waste in coolable conditions for about three decades and it is expected that most of this waste will lose its high gamma radioactivity in about 100 years.

The Solid Storage Surveillance Facility building has been designed to take care of long-term storage in technologically managed conditions.

In the meantime, we have a programme to develop an underground, deep geological repository in granite-based rock formations. Research in this direction is already in progress at our centre, and it will be directed forward to the next level by setting up an underground research laboratory to carry out field trials.

Areva's EPR-1650, which is to come up at Jaitapur in Maharashtra, is in the news. There are allegations that EPR-1650 is an untested and uncertified reactor and that it uses 5 per cent enriched uranium, while other reactors use only 3 per cent enriched uranium. Are these allegations true? Besides, critics say that British and American nuclear regulatory agencies have raised 2,300 safety issues, including on the instrumentation and control systems of EPR-1650. The UAE has dropped EPR-1650 in favour of South Korean reactors. Is it advisable to import these French reactors?

The EPR belongs, in general, to the Pressurised Water Reactor family of reactors. Its thermal hydraulics is in no way different from any of the existing PWRs in the world. Most of the operating reactors in the world nearly 60 per cent of them belong to the PWR category. Within this family, every reactor may have some distinctive design features. In the case of the EPR, particularly, these design features also address to a large extent safety against aircraft impact, and [it has] a provision to contain the core melt in the event of postulated severe accident conditions.

With a core-catcher?

With a core-catcher. These can be considered to be in addition to what is already a proven design. Enhancing the size of the reactor does not necessarily mean that it becomes an unproven design. Every nuclear power plant has to go through a series of safety reviews that include design safety as well as operational safety. All regulators follow certain stipulated practices and they follow codes and guides that are internationally accepted. However, the exact details of the country-specific regulations may vary.

Every regulator, therefore, does pose a large number of questions, the answers to which need to be fully documented, and it is nothing very alarming that questions are asked before the plant is allowed to be built or commissioned by the utility. It is a normal process, and this process is in place for all the reactors that we have built in our country.

EPR-1650, of course, is a large-sized plant, the largest in the world today. It has a slightly higher level of enriched uranium, which helps it deliver more energy from the same amount of fuel over a longer period. In effect, therefore, for the same energy produced, the quantity of spent fuel discharged will come down.

The design of a reactor, anywhere in the world, always ensures that the fuel temperature will be contained within a sufficiently safe margin so that no damage to the fuel takes place on account of any postulated conditions which go beyond normal design conditions. Within these constraints, the specific reactor design parameters may be different. I can give you the example of a small car and one big car. Just because a car is bigger than another car, it does not mean that the bigger car's engine is not safe. It is designed like that. It is designed to produce more power.

There is a fear that the electricity generated from EPR-1650 in India will cost Rs.8.50 a unit and that no State Electricity Board will be able to afford.

The reply to this should come from NPCIL. The Chairman and Managing Director, NPCIL [S.K. Jain], has already stated that NPCIL has calculated the costs, and if the reactor is not economically viable, it will not be set up. So you can say that the bottom line is that the unit energy cost of any imported reactor must be competitive against the cost of electricity generated by alternative modes in the region. This is the criterion that will be followed.

The Department of Atomic Energy (DAE) is going to set up a big uranium enrichment facility in Chitradurga district in Karnataka. Will the enriched uranium produced in Chitradurga be used to set up indigenous 700 MWe LWRs or for India's nuclear-powered submarines?

India has now fully mastered uranium enrichment technology. Our new research reactor to come up in Visakhapatnam will make use of low-enriched uranium. For the replacement of the original core of the Apsara reactor, we will have a fuel based on enriched uranium produced in our plant. We have a programme to develop our own LWRs and to build a capability to produce enriched uranium fuel for the imported LWRs as well. Towards this objective, the enrichment capability will be further augmented by setting up this plant [at Chitradurga].

Tell us about the new research reactor that is to come up in Visakhapatnam?

The Bhabha Atomic Research Centre plans to set up a high flux research reactor on its new campus in Visakhapatnam. The conceptual design of this reactor has been completed. This reactor will be a special reactor using an enriched uranium-based fuel, with several irradiation facilities located in a pool of water that will serve as a reflector. This reactor will be useful to meet the country's demand for high specific activity radioisotopes. The reactor will provide facilities for basic and applied research in the development and testing of nuclear fuel and reactor materials.

Why is Visakhapatnam preferred nowadays for new DAE facilities?

The Bhabha Atomic Research Centre, on this campus at Trombay, was set up more than five decades ago and its activities have grown exponentially. We do not find enough space here to grow further. For example, we do not have enough space to build another reactor of large enough size. We don't have enough space to expand our programmes to support the academic activities of the Homi Bhabha National Institute. We don't have enough space to carry forward our work on hydrogen generation systems and high temperature reactors. We, therefore, have to move to a new campus, and Visakhapatnam has been selected.

CIRUS (Canada India Research Utility Services, a research reactor) was shut down permanently last year after it was refurbished just three years ago. Was this because of the 123 Agreement between India and the United States?

CIRUS was the oldest reactor of its kind, built in the early 1960s. It had to be refurbished because its external systems had shown signs of ageing. There was particularly a concern about leakage in some of the components of the external systems. If we had not done this refurbishment, we would have had to retire the reactor a decade ago. To take care of the external systems, extensive refurbishment of the external systems was carried out.

In the meantime, we were observing symptoms of progressive degradation of the internals of the reactor, particularly in its aluminium channels. A major refurbishment, therefore, to take care of this degradation would have become necessary in this case and a decision to replace the calandria would have become due in the near future. However, the decision to shut down the reactor at the end of 2010 was a consequence of our international commitment.

Let me add that the new core of Apsara will deliver the same neutron flux as existed in CIRUS and will provide additional flexibility to experimenters on account of its mobile core in a swimming pool configuration.

Will the new Apsara be built in Visakhapatnam?

The new Apsara will be located at Trombay, taking advantage of the existing major structures that have been assessed to be robust. The latest core of Apsara had enriched uranium supplied by France. Under an international commitment, we are required to remove this fuel out of here [BARC campus at Trombay]. So Apsara fuel has been moved out of BARC, out of here. However, we had a long-standing requirement to refurbish the Apsara reactor and have a better core. In fact, this project was to have been completed by now but for our busy schedule of carrying out several experiments to optimise the shielding designs of the Prototype Fast Breeder Reactor [PFBR] and the Advanced Heavy Water Reactor [AHWR].

The shutdown of Apsara had to be postponed till the experiments were completed. It was, therefore, just appropriate that when we completed all these experiments in 2010, activities towards decommissioning [of Apsara] had started in parallel. The old fuel of the reactor was removed in December 2010.

The AHWR has undergone many peer reviews. When do you plan to have the ground-breaking ceremony for the reactor, which ought to have been held five years ago? Have you chosen the site for the reactor? There is an allegation that research in thorium-fuelled reactors will take a back seat because India is going to import 36 reactors.

Thorium will be the backbone it will be the main fuel of the Indian nuclear power programme a few decades from now when the country will have reached a large level of electricity generation capacity through Fast Breeder Reactors. Bringing thorium on a large scale earlier than necessary will slow down the breeding potential of the Fast Breeder Reactors, and thorium, therefore, has to be brought in only when necessary.

However, considering the importance of achieving a proven and mature technology in time, India has been engaged in a large volume of research in the field of the thorium fuel cycle, and thorium has already been irradiated in research and power reactors. Setting up the AHWR in a demonstration mode is the logical extension of these activities to prove thorium-related technology for commercial exploitation.

We have been working on the development of all aspects of the thorium fuel cycle. The AHWR Critical Facility at BARC has been loaded with a fuel cluster bearing thorium, and we have already done several experiments. The AHWR will also serve to demonstrate an extremely high level of passive safety that can enable in future, when large-scale deployment of nuclear power is done, the capacity to achieve safety levels that can qualify these reactors to be located close to population centres.

With these objectives, extensive engineering R&D work for the AHWR has been done. A very large-scale facility for simulating two coolant channels of the AHWR is under construction at Tarapur in collaboration with NPCIL. Using this facility, we will run these channels to almost two to three times the rated power of the AHWR.

Two to three times the rated power of the AHWR?

[The rated power of] only two channels is 17 MW-thermal. We will run the channels to demonstrate the margin of conservatism in the design of the reactor and, if possible, look for uprating of power. Regarding the AHWR construction, we are going ahead with the detailed design and preparation of documents on the conventional systems of the AHWR by awarding a contract to a major engineering consultant. The important structural features of the AHWR, requiring special manufacturing technologies, have been communicated to our Indian manufacturers for trials and development so that they will be available in time when the actual components go for manufacture.

We are in the process of locating a site for the AHWR. For a reactor with a capacity of only 300 MWe, it will not be justifiable to have a site all for itself. It is required to be co-located with some other facility of the DAE. Within these limits, the candidate sites for the AHWR are under investigation.

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