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#319, 11 May 2010

Modular Nuclear Reactors and Breeder Technology

Chair: Professor Amitabh Mattoo, School of International Studies, JNU
Speaker: PR Chari, Research Professor, IPCS
Discussant: Professor R Rajaraman, Emeritus Professor of Physics, JNU

Introduction: Professor Amitabh Mattoo

The Non-Proliferation Treaty (NPT) stands on three pillars. The first is non-proliferation; state actors within the NPT, both nuclear weapons states and non-nuclear weapon states, have undermined this pillar. The second pillar is Article VI, nuclear disarmament; there has been some progress including the New Start Treaty. Despite the momentum given by President Barack Obama, nuclear weapons are here to stay, even though the Nuclear Posture Review (NPR) has made qualifications on when nuclear weapons would be used as part of American strategic policy. Whether Article VI will be translated into reality seems distant. The third pillar was a part of the bargain, where non-nuclear weapon states would be given access to civilian nuclear energy and technological advances made. Because civilian nuclear energy and the technology that produces nuclear weapons could not be separated easily, access to civilian nuclear energy was not provided to the non-nuclear weapon states. However, a debate has emerged recently about producing proliferation resistant nuclear reactors.

Professor PR Chari

President Obama’s style is marked by rhetoric and retreat. He announced the agenda of Global Zero in Prague, but at the same time said it was not likely to happen in his lifetime. He qualified his statements in Prague later by saying that nuclear weapons would be required for providing nuclear deterrence and, still later, by saying that nuclear weapons would be required for the foreseeable future.

Over the last month, there have been several developments; the NPR, which seeks to reduce the salience of nuclear weapons in American strategy; a new START agreement which seeks to reduce long-range missiles in the American and Russian arsenals; and, finally, the Nuclear Security Summit which has identified the safety and security of nuclear materials as representing the present danger to nuclear non-proliferation. Differences have already appeared in the 2010 NPT Review Conference, like the issue of a nuclear weapons free zone in the Middle East; and criticism of the Indo-US deal.

Two main technological challenges to the non-proliferation regime, however, are not being recognized. The first is fast breeder technology where an atom of plutonium 238 (Pu238) fissions when it is struck by a neutron, which produces plutonium and another isotope of uranium which fissions further into plutonium 239 (Pu239). Pu239 is the isotope of plutonium used for fission in atomic weapons and is also usable as fuel in nuclear reactors. It has a half-life of 24,000 years;  after that time the radioactivity of Pu239 would reduce by half and it would require an additional 24,000 years to become a quarter.

There are five ways in which using breeder technology for reactors is a challenge; firstly, the capital costs are extremely high, at least 25% more than water cooled reactors amounting to $1,000 per kilowatt of power generation; secondly, safety issues are a concern, these reactors use a sodium coolant to make it efficient, but even a minor leak could rupture the tubes and lead to a major sodium-water fire; thirdly, plutonium breeder reactors produce more plutonium than they consume adding to proliferation problems; fourthly, breeder reactors need recycled plutonium, which can also be used for making nuclear weapons; fifthly, breeder reactors are useful to produce weapons grade plutonium directly, as done by France. India’s 500MW prototype fast breeder reactor is expected to go on stream this year. It can make, according to theoretical calculations, about 90kg weapons grade plutonium per year if the radial blanket is used, but if the radial and axial blankets were to be used then it can make up to 140kg per year. These figures are important because it takes about 3 to 5kg for one nuclear weapon. Both the Bhabha vision and the Sarabhai plan have emphasized that the end-goal of India’s nuclear program is premised on breeder reactors.   

The other technological challenge is small modular reactors (SMR) which is being promoted by the United States. President Obama has requested $39 million for a new program to get SMR designs licensed for widespread commercial use. SMRs have compact designs, could be made in factories and transported to sites by truck or rail, they reduce capital costs and construction time, and increase flexibility by being able to be added or withdrawn as demand increases or decreases. Therefore, they are suitable for small electrical grids or for being established in isolated places or for replacing fossil fuel plants. The downside of SMR’s is that the level of expertise that is required for their operation is no less than what is required to run a large commercial plant; besides the safety and security issues multiply due to their scattered locations. There are personnel issues that also arise from the need to post qualified persons to remote places, which makes it difficult to recruit them.

There is a reference to proliferation resistant reactors in the work plan issued after the Nuclear Security Summit. What are the options? First, reactors using Highly Enriched Uranium (HEU) could be redesigned to use Low Enriched Uranium (LEU). Second, instead of using HEU mixed uranium and plutonium oxide (MOX) could be as fuel, which cannot be used for making nuclear weapons. The problem with using MOX is that very high purities are required, making the fuel very expensive to manufacture. Third, the Global Nuclear Energy Partnership (GNEP) launched in 2006 envisages using fast neutron reactors to make spent reactor fuel less radioactive. The problem again is high costs, marginal benefits and very long time periods.

Professor R Rajaraman

Modular reactors are factory fabricated modules and connecting the modules greatly reduces the construction work required while increasing the ability to deploy these reactors in remote regions. Unlike large reactors, these reactors take half the time to build with much less cost. Being smaller in size increases their flexibility for utilities since they could add units as demand changes; and are ready to ‘plug and play’ on arrival.

Modular reactor is a common name for about fifteen different designs and typically generates 100MW of power. According to the IAEA the global demand for these could reach anywhere from 500 to 1,000 by 2040. This raises issues about whether the world can manage to safely keep these reactors and its output. A US based group, General Atomics, is developing one design, a gas turbine helium reactor. The US is not the only country with interest in SMR’s. The most advanced modular reactor project is in China, where they are preparing to build 200MW SMR’s. Since 1976 Siberia has housed four SMRs each producing 11MW of electricity.

South Africa has worked on a 200MW Pebble Bed Modular Reactor (PDMR). It was projected as the new generation reactor, but the plan to commercially make these reactors has unfortunately been abandoned owing to technical and economic reasons. The PBMR essentially comprises a steel pressure vessel which holds the enriched uranium dioxide fuel encapsulated in graphite spheres. The system is cooled with helium and heat is converted into electricity through a turbine.  It requires less expertise and its reactivity feedback is negative making it safer to use than breeders.

Breeder reactors are designed to breed fuel by producing more fissile material than it consumes. Neither the breeder reactor nor the fuel rods are a proliferation danger; it is the reprocessing unit that separates the plutonium which is a proliferation problem. Three countries have been using this technology, France, Japan and Russia. Before the Indo-US deal the need for breeders and the three-stage plan formulated by Dr. Homi Bhabha were a priority. Now, the scarcity of uranium and the need to use the abundant thorium resources is no longer an issue. India can continue the breeder programme and if it is not successful or commercially viable then it can be phased down.

Breeders have a history of not being successful apart from the scientific analysis. Reactor-grade plutonium is put into a breeder, which is not ideal for bombs, and out comes Pu239, which is ideal bomb material. It is not just the quantity that is replacing the earlier plutonium but you are getting better bomb material coming out. In a sense that makes the danger even more. One must remember that the breeder and the fuel rods are not a proliferation danger; it is the reprocessing unit, the process of chemically separating plutonium from other radioactive elements in the rod, which makes it a proliferation problem. This danger exists even in ordinary reactors, although it is true that breeders produce better weapon material than ordinary reactors do, even reactor-grade plutonium is weapon material. The danger exists as much in ordinary reactors as in breeder reactors, but all these dangers only come after reprocessing.


Modular Nuclear Reactors

• The South Africans abandoned the PDMR project due to technical reasons and chose not to sink more money into it. Now a Memorandum of Understanding (MOU) has been signed between the Chinese and the South African developers of pebble bed technology to collaborate on this project.
• Both safety and security issues are involved and if this cannot be ensured then there is a proliferation risk. Whether it be a large or small nuclear reactor it requires the same quality of technical personnel for running them. To persuade qualified scientists, engineers and technicians to relocate to remote places raises serious personnel issues.

Breeder Technology

• Breeder reactors do not just breed more fuel but can also be operated as burners.

Indian Context

• Breeder reactors form the second step in the three-stage strategy for nuclear power generation that is being pursued by India since the 1950’s. Following the Indo-US nuclear deal this strategy seems to have been abandoned.
• The problem in transporting reactor components is that India does not have adequate roads or bridges for their transportation from their places of manufacture. That is one reason why most of India’s atomic reactors are located along the coastline so that they can be brought by ship, and cooling becomes easy using sea water. This is why the modular aspect becomes critical since these reactors are small and can be made in a factory and transported.
• India is proficient in building Pressurized Heavy Water Reactors (PHWR) since this is the original design provided by the Canadians, also called ‘CANDU’ reactors. After the 1974 Pokhran explosion the Canadians withdrew their support, largely under American pressure. Thereafter India has perfected this technology and has upscaled 220MW to 550MW reactors. The relatively higher plutonium content of spent fuel in PHWR reactors has led to proliferation concerns.
• India has designed a new version of Advanced Heavy Water Reactors (AHWRs). These reactors are designed to be fueled by low enriched uranium along with thorium. Ordinary light water reactors are run with low enriched uranium as well; the thorium technology is the extent of the difference. The contaminants that are produced needs to be looked at to see whether it is good for proliferation. For instance, thorium makes Uranium 232, a radioactive substance, that is the sense in which thorium is considered proliferation unfriendly.

Report By:
Tara Sarin, Research Officer, IPCS


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