Saturday, April 16, 2011

The Future Of Nuclear Power And Rooppur

Japan’s nuclear disaster at Fukushima will have a significant impact on the future of nuclear power around the world and possibly on the Rooppur nuclear power project. The nuclear industry got its first major shock after the Three Mile Island accident in 1979 in the US and the second shock in 1986 after a more serious one in the Chernobyl nuclear power plant in the former Soviet Union (now in Ukraine). The industry took lessons from all such accidents, both major and minor, and improved the safety features of nuclear reactors over the last fifty years. True, it was believed that another major nuclear accident after Chernobyl was most unlikely. But it has happened, though the time gap increased from seven years between the first two major accidents to a quarter of a century between the second and the third ones. The only difference is that while the earlier two accidents occurred for manmade reasons, the Japanese disaster was caused by two successive natural calamities, an 8.9- magnitude earthquake followed by a 10 to 14 metre high tsunami, both being unprecedented in recorded history. It is too early to make any meaningful evaluation of the nuclear accident at Japan’s Fukushima nuclear power plant. A full picture of what has happened has yet to emerge. We need to know the exact sequence of events that unfolded at the plant. Every event will be critically and thoroughly analysed to find the reasons and remedies. Moreover, the crisis is not yet over. It is important to observe how the situation progresses and how it is finally resolved. For the time being, our hearts and prayers are with the Japanese people who have been struggling to overcome the aftermaths of three disasters including the one at the nuclear power plant. The workers at the plant site are doing a remarkable job.  Shaken physically and mentally by three consecutive catastrophic events, they are working hard day and night keeping cool in a high-radiation zone taking great personal risks. The plant workers and others engaged in the rescue and rehabilitation operations are the brave sons of Japan. They truly deserve our appreciation and applause.      Out of six boiling water reactors at the Fukushima plant site, units 1 , 2 and 3 were operating at the time of the earthquake. Units 4 , 5 and 6 were shut down earlier for routine maintenance. Unit 4 had its fuel removed from the reactor core. All the reactors had spent fuel pits close to the reactors where used nuclear fuel was being cooled by water for the removal of decay heat generated by the intense radiation within the fuel. Apparently, there was no damage to the nuclear reactors during the earthquake even though the ground acceleration at Fukushima unit 3 was 507 cm/sec. sq compared to the reactor design value of 449 cm/sec. sq. All the three operating reactors shut down automatically as expected and, in absence of any power from the grid, the captive diesel generators started to supply electricity to the emergency cooling systems for the removal of the decay heat from the cores. The emergency generators, however, were knocked out by the tsunami. The cooling systems of the nuclear reactors and the spent fuel pits thus became inoperative. The reactor cores and the spent fuel began to overheat. A mixture of steam and hydrogen produced by the intense heat caused explosions in the reactor buildings in units 1 , 2 and 3.  The high temperature of the spent fuel in unit 4 caused fires in the building. It is believed that the cores of units 1 , 2 and 3 have been damaged badly, probably resulting in partial meltdowns. Offsite power has now been restored to the reactor site and is being used to cool the reactors of units 1 , 2 and 3 by injecting fresh water, instead of seawater pumped earlier. Efforts are being made to restore the reactor cooling systems. Water is being sprayed in spent fuel pits in units 1 to 4. Cooling of spent fuel in units 5 and 6 has been restored. The radiation levels around the site are fluctuating. Areas around the reactor site up to Tokyo have been contaminated. Two leakage paths from unit 2 were detected and later sealed. Huge quantities of contaminated water have accumulated inside the reactor and turbine buildings. Some contaminated water was released to the sea for shortage of storage space resulting in increase of radioactivity of the sea water. Clean-up of the reactors may take years once the core temperatures stabilize. If the recovery of the damaged fuel from the reactors becomes too difficult and risky, the reactors of units 1 to 4 may be entombed like that at Chernobyl. Following the Fukushima disaster, questions are being raised about the future of nuclear power around the world. Germany has temporarily shut down seven of its oldest power plants whose operating lives were extended after expiry of their design lives. This prompt decision is believed to have been taken more on political grounds than on technical reasons, mainly to woo voters at the state elections. The safety aspects of all nuclear power plants in the US are being reviewed. EU countries agreed to carry out assessment of possible damage by earthquakes and other natural calamities on the 143 nuclear power plants located in 14 countries. Spain and Portugal are in favour of gradually phasing out nuclear power, a move opposed by France and Britain. French President Nicolas Sarkozy has called for new international nuclear safety standards during his recent visit to Japan. Russia is also reviewing its nuclear policy. Russia, China and India have significant long-term programmes for the expansion of nuclear power. Opponents of nuclear power are advocating closing down all operating nuclear power plants and not to build new ones. Is this proposition feasible? There are now 442 nuclear power plants with a combined installed capacity of about 375 ,000 MW in operation and 65 nuclear plants with a combined capacity of about 63 ,000 MW are under construction worldwide. In 2009 , the share of electricity generated by nuclear power plants was about 13.5 % of the total generation. The closure of all the nuclear power plants in operation and under- construction will have a tremendous impact on the demand of other sources of energy, mainly oil and coal, raising their prices to prohibitive levels. This will make energy as a whole too expensive and practically unaffordable. As a result, the global economy will be badly affected, perhaps initiating another recession. A greater share of fossil fuels in electricity generation will also increase the concentration of carbon dioxide in the atmosphere, thus accelerating global warming and climate changes.  It may be noted that not many nuclear power plants were closed down after either the Three Mile Island accident or the Chernobyl accident. A few nuclear power plants under construction were abandoned in the States because of the delay in getting construction permits. One nuclear power plant in Austria was never fuelled and started up after completion of construction because of a referendum against it. A few Chernobyl type nuclear reactors in the former Soviet Union had their cores modified for reasons of safety or were phased out. One reactor in the Philippines was mothballed because of design faults. These are only isolated cases of closures for specific reasons. The probability of any large-scale closure of nuclear reactors after the Fukushima disaster should, therefore, be ruled out. It will be difficult to phase out even the reactors which operated for 30 years or more as there are now 173 reactors which fall in this category. Most of the countries with operating nuclear power plants are likely to review their safety features in the light of the Fukushima accident and make necessary modifications. Only the very old ones which do not conform to modern safety standards deserve to be retired. Modern generation-III nuclear power reactors incorporate passive safety features which make the reactors inherently safe. For example, generation-III nuclear reactors can have their emergency core cooling systems in operation without any electricity, the flow of water through the core being governed by gravity and convection. Both gravity and convection flows are natural processes which cannot fail.  The proposed nuclear power plant at Rooppur will be based on generation-III pressurised water reactors with containment buildings like those built in the US and Europe. The containment building can hold any radioactivity that may leak out of the reactor and prevents its leakage into the atmosphere. Modern reactor containment buildings are designed to withstand severe shocks including the impacts of Boeing 747 airplanes. The reactors at Rooppur will be designed to withstand all probable natural calamities like earthquakes, tsunamis (if any), tornados, cyclones, floods, river erosion, etc. The maximum ground acceleration at Rooppur is unlikely to exceed 0.25 g i.e. 245 cm/ sec. sq, which is less than half of that experienced at Fukushima on March 11. Moreover, the design philosophy of the Rooppur plant must also take into consideration whatever lessons we may learn from the Fukushima nuclear accident. There is, therefore, no reason to abandon the Rooppur nuclear power project at this stage. It will, however, be advisable to take a pause and incorporate whatever additional safety features are necessary in the light of the Fukushima experience. The supply contract for Rooppur must have a clause to take advantage of any improvement or innovation in design, particularly on safety systems, that may take place during the tenure of the contract.   Compared to other available alternatives, nuclear power is still the safest and the cleanest form of energy. In terms of fatalities, it has the lowest fatality rate per unit of energy generated compared with other forms of energy. Nuclear reactors produce practically no greenhouse gases. The world is, therefore, likely to depend on nuclear power, like it did during the last fifty years, for generation of electricity for a long time to come even after the Fukushima nuclear disaster.