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Is it worth to build nuclear power plants in Poland in the light of events in Japan?

Published on June 28, 2011 by: in: Society

Poland has good reasons to build nuclear power plants. They existed before the earthquake in Japan – and the still exist. However, considering the failure of the Fukushima nuclear power plant and the concern of people about the possible consequences it is better to first understand what really happened in Japan – and whether it could happen here. Only then – if it turns out that there is no reason to fear – we may calmly consider whether it is worth to build nuclear plants in Poland.

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What happened in Fukushima?

There is no such devices in the world which would endure everything – and nuclear reactors are no exception. Although they went a long way to evolve and improve, they are resistant to many risks caused by equipment failures, human errors and natural disasters, it still depends on a man, who sets out the design assumptions, what  earthquakes, floods and plane hit can withstand a nuclear power plant.

Requirements for the construction of reactor grow with each decade, not only as a result of the conclusions to draw from the failures that have already occurred or might have occurred, but also through analysis and research operated by the reactor industry so that the accident should not happen. Reactors of III generation already built in Finland, France and China are carefully designed to be proof to such disasters as earthquakes and tsunamis in the region of Fukushima.

We might expect that the reactors built in Japan should be able to withstand an earthquake. After all, Japan is on the “Ring of Fire” surrounding the entire Pacific Ocean and earthquakes often come about there. But reactors in Fukushima were designed long ago – the first one in 1965 – when the safety requirements and technical capabilities were significantly lower than the present ones. When designing, an earthquake was taken into account- but no one has provided for such a massive tsunami.

When projecting the cooling systems in Fukushima, an earthquake was taken into consideration. Therefore, reactors in Fukushima, like others reactors in Japan, survived the earthquake without damage. Even though it was the strongest one recorded in the history of this country and the liberated energy was so huge that it caused a shift of the main island of Japan by 2.4 meters.

At a time when the upheavals were going on, the reactors shut down- as they should have done- and the heat generation due to fission reaction ceased. The fuel emitted only the heat called “afterheat” generated by the emission of radiation caused by the decay of fission products, such as gamma or beta rays, released by the collapse of the iodine and krypton. The intensity of the heat two hours after the reactor’s turn off is about 1% of full power before shutting down of the reactor. Not so much, but for a reactor with a capacity of 3000 thermal MW it is still 30 MW. For reception of afterheat there are used special cooling systems – in Fukushima they turned on properly and for nearly an hour after the earthquake they successfully absorbed heat from the reactor. Fuel cooled down and the heat received from the reactor was taken over by water flowing in systems of pipes and pumps out a nuclear power plant. Although as a result of the earthquake the power grid of Japan run out and the power plant could not receive power supply from the outside, the cooling systems kept working effectively, because the plant had its own emergency power sources. But one hour later the tsunami attacked…

The plant engineers during its construction got from experts at hydrology and seismology clear guidelines, against which phenomena they should protect the plant. In accordance with the principles of defence in depth, they designed the plant so strong that it endured the biggest earthquake in the Japanese history. Unfortunately, the tsunami went beyond all expectations. The wall protecting the plant before the tsunami was 6.5 meters high while tsunami was taller, about 10 – 12 meters. A cascading water shaft poured over the preserving wall and destroyed everything that was not protected by the reactor containment. Unfortunately, pumps and pipelines connecting the cooling systems in reactors with cooling pools outside the reactors were not protected by powerful shields as reactors are. Also diesel engines were not sufficiently protected – tsunami blow caused flooding and damage, the plant remained without power, water and energy. Tsunami blow at the buildings where emergency power generators worked, resulted in inundation of fuel tanks. The attempts to connect the small diesel engines, which could be brought to power plant, turned out ineffective – the electric power could not be restored.

Although the level of afterheat decreased with every hour, it was still significant – after 24 hours off the power of the reactor No. 2 it was about 0.5% of full capacity, which is about 12 thermal MW. Meanwhile, there was no possibility that the heat transferred from a core to water tanks could have been picked out of the reactor. The water in the tanks was heating up until it reached saturation level and began to evaporate. Then, the water above the reactor core evaporated as well (Fig. 1). Water table subsided, the upper parts of the fuel revealed and overheated . The surface temperature of the fuel has reached 1000 ° C and continued to increase. At high temperatures the chemical reaction occurs causing the exhalation of hydrogen – as it was the case in Fukushima- and when the operators have decided to lower the pressure in the reactor and released the water vapour, hydrogen escaped with the steam into the air and exploded. This resulted in breakage of the reactor buildings and the outflow of radioactive substances. Thus the reactors in Fukushima defended themselves by several hours, due to lack of electricity and cooling water they have been eventually damaged.

Radiological consequences of failure – contrary to alarmist media reports – are insignificant. No one was killed by radiation, nor among the plant staff, nor among the population. In Fukushima plant three workers were killed by the earthquake and tsunami. However, it was not due to radiation, but the injuries caused by ground shocks. It should be strongly emphasized, because the earthquake and tsunami in Japan caused huge losses – more than
10 000 deaths and over 15,000 missing persons. The failure of the one of many Japanese nuclear power plants, even bringing about temporary evacuation of the population and loss of power, is much smaller loss for the society than thousands of deaths. We should keep it in mind, because when we read about the thousands of victims in Japan, it seems that the radiation provoked these victims. Don’t make ourselves intimidated – the destruction of Japan and thousands of victims are engendered by earthquake and tsunami, not by failure in Fukushima.

Are we threatened by the similar failure as the one in Fukushima?

Poland is not exposed to important earthquakes or tsunamis. Hurricanes and the rainfalls are not likely to threaten power plants of III generation. The accident in Fukushima will trigger
a series of safety analysis of currently operating reactors and those being designed or under construction all around the world. It is expected that the required margins of safety against natural disasters will increase. Resistance requirements to severe failures will be confirmed, in particular with regard to the control of risks associated with hydrogen explosions and the provision of an additional line of defence in depth in the form of extra sources of electrical power apart from an external network and emergency diesel generators. Guidelines for action in case of serious accidents will be reviewed and power plants will furnish appropriate supplements to ensure that the operator can effectively implement these guidelines. It can be foreseen that the oldest reactors will have to make significant improvements or will be turned off and the new ones will be constructed in their place. However, in relation to the reactors
of III generation we should not expect any significant changes.

According to current knowledge, the reactors of III generation are insusceptible to threats, even such great as in Japan. For example, the EPR reactor offers the following safety features:

  • resistance to the earthquake – the standard 0.3 g, may be extended;
  • resistance not only to the tsunami- to the terrorist attack as well;
  • control of hydrogen concentration by means of passive autocatalytic systems recombining hydrogen and oxygen;
  • a powerful security cabinet which covers the whole reactor, as well as placing the safety systems and emergency power supply in the massive bunkers able to withstand not only tsunamis, but also plane hit.

AP1000 and ESBWR reactors can operate without electrical power. The EPR power is autonomously ensured and resistant to catastrophes. Reactors of III generation were designed before the failure in Japan. But the conclusions driven from previous failures were enough to make them immune to threats, such as in Japan.

So should we build nuclear power plants in Poland or not?

We want to build nuclear power plants, because we have to diversify our energy sources. We cannot just continue to use coal. Moreover, the renewable energy sources are still very expensive and work with interruptions and we cannot rely on their energy supply when needed. Nuclear energy produces clean electricity without air or water harmful emissions and is cheap, which is important for each country (especially for Poland where the life is still much harder than in the countries of the former European Union). The amount of electricity used by the average Polish citizen is more than twice lower than the average energy consumption in the countries of the former EU. Only three countries in the nowadays European Union use less electricity than we do: Romania, Latvia and Lithuania. If we want to join the economically powerful countries in the European Union we need more energy. And its clean and cheap source is nuclear power.

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About Andrzej Strupczewski

Vice-president of Ecologists for Nuclear Energy Association.

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