Saturday 23 July 2011

What we learnt from nuclear catastrophe in Japan.

From: TCG Menon
Date: 13 April 2011 13:51
Subject: What we learnt from nuclear catastrophe in Japan.


Please read the articles given below:- What we learnt from nuclear catastrophe in Japan.
So far a very few Indians have understood the serious implications of this natural calamity which befell Japan. The UPA Govt. is least bothered because they have signed many dangerous nuclear deals with USA and France for untested critical nuclear reactors without taking into account the actual power requirement . Probably UPA will be getting huge amounts from these deals as commission. I was waiting to know what really went wrong in a country like Japan, which has more experience than any other country to tackle radioactive materials . Now I got a report explaining the full details. What happened in Japan is a clear proof that there is a super natural power which controls the universe. I am quoting below some of the important happenings, what went wrong and what are the safety devices which were provided in the plant to meet any eventuality, but all these failed beyond anybody’s imagination. In this scenario where do we stand/? How safe are our reactors, particularly those situated near the seashore? Please read the article given below:-
Attributed To: Dr. Josef Oehmen, MITIn order to control the nuclear chain reaction the reactor operators use so called “moderator rods”. The moderator rods absorb the neutrons and kill the chain reaction instantaneously. A nuclear reactor is built in such a way, that when operating normally, you take out all the moderator rods. The coolant water then takes away the heat (and converts it into steam and electricity) at the same rate as the core produces it. And you have a lot of leeway around the standard operating point of 250°C. The challenge is that after inserting the rods and stopping the chain reaction, the core still keeps producing heat. But a number of intermediate radioactive elements are created by the uranium during its fission process, most notably Cesium and Iodine isotopes, i.e. radioactive versions of these elements that will eventually split up into smaller atoms and not be radioactive anymore. Those elements keep decaying and producing heat. Because they are not regenerated any longer from the uranium (the uranium stopped decaying after the moderator rods were put in), they get less and less, and so the core cools down over a matter of days,
“What happened at Fukushima I will try to summarize the main facts.”
The earthquake that hit Japan was 7 times more powerful than the worst earthquake the nuclear power plant was built for (the Richter scale works logarithmically; the difference between the 8.2 that the plants were built for and the 8.9 that happened is 7 times, not 0.7). So the first hooray for Japanese engineering, everything held up.
When the earthquake hit with 8.9, the nuclear reactors all went into automatic shutdown. Within seconds after the earthquake started, the moderator rods had been inserted into the core and nuclear chain reaction of the uranium stopped. Now, the cooling system has to carry away the residual heat. The residual heat load is about 3% of the heat load under normal operating conditions. The earthquake destroyed the external power supply of the nuclear reactor. That is one of the most serious accidents for a nuclear power plant, and accordingly, a “plant black out” receives a lot of attention when designing backup systems. The power is needed to keep the coolant pumps working. Since the power plant had been shut down, it cannot produce any electricity by itself any more.
Things were going well for an hour. One set of multiple sets of emergency Diesel power generators kicked in and provided the electricity that was needed. Then the Tsunami came, much bigger than people had expected when building the power plant (see above, factor 7). The tsunami took out all multiple sets of backup Diesel generators.
When designing a nuclear power plant, engineers follow a philosophy called “Defense of Depth”. That means that you first build everything to withstand the worst catastrophe you can imagine, and then design the plant in such a way that it can still handle one system failure (that you thought could never happen) after the other. A tsunami taking out all backup power in one swift strike is such a scenario.
The last line of defense is putting everything into the third containment (see above), that will keep everything, whatever the mess, moderator rods in our out, core molten or not, inside the reactor. When the diesel generators were gone, the reactor operators switched to emergency battery power. The batteries were designed as one of the backups to the backups, to provide power for cooling the core for 8 hours. And they did. Within the 8 hours, another power source had to be found and connected to the power plant. The power grid was down due to the earthquake.
The diesel generators were destroyed by the tsunami. So mobile diesel generators were trucked in. This is where things started to go seriously wrong. The external power generators could not be connected to the power plant (the plugs did not fit). So after the batteries ran out, the residual heat could not be carried away any more.
At this point the plant operators begin to follow emergency procedures that are in place for a “loss of cooling event”. It is again a step along the “Depth of Defense” lines. The power to the cooling systems should never have failed completely, but it did, so they “retreat” to the next line of defense. All of this, however shocking it seems to us, is part of the day-to-day training you go through as an operator, right through to managing a core meltdown. It was at this stage that people started to talk about core meltdown. Because at the end of the day, if cooling cannot be restored, the core will eventually melt (after hours or days), and the last line of defense, the core catcher and third containment, would come into play.
But the goal at this stage was to manage the core while it was heating up, and ensure that the first containment (the Zircaloy tubes that contains the nuclear fuel), as well as the second containment (our pressure cooker) remain intact and operational for as long as possible, to give the engineers time to fix the cooling systems. Because cooling the core is such a big deal, the reactor has a number of cooling systems, each in multiple versions (the reactor water cleanup system, the decay heat removal, the reactor core isolating cooling, the standby liquid cooling system, and the emergency core cooling system). Which one failed when or did not fail is not clear at this point in time.
So imagine our pressure cooker on the stove, heat on low, but on. The operators use whatever cooling system capacity they have to get rid of as much heat as possible, but the pressure starts building up. The priority now is to maintain integrity of the first containment (keep temperature of the fuel rods below 2200°C), as well as the second containment, the pressure cooker. In order to maintain integrity of the pressure cooker (the second containment), the pressure has to be released from time to time. Because the ability to do that in an emergency is so important, the reactor has 11 pressure release valves. The operators now started venting steam from time to time to control the pressure. The temperature at this stage was about 550°C. This is when the reports about “radiationleakage” starting coming in.” Inserting moderator rods is tricky. Moderator rods will not be able to insert inside the core in case of any slight misalignment between the core and the moderator rod due to earth quake. But in the case of Japan it is not clear whether the moderator rod was fully inserted inside the core in all the six reactors. Considering that they are still struggling to bring down the reactor temperature, it is quite possible that the moderator rods were not fully inserted inside the cores. It is a well known fact that mechanical equipments get jammed in case of slight misalignment in the device. So they are not at all suitable for earth quake- prone areas.
Now let see what the condition in India .
We have three types of reactors.
1) Light water reactor ( Boiling type reactors) . Here we use enriched Uranium as fuel and light water for cooling.
2) Heavy water reactors use ordinary uranium with heavy water for cooling and as a moderator.
3) One Fast breeder reactor ( FBR) of 500 Mw capacity is under construction with indigenous know- how to use thorium as mixed fuel to produce U 233 from Thorium U232. for our third stage as per the vision of our great nuclear scientist, the late Homi Bhabha. Initially U233 produced from FBR will be used with Thorium U 232 in another reactor for producing electricity. Since no plutonium is generated in a Thorium cycle, the spent fuel is not highly radioactive as in the case of uranium cycle.
“The KAMINI (Kalpakkam Mini) reactor is a Uranium-233 fueled, demineralized light water moderated and cooled, beryllium oxide reflected, low power nuclear research reactor. It is located in the post irradiation examination facility of Radio Metallurgy Laboratory, Indira Gandhi Centre for Atomic Research, Kalpakkam, India. “
People of this country should know that India is far ahead than any other country in the world in Thorium cycle. Only problem is that we have to continue to use heavy water reactors and Fast breeder reactors to get enough U233 to use in the third stage with thorium U232.
Read more: http://wiki.answers.com/Q/Where_is_the_nuclear_reactor_KAMINI_located#ixzz1ItjZnhhDIn the light water reactor and heavy water reactor we have to replace the fuel every two years. We can put new fuel or can recycle the used fuel. Actually we are using about 4% of the fuel in two years . But we have to remove the highly radio -active plutonium while recycling to get full capacity after two years.. Since the plutonium is of weapon grade, countries like USA and Australia are not allowing us to reprocess the spent fuel, as we have not signed the NPT. Storage of the highly radioactive fuel is a very costly and dangerous affair. In Japan, the water entered in to the stored spent fuel and the whole water got contaminated with radioactive material.
The major problem with all these rectors is that there are no devices so far invented to bring down the temperature to prevent core melting in case circulating cooling water system failed after stopping the chain reaction immediately in case of accident. A nuclear reactor is like a pressure cooker. So it is not advisable to increase the number of reactors particularly imported reactors at double the cost of the indigenous one.
In a nuclear reactor the heart of the system is coolants and its proper working. The most unfortunate part in the case of Japan is that all the backup protections failed due to natural calamities.
What is the solution for all these problems?
Some countries including India is trying to develop Accelerator Driven Sub-Critical Systems (ADS) nuclear reactor . In this connection a report is given below:-The best thing should be to develop Accelerator Driven Sub-Critical Systems (ADS) nuclear reactor .Development of Accelerator Driven Sub-Critical Systems (ADS) nuclear reactor is the latest addition to the Indian nuclear programme. ADS can provide a strong technology base for large scale thorium utilisation. As a first step towards realisation of ADS, DAE has launched to development of proton injector. To carry out experimental studies on sub-critical assemblies, a 14 MeV neutron generator has also been upgraded with a higher current ion source.
Norway and Australia are interested to develop ADS as they have large quantity of thorium like India. This is the safest reactor as the chain reaction stops immediately when we switch off proton injecter in the case of Thorium-based nuclear energy. But here also cooling is important after stopping the chain reaction in the reactor to avoid core melt down. Even if there is blow out the material coming out from the reactor is not highly radioactive like uranium reactors. The problem with nuclear reactor is that it is not exposed to natural cooling like conventional boilers or furnaces. So it has to be cooled through circulation of coolants. The complicated process of insertion of moderator rod can be avoided in the case of Accelerator Driven Sub-Critical Systems (ADS) nuclear reactor . We can recycle the fuel as it does not produce weapon - grade plutonium. Slowly we can decommission the existing critical reactors. In this connectio please read the Interview with Professor Egil Lillest- Go
In Norway, there has been a passionate debate about whether the country should convert to nuclear energy or not. Since April last year, Professor Lillest has been on the TV and radio advocating nuclear energy. But not just any form of nuclear energy — his ideas are based on the new technology of thorium, which promises what uranium has never delivered: abundant, safe and clean energy — and a way to burn up old radioactive waste. In addition, there is no by-product that can be used for nuclear bombs — one more reason for developing this technology!
Professor Lillest? l is not a newcomer to the field of nuclear energy. For more than forty years, he has dedicated his life to physics, and in particular nuclear physics, spending his time between the University in Bergen, where he is Professor of Physics, and CERN — the European Organization for Nuclear Research, where he has been the Vice Director for the Physics Department. Professor Lillest?l has also had PhD students from some of the most prestigious universities in Europe, such as the French ?cole politechnique, the ?cole normale sup?rieure and the Coll?ge de France.
We were able to meet him in Geneva where he told us about his commitment and why nuclear energy is be-coming so important. So we leave the floor to Professor Lillest?l …
Let me first give you some background information. Over the last ten years, average energy consumption has increased by more than 3% annually, which would imply that it doubled ever twenty-four years. How-ever, the progonoses are that by the end of the twenty-first century, it will be about four to six times higher than it is today. This is a huge challenge, and very few people are really aware of the seriousness of the problem. I did not invent these figures; everybody can read them in international studies. Unless something is done, we are heading towards huge energy problems in the future. To my mind, there are only two possibilities: nuclear energy and direct conversion of solar heat.
Q: Why should Norway support the building of a nuclear reactor and why should it start work on an international research project on thorium-based nuclear energy?
This is all related to my collaboration with Carlo Rubbia, the 1984 Nobel Prize Laureate in Physics. He was the man behind the idea of an accelerator driven thorium-based nuclear reactor that offers no possibility of a meltdown. His research was so promising that I was sure that the first prototype would soon be built. However, it has never happened due to the different agendas of countries like France, that prefer to replace their existing nuclear power plants with new ones instead of investing in this project. The reason why there has been no action is due to several factors — lack of expertise, lack of funding, etc.
Then this idea came to me that Norway should do it first. First of all, Norway is an important energy nation with advanced technology and with large thorium reserves. It should take special responsibility for the development of such a nuclear reactor. This would, in my mind, be an important Norwegian contribution to preserve the standard of living for future generations.
It is a huge project costing some 550 million Euros, but I am not suggesting that Norway should finance it alone. It should at least guarantee it so that the first proto-type could be built and that we could gather expertise somewhere in order to work on this project for the benefit of the whole world, and not only for one single country. It would not only boost education and expertise in this field in Norway, but also elsewhere.
Q: Is this thorium-based power plant just as efficient as traditional nuclear power stations?
If you burn one kilogram (kg) of thorium, in comparison with today’s use of uranium, you will get 250 times more energy out of it than you would out of the uranium. So, first of all, thorium is far more efficient energy-wise and, secondly, there exists three to four times more thorium in the world than there is uranium — you find it in the United States, Australia, India and Norway. However, if you look for it, important reserves of thorium will be found in many other countries.
CERN’s 1984 Nobel prizewinners Carlo Rubbia (left) and Simon van der Meer © CERN
Q: Talking about nuclear energy, the Chernobyl accident comes to people’s minds.
With the Carlo Rubbia concept, it’s impossible to have the kind of accident that happened in Chernobyl, simply because the reactor will not melt down like it did then. You cannot give that same guarantee in terms of safety for the new nuclear power plants (often called the fourth generation); although I think they will be safer than those constructed earlier.
In addition, by using the Carlo Rubbia concept the problem of nuclear waste will be reduced substantially. Not only will you get less waste, but you will also not obtain the large quantities of plutonium that nations can use for making bombs. Looking at Iran and North Korea, one can wonder whether it is the energy aspect that they were most interested in or the bombs …
What more can we hope? That Professor Lillest?l will succeed in this endeavour and that Norway and other countries will support his battle for this new energy which sounds very appealing…
The new generation of nuclear power plants must have solutions for all of these problems and Accelerator Driven subcritical reactors provide such solutions.



Accelerator Driven Sub-critical Nuclear Reactors for Safe Energy Production and Nuclear Waste Incineration[1]
S.R. Hashemi-Nezhad[2]
School of Physics, A28, University of Sydney, NSW 2006, Australia

Solution to the nuclear safety issue
An ADS will operate under sub-critical conditions (e.g , keff = 0.95-0.98) and the operation of the reactor is directly linked to the operation of the attached accelerator which provides a high energy ion beam to produce spallation neutrons. These neutrons keep the ADS operational i.e. the system remains operational as long as the accelerator functions. The proton beam plays the role of the control bars in the current reactor, with the difference that if it fails, the fission reaction in the system dies out and it can never lead to overheating.
There are many ways to shutdown an accelerator (an electric device) or divert its beam away from the sub-critical reactor core.
Two major nuclear accidents (the Three Mile Island and the Chernobyl) both caused by critical power excursions.
Moreover an ADS fuelled with thorium does not contain 238U and therefore will not breed 239Pu which can be diverted to military applications. In a thorium fuelled ADS the approximate uranium isotope mixture in the subcritical core after an integrated neutron exposure of 3´1022 cm-2 will be[11]; 233U (44%), 234U (30%), 235U (4%), 236U (22%) and 238U (negligible). A very difficult and extremely intensive isotope separation is required to separate “weapon grade” 233U from this type of mixture.
3.3 "Thorium Furnaces"
Our group believes that Australia can become technically and commercially involved in a future commerce in modular ADS/Thorium reactors for both power generation alone in "greenfield" sites and for high level nuclear waste disposal at "brownfield sites" - those existing power stations where demand dictates increased capacity but where accumulating waste is a problem. We believe that Australians can certainly develop and construct the high flux accelerator component. We are negotiating to form a strategic alliance with an experienced European reactor constructor to assist with the reactor component.
The modules are envisaged to be in the 100 megawatt - 1 gigawatt range of output. We call them Thorium furnaces.
The selling points are simple: these units will provide clean, green and safe power, free of any proliferation risks, for any community for the foreseeable future.
We place this vision within about 20 year’s time frame.Basic principles of the ADS operation
The basic principles of the operation of ADS are shown in Fig.5. When this pictorial representation of the ADS is compared with that of the conventional thermal reactors it becomes obvious that the design of a subcritical nuclear reactor will not be dramatically different from that of the conventional reactor. This by itself is an advantage because over 60 years of experience with nuclear reactors can and will be an asset and foundation in design and operation of this new generation of reactors. However major effort must be put to the design of accelerator, beam window, spallation target and fuel rods. Also the type of material that can be used in an ADS must be radiation resistant and can handle large exposure to high energy nuclear particles.

An ADS like any other reactor has a core which in this case has fuel elements made of pellets composed of mixed oxides (MOX) of 232ThO2 and 233UO2 enclosed in an appropriate cladding. The initial amount of the 233U in the rods is for startup purposes, during the ADS operation the consumed 233U will be replaced by 233U bred from 232Th according to the reaction (2). The core and ADS as whole designed in a way that keff < 1. The spallation target is positioned between the fuel rods in the core. The beam of protons from a high-power accelerator is directed towards the spallation target (e.g. lead) to produce spallation neutrons and thus sustain the chain reaction in the system. The reactor core and target are embedded within an environment that acts as neutron and heat storage medium as well as the neutron moderator. We will refer to this medium as M-medium. The type of the material that can be used for M-medium depends on the type of the ADS whether it is a fast or thermal ADS and it must be compatible with the type of the material used for cladding. For fast ADS it is proposed to use the lead as both target and M-medium[16]. In such a case the M-medium will be molten lead.

If material of the M-medium is different from that of the target then target must be enclosed in a leak proof container made of a substance that is corrosive resistant and has high thermal conductivity and high melting point. Tungsten can be a good candidate for this purpose. As most of the energy deposition by the beam happens within the first 20 cm of the target length and considering the beam power of more than 10 MW such a target-system must rapidly dissipate the absorbed heat to the surrounding medium.
The ADS control unit can be equipped with temperature, neutron and other sensors, which will send electronic signals to the accelerator if reading level(s) exceed desired limit, triggering beam abort away from the core. Extra redundant safety units such as those used in conventional reactors can also be added for further safety.

Fig. 5. An Accelerator Driven System equipped with a long-lived fission product transmutation (incineration) facility. A high power proton accelerator is coupled to the subcritical assembly producing spallation neutrons in the lead target which sustain the chain reaction in the core. The fuel rods are made of mixed oxides of thorium and U-233 (or plutonium and minor actinides from the nuclear waste of the conventional reactors). M-material in the diagram referrers to the environment that acts as neutron and heat storage medium as well as neutron moderator.

The heat produced by the fission of the fissile material in the core is stored in the M-medium from which it is transferred to the heat exchangers and electricity generating units in conventional manner.

Inside the reactor vessel and in the vicinity of the core we have placed a fission product transmutation container (FPTC). This is used to consume the available excess neutrons in the system for transmutation of the long-lived fission product isotopes such as 129I and 99Tc. The FPTC is accessible from the outside of the main reactor vessel for loading and discharging the waste in liquid phase.

To exploit all the capabilities of the ADS, its fuel must follow a closed cycle. That is the spent fuel must be processed and partitioned according to the best available methods and technologies. Fig. 6 shows different stages of the closed ADS fuel cycles. After initial cooling stage of the spent fuel, the fissile materials and unused thorium in the spent fuel are separated and are used in new fuel rod fabrication. The long-lived and transmutable fission products are separated for injection into the FPTC. The final un-transmutable wastes are sent to an appropriate waste storage facility where they will be kept for a period of about 500 years. Today’s technology allows us to be confident that such a waste storage will be safe and environmentally harmless.

Obviously the nuclear waste that can be used as fuel and transmutation material is not limited to the waste produced by the ADS itself. In the fabrication of the ADS fuel rods the waste from the conventional critical reactors can be and will be used as well. This provides the long awaited solution for the public concern on the stockpiles of the nuclear waste produced over the last 60 years of operation of nuclear reactors. Fig. 6. A closed fuel cycle for ADS. The MOX fuel refers to the one that is made of mixed oxides of the fissile materials.

Some predictions for future electricity generation in Australia

The electricity generation from fossil fuels, especially coal, will continue for many years although in an improved and more environmentally friendly manner. Due to the massive world demand for energy, the export of the coal and natural gas will not be reduced as a result of installations of the nuclear power plants in Australia and other parts of the world for several decades to come.

Activities in R&D and eventually production of energy from renewable sources will continue and even may accelerate.

For immediate economical, environmental and geopolitical reasons it is not difficult to predict that Australia’s initial involvement in the field of nuclear energy will be in terms of conventional generation three thermal nuclear reactors. Alongside of which uranium enrichment and fuel processing plants will be established. However it will not be possible to avoid ADS technology because of the fact that this type of nuclear system provides the only known and logical method for handling, managing and eliminating the dangerous and environmentally harmful nuclear waste. Australia’s future nuclear power plants beyond those that may be installed after the conclusion of the current nuclear debate will be ADS technology because of the massive thorium recourses of Australia, the safety of these reactors and the cleanness of energy production by the ADS method.

It must be mentioned that involvement in ADS research and development and eventually installations of thorium based Accelerator Driven Systems in Australia will not affect the uranium export. This is due to the number of existing commercial uranium burning nuclear reactors in world (441) and those that are under construction (~15) and those that will be constructed in the future (including those in Australia). The demand for uranium in the world market not only will not decrease but it is expected to increase as fossil fuels become scarcer and willingness for their massive use diminishes.

The impact of the ADS technology to the Australian economy is enormous. Calculations show that if the known thorium resources of Australia (300,000 tonnes) are burnt in accelerator driven sub-critical reactors, it will provide an energy equivalent of 4.31012 barrels of oil. This amount is equivalent to 5800 years of oil export, at a rate of 2 million barrels per day (similar to that of a major oil producing country in the Persian Gulf) or an income of ~ AUS$70109 (US$52109) per year for 5800 years at today’s oil price.
Accelerator driven subcritical nuclear reactors besides producing clean and cheap energy, provide a unique solution for the elimination of plutonium, minor actinides and long-lived fission products in conventional nuclear reactor waste as well as the plutonium from warheads: one of mankind’s unnecessary, unwise, self-destructive, cruel and crude technical achievements, for a peaceful and environmentally clean Earth.

Accelerator driven nuclear reactors can be developed with in 20 years. So what is the point in planning our energy requirement for coming 5o years and procuring unsafe reactors from France and USA at this stag? Instead of spending billions of dollars on these reactors we should spend that money for the development of Accelerator driven subcritical nuclear reactors. I am sure our engineers and scientist are capable of doing it, provided the Govt. gives full support and facility for the purpose. If required we should go in for a joint venture with Norway or Russia like we developed supersonic cruise missiles Brahmos with Russia

Tcg

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