Online Survey Result on Nuclear Energy

Here are the results that we obtained from online survey that we have posted on November 28, 2011. This is important in bringing public awareness and opinion on builds nuclear power plant in Malaysia. It will help government to make decision to build or abort their plan to generate electricity using nuclear energy.
Click on the image to zoom in.

                      

The survey has 109 respondent which concentrate on young generation (17-30). The nuclear power plant is plan to be start operate in 2025*. Hence, the young generation now will run the operation and maintenance of the nuclear power plant in the future.

*Source: TNB,Nuclear Roadmap For Malaysia, 2009

For question 1 in the survey, it shows that most of the respondent (52%) agree to use nuclear energy to generate electricity in Malaysia. While 33% against the plan and 15% is neutral about it.

For question 2, majority (32%) of the respondent choose continues energy supply to generate electricity as the reason for them to support nuclear energy. Beside that, the reason for other respondents choose to support is to reduce carbon emission (22%), to keep tariff electric low (16%) and other reason (6%). Yet there are still 24% didn't support it.

                      

For question 3, it can be seen that most people are concern about the nuclear safety. This is because if an accident happened at a nuclear power plant, it can affect in a huge area. This area could be known as "black area" because no one could be living there anymore. An example of this situation can be seen at Chernobyl, Ukraine. Till then, there is no human being live in that area.

For question 4, it shown that people are willing to pay up to 5% tariff. Not many people are willing to pay 10% tariff because they might think it is too expensive to spend on renewable energy.This is why nuclear could be considered as one of the main source energy energy due to the energy that it could be generated.It can be consider low in cost because nuclear can generate huge amount of energy with a small amount of uranium and the power plant does not need a huge area of land.

For question 5,  this bar chart shows that the source of energy that most people prefer is solar. second is the hydro and next is wind and nuclear. From this chart, we can conclude that most people may not know the advantages of nuclear energy. They probably just know that nuclear is dangerous to be used.Therefore, we need to make sure that everyone out there realize that nuclear should become one of the main source of energy due to its benefits in using them as energy source.

For question 6 the response from the respondents to give comment regarding nuclear power are encouraging. There are few good comment that support and against nuclear power. Below are some of the comment:

"I don't think Malaysia is a suitable place to build a nuclear power plant. We have lots of other resources that we can rely on. Why we want to danger our citizens with a power plant that can give a destruction to our community. Nice survey. "

"I would say that I'm very much into it.
But then as stated above, it's about the safety that I'm being very concerned about.

"Thus, if the nuclear plant that are going to be build in Malaysia could meet  all the strict precautionary measures provided by the trusted non-profitable body, then I would be the first person to support the plan. However, realizing the gravity of the problem that could arise from the plan; to build the nuclear power plant, I would suggest the government to wait for several more years until they are REALLY sure that they can handle any probable problem that could happen in the future. "

"It is good. But safety must always be the main priority. Also the main concern is the waste. Proper knowledge on how to dump the waste is important."

"Malaysia has continuous sunshine with long daytime too.Not forgetting the rich plantation and farming all around malaysia. so,solar n biomass first please!"

As conclusion, from the survey people are aware on nuclear power generation. But to convince people to support nuclear power is not an easy task. There are more things that need to be done in order to get people to go for nuclear!

Process of uranium mining is not green? (Fan mail question)

Hiya all~ It is a very strange and awkward day as for once we actually have fan mail…

Anyway, I digress.

Recently a Nuclear Edition reader stated a very interesting fact, that the process of uranium mining is not green! While thinking about it, it does really ring a bell. Although the nuclear plant operation might be green, the process in which to produce it might not be environment friendly!

So we take a little online detour to the uranium mine hunt. Uranium is typically mined from the earth crust, 

where there could be ‘open pit’ mining, underground mining and in-situ leeching.

The open pit mining method is done for deposits that are located close to the surface of the earth crust, of about 100m. How the open pit works is it require large holes on the surface, larger than the size of the deposits because the walls of the pit must be sloped for structural integrity. The walls will collapse if not sloped. 

 An open mine

For underground mining, this method is for deposits that are over 100m below the surface. Tunnels will be bored down and ore is raised to the surface in carts. This method is potentially dangerous for miners and requires powerful ventilation systems, use of respirators and there’s limited amount of time that can be spent underground.

 Photo of a worker in a deep mine

Finally about in-situ leaching, this method is non-invasive and claimed to be environmentally friendly. This method extracts uranium by pumping weak acid underground to dissolve ore deposits and pumping the deposits to the surface.

 Diagram of in-situ leaching

Mining has always had huge impacts on the environment where massive craters are formed and these places would then be barren of life once mining operations are completed. Even in in-situ leaching, there is the risk of the acid to contaminate underground water sources.

So, is nuclear energy really clean?In fact, a lot of policies and regulations are imposed in any mining activity, uranium mining included. The mining activities even require external audits. There is no question that mining will have adverse effects on the environment but it seems as if it is a necessary to sacrifice a little to gain a lot.

Link:
http://www.themoreyoudig.com/?p=1731
http://www.indiatalkies.com/2011/05/meghalaya-dithers-uranium-mining.html
http://www.bloomberg.com/news/2010-12-01/uranium-miner-fights-floods-skepticism-as-stockpile-dwindles.html

Deepak Chopra and nuclear experts gather

Deepak Chopra and Nuclear experts gather to talk about shutting down Indian Point

Deepak at Homebase: Nuclear cautions & parallels

Fukushima & Indian Point

Friday, April 15,2011, 6-8pm NYC

Where: Deepak Homebase on the Mezzanine, 888 Broadway at East 19th Street.

The conversation with Deepak Chopra

Arnold Gundersen, nuclear engineer, Vermont Yankee expert witness; Harvery Wasserman, journalist, one of the first to cover the Fukushima Leak; Paul Gallay, Riverkeeper ED, working to permanently shut down Indian Point; and Duane Peterson, progressive political campaigner and non-profit environmental activist.

From: http://deepakchopra.com/engage/events

Fun Facts #5

Did you know?

On December 2, 2011 is the 69th years anniversary of nuclear energy. Back in 1942 at this date, Enrico Fermi, Leo Szilard and their colleagues successfully achieved the first man made and controlled nuclear chain reaction. More interesting it was made in squash court of University of Chicago's Stagg Field.

Fermi also play major role in establishing the American Nuclear Society (ANS) in December 11, 1954.

Also on December 2, 1957, the first full scale commercial nuclear power plant in the world went full power in Shippingport, Pennsylvania.

A 1957 view of the Shipping port of Atomic Power Station

Talk by Michihiro Furusaka, 8th December 2011, UNITEN

On the said date, we were blessed to have a very renowned professor, Mr Michihiro Furusaka, to present to us his present work. Mr Michihiro is professor from the Graduate School of Engineering at Hokkaido University, with involvements in various engineering fields, especially with regards to quantum engineering and neutrons.

Professor Michihiro Furusaka

Mr Michi presented to us about his involvement in neutron acceleration and neutron scattering. Allow me to explain a little bit about neutron scattering. According to Wiki, neutron scattering is a physical process and experimental technique to investigate materials, in which is very important in nuclear engineering. 

In Mr Michi's presentation, nuclear scattering devices are normally very large. Mr Michi has himself invented a compact neutron scattering device. This device uses lenses to focus the neutron beams. This technique saves space and allows the experimentation of wide neutron scattering. Compared to large neutron scattering devices, since the instruments are very long, it is very difficult to detect wide neutron scattering (it would require a VERY large sensor area to detect the wide scatters). The compact device solves the problem by being in itself, compact! It minimises the sensor area to detect the neutron scattering. As Mr Michi would say, Japanese loves compact things.

Mr Michi is also very involved in nuclear therapy. He gave us an interesting introduction to the subject with the beginning of x-rays, which lead to a very profound advance in radio-therapy. Examples are the use of 3D imagine in CT scans and in cancer imaging. It has had a very huge impact on medical sciences to date.

 An Example of CT Scan

Further presentation touched on the hair! Unfortunately, as time was short, I myself did not really understand about the purpose of hair research. However, what was found that hair itself, has 2 parts, the living part and the dead part. The living part, in the follicle, is the main source of the hair, producing keratin, the main component of hair. This protein, keratin, will 'die' when too much of it is produced, thus creating hair.

This research has led to scientists to be able to distinguish the shape of cells near the human brain. With such identification, this has been hugely applied in Parkinson's disease research. It seems that the shape of proper healthy cells is much different from cells that are afflicted with the disease. With this breakthrough, it could be possible to isolate these deiseased cells for treatment.

And so ends the short lecture from Mr Michi! It was a very informative presentation, covering a very wide range of topics. Hopefully, UNITEN would be able to organise more talks and to properly conduct it in such a way that befits and properly honours it.

Links:

http://www.nlm.nih.gov/medlineplus/ency/imagepages/19237.htm

Nuclear Power VS Fossil Fuel (Part 2)

What is nuclear energy? How it generates power?

Nuclear energy is the energy stored in the nucleus of an atom. The energy originates from the splitting of uranium atoms in a process called fission. At the power plant, the fission process is used to generate heat for producing steam, which is used by a turbine to generate electricity. Nuclear energy is cleaner while generating electricity. Nuclear fission provides energy without releasing greenhouse gases such as carbon dioxide. Since nuclear power plants use so little fuel, the volume of nuclear waste is much smaller  the volume of waste from fossil fuel power plants.  Eventhough nuclear waste is highly radioactive, its small volume enables safe isolation from society. 

What is the disadvantage of using Nuclear Energy?

• Nuclear power has some disadvantages worthy of attention: Nuclear power plants have dangerously high radioactive levels.  The radioactivity is entirely contained within the plant, but the possibility exists that some of it might leak to the outside environment during an accident.  Over time, new designs, stricter regulations and better  technology are reducing the risk of radioactive leaks
• Waste produced by the power plant must be disposed somewhere, but it remains intensely  radioactive for long periods of time.  Therefore, nuclear waste must be permanently isolated from society in special facilities.  Building suitable facilities requires a lot of time and money to ensure complete isolation
• New nuclear power plant designs take a long time to implement.  This time delay is due to multiple regulatory agencies and boards of approval that the nuclear industry must satisfy
• At the end of their lifetimes, usually about 40 years of operation, nuclear power plants must be decommissioned.  Plant materials remain fairly radioactive for many years after operation has ceased, so disassembly cannot occur until the levels return to a safe range.  This waiting period usually takes about 20 years
• Anti-nuclear activists believe that the nuclear industry greatly increases the chance of plutonium theft.  Conceivably, terrorists could steal stores of plutonium and attempt to make a nuclear weapon.  To deter such an endeavor, plutonium is weighed before and after shipment.  Furthermore, constructing a nuclear weapon requires extreme expertise.  Still, the possibility does exist.

These disadvantages include some serious issues that cannot be ignored.  Equally important, though, are the advantages that nuclear power offers.  Unlike some of the disadvantages, the positive aspects of nuclear power are based upon facts rather than slim probabilities. 

What is the major advantage of using Nuclear Energy?

• Nuclear power plants emit far fewer atmospheric pollutants than the competition.  They do not emit any sodium dioxide, nitrogen oxide or dust from burning fuel.
• Nuclear power plants do not emit any carbon dioxide, the gas widely believed to be the  primary contributor to the greenhouse effect.  The greenhouse effect, of course, causes global warming.  In the United States, coal-fired power plants release approximately 2 billion tons of carbon dioxide each year.  However, the limit and even the existence of global warming is still the subject of much debate.
• Nuclear power plants only need refueling once every year to 18 months.  The new store of fuel constitutes about 2 metric tons, or 6 truckloads of uranium.  Coal power plants require a new trainload of about 100 tons of coal every day
• According to PBS Online, US nuclear power is not responsible for any deaths in its entire history. Due to mining accidents and respiratory complications, over 30 thousand deaths have been attributed to US coal mining since the 1930's
• Since nuclear power plants use so little fuel, the volume of nuclear waste is much smaller than the volume of waste from fossil fuel power plants.  Even though nuclear waste is highly radioactive, its small volume enables safe isolation from society
• Nuclear power is economically competitive with coal, and generally considered much cheaper than oil or natural gas.  In one joint study by several agencies and independent groups, 11 out of 19 counties found nuclear power to be at least 10% cheaper than coal- fired power.  7 more of the countries found the prices to be nearly equivalent

Source: http://128.143.168.25/classes/200R/Projects/Fall_1997/NuclearPower

Nuclear Power VS Fossil Fuel (Part 1)

This post will explain briefly the advantages and disadvantages of fossil fuel as the main current energy source today and nuclear power as the potential alternative energy in the future.

What is Fossil Fuel? How it generates power?

Fossil fuels are hydrocarbons that are formed from the remains of dead plants and animals. Examples of fossil fuels are coal, fuel oil and natural gas. Fossil fuels, primarily coal are by far the largest source of electricity in the world today. In fossil fuel power plant, power generated from burning the fossil fuel to generate heat, and then the heat will be used to generate steam. This steam drives turbines, which powers generators to convert mechanical energy to electrical energy.

What is the advantage of using Fossil Fuel?

A major advantage of fossil fuels is their capacity to generate huge amounts of electricity in just a single location.

• Fossil fuels are very easy to find. 
• When coal is used in power plants, they are very cost effective. Coal is also in abundant supply. 
• Transporting oil and gas to the power stations can be made through the use of pipes making it an easy task. 
• Power plants that utilize gas are very efficient. 
• Power stations that make use of fossil fuel can be constructed in almost any location. This is possible as long as large quantities of fuel can be easily brought to the power plants. 

What are the disadvantages of using Fossil Fuels?

• Pollution is a major disadvantage of fossil fuels. This is because they give off carbon dioxide when burned thereby causing a greenhouse effect. This is also the main contributory factor to the global warming experienced by the earth today.
• Coal also produces carbon dioxide when burned compared to burning oil or gas. Additionally, it gives off sulphur dioxide, a kind of gas that creates acid rain.
• Environmentally, the mining of coal results in the destruction of wide areas of land. Mining this fossil fuel is also difficult and may endanger the lives of miners. Coal mining is considered one of the most dangerous jobs in the world.
• Power stations that utilize coal need large amounts of fuel. In other words, they not only need truckloads but trainloads of coal on a regular basis to continue operating and generating electricity. This only means that coal-fired power plants should have reserves of coal in a large area near the plant’s location.
• Use of natural gas can cause unpleasant odors and some problems especially with transportation.
• Use of crude oil causes pollution and poses environmental hazards such as oil spills when oil tankers, for instance, experience leaks or drown deep under the sea. Crude oil contains toxic chemicals which cause air pollutants when combusted. 
• Fossil fuel sources are gradually depleting, thus it might lead to shortage of energy in the future.

Source/Reference: http://www.ecology.com, http://thegreenstep.com

Nuclear Energy: Misunderstood Power Source

Nuclear energy is one of the potential power source that is clean,safe and efficient. But, people always misunderstood about nuclear energy, saying it is unsafe and not clean. The video above explained about the misconception in nuclear power and the advantages by using nuclear power as an alternative to replace fossil fuel.

Radioactive Water Leakage from Fukushima Dai-Ichi

Dec 5 - As much as 45,000 liters (11,870 gallons) of highly radioactive water leaked from Japan's crippled Fukushima nuclear station at the weekend and some may have reached the sea, Tokyo Electric Power Co. said.

Tepco said the leaked water contained 16,000 becquerels and 29,000 becquerels per liter of radioactive cesium 134 and 137 respectively. Those levels exceed government safety limits by 267 and 322 times, according to Bloomberg calculations.

The study by the French government-funded Institute for Radiological Protection and Nuclear Safety said radioactive cesium that flowed into the sea from the Fukushima Dai-Ichi nuclear plant was 20 times the amount estimated by Tepco.

Prolonged exposure to high levels of radiation can cause leukemia and other forms of cancer, according to the World Nuclear Association.

As a student in an Intro. to Nuclear Tech. class, the one thing that I can be sure to hear about every lecture is Safety. Safety system that, safety procedure this. It is definitely disheartening to read about this incident, especially so short after the Fukushima accident. There are so many safety features implemented in nuclear reactors that perhaps people are overlooking about what to do after an accident. This incident will not only damage the environment (no more fresh sushi) but it will also damage the reputation of nuclear energy in Malaysia, at least what ever is left of it.

Source: BusinessWeek

Nuclear Power Plant Safety | Tomorrow Today

Many countries are relying on nuclear power as a vital part of their energy mix. At least 60 new nuclear power stations are being built or planned world-wide. The disaster in Japan has raised awareness of the risks posed by the technology. The situation shows that even today, after decades of operation atomic power plants, unforeseen events can cause problems that have not been anticipated in safety plans. Scientists at the Institute of Energy and Climate Research in Julich have long been exploring the issues surrounding nuclear safety. One thing they have done is simulate the synthesis of hydrogen within reactors. It is a risk that became a reality at the Fukushima power plant.

Fukushima Nuclear Reactor Problem Explained

This is the explanation video about the chain of events which have caused nuclear reactor

problems in Fukushima Nuclear Power Plant in Japan. These problems were caused by

earthquake and following tsunami near to Sendai town in north-east of Tokyo.

The History of Nuclear Energy - First Nuclear Accident

Previously we have covered a number of topics regarding nuclear energy's first milestones, including the building of the first civilian nuclear reactor, the Obninsk Reactor. Today, the Nuclear Edition will cover a slightly bleaker topic, the first civilian nuclear reactor accident.

Chalk River Nuclear Laboratories

Chalk River Laboratories (CRL), formerly known as Chalk River Nuclear Laboratories (CRNL), is a Canadian nuclear research facility about 180 km north west of Ottawa in the province of Ontario. This site is a major research and development site for CANDU reactor technology, now widely used in Canada.

On 12 December 1952, a reactor shutoff rod failure, combined with operator errors, led to a major power excursion of more than double the reactor's rated output. The operators purged the reactor's moderator (heavy water), and the reaction halted in under 30 seconds. A cover gas system failure led to hydrogen explosions, damaging the reactor core. As a result, 30 kg of uranium were released, with irradiated water coolant leaking into the reactor building. Fortunately, this accident caused no immediate fatalities or injuries, and none of the exposed workers showed long term health effects.

This incident, while not disastrously fatal, may have lead some people to dismissing nuclear energy as a feasible source of energy due to the risks involved. Some may even go so far as to say, if the Chalk River Nuclear Laboratories were not built in the first place, no accident would have happened. I of course agree with that statement. However, advancements come with risks and sacrifices. Surely there were accidents when fire was first used. People have died in coal mines. Offshore oil platforms are not the safest place in the world either. 100 years in the future, no one would even think about dismissing nuclear energy, because it is the only viable source of clean and sustainable energy our planet has right now.

Future 39th US President Jimmy Carter, then a Lieutenant in the US Navy, was among the cleanup crew.


Source: www.wikipedia.org

Top 10 Countries using Nuclear Power

Nowadays, nuclear energy has contributes a lot on generating power to meet the demands that is increasing each year. Although nuclear energy has created more fears to the public since Fukushima incident yet more nuclear power plant is expected to operate in the future. Nuclear energy may become an option to Malaysia and other countries which reach in energy resources. Some of countries may have nuclear energy as main power generating due to lack of energy resources. Below is the countries which highly depends on nuclear energy to generate power.

10. Hungary (37%)

9. Switzerland (39%)

8. Armenia (40%)

7. Slovenia (41%)

6. Sweden (42%)

5. Ukraine (47%)

4. Belgium (54%)
3. Slovakia (56%)

2. Lithuania (72%)

1. France (76%)

17 posts later....and Video Games!

Hiya! It has been around 17 posts in this blog. This blog has covered various aspects of the nuclear world, from its history, its technology, its advantages, its detrimental effects, public opinion and so forth. Mostly technical aspects, involving walls of texts.

Today, I am going to go with something new, the effects of nuclear power in video-gaming culture!

It seems that the power of nuclear is so strong, video game developers even create such nuclear-themed based games, mostly on post-apocolyptic in nature however. For some reason however, such games receive quite positive reviews from gamers! Although there are of course other aspects of the game that make it popular such as the play-style, plot, and so forth, having nuclear themed genres seem to give it a fresh look for gamers.

Such an example is the video-game S.T.A.L.K.E.R., developed from GSC Game World. This game centres upon a fictional second nuclear meltdown in Chernobly power plants. This exposed the surrounding area to massive radiation which has adverse effects on it. Mutations of flora and fauna as well as anomalies were the subsequent effects of the meltdown.

A poster of the game

 Well, this is of course a fictional game, with fictional plots and environments. However, such games do paint a bleak picture about nuclear power, painting the most extreme and impossible situation that can ever happen from a nuclear accident. In video-games too, themes centering about nuclear war-fare are in abundance.

So, what could we possibly learn from such 'games'? Humankind would perhaps have to take a step back, reconsider and upgrade policies, laws, methods and technologies to ensure that nuclear safety is of utmost priority and enforced with due diligence.

links: http://stalker-game.ru/en/wallpapers_frame.php?id=1&res=1

http://en.wikipedia.org/wiki/S.T.A.L.K.E.R.:_Shadow_of_Chernobyl

Protesters Interrupt German Nuclear Waste Shipment

Eight Castor Nuclear Waste Container

One of eleven Castor (Cask of storage and Transport of Radioactive material) nuclear waste containers is lifted from a train onto a truck at an embarking station.

 Two girls have their faces fainted with the symbol for nuclear radiation as they attend a demostration by pupils from a local school againts the unsafe storage of nuclear waste

A masked environment activist throws fireworks to the police during protest

                                         Anti Nuclear protesters sit on the railway tracks

On November 23, a train carrying 11 tubular containers of highly radioactive nuclear waste departed Normandy, France. The nuclear waste, which originated in German reactors years ago and was processed for storage by a French firm, is now bound for a temporary storage facility in a former salt mine near Gorleben, Germany. The 750-mile trip has taken far longer than anticipated, due to thousands of protesters causing disruptions along the way. Staging sit-ins, chaining themselves to the rails, and even sabotaging the railway, demonstrators are denouncing the transportation of dangerous material through populated areas. This is the last of 12 contractually obligated shipments of nuclear waste from France. France has forecast this activist will swarm Germany when the train enters and had alerted them on the activist activity. Therefore Germany had deployed 19.000 police to secure the shipment route are and hundreds of demonstrators were removed from railroads. Germany recently pledged a complete phase-out of nuclear power within a decade and has already shut down 8 of its 17 reactors.

The protesters who claimed themselves as Greenpeace had already crossed the boundry. The peaceful protest they claimed had turned to violent action by chaining themselves to the rails, sabotaging the railway and throwing fireworks to the police. From my point of view, I understand the concern and need for protest but isn't there a potential for a derailment and nuclear spill if the demonstrators are sabotaging the rails?  That would lead to negative press and the complete opposite of the outcome they hope to achieve. They should realize that the most important thing is to let the shipment reached final destination without any accident.

Source/ References : http://www.guardian.co.uk, http://www.spiegel.de, http://www.theatlantic.com

All pictures taken from: http://www.theatlantic.com,

Online Survey on Nuclear Energy

Is This True?

But

So, do we want to build nuclear reactor?

Nuclear Fuel Cycle

These are the various steps that together make up the entire Nuclear Fuel Cycle:

1. Mining and milling

Uranium is usually mined by either surface (open cut) or underground mining techniques, depending on the depth at which the ore body is found. In Australia the Ranger mine in the Northern Territory is open cut, while Olympic Dam in South Australia is an underground mine (which also produces copper, with some gold and silver). The newest Canadian mines are underground.

From these, the mined uranium ore is sent to a mill which is usually located close to the mine. At the mill the ore is crushed and ground to a fine slurry which is leached in sulfuric acid to allow the separation of uranium from the waste rock. It is then recovered from solution and precipitated as uranium oxide (U₃0₈) concentrate.*

* Sometimes this is known as "yellowcake", though it is finally khaki in colour.

Some mines, notably in the USA and Kazakhstan, use in situ leaching (ISL) to extract the uranium from the ore body underground and bring it to the surface in solution. It is recovered in much the same fashion.

U₃0₈ is the uranium product which is sold. About 200 tonnes is required to keep a large (1000 MWe) nuclear power reactor generating electricity for one year.

2. Conversion

Because uranium needs to be in the form of a gas before it can be enriched, the U₃0₈ is converted into the gas uranium hexafluoride (UF₆) at a conversion plant.

3. Enrichment

The vast majority of all nuclear power reactors in operation and under construction require 'enriched' uranium fuel in which the proportion of the U-235 isotope has been raised from the natural level of 0.7% to about 3.5% to 5%. The enrichment process removes about 85% of the U-238 by separating gaseous uranium hexafluoride into two streams: One stream is enriched to the required level and then passes to the next stage of the fuel cycle. The other stream is depleted in U-235 and is called 'tails'. It is mostly U-238*.

* Figures in the diagram assume enrichment to 3.5% U-235 and a tails assay of 0.25%. The 220t figure should be 172t (146 tU)

So little U-235 remains in the tails (usually less than 0.25%) that it is of no further use for energy, though such 'depleted uranium' is used in metal form in yacht keels, as counterweights, and as radiation shielding, since it is 1.7 times denser than lead.

Today's enrichment plants use the centrifuge process, with thousands of rapidly-spinning vertical tubes. A few older plants also continue. Research is being conducted into laser enrichment, which appears to be a promising new technology.

A small number of reactors, notably the Canadian CANDU reactors, do not require uranium to be enriched.

4. Fuel fabrication

Enriched UF₆ is transported to a fuel fabrication plant where it is converted to uranium dioxide (UO₂) powder and pressed into small pellets. These pellets are inserted into thin tubes, usually of a zirconium alloy (zircalloy) or stainless steel, to form fuel rods. The rods are then sealed and assembled in clusters to form fuel assemblies for use in the core of the nuclear reactor.

Some 27 tonnes of fresh fuel is required each year by a 1000 MWe reactor.

5. The nuclear reactor

Several hundred fuel assemblies make up the core of a reactor. For a reactor with an output of 1000 megawatts (MWe), the core would contain about 75 tonnes of low-enriched uranium. In the reactor core the U-235 isotope fissions or splits, producing heat in a continuous process called a chain reaction. The process depends on the presence of a moderator such as water or graphite, and is fully controlled.

Some of the U-238 in the reactor core is turned into plutonium and about half of this is also fissioned, providing about one third of the reactor's energy output.

As in fossil-fuel burning electricity generating plants, the heat is used to produce steam to drive a turbine and an electric generator, in this case producing about 7 billion kilowatt hours of electricity in one year.

To maintain efficient reactor performance, about one-third of the spent fuel is removed every year or 18 months, to be replaced with fresh fuel.

6. Used fuel storage

Storage pond for used fuel at UK reprocessing plant

Used fuel assemblies taken from the reactor core are highly radioactive and give off a lot of heat. They are therefore stored in special ponds which are usually located at the reactor site, to allow both their heat and radioactivity to decrease. The water in the ponds serves the dual purpose of acting as a barrier against radiation and dispersing the heat from the spent fuel.

Used fuel can be stored safely in these ponds for long periods. It can also be dry stored in engineered facilities, cooled by air. However, both kinds of storage are intended only as an interim step before the used fuel is either reprocessed or sent to final disposal. The longer it is stored, the easier it is to handle, due to decay of radioactivity.

There are two alternatives for used fuel:

• reprocessing to recover the usable portion of it
• long-term storage and final disposal without reprocessing.

7. Reprocessing

Used fuel still contains approximately 96% of its original uranium, of which the fissionable U-235 content has been reduced to less than 1%. About 3% of used fuel comprises waste products and the remaining 1% is plutonium (Pu) produced while the fuel was in the reactor and not "burned" then.

Reprocessing separates uranium and plutonium from waste products (and from the fuel assembly cladding) by chopping up the fuel rods and dissolving them in acid to separate the various materials. Recovered uranium can be returned to the conversion plant for conversion to uranium hexafluoride and subsequent re-enrichment. The reactor-grade plutonium can be blended with enriched uranium to produce a mixed oxide (MOX) fuel*, in a fuel fabrication plant.

* MOX fuel fabrication occurs at facilities in Belgium, France, Germany, UK, Russia and Japan, with more under construction. There have been 25 years of experience in this, and the first large-scale plant, Melox, commenced operation in France in 1995. Across Europe about 30 reactors are licensed to load 20-50% of their cores with MOX fuel and Japan plans to have one third of its 54 reactors using MOX by 2010.

The remaining 3% of high-level radioactive wastes (some 750 kg per year from a 1000 MWe reactor) can be stored in liquid form and subsequently solidified.

Reprocessing of used fuel occurs at facilities in Europe and Russia with capacity over 5000 tonnes per year and cumulative civilian experience of 90,000 tonnes over almost 40 years.

8. Vitrification

After reprocessing, the liquid high-level waste can be calcined (heated strongly) to produce a dry powder which is incorporated into borosilicate (Pyrex) glass to immobilise the waste. The glass is then poured into stainless steel canisters, each holding 400 kg of glass. A year's waste from a 1000 MWe reactor is contained in 5 tonnes of such glass, or about 12 canisters 1.3 metres high and 0.4 metres in diameter. These can be readily transported and stored, with appropriate shielding.

This is as far as the nuclear fuel cycle goes at present. The final disposal of vitrified high-level wastes, or the final disposal of spent fuel which has not been reprocessed used fuel, has not yet taken place.

Resource from World Nuclear Association