April 27, 2011
We like this new interactive map. Make sure that you listen to the audio clip. You’ll hear a brief overview of the development of the nuclear industry around the world at the same time you see it on the map.
The data that went into building the map is sourced from the International Nuclear Energy Association.
April 7, 2011
All nuclear reactors do the same thing – create heat from the decay and fission of radioactive materials. However, there are six different types of reactors used to generate electricity, differentiated by fuel, coolant and moderator.
|Pressurized Water||US, France, Japan, Russia, China||265||Enriched UO2||Water||Water|
|Boiling Water||US, Japan, Sweden||94||Enriched UO2||Water||Water|
|Pressurized Heavy Water||Canada||44||Natural UO2||Heavy Water||Heavy Water|
|Gas-cooled||UK||18||Enriched & Natural UO2||CO||Graphite|
|Light Water Graphite||Russia||12||Enriched UO2||Water||Graphite|
|Fast Neutron||Japan, France, Russia||2||PuO2, UO2||Liquid Sodium||None|
Source: World Nuclear Association
The fuel is usually uranium oxide (UO2) in cylindrical pellets placed end-to-end in long tubes. Most reactors use enriched uranium which contains from 3.5 to 5.0 per cent U-235 (the really active ingredient) and from 95.0 to 96.5 U-238. A few reactors use natural uranium which consists of 0.7 per cent U-235 and more than 99.2 per cent U-238. In Fast Neutron reactors, plutonium oxide (PuO2) is used
The moderator slows neutrons released during fission so that there is more chance they will collide with uranium atoms in the reactor core, releasing more neutrons and heat energy and sustaining a chain reaction.
The coolant is what carries the heat from the core to the either a steam generator or the turbines.
All reactors operate in the same basic way. The fuel is induced into a fission reaction wherein unstable U-235 atoms release neutrons and heat. The released neutrons are slowed by the moderator and collide with other atoms and more neutrons are released and a self-sustaining chain reaction develops. The coolant, contained in separate pipes running through the reactor core, absorbs the heat and, in all reactors but Boiling Water Reactors, carries it to a steam generator. The steam generator is a separate circuit in which water is turned to steam that turns the turbine that turns the generator. After passing through the turbine, the steam is condensed into water and continues the cycle. All this is housed in a containment structure designed to contain any material or vapour that could escape from the reactor in the event of a nuclear mishap.
With Pressurized Water Reactors, the water used as coolant is kept at very high pressure, and consequently, very high temperatures without boiling.
In Boiling Water Reactors, the coolant water is allowed to boil and become steam and that steam drives the turbine. There is no secondary steam circuit.
Pressurized Heavy Water Reactors operate are identical to Pressurized Water Reactors except they use heavy water as both coolant and moderator. Heavy water consists of deuterium oxide. Deuterium is an isotope of hydrogen with two neutrons instead of one. Heavy water slows neutrons so efficiently that the uranium fuel doesn’t need to be enriched, and natural uranium can be used. The primary Pressurized Heavy Water Reactor is the CANDU reactor, developed in Canada, hence the name – CANada DUterium.
Graphite-moderated reactors sit in a solid block of graphite and use either light water or carbon monoxide as coolant.
Fast neutron reactors use neutrons from plutonium derived from U-238 surrounding the plutonium. They are sometimes called Breeder Reactors.
All of the reactors generating electricity in Canada are Pressurized Heavy Water CANDU Reactors. The reactors at Fukushima Dai-ichi are Boiling Water Reactors. The Chernobyl reactor was a Light Water Graphite Reactor with no containment structure. Three Mile Island was a Pressurized Water Reactor.
April 4, 2011
The two major concerns at the crippled Fukushima Dai-ichi nuclear power plant are keeping the damaged reactors cool and dealing with contaminated water. Unfortunately the contaminated water is the result of cooling efforts, which primarily consist of spraying the reactors and spent fuel rods with tonnes of water daily.
The key is finding the balance in which neither risk grows.
The water, at first pooled in concrete tanks and ditches on the grounds of the reactor complex, but last week, contamination was found to have made its way to the ocean.
Workers found a crack in a maintenance pit on Saturday that could be the source of the leak, and have been trying to plug it since that time. Initial efforts using concrete failed as did later efforts using paper, sawdust and expanding polymers.
The Japanese Nuclear and Industrial Safety Agency said the first step will be to pump the radioactive water into storage tanks, after which they will focus on restoring the cooling systems.
The Japanese government said that could take months, and it could be years before the area is cleaned up. Authorities have decided that there is no hope in repairing the damaged reactors; they will all have to be decommissioned.
The bodies of two workers missing since March 11 were found last Wednesday. They are believed to have died from the initial impact of the tsunami.
In Canada, higher levels of radiation have been detected on the west coast, but health authorities are saying that the amounts are so low, there is no health risk. Most of the contamination is in the form of iodine-131 which has a half life of about eight days.
March 18, 2011
Despite there being in excess of 9,000* safe reactor years in the nuclear power industry since Chernobyl, the global reaction to the situation in Japan has been to douse the so-called nuclear renaissance.
Three mile Island image: Photo newstrending.net | Chernobyl image: Photo Reuters
After the nuclear accidents at Three Mile Island in 1979 and Chernobyl in 1986, both of which were the result of mechanical failure and human error, nuclear power was deemed potentially too hazardous, and construction of new facilities virtually ceased. However, nuclear power is now seen as an emissions-free alternative to fossil fuel fired electricity generation and as of year-end 2010, 61 new nuclear plants were under construction and 158 were in the planning stages.
However, over the past few days, that has all changed.
Australia, which does not currently generate electricity from nuclear power, was firm that nuclear would not be part of its future. This despite the country having uranium exports worth more than $1.1 billion in 2009.
Building and replacing nuclear plants in Switzerland will be put on hold until safety standards are reviewed.
Germany reacted by proposing a three-month moratorium on the decision to extend the operating lives of its 17 nuclear power plants, although this is seen by some as a means of stalling a final decision on nuclear power until after this month’s elections.
Austria wants all of Europe to ensure all nuclear power plants are earthquake proof.
In the United States, politicians from both parties are re-thinking proposed green energy legislation that promotes a large role for nuclear power. Senator Joe Lieberman wants the U.S. to “put the brakes on right now until we understand the ramifications of what’s happened in Japan.”
Even China, which currently has 27 nuclear power plants under construction, announced it will stop approval of new nuclear plants until safety inspections are complete on all facilities under construction.
Only Ontario, it seems, is still damn the torpedoes, full speed ahead, when it comes to new construction. A spokesperson for Ontario Energy Minister Brad Duguid said the government remained committed to building two new units at the Darlington Nuclear Generating Station in Clarington, Ont.
The question is, “Are people overreacting?” Here are a few points to consider.
Japan is situated in a region prone to earthquakes and tsunamis. The nuclear reactors at the Fukushima Dai-ichi power plant withstood both the earthquake and the tsunami; it was the back-up systems that failed due to inadequate protection from the tsunami. The four units at the Fukushima Dai-ni power plant 11.5 kilometres to the south were successfully shut down after initial problems with the cooling systems. No problems were encountered with the other 48 reactors in Japan.
In North America, only five of the 121 operating reactors are near the seismically active west coast. The others are in seismically stable regions of the mid-west and eastern parts of the continent where there is very little chance major earth quakes and tsunamis.
According to the European Seismological Commission, the risk of earthquakes in Europe, other than Italy, Greece and the Balkans, is low. There are currently more than 400 nuclear reactors safely providing power world wide. Since the beginning of the nuclear power industry, there have been more than 14,000** reactor years of operations during which there were two serious accidents.
With nuclear though, is seems two is the only number many need.
*9,000* safe reactor years was calculated by taking the number of years since Chernobyl (2011-1986=25) and multiplying it by the average number of reactors in service between 1986 and 2011 (388.3). 25 years x 388.3 reactors = 9,707.5 reactor-years. The average number of reactors on line was determined from World Nuclear Association data.
14.000** reactor years figure comes from the World Nuclear Association home page. They have ticker that says “As of Today: 14,424 Reactor-Years of Worldwide Experience in Producing Civil Nuclear Power.” That number is derived by multiplying the number of years from when the first commercial reactor went on line in 1954 to the present (2011-1954=57) by the average number of reactors on line during that time, which is 253.
March 18, 2011
High levels of radiation seem to have lessened over night. Power to the cooling systems at reactors 1 and 2 is expected to be restored Friday and to reactors 3 and 4 by Sunday.
Japan’s Nuclear and Industrial Safety Agency has raised the level of the nuclear emergency at Fukushima Dai-ichi to five on the seven-level International Nuclear and Radiological Event Scale (INES). Level 5 is termed “accident with wider consequences” and is characterized by:
- Severe damage to reactor core
- Release of large quantities of radioactive material within an installation with a high probability of significant public exposure.
- Several deaths from radiation
For comparison, the Three Mile Island accident was categorized as Level 5 while Chernobyl was categorized as a Level 7.
March 17, 2011
Japanese emergency workers are using two Chinook helicopters, often used to fight forest fires, and truck-mounted water cannons to dump water on the No. 3 and No. 4 reactors and their spent fuel pools at the Fukushima Dai-ichi nuclear power plant.
Workers are also installing a power line to provide electricity to existing cooling systems, which were disabled by last Thursday’s tsunami.
The helicopters made four passes over the No. 3 reactor, dumping abot 7,500 litres o0f sea water each time.
There are conflicting opinions as to the No. 4 reactor’s spent fuel pool. While the plant’s owner, Tokyo Electric Power Co., says the fuel rods are submerged in water, Gregory Jaczko, chairman of the U.S. Nuclear Regulatory Commission Chairman, said that there was no water in the unit’s spent fuel pool.
Yuichi Sato, an official with Japan’s nuclear safety agency, said “Considering the amount of radiation released in the area, the fuel rods are more likely to be exposed than to be covered.”
Meanwhile in Canada, an earthquake measuring 4.3 on the Richter scale was felt in southwestern Quebec and eastern Ontario yesterday. There were no reports of damage.
March 16, 2011
While one can never say never; one can say that it would be very highly unlikely.
For one thing, Japan is situated on the most active part of the Ring of Fire, a 40,000-kilometre band circumscribing the Pacific Ocean from South America northward to the Aleutian Islands and southward to the Philippines. The Ring of Fire is defined by tectonic plate boundaries and the inherent volcano and earthquake activity. In fact, about 80 per cent of the world`s earthquakes occur along the ring.
And while Canada`s west coast is part of the Ring of Fire, Canada`s nuclear power plants are all on the other side of the country. Ontario has three plants with a total of 16 operating reactors, Quebec has one plant with one reactor and New Brunswick has one plant with one reactor, which is currently being refurbished.
Despite the fact that this area of the country is relatively stable geologically, all of Canada`s nuclear plants are designed to withstand the strongest earthquake likely to occur in 1,000 years. Case in point, the 2010 earthquake that stuck 60 kilometres north of Ottawa measured 5.0 on the Richter Scale, but had no effect on any of the nuclear plants in Canada.
As well, tsunamis are very unlikely to form in the Great Lakes.
Geography and geology aside, nuclear power plant reactors in Canada are all CANDU reactors, which are designed with numerous safety features, each equipped with independent back-up systems.
March 15, 2011
Japan generates about 30 per cent of its electricity from 55 nuclear reactors operating in 18 nuclear power plants. Because Japan is in a region with a large amount of seismic activity, all nuclear plants are constructed to exacting safety standards. One aspect of these standards is systems that automatically shut down reactors in the event of an earthquake.
The problem is we can shut down a reactor, but we can’t completely shut down the reaction.
Part of the reaction is fission, which occurs when a uranium 235 (U235) atom collides with a stray neutron. The atom splits into smaller atoms and releases more neutrons and heat energy. The new neutrons collide with more atoms and the process becomes self sustaining – a nuclear chain reaction.
Another part of the reaction is radioactive decay, which is the random and spontaneous decay of an unstable nucleus. Radioactive decay cannot be controlled.
Fission can be regulated by raising or lowering control rods in the reactor. Control rods are made of substances that inhibit fission by absorbing neutrons. To shut down a reactor, the control rods are lowered completely into the reactor core which effectively stops nuclear fission.
However, the core of the reactor is still hot, and radioactive decay is still ongoing, so it must be cooled, usually by circulating cold water through it.
The Fukushima-Dai-ichi nuclear power plant survived both the earthquake of March 11 and the subsequent tsunami without suffering major damage. The local electricity system, however, was severely damaged and put out of commission, as were back-up systems at the power plant. Although the control rods at the plant were lowered and the reactors automatically shut down, the lack of electricity prevented the water circulation necessary to cool the cores of Units 1, 2 and 3. Auxiliary diesel pumps were brought in and the containment structures were flooded with sea water. Units 4, 5, and 6 were under maintenance at the time of the earthquake.
All four units at the nearby Fukushima Dai-ni nuclear power plant were shut down safely following similar cooling problems.
However, at each of Fukushima Dai-ichi, Units 1, 2, and 3, the heat of the core vapourized the water almost as fast as it could be pumped in. The increasing amount of vapour raised the internal pressure to the point where some of the steam had to be vented to prevent damage to the containment structure. The released steam contained hydrogen that exploded when it came in contact with oxygen in the atmosphere. At Units 1 and 3, the explosions damaged the reactor buildings, but left the containment structures intact. The explosion Tuesday at Unit 2 damaged the suppression pool within the Unit 2 containment structure.
Under normal circumstances, venting radioactive steam is avoided; however, in this case, it was the lesser of two evils. A rupture of the containment structures would have had catastrophic results.
As of Tuesday, there are fears that the cores of the three units have suffered partial meltdown.
Wind is dispersing radiation from the three units out over the Pacific Ocean, reducing the immediate danger in the area. The Canadian Federal government does not expect the dispersed radiation to pose a health threat to Canadians living on the west coast.
While the situation is still critical, there is little danger of a Chernobyl-scale disaster. While the reactors, containment structures and reactor buildings survived the earthquake and tsunami, the backup systems and emergency power systems proved inadequate.
February 21, 2011
The idea for using nuclear power to generate electricity was still fairly avant-garde in 1953 when President Eisenhower announced his “Atoms for Peace” program. Prior to the program, nuclear research had been primarily focused on weapons. And electricity was mainly fuelled by coal.
In 1954, the Russians were the first to go on line with nuclear powered electricity generation, using a five-megawatt reactor at the Institute of Physics and Power Engineering in Obninsk. England built the first commercial-scale power plant at Calder Hall. The first of its four 50-megawatt reactors went online in 1956. Calder Hall provided electricity for 47 years and was shut down in 2003.
Another seven reactors began generating electricity in the late 1950s. Suddenly, nuclear power was all the rage. The United States was the pace setter with 85 reactors by the end of the 1970s. Canada (CNA 1960-2010, 2.5MB PDF) built 20 in Ontario, and one each in Quebec and New Brunswick. World-wide, 42 new reactors came on line in 1985 alone.
But by the 1990s, the number of reactors being built had dropped significantly. Some blame the accidents at Three Mile Island in 1979 and Chernobyl in 1986 but, because it takes up to 15 years to plan and build a nuclear power plant, decisions regarding the future of nuclear power were actually made in the mid-1970s. The primary concerns focused on reactor safety, accumulating nuclear waste and proliferation of nuclear weapons. Nuclear power became soooo passé.
Angst, like fashion, changes with time. Fears of nuclear Armageddon and atomic waste gave way to concerns about climate change and greenhouse gasses. But electricity generation from nuclear power doesn’t emit GHGs. By 2000, nuclear power was chic once again.
Sort of. It all depends on where you are. Of the 61 nuclear power plants currently under construction, 27 are in China, 10 are in Russia and six are in India. Only three are in the Western Hemisphere. Of the 158 in the planning stage, 50 are in China, 18 are in India, 14 are in Russia and nine are in the United States. The west is no longer the trend setter.
October 1, 2010
CANDU nuclear reactors have been operating in Canada for more than 48 years, beginning in 1962 with the Nuclear Power Demonstration (NPD), in Rolphton, Ontario. Since then the country has had a long history with nuclear power, and its total installed capacity has grown to 12,612 megawatts.
With a long history, though, it’s no surprise that the country’s five nuclear plants have to get a little work done every now and then to keep them in ship shape. But as with a lot of work, it doesn’t always happen on the chosen schedule. Quebec, for example, recently announced that its only nuclear power plant would have to wait a year for its planned refurbishment.
Hydro-Québec has decided to postpone the start of refurbishing work at the 25-year-old Gentilly-2 nuclear generating station from 2011 until 2012. According to Hydro-Québec’s press release, the delayed refurbishment is due to other similar projects currently underway in New Brunswick (Point Lepreau generating station) and Wolsong, South Korea. According to Atomic Energy of Canada Limited, there are currently 48 reactors based on the CANDU design in operation, under construction, or under refurbishment worldwide.
Gentilly-2 is still the only nuclear facility in Quebec, and because of Quebec’s heavy reliance on hydropower, don’t expect the shutdown of a 675-MW plant to cripple the la belle province — Gentilly-2 only represents about 3 per cent of the province’s electricity generation. The remaining 97 per cent comes virtually entirely from hydroelectric dams. So, while the refurbishment might have hit a slight hiccup, it’s hardly the end of the world. The old girl needs work, but she can wait another year.
Check out The Canadian Centre for Energy Information’s main page for a complete list of Canada’s nuclear power facilities.