Radioactive Dispersal Devices / Sources of pollution

Radioactive Dispersal Devices

Since the 11^th September, 2001 terrorist attacks in the USA there has been much speculation about the possibility of terrorists making a radioactive dispersal device or 'dirty bomb' using conventional explosives and a stolen radioactive source. Such a bomb could not cause a nuclear explosion, but could disperse radioactive material over an area up to a square kilometre or so. While this might, like the accidents described previously, cause a small number of local casualties, the overall radiation effects would be limited. The wider the material is dispersed, the more diluted it will be and the lower the doses are that people could receive. Nevertheless severe social disruption could arise. The construction of such a device would be likely to entail dangerously high radiation doses to the terrorists, but would be Possible if they were able to obtain a Source and were not concerned for their Own safety. This possibility reinforces the need for effective measures to ensure that radioactive Sources are kept securely under control until they are disposed of permanently.

Transport of radioactive materials / Sources of pollution

Transport of radioactive materials

Radioactive materials are routinely transported all around the world by air, sea, road. and rail. These materials include those associated with the nuclear fuel cycle - from uranium ores to spent fuel and radioactive waste - but also radionuclides for nuclear medicine and research, and radioactive sources for industry and radiotherapy. Although the safety record of these transports is excellent, they sometimes cause con­cern in the areas through which they pass. For example, a number of countries have expressed particular concern about ships carrying radioactive waste passing through or close to their territorial waters.

Regulations are, therefore, needed not just to ensure that the chances of an accident, which could result in radio­active material being dispersed in the environment, are kept to a minimum, but also to ensure that the workers involved in transport - including those load­ing and unloading shipments as well as drivers/pilots - are protected. Because much of this transport is international, transport safety was one of the first areas in which the IAEA developed safety standards. The IAEA Regulations for the Sale Transport of Radioactive Material were first published in 1961 and have been revised periodically since.

The Regulations govern the necessary packaging, shielding, labelling and other precautions that must be taken when transporting various types of radioactive material, including tests that packages must undergo to prove that they can withstand possible accidents. The requirements are graded according to the level of activity of the mate­rials to be transported. In general, more hazardous radioactive materials need more extensive and more robust packaging and stricter quality and administrative controls.

The regulations for the different modes of transport are issued by different organizations, particularly the International Civil Aviation Organization ( ICAO ) for air transport, the Internationial Maritime Organization (IMO) for transport by sea, and regional organizations such as the Inland Transport Committee of the UN Economic Commission for Europe for transport by land and inland waterways. These organizations' regulations cover all types of hazardous material, and the parts that deal with radioactive materials are based the IAEA Transport Regulations.

Depleted uranium / Sources of pollution

Depleted uranium

Munitions using depleted uranium (DU) were used during the Gulf War in 1991 and in the conflicts during the 1990s surrounding the break-up of Yugoslavia. The risks of harm to military personnel on a battlefield should be put in context of the other self­evident risks, but the use of depleted uranium ordnance has raised concerns about subsequent health consequences, both to service personnel and to the public after the conflict.

As has already been discussed, uranium occurs naturally in the environment. It is widely dispersed in the Earth's crust, and in fresh water and sea water. As a result, we are all exposed to uranium isotopes and their decay products, and there are wide variations in doses received depending on local circumstances. DU is a by-product of the uranium fuel cycle where natural uranium is enriched to provide suitable fuel for nuclear power. It is called depleted because it has had some of its uranium-235 isotope removed. A large fraction of decay products of the uranium isotopes is removed during the fuel enrichment process.

Depleted uranium in munitions is in a concentrated metallic form, and there are under­standable concerns about elevated levels in the environment due to spent munitions. There are also worries about people handling intact depleted uranium metal. Assess­ments of dose to military personnel who entered a tank shortly after it was hit by a DU weapon indicate possible doses of up to a few tens of mSv from inhalation of vapours and dust. In contrast, doses to people exposed some time afterwards to resuspended dust in the same local environment are likely to be a thousand times less, typically a few tens of µSv. Contact doses when handling bare DU metal are approximately 2.5 mSv/h, primarily from beta radiation, which is not penetrating and so affects only the skin. Even so, the collection of bare DU munitions needs to be discouraged and, if possible, avoided completely.

Doses from depleted uranium are, therefore, real and, in some circumstances, they could be appreciable for military personnel. Doses to people in the post-conflict phase are likely to be much lower and should be relatively easy to avoid.

Radioactive discharges / Sources of pollution

Radioactive discharges Radionuclides of artificial origin are discharged to the environment by the nuclear power industry, military establishments. research organizations, hospitals and general industry. Discharges of any significance should be subject to statutory control; they must be authorized and monitored. Owners or operators of the facilities from which radionuclides are discharged carry out monitoring programmes, as do some regulatory agencies.

The nuclear power industry discharges the most activity. At each stage of the nuclear fuel cycle, a variety of radionuclides are released in the form of liquids. gases, or solid particles. The nature of the effluent depends on the particular operation or process.

Each year, nuclear power reactors generate about 20 per cent of the world's electrical energy. During routine operation of nuclear installations, the releases of radionuclides are low and normally exposures have to be estimated with environmental transfer models. For all nuclear fuel cycle operations, including mining and milling, fuel fabrication, reactor operation and fuel reprocessing, the local and regional exposures are estimated by UNSCEAR to be about 0.9 man Sv per gigawatt-year (GW a). The present world nuclear energy generation is about 250 (GW a) annually, and so the total collective dose from a year's generation of nuclear energy is about 200 man Sv. Generally individual doses are low, being below 1 µSv in a year. However certain individuals might receive higher doses because of where they live and what they eat and these should be subject to dose constraints, the maximum value being 300 µSv in a year.

In the case of accidents where there has been significant local contamination, the local doses can be significantly greater than the dose constraint. Where appropriate, mea­sures are taken to minimize doses to people, such as the establishment of restricted areas in the vicinity of Chernobyl. Such measures can reduce both the individual and collective doses substantially. Discharges from fuel reprocessing facilities give annual doses to the most exposed people - those who eat local seafood - up to 0.14 mSv mainly from actinides. Discharge to air of strontium-90 and other radionuclides leads to individual doses that are less than 0.05 mSv annually from the consumption of local milk and vegetables.The collective dose from airborne discharges, mainly due to carbon-14 in foodstuffs, is approximately 500 man Sv annually. From liquid discharges, it is about 4000 man Sv annually mainly due to caesium-137 in fish.

Collective dose (man Sv) Most exposed people(mSv) Type of effluent Stage of cycle 350 0.01 Airborne Fuel fabrication 0.01 Liquid 380 0.001 Airborne Reactor operation 0.004 Liquid 0.05 Airborne Fuel reprocessing 4500 Liquid 0.14 Table (14): Annual doses due to discharges from the nuclear fuel cycle

Although radioactive discharges to the environment are now strictly controlled in most countries, in the past they have not always been managed as they should have been. In particular, some military facilities operating during the Cold War adopted waste management methods that would be unacceptable for a modern civilian facility.

Nuclear Accidents / Sources of pollution

Nuclear Accidents a) The Chernobyl Accident
In April 1986, the Chernobyl nuclear power plant in the ­Soviet Ukraine exploded, dispersing more than 1016 Bq of ra­dioactive material into the atmosphere. In the figure technicians are observed checking for radiation inside the damaged Chernobyl nuclear power plant. Two peo­ple were killed in the explosion, and hundreds more died of radiation sickness. Fallout affected much of eastern Europe and Scandinavia, and tens of thousands of people are expected to develop fatal cancers as a result. Details of the Chernobyl accident illustrate many aspects of basic nuclear physics and of reactor engineering and control.
	Ironically, the accident occurred during a test of the power supply for the emergency core-cooling system (ECCS), de­signed to dump water on the reactor core in the event of a loss-of-coolant accident. Mismanagement of the test, serious operator errors, and reactor design all contributed to the Cher­nobyl disaster. Sequence of events leading to the Chernobyl reactor explo­sion, shown as a plot of reactor power as a function of time. Time scale is not linear.
Preparation for the test began at 1 :00 A.M. on April 25 as operators slowly decreased the reactor output from its normal 3200 MW thermal power to 1600 MW, a process that took 12 hours. Then, following the test plan, they disconnected the turbine-generator and disabled the emergency core-cooling system. Although the plan called for shutting off the ECCS to prevent its coming on and disturbing the test, this move vio­lated the reactor's operating procedures. When the operators resumed lowering the reactor power, one of them failed to set an automatic control that would have maintained a thermal power at 700 to 1000 MW. The power level plunged to a mere 30 MW. We know that fission products act as "poisons," ab­sorbing neutrons and thereby inhibiting fission. A particularly virulent reactor poison is xenon-135, whose cross section for neutron absorption is 4400 times that of 235U. Xenon-135 forms in the 6.7-h-half-life decay of 135I. In normal operation, the 135Xe concentration reaches a steady level in which neutron capture destroys the isotope as quickly as 135I decay creates it. But when reactor power decreases, neutron production drops and with it the destruction of 135Xe. But 135I continues to decay into 135Xe, so xenon concentration increases. The "poisoning" effect then makes it difficult to raise the reactor power until several of the xenon's 9.2-h half-lives have passed.
At Chernobyl, an operator's error had resulted in a rapid power drop, leading to high 135Xe concentration. Impatient to complete the test, operators committed another safety viola­tion: To compensate for neutron absorption in the xenon, they withdrew too many control rods. By 1: 19 A.M. on April 26, they had managed to raise the power to 200 MW, still well below the 700 MW minimum needed for the test. About the same time they turned on two additional cooling water pumps, as called for in the test procedures. In a US. light-water reactor, the cooling water is also the moderator. But in a graphite-moderated reactor like Cher­nobyl, the dominant effect of water is to absorb neutrons. So the additional water required withdrawal of still more control rods. Now the reactor was in a dangerous situation: An increase in power would boil water, decreasing neutron absorption and thus increasing the fission rate. That would make the water boil even faster, increasing the power even more, and a runaway reaction could result. Worse, with so few control rods in place, the reaction might be sustained by prompt neutrons alone, resulting in a power increase too rapid to halt with mechanical control rods.
The Chernobyl operators realized they had too much water, and at 1 :22 A.M. they reduced the flow. But they did not imme­diately reinsert control rods. Thirty seconds later a computer warned that the reactor should be shut down. Ignoring the warning, operators continued the test by diverting steam from the turbine-generator. The decreased load caused more water to boil, again reducing neutron absorption. The reactor went supercritical from prompt neutrons alone, and the power level soared by a factor of 4000 in 5 seconds.
The power surge ruptured water pipes, causing a steam explosion that lifted the heavy concrete reactor cover. A second explosion followed, caused perhaps by hydrogen generated from steam reacting with the zirconium cladding on the fuel rods. The graphite moderator caught fire, and heavy smoke carried highly radioac­tive fission products into the atmosphere. Substantial radiation release continued for 10 days, and fallout dropped on much of Europe . The distribution of 137Cs following Chernobyl accident is shown in the map.
Could a Chernobyl accident happen in the United States? I For commercial light-water reactors the answer is decidedly no. Loss of the water coolant/moderator in a light-water reactor immediately halts the chain reaction, making a runaway reac­tion impossible. But that doesn't mean light-water reactors are entirely safe. Even after the chain reaction stops, the immense heat generated by radioactive decay is enough to melt the core.
Chernobyl Health Effects An explosion in a nuclear reactor at the Chernobyl nuclear power plant on 26 April 1986 caused the release of substantial quantities of radionuclides during a period of ten days. Airborne material was dispersed throughout Europe from the site in Ukraine. As the contaminated air spread throughout Europe and beyond, local weather condi­tions largely determined where the radionuclides were to fall. Rainfall caused more radionuclides to be deposited in some areas rather than others.
The accident had a catastrophic effect locally and high radiation expo­sures of emergency workers led to the deaths of 31 people, including 28 firemen. The firemen received large external doses from deposited radionuclides, between 3 and 16 Sv, and contamination on their skin led to severe erytherna, mostly due to beta emitters. A further 209 people were hospitalized of whom 106 were diagnosed as having acute radiation sick­ness. Fortunately all of these people recovered and were able to leave hospital within a few weeks or months.
In terms of doses to people in the vicinity and beyond, the most significant radionuclides were iodine-131, caesium-134 and caesium-137. Almost all the dose was caused by external irradiation from radionuclides on the ground, by inhalation of iodine-131 giving rise to thyroid doses, and by internal irradiation from radionuclides in foodstuffs.
Following the accident, over 100 000 people were moved from their homes in what are now Belarus, Ukraine and the Russian Federation, and various areas became "restricted" because of the levels of fallout on the ground. A vast clean-up operation was mounted at the Chernobyl reactor site itself involving over 750000 people. The people doing the decontamination work became known as "liquidators", and some of them received doses above the ICRP dose limit of 50 mSv. Such exposures may be justified in accident situations and ICRP recommends that exposures should not exceed 500 mSv in such circumstances. This ensures that workers could not experi­ence any deterministic effects of radiation exposure, and published data from monitor­ing teams show that the average doses were kept below 165 mSv in the first year after the accident. In subsequent years, they were gradually reduced to below 50 mSv.
There have been exhaustive studies of populations in the vicinity of Chernobyl and elsewhere, looking for possible health effects from the accident. The only significant effect that has so far been shown to be caused by radiation is in children in regions of Belarus and Ukraine, who have an increased incidence of thyroid cancer due to intakes of iodine-131 , particularly through drinking milk contaminated with iodine. Iodine-131 is a short lived radionuclide (8 days half life) known to concentrate in the thyroid, and using monitoring and other data it has been possible to estimate risk factors for this health effect in children. In 2000, UNSCEAR published a review of the effects of the Chernobyl accident. Their scientific assessments indicated that there had been about 1800 cases of thyroid cancer in children who were exposed at the time of the accident. Fortunately, in the great majority of cases, it is not a fatal condition, although it is a serious illness.
UNSCEAR found no scientific evidence of increases to date in the incidence of any other health effects that could be related to radiation exposure. This does not mean that there will not be any other effects – the most highly exposed individuals have an increased risk of suffering radiation-associated effects in the Mure - but UNSCEAR concluded that the great majority of the popula­tion are not likely to experience serious health consequences attributable to radiation from the accident.
The other serious health effects seen in local populations appear to be the result of the stress and anxiety caused by the accident, including the fear of radiation itself. Although these effects are different in kind to the thyroid disorders mentioned above, they are no less real and occurred widely throughout Europe in regions affected by the fallout. For example in Scandinavia, doses of about 0.1 mSv were received on average during the first few weeks after the accident, and many people reported to their doctors feelings of nausea. headaches, diarhea and some skin rashes. Following a century of scientific study of the effects of radiation, it can be concluded that it is not possible that such Iow doses could lead directly to the effects reported. However, a potent fear of radiation is obviously real for some people, and this was one of the lessons of the Chernobyt accident.
b) Three Mile Island Accident A partial meltdown occurred in the 1979 Three Mile Island accident in Pennsylvania, but fortunately the reactor's containment structure held in nearly all the radioactivity. The threat of a hydrogen explosion during that accident-a possibility not previously considered in reactor accident scenarios-showed that we may not yet realize all the potentially dangerous situations possible in a system as complex as a nuclear power plant .

Nuclear weapon tests / Sources of pollution

Nuclear weapon tests

When nuclear weapons were tested above ground, they propelled a variety of radionuclides from hydrogen-3 (tritium) to plutonium-241 into the upper atmosphere. From there, the radionuclides transferred slowly to the lower atmosphere and then to the Earth's surface. Around 500 atmospheric explosions were conducted before the limited test treaty was enacted in 1963, with a few more until 1980. The concen­trations of radionuclides in air, rain and human diet are now much lower than the peak values in the early 1960s. Globally, the most important radionuclides from testing in terms of human exposure are now carbon-14, strontium-90 and caesium-137. Minute quantities of these are ingested with food and drink. Residual activity from radionuclides in the ground that emit gamma rays also causes a slight degree of human exposure. Internal and external irradiation contribute about equally to the global average effective dose of 0.005 mSv in a year. This compares with a peak of more than 0.1 mSv in 1963. Some groups of people who receive significantly higher, doses from global fallout than average have been identified. For example, it was' found in the 1960s that reindeer and caribou herders in northern Europe and Canada received significantly higher doses than other people, because they eat the meat of animals that eat lichen, which is a very efficient collector of airborne caesium-137. The global collective dose from weapon tests fallout is now about 30 000 man Sv annually, assuming a world population of 6 000 million.

The Nuclear Fuel Cycle / Sources of pollution

The Nuclear Fuel Cycle
Like coal, oil and natural gas, uranium is an energy resource which must be processed through a series of steps to produce an efficient fuel for use in the generation of electricity. Each fuel has its own distinctive fuel cycle: however the uranium or 'nuclear fuel cycle' is more complex than the others. To prepare uranium for use in a nuclear reactor, it undergoes the steps of mining and milling, conversion, enrichment and fuel fabrication. These steps make up the 'front end' of the nuclear fuel cycle. After uranium has been used in a reactor to produce electricity it is known as 'spent fuel' and may undergo a further series of steps including temporary storage, reprocessing, and recycling before eventual disposal as waste. Collectively these steps are known as the 'back end' of the fuel cycle. These are the various steps that together make up the entire Nuclear Fuel Cycle:
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. 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. 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.
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 in Europe, Russia or North America.
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% or slightly more. In natural Uranium for every 235U atom there is 140 238U atoms.
The enrichment process by centrifuge 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.
The figures in the diagram assume enrichment by centrifuge to 3.5% U-235 and a tails assay of 0.25%. 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. The first enrichment plants were built in the USA and used the gaseous diffusion process, but more modern plants in Europe and Russia use the centrifuge process. This has the advantage of using much less power per unit of enrichment and can be built in smaller, more economic units. Research is being conducted into laser enrichment, which appears to be a promising new technology. A small number of reactors, notably the Canadian CANDU and early British gas-cooled reactors, do not require uranium to be enriched.
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 25 tonnes of fresh fuel is required each year by a 1000 MWe reactor.
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 is 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.
Spent fuel storage
Spent 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.
Spent fuel can be stored safely in storage 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 transient step before the spent 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 spent fuel: reprocessing to recover the usable portion of it long-term storage and final disposal without reprocessing.
Reprocessing
Spent 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 spent fuel comprises waste products and the remaining 1% is plutonium (Pu) produced while the fuel was in the reactor and not "burned" then, according to the following reactions 23892U + n ---- β- ----> 23992U ---- β- ----> 239Np ----- β- -----> 23994Pu. 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.
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 spent fuel, has not yet taken place.
Final disposal
The waste forms envisaged for disposal are vitrified high-level wastes sealed into stainless steel canisters, or spent fuel rods encapsulated in corrosion-resistant metals such as copper or stainless steel. The most widely accepted plans are for these to be buried in stable rock structures deep underground. Many geological formations such as granite, volcanic tuff, salt or shale will be suitable. The first permanent disposal is expected to occur about 2010.
Most countries intend to introduce final disposal sometime after about 2010, when the quantities to be disposed of will be sufficient to make it economically justifiable.
Keeping the fuel cycle civil
Much of the civil nuclear fuel cycle evolved half a century ago from military programs and from naval use of reactors to power warships, particularly submarines. Ever since then the prospect of wider use of nuclear energy for power generation has created a concern to ensure that this did not lead to the proliferation of nuclear weapons in countries which did not already have them. Safeguards are accounting and auditing procedures applied to all nuclear materials in NPT countries, so that when they are used or traded their civil use can be verified. It follows that uranium cannot be traded with any country which does not permit it to remain under NPT safeguards. Under the "Additional Protocol" some countries are now accepting "strengthened safeguards" under which IAEA inspectors probe more widely than simply known nuclear materials. The IAEA's goal is to win universal acceptance of the Additional Protocol.
India and Pakistan have agreed to IAEA safeguards on certain reactors, even though those countries are not signatories of the NPT. Certain countries comprising the Nuclear Suppliers' Group have entered into a non-treaty agreement not to engage in nuclear commerce (materials or equipment) with any country not a party to the NPT. The NPT is based on an agreement between the five main nuclear weapons states and the other countries interested in nuclear technology. The deal was that assistance and cooperation in developing nuclear power and related technologies would depend on pledges, backed by international security, that no plant or material would be diverted to weapons use. Those who refused to be part of the deal would be excluded from international cooperation or trade involving nuclear technology.
In addition to the NPT, Australia and Canada have systems of bilateral agreements with customer countries which further tighten the control of uranium which is supplied. These accounting systems follow uranium from when it is produced and packed for export, to the time it is reprocessed or stored as nuclear waste, anywhere in the world. They also include plutonium which is in the spent fuel. These systems operate in addition to safeguards applied by the IAEA which keep track of the movement of nuclear materials through fuel cycle facilities in other countries and which verify inventories. Total cost is thus about US$ 860 for 1 kg enriched fuel, plus about $240 for actual fuel fabrication. This will yield about 3900 GJ thermal energy at modern burn-up rates, or about 360,000 kWh of electricity (at 33% thermal efficiency), and does the same job as about 160 tonnes of steaming coal for a total cost of 0.31 cents/kWh (US$).