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2024 June

Notes • Quotation Sources

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Notes

Page 2 — A near–duplicate…
The visible difference between Calder Hall and Chapelcross stations is that the four cooling towers at Calder Hall are clustered, two at each end, while at Chapelcross they are spaced out, one for each reactor. These were the only British nuclear power plants to be accompanied by cooling towers. At all subsequent stations, direct seawater (lake–water at Trawsfynydd) cooling has been employed.
Calder Hall was initially ordered as a two–reactor station, sometimes referred to as Calder A, and a second or B station was added during the course of construction, while Chapelcross was ordered as four units from the beginning, but with the same configuration of two turbine halls set between paired reactors. The principal technical difference between them is that, at Calder Hall, the steam from all eight boilers associated with each reactor pair flows first to a steam receiver and thence to the turbines. In the case of unreliability either on the steam or the nuclear side, this would have improved overall station availability.
Page 3 — Toward a Durable Peace
This is the subtitle of the book Soft Energy Paths by Amory Lovins. A review by Alvin Weinberg, originally published in Energy Policy (1978 March, page 85), is reprinted in Continuing the Nuclear Dialogue (American Nuclear Society, 1985).
Page 5 — Or do we follow the hard path?
Lovins, undoubtedly, does not mean to suggest by soft path that he is leading us to sink into a bog. What he says is, Low–energy futures can (but need not) be normative and pluralistic, whereas high–energy futures are bound to be coercive and to offer less scope for social diversity and individual freedom (Non–Nuclear Futures, p xxi). The grounds for this sweeping assertion are unclear, and it hardly seems to agree with much of human experience.
Page 9 — The pioneers of the field…
When W Bennett Lewis of AECL raised this point, during a discussion session at the 1971 Fourth International Conference on the Peaceful Uses of Atomic Energy at Geneva, it caused quite a furore. Alvin Weinberg was especially nonplussed. See volume 11 of the Proceedings, pp 465—467.
Page 9 — Even in the most unfavorable scenario…
As given by RS Pease, FRS, in introductory remarks to a Royal Society discussion meeting held 24–25 May 1989, printed in Philosophical Transactions of the Royal Society of London, Series A, volume 331, number 1619 ; reprinted as The Fast–Neutron Breeder Fission Reactor, G McHugh and AR Merrick, editors.
For coal waste (ash) as a source of uranium, see our previous number.
Page 13 — A safer place…
We might suppose that the metal–alloy fuel in each fuel assembly of the fast–neutron breeder reactor illustrated in our previous number contains 80 kg of uranium and 20 kg of plutonium. Further suppose the plutonium contained to be suitable for making simple atomic bombs (although it probably is not). The amount of weapons–grade Pu required for such a bomb is understood to be about 6 kg, so such an assembly could potentially make three bombs. Once loaded into the reactor core, it will be much too hot to handle without specialized equipment. Theft of the fuel on the way from the fabrication plant to the reactor, or of the raw material on its way from reprocessing to fabrication, must therefore be prevented at all costs.
All of these reactors, fabrication plants, and reprocessing plants are accordingly located in fuel cycle centers, under close and continuous international supervision, to prevent diversion of weapons–usable material by national governments or criminal groups. The centers themselves may even be owned by multinational consortia or cooperatives. The only material which crosses the site boundary is crude uranium and thorium, spent fuel coming in from converter–reactor power plants (along with research reactors and other minor uses) for reprocessing, and fresh converter fuel going out in the same heavy flasks used for the spent fuel. The incoming items are very unpromising in terms of bomb–making. What of the outgoing? A typical CANDU bundle contains about 30 kg of the heavy elements, in the form of a ceramic (oxide, or potentially carbide for future reactors). Assume that the fissile content is some mixture of 233U, 235U, and plutonium, containing about 5 g Pu per kg. Then a bundle contains about 150 g Pu, and it would be necessary to steal at least 40 bundles to make a bomb. This is the sort of operation that could be easily guarded against, and the work of extracting the dilute plutonium would give time to track down and apprehend any thieves who succeeded.
Page 14—15 : Closing the Plastic Cycle
The main product of the Fischer–Tropsch synthesis is a mixture of largely paraffin (alkane or straight–chain) hydrocarbons, with the general formula CnH2n+2. This series starts with methane, CH4, n=1 ; liquid fuels fall mostly in the range of n=6 to n=20, with lubricating oils and paraffin wax beyond that. (The hydrogen molecule may be considered the special case of n=0.) Polyethylene is an alkane with a value of n typically in the thousands, at which point the +2 has become entirely negligible. Extra steps are required to produce such long–chain molecules, but the basic process is much the same. A different selection of hydrocarbons is produced by the Bergius process of treating coal with hydrogen at high pressure.
The reader may object that the problem of microplastics, which has recently begun to be recognized, is a bigger obstacle to the continued use of plastics than the accumulation of bulk plastic waste, and the approach illustrated does nothing to address this. The value of the flowsheet illustrated does not begin and end with the production of plastics. The Fischer–Tropsch and related processes, with suitable selection of catalysts, modification of operating conditions, and so on, can be used to produce an almost unlimited range of carbon–hydrogen and carbon–hydrogen–oxygen compounds, not just liquid fuels and lubricant oils, but alcohols and even high–quality edible fats. (This last, it will be noted, is effectively the inverse of the use of vegetable oils for fuel, which has caused such environmental damage in Indonesia.) Thus, the plant illustrated would be able to furnish useful, salable products, even in the (highly unlikely) case of a total worldwide ban on plastics production.
Page 16 — It never ceases to amaze…
The Norwegian group Bellona is a case in point. When the Halden research reactor was shut down, they called this a victory for the environment, saying that (among other complaints) the reactor had produced 10 tonnes of spent fuel, out of a total of 17 in the history of nuclear work in Norway. 10 tonnes of uranium oxide occupies a volume of less than one cubic meter. It seems unlikely that this cannot be safely stored in a country with so low as population density as Norway.
At the same time, they endorsed carbon capture and storage as the way to solve the climate puzzle. CO2 emissions are the greatest threat to our climate. CCS must provide the bridge between our current condition and our destination of a low–carbon society. For several energy–intensive industries, CCS is the only available technology to reduce emissions sufficiently in the foreseeable future. Yet until we roll–out CCS on a large scale, power plants and industrial production facilities, old and new, continue to fill the atmosphere with CO2. The only solution after you have excluded all those that make sense!
The release of carbon dioxide gas from Lake Nyos in Cameroon in 1986 is believed to have killed 1746 people. This followed a similar event at Lake Monoun two years earlier, which killed 37 people.
Page 18 — Conventional water reactors…
While the gasification reaction (C in the figure on page 14) is endothermic, absorbing energy in the form of heat, the synthesis reaction (E) is strongly exothermic. As a result, heat may be recovered from the waste gases (3) to assist in raising steam, but the yield of more valuable longer–chain molecules falls, and the yield of methane rises, with increasing temperature. Hence recovered heat cannot be used to superheat the steam to the temperature required by the gasifier. This consideration practically excludes the use of steam raised in a lower–temperature reactor.
For the synthesis of methanol from steam and heavy oil, a steam temperature of 825 °C is typical. The coolant outlet temperatures typical of water–cooled fission reactors are typically 275—325 °C. Sodium–cooled reactors typically produce steam at 500—550 °C. Steam plant does not become much more efficient at higher temperatures, and does get much more costly to build, so high–temperature helium–graphite reactors intended for electricity production have typically been designed for a coolant temperature of around 750 °C. The AVR pebble–bed prototype at Jülich, Germany, ran for extended periods with a coolant gas temperature of 1000 °C, to demonstrate that this was practical and would not cause damage to the fuel. This shows that the HTR is adaptable to the production of modest volumes of super–hot steam for chemical industry processes, as well as large volumes of medium–high temperature steam for power generation.
Page 24 — Combined heat–and–power…
For further discussion of CHP, with special reference to the absorption chiller, see our previous number.

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