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A cryptocurrency is a digital currency that is created and managed through the use of advanced encryption techniques known as cryptography. Cryptocurrency made the leap from being an academic concept to (virtual) reality with the creation of bitcoin in 2009. While Bitcoin attracted a growing following in subsequent years, it captured significant investor and media attention in April 2013 when it peaked at a record $266 per bitcoin after surging 10-fold in the preceding two months. Bitcoin sported a market value of over $2 billion at its peak, but a 50% plunge shortly thereafter sparked a raging debate about the future of cryptocurrencies in general and Bitcoin in particular. So, will these alternative currencies eventually supplant conventional currencies and become as ubiquitous as dollars and euros someday? Or are cryptocurrencies a passing fad that will flame out before long? The answer lies with Bitcoin.A lot of people do not know there are so many ways to earn cryptocurrencies by investing legitimately in platforms like www.coastminers.tech where they can get double of their investment in 7 days without losing them(thank me later).The Future of CryptocurrencySome economic analysts predict a big change in crypto is forthcoming as institutional money enters the market. Moreover, there is the possibility that crypto will be floated on the Nasdaq, which would further add credibility to blockchain and its uses as an alternative to conventional currencies. Some predict that all that crypto needs is a verified exchange traded fund (ETF). An ETF would definitely make it easier for people to invest in Bitcoin, but there still needs to be the demand to want to invest in crypto, which some say may not automatically be generated with a fund.Understanding Bitcoinbitcoin is a decntralized currency that uses peer-to-peer technology, which enables all functions such as currency issuance, transaction processing and verification to be carried out collectively by the network. While this decentralization renders Bitcoin free from government manipulation or interference, the flipside is that there is no central authority to ensure that things run smoothly or to back the value of a Bitcoin. Bitcoins are created digitally through a “mining” process that requires powerful computers to solve complex algorithms and crunch numbers. They are currently created at the rate of 25 Bitcoins every 10 minutes and will be capped at 21 million, a level that is expected to be reached in 2140.These characteristics make Bitcoin fundamentally different from a fiat currency, which is backed by the full faith and credit of its government. Fiat currency issuance is a highly centralized activity supervised by a nation’s central bank. While the bank regulates the amount of currency issued in accordance with its monetary policy objectives, there is theoretically no upper limit to the amount of such currency issuance. In addition, local currency deposits are generally insured against bank failures by a government body. Bitcoin, on the other hand, has no such support mechanisms. The value of a Bitcoin is wholly dependent on what investors are willing to pay for it at a point in time. As well, if a Bitcoin exchange folds up, clients with Bitcoin balances have no recourse to get them back.Bitcoin Future OutlookThe future outlook for bitcoin is the subject of much debate. While the financial media is proliferated by so-called crypto-evangelists, Harvard University Professor of Economics and Public Policy Kenneth Rogoff suggests that the “overwhelming sentiment” among crypto advocates is that the total “market capitalisation of cryptocurrencies could explode over the next five years, rising to $5-10 [trillion].”The historic volatility of the asset class is “no reason to panic,” he says. Still, he tempered his optimism and that of the “crypto evangelist” view of Bitcoin as digital gold, calling it “nutty,” stating its long-term value is “more likely to be $100 than $100,000.”Rogoff argues that unlike physical gold, Bitcoin’s use is limited to transactions, which makes it more vulnerable to a bubble-like collapse. Additionally, the cryptocurrency’s energy-intensive verification process is “vastly less efficient” than systems that rely on “a trusted central authority like a central bank.”Increasing ScrutinyBitcoin’s main benefits of decentralization and transaction anonymity have also made it a favored currency for a host of illegal activities icluding money laundering, drug peddling, smuggling and weapons procurement. This has attracted the attention of powerful regulatory and other government agencies such as the Financial Crimes Enforcement Network (FinCEN), the SEC, and even the FBI and Department of Homeland Security (DHS). In March 2013, FinCEN issued rules that defined virtual currency exchanges and administrators as money service businesses, bringing them within the ambit of government regulation. In May that year, the DHS froze an account of Mt. Gox – the largest Bitcoin exchange – that was held at Wells Fargo, alleging that it broke anti-money laundering laws. And in August, New York’s Department of Financial Services issued subpoenas to 22 emerging payment companies, many of which handled Bitcoin, asking about their measures to prevent money laundering and ensure consumer protection.Alternatives to BitcoinDespite its recent issues, Bitcoin’s success and growing visibility since its launch has resulted in a number of companies unveiling alternative cryptocurrencies, such as:Litecoin – Litecoin is regarded as Bitcoin's leading rival at present, and it is designed for processing smaller transactions faster. It was founded in October 2011 as "a coin that is silver to Bitcoin’s gold,” according to founder Charles Lee. Unlike the heavy computer horsepower required for Bitcoin mining, Litecoins can be mined by a normal desktop computer. Litecoin’s maximum limit is 84 million – four times Bitcoin’s 21-million limit – and it has a transaction processing time of about 2.5 minutes, about one-fourth that of Bitcoin.Ripple – Ripple was launched by OpenCoin, a company founded by technology entrepreneur Chris Larsen in 2012. Like Bitcoin, Ripple is both a currency and a payment system. The currency component is XRP, which has a mathematical foundation like Bitcoin. The payment mechanism enables the transfer of funds in any currency to another user on the Ripple network within seconds, in contrast to Bitcoin transactions, which can take as long as 10 minutes to confirm.MintChip – Unlike most cryptocurrencies, MintChip is actually the creation of a government institution, specifically the Royal Canadian Mint. MintChip is a smartcard that holds electronic value and can transfer it securely from one chip to another. Like Bitcoin, MintChip does not need personal identification; unlike Bitcoin, it is backed by a physical currency, the Canadian dollar.The FutureSome of the limitations that cryptocurrencies presently face – such as the fact that one’s digital fortune can be erased by a computer crash, or that a virtual vault may be ransacked by a hacker – may be overcome in time through technological advances. What will be harder to surmount is the basic paradox that bedevils cryptocurrencies – the more popular they become, the more regulation and government scrutiny they are likely to attract, which erodes the fundamental premise for their existence.While the number of merchants who accept cryptocurrencies has steadily increased, they are still very much in the minority. For cryptocurrencies to become more widely used, they have to first gain widespread acceptance among consumers. However, their relative complexity compared to conventional currencies will likely deter most people, except for the technologically adept.A cryptocurrency that aspires to become part of the mainstream financial system may have to satisfy widely divergent criteria. It would need to be mathematically complex (to avoid fraud and hacker attacks) but easy for consumers to understand; decentralized but with adequate consumer safeguards and protection; and preserve user anonymity without being a conduit for tax evasion, money laundering and other nefarious activities. Since these are formidable criteria to satisfy, is it possible that the most popular cryptocurrency in a few years’ time could have attributes that fall in between heavily-regulated fiat currencies and today’s cryptocurrencies? While that possibility looks remote, there is little doubt that as the leading cryptocurrency at present, Bitcoin’s success (or lack thereof) in dealing with the challenges it faces may determine the fortunes of other cryptocurrencies in the years ahead.Should You Invest in Cryptocurrencies?If you are considering investing in cryptocurrencies, it may be best to treat your “investment” in the same way you would treat any other highly speculative venture. In other words, recognize that you run the risk of losing most of your investment, if not all of it. As stated earlier, a cryptocurrency has no intrinsic value apart from what a buyer is willing to pay for it at a point in time. This makes it very susceptible to huge price swings, which in turn increases the risk of loss for an investor. Bitcoin, for example, plunged from $260 to about $130 within a six-hour period on April 11, 2013. If you cannot stomach that kind of volatility, look elsewhere for investments that are better suited to you. While opinion continues to be deeply divided about the merits of Bitcoin as an investment – supporters point to its limited supply and growing usage as value drivers, while detractors see it as just another speculative bubble – this is one debate that a conservative investor would do well to avoid.ConclusionThe emergence of Bitcoin has sparked a debate about its future and that of other cryptocurrencies. Despite Bitcoin’s recent issues, its success since its 2009 launch has inspired the creation of alternative cryptocurrencies such as Litecoin, Ripple and MintChip. A cryptocurrency that aspires to become part of the mainstream financial system would have to satisfy very divergent criteria. While that possibility looks remote, there is little doubt that Bitcoin’s success or failure in dealing with the challenges it faces may determine the fortunes of other cryptocurrencies in the years ahead.

A cryptocurrency is a digital currency that is created and managed through the use of advanced encryption techniques known as cryptography. Cryptocurrency made the leap from being an academic concept to (virtual) reality with the creation of bitcoin in 2009. While Bitcoin attracted a growing following in subsequent years, it captured significant investor and media attention in April 2013 when it peaked at a record $266 per bitcoin after surging 10-fold in the preceding two months. Bitcoin sported a market value of over $2 billion at its peak, but a 50% plunge shortly thereafter sparked a raging debate about the future of cryptocurrencies in general and Bitcoin in particular. So, will these alternative currencies eventually supplant conventional currencies and become as ubiquitous as dollars and euros someday? Or are cryptocurrencies a passing fad that will flame out before long? The answer lies with Bitcoin.These days, there are a lot of legitimate offers online that gives great advantage to cryptocurrency investors where they get double of their invested cryptocurrency on platforms like www.underatedcryptos.store. These are opportunities that need to be really utilized to its maximum.The Future of CryptocurrencySome economic analysts predict a big change in crypto is forthcoming as institutional money enters the market. Moreover, there is the possibility that crypto will be floated on the Nasdaq, which would further add credibility to blockchain and its uses as an alternative to conventional currencies. Some predict that all that crypto needs is a verified exchange traded fund (ETF). An ETF would definitely make it easier for people to invest in Bitcoin, but there still needs to be the demand to want to invest in crypto, which some say may not automatically be generated with a fund.Understanding BitcoinBitcoin is a decentarlized currency that uses peer to peer technology, which enables all functions such as currency issuance, transaction processing and verification to be carried out collectively by the network. While this decentralization renders Bitcoin free from government manipulation or interference, the flipside is that there is no central authority to ensure that things run smoothly or to back the value of a Bitcoin. Bitcoins are created digitally through a “mining” process that requires powerful computers to solve complex algorithms and crunch numbers. They are currently created at the rate of 25 Bitcoins every 10 minutes and will be capped at 21 million, a level that is expected to be reached in 2140.These characteristics make Bitcoin fundamentally different from a fiat currency, which is backed by the full faith and credit of its government. Fiat currency issuance is a highly centralized activity supervised by a nation’s central bank. While the bank regulates the amount of currency issued in accordance with its monetary policy objectives, there is theoretically no upper limit to the amount of such currency issuance. In addition, local currency deposits are generally insured against bank failures by a government body. Bitcoin, on the other hand, has no such support mechanisms. The value of a Bitcoin is wholly dependent on what investors are willing to pay for it at a point in time. As well, if a Bitcoin exchange folds up, clients with Bitcoin balances have no recourse to get them back.Bitcoin Future OutlookThe future outlook for bitcoin is the subject of much debate. While the financial media is proliferated by so-called crypto-evangelists, Harvard University Professor of Economics and Public Policy Kenneth Rogoff suggests that the “overwhelming sentiment” among crypto advocates is that the total “market capitalisation of cryptocurrencies could explode over the next five years, rising to $5-10 [trillion].”The historic volatility of the asset class is “no reason to panic,” he says. Still, he tempered his optimism and that of the “crypto evangelist” view of Bitcoin as digital gold, calling it “nutty,” stating its long-term value is “more likely to be $100 than $100,000.”Rogoff argues that unlike physical gold, Bitcoin’s use is limited to transactions, which makes it more vulnerable to a bubble-like collapse. Additionally, the cryptocurrency’s energy-intensive verification process is “vastly less efficient” than systems that rely on “a trusted central authority like a central bank.”Increasing ScrutinyBitcoin’s main benefits of decentralization and transaction anonymity have also made it a favored currency for a host of illegal activities including money laundering, drug peddling, smuggling and weapons procurement. This has attracted the attention of powerful regulatory and other government agencies such as the Financial Crimes Enforcement Network (FinCEN), the SEC, and even the FBI and Department of Homeland Security (DHS). In March 2013, FinCEN issued rules that defined virtual currency exchanges and administrators as money service businesses, bringing them within the ambit of government regulation. In May that year, the DHS froze an account of Mt. Gox – the largest Bitcoin exchange – that was held at Wells Fargo, alleging that it broke anti-money laundering laws. And in August, New York’s Department of Financial Services issued subpoenas to 22 emerging payment companies, many of which handled Bitcoin, asking about their measures to prevent money laundering and ensure consumer protection.Alternatives to BitcoinDespite its recent issues, Bitcoin’s success and growing visibility since its launch has resulted in a number of companies unveiling alternative cryptocurrencies, such as:Litecoin – Litecoin is regarded as Bitcoin's leading rival at present, and it is designed for processing smaller transactions faster. It was founded in October 2011 as "a coin that is silver to Bitcoin’s gold,” according to founder Charles Lee. Unlike the heavy computer horsepower required for Bitcoin mining, Litecoins can be mined by a normal desktop computer. Litecoin’s maximum limit is 84 million – four times Bitcoin’s 21-million limit – and it has a transaction processing time of about 2.5 minutes, about one-fourth that of Bitcoin.Ripple – Ripple was launched by OpenCoin, a company founded by technology entrepreneur Chris Larsen in 2012. Like Bitcoin, Ripple is both a currency and a payment system. The currency component is XRP, which has a mathematical foundation like Bitcoin. The payment mechanism enables the transfer of funds in any currency to another user on the Ripple network within seconds, in contrast to Bitcoin transactions, which can take as long as 10 minutes to confirm.MintChip – Unlike most cryptocurrencies, MintChip is actually the creation of a government institution, specifically the Royal Canadian Mint. MintChip is a smartcard that holds electronic value and can transfer it securely from one chip to another. Like Bitcoin, MintChip does not need personal identification; unlike Bitcoin, it is backed by a physical currency, the Canadian dollar.The FutureSome of the limitations that cryptocurrencies presently face – such as the fact that one’s digital fortune can be erased by a computer crash, or that a virtual vault may be ransacked by a hacker – may be overcome in time through technological advances. What will be harder to surmount is the basic paradox that bedevils cryptocurrencies – the more popular they become, the more regulation and government scrutiny they are likely to attract, which erodes the fundamental premise for their existence.While the number of merchants who accept cryptocurrencies has steadily increased, they are still very much in the minority. For cryptocurrencies to become more widely used, they have to first gain widespread acceptance among consumers. However, their relative complexity compared to conventional currencies will likely deter most people, except for the technologically adept.A cryptocurrency that aspires to become part of the mainstream financial system may have to satisfy widely divergent criteria. It would need to be mathematically complex (to avoid fraud and hacker attacks) but easy for consumers to understand; decentralized but with adequate consumer safeguards and protection; and preserve user anonymity without being a conduit for tax evasion, money laundering and other nefarious activities. Since these are formidable criteria to satisfy, is it possible that the most popular cryptocurrency in a few years’ time could have attributes that fall in between heavily-regulated fiat currencies and today’s cryptocurrencies? While that possibility looks remote, there is little doubt that as the leading cryptocurrency at present, Bitcoin’s success (or lack thereof) in dealing with the challenges it faces may determine the fortunes of other cryptocurrencies in the years ahead.Should You Invest in Cryptocurrencies?If you are considering investing in cryptocurrencies, it may be best to treat your “investment” in the same way you would treat any other highly speculative venture. In other words, recognize that you run the risk of losing most of your investment, if not all of it. As stated earlier, a cryptocurrency has no intrinsic value apart from what a buyer is willing to pay for it at a point in time. This makes it very susceptible to huge price swings, which in turn increases the risk of loss for an investor. Bitcoin, for example, plunged from $260 to about $130 within a six-hour period on April 11, 2013. If you cannot stomach kind of volatility, look elsewhere for investments that are better suited to you. While opinion continues to be deeply divided about the merits of Bitcoin as an investment – supporters point to its limited supply and growing usage as value drivers, while detractors see it as just another speculative bubble – this is one debate that a conservative investor would do well to avoid.ConclusionThe emergence of Bitcoin has sparked a debate about its future and that of other cryptocurrencies. Despite Bitcoin’s recent issues, its success since its 2009 launch has inspired the creation of alternative cryptocurrencies such as Litecoin, Ripple and MintChip. A cryptocurrency that aspires to become part of the mainstream financial system would have to satisfy very divergent criteria. While that possibility looks remote, there is little doubt that Bitcoin’s success or failure in dealing with the challenges it faces may determine the fortunes of other cryptocurrencies in the years ahead.

The dangers are listed further down thepost. But its quite safe compared to other reactors and much much safer compared to fossil fuelA Nuclear Reactor That Consumes Nuclear Waste? No Loss of Coolant Accidents? No Steam Explosions? Are You Dreaming?What if we could design and build a reactor :• that uses no water and so can't have high pressure steam or hydrogen explosions,• with fuel that can't have a nuclear melt down,• that fissions over 99% of its fuel so there's no waste needing storage for hundreds of thousands of years,• that can consume spent nuclear fuel from other reactorsWell, we've already built one, and we ran it for 5 years! (But you never heard about it...)Nuclear Reactor That Can't Melt Down? No High Pressure? Consume Nuclear Waste? Build it Again!SafetyInherent safety. LFTR designs use a strong negative temperature coefficient of reactivity to achieve passive inherent safety against excursions of reactivity. The temperature dependence comes from 3 sources. The first is that thorium absorbs more neutrons if it overheats, the so-called Doppler effect.[42] This leaves fewer neutrons to continue the chain reaction, reducing power. The second part is heating the graphite moderator, that usually causes a positive contribution to the temperature coefficient.[42] The third effect has to do with thermal expansion of the fuel.[42] If the fuel overheats, it expands considerably, which, due to the liquid nature of the fuel, will push fuel out of the active core region. In a small (e.g. the MSRE test reactor) or well moderated core this reduces the reactivity. However, in a large, under-moderated core (e.g. the ORNL MSBR design), less fuel salt means better moderation and thus more reactivity and an undesirable positive temperature coefficient.Stable coolant. Molten fluorides are chemically stable and impervious to radiation. The salts do not burn, explode, or decompose, even under high temperature and radiation.[43] There are no rapid violent reactions with water and air that sodium coolant has. There is no combustible hydrogen production that water coolants have.[44] However the salt is not stable to radiation at low (less than 100 C) temperatures due to radiolysis.Low pressure operation. Because the coolant salts remain liquid at high temperatures,[43] LFTR cores are designed to operate at low pressures, like 0.6 MPa[45] (comparable to the pressure in the drinking water system) from the pump and hydrostatic pressure. Even if the core fails[clarification needed], there is little increase in volume. Thus the containment building cannot blow up. LFTR coolant salts are chosen to have very high boiling points. Even a several hundred degree heatup during a transient or accident does not cause a meaningful pressure increase. There is no water or hydrogen in the reactor that can cause a large pressure rise or explosion as happened during the Fukushima Daiichi nuclear accident.[46][unreliable source]No pressure buildup from fission. LFTRs are not subject to pressure buildup of gaseous and volatile fission products. The liquid fuel allows for online removal of gaseous fission products, such as xenon, for processing, thus these decay products would not be spread in a disaster.[47] Further, fission products are chemically bonded to the fluoride-salt, including iodine,[dubious – discuss] cesium, and strontium, capturing the radiation and preventing the spread of radioactive material to the environment.[48]Easier to control. A molten fuel reactor has the advantage of easy removal of xenon-135. Xenon-135, an important neutron absorber, makes solid fueled reactors difficult to control. In a molten fueled reactor, xenon-135 can be removed. In solid-fuel reactors, xenon-135 remains in the fuel and interferes with reactor control.[49]Slow heatup. Coolant and fuel are inseparable, so any leak or movement of fuel will be intrinsically accompanied by a large amount of coolant. Molten fluorides have high volumetric heat capacity, some such as FLiBe, even higher than water. This allows them to absorb large amounts of heat during transients or accidents.[33][50]Passive decay heat cooling. Many reactor designs (such as that of the Molten-Salt Reactor Experiment) allow the fuel/coolant mixture to escape to a drain tank, when the reactor is not running (see "Fail safe core" below). This tank is planned to have some kind (details are still open) of passive decay heat removal, thus relying on physical properties (rather than controls) to operate.[51]Fail safe core. LFTRs can include a freeze plug at the bottom that has to be actively cooled, usually by a small electric fan. If the cooling fails, say because of a power failure, the fan stops, the plug melts, and the fuel drains to a subcritical passively cooled storage facility. This not only stops the reactor, also the storage tank can more easily shed the decay heat from the short-lived radioactive decay of irradiated nuclear fuels. Even in the event of a major leak from the core such as a pipe breaking, the salt will spill onto the kitchen-sink-shaped room the reactor is in, which will drain the fuel salt by gravity into the passively cooled dump tank.[19]Less long-lived waste. LFTRs can dramatically reduce the long-term radiotoxicity of their reactor wastes. Light water reactors with uranium fuel have fuel that is more than 95% U-238. These reactors normally transmute part of the U-238 to Pu-239, a long-lived isotope. Almost all of the fuel is therefore only one step away from becoming a transuranic long-lived element. Plutonium-239 has a half life of 24,000 years, and is the most common transuranic in spent nuclear fuel from light water reactors. Transuranics like Pu-239 cause the perception that reactor wastes are an eternal problem. In contrast, the LFTR uses the thorium fuel cycle, which transmutes thorium to U-233. Because thorium is a lighter element, more neutron captures are required to produce the transuranic elements. U-233 has two chances to fission in a LFTR. First as U-233 (90% will fission) and then the remaining 10% has another chance as it transmutes to U-235 (80% will fission). The fraction of fuel reaching neptunium-237, the most likely transuranic element, is therefore only 2%, about 15 kg per GWe-year.[52] This is a transuranic production 20x smaller than light water reactors, which produce 300 kg of transuranics per GWe-year. Importantly, because of this much smaller transuranic production, it is much easier to recycle the transuranics. That is, they are sent back to the core to eventually fission. Reactors operating on the U238-plutonium fuel cycle produce far more transuranics, making full recycle difficult on both reactor neutronics and the recycling system. In the LFTR, only a fraction of a percent, as reprocessing losses, goes to the final waste. When these two benefits of lower transuranic production, and recycling, are combined, a thorium fuel cycle reduces the production of transuranic wastes by more than a thousand-fold compared to a conventional once-through uranium-fueled light water reactor. The only significant long-lived waste is the uranium fuel itself, but this can be used indefinitely by recycling, always generating electricity.If the thorium stage ever has to be shut down, part of the reactors can be shut down and their uranium fuel inventory burned out in the remaining reactors, allowing a burndown of even this final waste to as small a level as society demands.[53] The LFTR does still produce radioactive fission products in its waste, but they don't last very long - the radiotoxicity of these fission products is dominated by cesium-137 and strontium-90. The longer half-life is cesium: 30.17 years. So, after 30.17 years, decay reduces the radioactivity by a half. Ten half-lives will reduce the radioactivity by two raised to a power of ten, a factor of 1,024. Fission products at that point, in about 300 years, are less radioactive than natural uranium.[54][55] What's more, the liquid state of the fuel material allows separation of the fission products not only from the fuel, but from each other as well, which enables them to be sorted by the length of each fission product's half-life, so that the ones with shorter half-lives can be brought out of storage sooner than those with longer half-lives.Proliferation resistance. In 2016, Nobel Laureate physicist Dr Carlo Rubbia, former Director General of CERN, claimed a primary reason for the United States cutting thorium reactor research in the 1970s is what makes it so attractive today: thorium is difficult to turn into a nuclear weapon.[56][unreliable source?]The LFTR resists diversion of its fuel to nuclear weapons in four ways: first, the thorium-232 breeds by converting first to protactinium-233, which then decays to uranium-233. If the protactinium remains in the reactor, small amounts of U-232 are also produced. U-232 has a decay chain product (thallium-208) that emits powerful, dangerous gamma rays. These are not a problem inside a reactor, but in a bomb, they complicate bomb manufacture, harm electronics and reveal the bomb's location.[57] The second proliferation resistant feature comes from the fact that LFTRs produce very little plutonium, around 15 kg per gigawatt-year of electricity (this is the output of a single large reactor over a year). This plutonium is also mostly Pu-238, which makes it unsuitable for fission bomb building, due to the high heat and spontaneous neutrons emitted. The third track, a LFTR doesn't make much spare fuel. It produces at most 9% more fuel than it burns each year, and it's even easier to design a reactor that makes only 1% more fuel. With this kind of reactor, building bombs quickly will take power plants out of operation, and this is an easy indication of national intentions. And finally, use of thorium can reduce and eventually eliminate the need to enrich uranium. Uranium enrichment is one of the two primary methods by which states have obtained bomb making materials.[8]DisadvantagesLFTRs are quite unlike today's operating commercial power reactors. These differences create design difficulties and trade-offs:Highly questionable economics - although proponents of LFTR technology list a wide variety of claimed economic advantages, detailed studies of their economics invariably conclude there is no real advantage in overall terms. A number of the claims, like the ambient pressure operation and high-temperature cooling loops, are already used on a number of conventional designs and have failed to produce the economic gains claimed. In other cases, there is simply not enough data to justify any conclusion. When the entire development is considered, the conclusions are invariably something along the lines of one report's summary: "... the difference in cost, given the current industry environment, remains insufficient to justify the creation of a new LFTR."[71]Still much development needed - Despite the ARE and MSRE experimental reactors already built in the 1960s, there is still a lot of development needed for the LFTR. This includes most of the chemical separation, (passive) emergency cooling, the tritium barrier, remote operated maintenance, large scale Li-7 production, the high temperature power cycle and more durable materials.Startup fuel - Unlike mined uranium, mined thorium does not have a fissile isotope. Thorium reactors breed fissile uranium-233 from thorium, but require a small amount of fissile material for initial start up. There is relatively little of this material available. This raises the problem of how to start the reactors in a short time frame. One option is to produce U-233 in today's solid fueled reactors, then reprocess it out of the solid waste. An LFTR can also be started by other fissile isotopes, enriched uranium or plutonium from reactors or decommissioned bombs. For enriched uranium startup, high enrichment is needed. Decommissioned uranium bombs have enough enrichment, but not enough is available to start many LFTRs. It is difficult to separate plutonium fluoride from lanthanide fission products. One option for a two-fluid reactor is to operate with plutonium or enriched uranium in the fuel salt, breed U-233 in the blanket, and store it instead of returning it to the core. Instead, add plutonium or enriched uranium to continue the chain reaction, similar to today's solid fuel reactors. When enough U-233 is bred, replace the fuel with new fuel, retaining the U-233 for other startups. A similar option exists for a single-fluid reactor operating as a converter. Such a reactor would not reprocess fuel while operating. Instead the reactor would start on plutonium with thorium as the fertile and add plutonium. The plutonium eventually burns out and U-233 is produced in situ. At the end of the reactor fuel life, the spent fuel salt can be reprocessed to recover the bred U-233 to start up new LFTRs.[72]Salts freezing - Fluoride salt mixtures have melting points ranging from 300 to 600 °C (572 to 1,112 °F). The salts, especially those with beryllium fluoride, are very viscous near their freezing point. This requires careful design and freeze protection in the containment and heat exchangers. Freezing must be prevented in normal operation, during transients, and during extended downtime. The primary loop salt contains the decay heat-generating fission products, which help to maintain the required temperature. For the MSBR, ORNL planned on keeping the entire reactor room (the hot cell) at high temperature. This avoided the need for individual electric heater lines on all piping and provided more even heating of the primary loop components.[18](p311) One "liquid oven" concept developed for molten salt-cooled, solid-fueled reactors employs a separate buffer salt pool containing the entire primary loop.[73] Because of the high heat capacity and considerable density of the buffer salt, the buffer salt prevents fuel salt freezing and participates in the passive decay heat cooling system, provides radiation shielding and reduces deadweight stresses on primary loop components. This design could also be adopted for LFTRs.[citation needed]Beryllium toxicity - The proposed salt mixture FLiBe, contains large amounts of beryllium, which is toxic to humans (although nowhere near as toxic as the fission products and other radioactives). The salt in the primary cooling loops must be isolated from workers and the environment to prevent beryllium poisoning. This is routinely done in industry.[74](pp52–66) Based on this industrial experience, the added cost of beryllium safety is expected to cost only $0.12/MWh.[74](p61) After start up, the fission process in the primary fuel salt produces highly radioactive fission products with a high gamma and neutron radiation field. Effective containment is therefore a primary requirement. It is possible to operate instead using lithium fluoride-thorium fluoride eutectic without beryllium, as the French LFTR design, the "TMSR", has chosen.[75] This comes at the cost of a somewhat higher melting point, but has the additional advantages of simplicity (avoiding BeF2 in the reprocessing systems), increased solubility for plutonium-trifluoride, reduced tritium production (beryllium produces lithium-6, which in turn produces tritium) and improved heat transfer (BeF2 increases the viscosity of the salt mixture). Alternative solvents such as the fluorides of sodium, rubidium and zirconium allow lower melting points at a tradeoff in breeding.[1]Loss of delayed neutrons - In order to be predictably controlled, nuclear reactors rely on delayed neutrons. They require additional slowly-evolving neutrons from fission product decay to continue the chain reaction. Because the delayed neutrons evolve slowly, this makes the reactor very controllable. In an LFTR, the presence of fission products in the heat exchanger and piping means a portion of these delayed neutrons are also lost.[76] They do not participate in the core's critical chain reaction, which in turn means the reactor behaves less gently during changes of flow, power, etc. Approximately up to half of the delayed neutrons can be lost. In practice, it means that the heat exchanger must be compact so that the volume outside the core is as small as possible. The more compact (higher power density) the core is, the more important this issue becomes. Having more fuel outside the core in the heat exchangers also means more of the expensive fissile fuel is needed to start the reactor. This makes a fairly compact heat exchanger an important design requirement for an LFTR.[citation needed]Waste management - About 83% of the radioactive waste has a half-life in hours or days, with the remaining 17% requiring 300 year storage in geologically stable confinement to reach background levels.[63] Because some of the fission products, in their fluoride form, are highly water-soluble, fluorides are less suited to long-term storage. For example, cesium fluoride has a very high solubility in water. For long term storage, conversion to an insoluble form such as a glass, could be desirable.[citation needed]Uncertain decommissioning costs - Cleanup of the Molten-Salt Reactor Experiment was about $130 million, for a small 8 MW(th) unit. Much of the high cost was caused by the unexpected evolution of fluorine and uranium hexafluoride from cold fuel salt in storage that ORNL did not defuel and store correctly, but this has now been taken into consideration in MSR design.[77] In addition, decommissioning costs don't scale strongly with plant size based on previous experience,[78] and costs are incurred at the end of plant life, so a small per kilowatthour fee is sufficient. For example, a GWe reactor plant produces over 300 billion kWh of electricity over a 40-year lifetime, so a $0.001/kWh decommissioning fee delivers $300 million plus interest at the end of the plant lifetime.Noble metal buildup - Some radioactive fission products, such as noble metals, deposit on pipes. Novel equipment, such as nickel-wool sponge cartridges, must be developed to filter and trap the noble metals to prevent build up.Limited graphite lifetime - Compact designs have a limited lifetime for the graphite moderator and fuel / breeding loop separator. Under the influence of fast neutrons, the graphite first shrinks, then expands indefinitely until it becomes very weak and can crack, creating mechanical problems and causing the graphite to absorb enough fission products to poison the reaction.[79] The 1960 two-fluid design had an estimated graphite replacement period of four years.[1](p3) Eliminating graphite from sealed piping was a major incentive to switch to a single-fluid design.[18](p3) Replacing this large central part requires remotely operated equipment. MSR designs have to arrange for this replacement. In a molten salt reactor, virtually all of the fuel and fission products can be piped to a holding tank. Only a fraction of one percent of the fission products end up in the graphite, primarily due to fission products slamming into the graphite. This makes the graphite surface radioactive, and without recycling/removal of at least the surface layer, creates a fairly bulky waste stream. Removing the surface layer and recycling the remainder of the graphite would solve this issue.[original research?] Several techniques exist to recycle or dispose of nuclear moderator graphite.[80] Graphite is inert and immobile at low temperatures, so it can be readily stored or buried if required.[80] At least one design used graphite balls (pebbles) floating in salt, which could be removed and inspected continuously without shutting down the reactor.[81] Reducing power density increases graphite lifetime.[82](p10) By comparison, solid-fueled reactors typically replace 1/3 of the fuel elements, including all of the highly radioactive fission products therein, every 12 to 24 months. This is routinely done under a protecting and cooling column layer of water.Graphite-caused positive reactivity feedback - When graphite heats up, it increases U-233 fission, causing an undesirable positive feedback.[42] The LFTR design must avoid certain combinations of graphite and salt and certain core geometries. If this problem is addressed by employing adequate graphite and thus a well-thermalized spectrum, it is difficult to reach break-even breeding.[42] The alternative of using little or no graphite results in a faster neutron spectrum. This requires a large fissile inventory and radiation damage increases.[42]Limited plutonium solubility - Fluorides of plutonium, americium and curium occur as trifluorides, which means they have three fluorine atoms attached (PuF3, AmF3, CmF3). Such trifluorides have a limited solubility in the FLiBe carrier salt. This complicates startup, especially for a compact design that uses a smaller primary salt inventory. Of course, leaving plutonium carrying wastes out of the startup process is an even better solution, making this a non issue. Solubility can be increased by operating with less or no beryllium fluoride (which has no solubility for trifluorides) or by operating at a higher temperature[citation needed](as with most other liquids, solubility rises with temperature). A thermal spectrum, lower power density core does not have issues with plutonium solubility.Proliferation risk from reprocessing - Effective reprocessing implies a proliferation risk. LFTRs could be used to handle plutonium from other reactors as well. However, as stated above, plutonium is chemically difficult to separate from thorium and plutonium cannot be used in bombs if diluted in large amounts of thorium. In addition, the plutonium produced by the thorium fuel cycle is mostly Pu-238, which produces high levels of spontaneous neutrons and decay heat that make it impossible to construct a fission bomb with this isotope alone, and extremely difficult to construct one containing even very small percentages of it. The heat production rate of 567 W/kg[83] means that a bomb core of this material would continuously produce several kilowatts of heat. The only cooling route is by conduction through the surrounding high explosive layers, which are poor conductors. This creates unmanageably high temperatures that would destroy the assembly. The spontaneous fission rate of 1204 kBq/g[83] is over twice that of Pu-240. Even very small percentages of this isotope would reduce bomb yield drastically by "predetonation" due to neutrons from spontaneous fission starting the chain reaction causing a "fizzle" rather than an explosion. Reprocessing itself involves automated handling in a fully closed and contained hot cell, which complicates diversion. Compared to today's extraction methods such as PUREX, the pyroprocesses are inaccessible and produce impure fissile materials, often with large amounts of fission product contamination. While not a problem for an automated system, it poses severe difficulties for would-be proliferators.[citation needed]Proliferation risk from protactinium separation - Compact designs can breed only using rapid separation of protactinium, a proliferation risk, since this potentially gives access to high purity 233-U. This is difficult as the 233-U from these reactors will be contaminated with 232-U, a high gamma radiation emitter, requiring a protective hot enrichment facility[63] as a possible path to weapons-grade material. Because of this, commercial power reactors may have to be designed without separation. In practice, this means either not breeding, or operating at a lower power density. A two-fluid design might operate with a bigger blanket and keep the high power density core (which has no thorium and therefore no protactinium).[citation needed] However, a group of nuclear engineers argues in Nature (2012) that the protactinium pathway is feasible and that thorium is thus "not as benign as has been suggested . . ." [84]Proliferation of neptunium-237 - In designs utilizing a fluorinator, Np-237 appears with uranium as gaseous hexafluoride and can be easily separated using solid fluoride pellet absorption beds. No one has produced such a bomb, but Np-237's considerable fast fission cross section and low critical mass imply the possibility.[85] When the Np-237 is kept in the reactor, it transmutes to short lived Pu-238. All reactors produce considerable neptunium, which is always present in high (mono)isotopic quality, and is easily extracted chemically.[85]Neutron poisoning and tritium production from lithium-6 - Lithium-6 is a strong neutron poison; using LiF with natural lithium, with its 7.5% lithium-6 content, prevents reactors from starting. The high neutron density in the core rapidly transmutes lithium-6 to tritium, losing neutrons that are required to sustain break-even breeding. Tritium is a radioactive isotope of hydrogen, which is nearly identical, chemically, to ordinary hydrogen.[86] In the MSR the tritium is quite mobile because, in its elemental form, it rapidly diffuses through metals at high temperature. If the lithium is isotopically enriched in lithium-7, and the isotopic separation level is high enough (99.995% lithium-7), the amount of tritium produced is only a few hundred grams per year for a 1 GWe reactor. This much smaller amount of tritium comes mostly from the lithium-7 - tritium reaction and from beryllium, which can produce tritium indirectly by first transmuting to tritium-producing lithium-6. LFTR designs that use a lithium salt, choose the lithium-7 isotope. In the MSRE, lithium-6 was successfully removed from the fuel salt via isotopic enrichment. Since lithium-7 is at least 16% heavier than lithium-6, and is the most common isotope, lithium-6 is comparatively easy and inexpensive to extract. Vacuum distillation of lithium achieves efficiencies of up to 8% per stage and requires only heating in a vacuum chamber.[87] However, about one fission in 90,000 produces helium-6, which quickly decays to lithium-6 and one fission in 12,500 produces an atom of tritium directly (in all reactor types). Practical MSRs operate under a blanket of dry inert gas, usually helium. LFTRs offer a good chance to recover the tritium, since it is not highly diluted in water as in CANDU reactors. Various methods exist to trap tritium, such as hydriding it to titanium,[88] oxidizing it to less mobile (but still volatile) forms such as sodium fluoroborate or molten nitrate salt, or trapping it in the turbine power cycle gas and offgasing it using copper oxide pellets.[89](p41) ORNL developed a secondary loop coolant system that would chemically trap residual tritium so that it could be removed from the secondary coolant rather than diffusing into the turbine power cycle. ORNL calculated that this would reduce Tritium emissions to acceptable levels.[86]Corrosion from tellurium - The reactor makes small amounts of tellurium as a fission product. In the MSRE, this caused small amounts of corrosion at the grain boundaries of the special nickel alloy, Hastelloy-N. Metallurgical studies showed that adding 1 to 2% niobium to the Hastelloy-N alloy improves resistance to corrosion by tellurium.[54](pp81–87) Maintaining the ratio of UF 4/UF3 to less than 60 reduced corrosion by keeping the fuel salt slightly reducing. The MSRE continually contacted the flowing fuel salt with a beryllium metal rod submerged in a cage inside the pump bowl. This caused a fluorine shortage in the salt, reducing tellurium to a less aggressive (elemental) form. This method is also effective in reducing corrosion in general, because the fission process produces more fluorine atoms that would otherwise attack the structural metals.[90](pp3–4)Radiation damage to nickel alloys - The standard Hastelloy N alloy was found to be embrittled by neutron radiation. Neutrons reacted with nickel to form helium. This helium gas concentrated at specific points inside the alloy, where it increased stresses. ORNL addressed this problem by adding 1–2% titanium or niobium to the Hastelloy N. This changed the alloy's internal structure so that the helium would be finely distributed. This relieved the stress and allowed the alloy to withstand considerable neutron flux. However the maximum temperature is limited to about 650 °C.[91] Development of other alloys may be required.[92] The outer vessel wall that contains the salt can have neutronic shielding, such as boron carbide, to effectively protect it from neutron damage.[93]Long term fuel salt storage - If the fluoride fuel salts are stored in solid form over many decades, radiation can cause the release of corrosive fluorine gas and uranium hexafluoride.[94] The salts must be defueled and wastes removed before extended shutdowns and stored above 100 degrees Celsius.[77] Fluorides are less suitable for long term storage because some have high water solubility unless vitrified in insoluble borosilicate glass.[95]Business model - Today's solid-fueled reactor vendors make long term revenues by fuel fabrication.[dubious – discuss] Without any fuel to fabricate and sell, an LFTR would adopt a different business model. There would be significant barrier to entry costs to make this a viable business. Existing infrastructure and parts suppliers are geared towards water-cooled reactors. There is little thorium market and thorium mining, so considerable infrastructure that would be required does not yet exist. Regulatory agencies have less experience regulating thorium reactors, creating potentials for extended delays.Development of the power cycle - Developing a large helium or supercritical carbon dioxide turbine is needed for highest efficiency. These gas cycles offer numerous potential advantages for use with molten salt-fueled or molten salt-cooled reactors.[96] These closed gas cycles face design challenges and engineering upscaling work for a commercial turbine-generator set.[97] A standard supercritical steam turbine could be used at a small penalty in efficiency (the net efficiency of the MSBR was designed to be approximately 44%, using an old 1970s steam turbine).[98] A molten salt to steam generator would still have to be developed. Currently, molten nitrate salt steam generators are used in concentrated solar thermal power plants such as Andasol in Spain. Such a generator could be used for an MSR as a third circulating loop, where it would also trap any tritium that diffuses through the primary and secondary heat exchanger[99]Liquid fluoride thorium reactor - Wikipedia