The world is in the middle of a crisis concerning nuclear energy. Fukushima, reprocessing breaches, loss of coolant, fuel melts, release of radioactives into the environment – a host of nuclear hobgoblins beat about our heads, screech our ears. Are there sensible solutions?
I believe the answer is yes – we could, should we so choose, have nuclear power generation that provides for safety in as much as there is safety in anything.
Addendum: 2011 May 25. Matthew Wald published an article in the New York Times today discussing storage of spent fuel, the principal topic for our current post this post. There is a good map of US reactors and the amount of stored radioactives at each. This is an article on a report by Robert Alvarez of the Institute for Policy Studies where it is available as a PDF, also a 1 page Fact Sheet in PDF format. This set of reports fully support the analysis presented here.
Decisions-1 covered the sorry history of nuclear accidents and identified loss of coolant and waste storage as the main events that lead to environmental disruption, or worse.
Although bad events have happened during reactor operations, none have ever degenerated into a worst-case incident. We are lucky that our known incidents have only been very close misses. Even the fuel melt at Chernobyl was not as bad as it could have been.
• Loss of coolant and fuel melt issues were considered in Decisions-2. This top (superficial) level review pointed out that for more than 4 decades, designs of intrinsically safe reactors have been available. A high temperature helium cooled reactor is self stabilizing to LOCA events; it would naturally park itself at a safe operating point if something interfered with the flow of the cooling gas.
Reactor design is currently undergoing re-analysis with the proposed Generation III reactors, expected to start coming on line about 2015. Most of these are safer forms of our same old boiling water and pressurized water reactors, using highly simplified control design and special passive mechanisms in an attempt to make the active controls more reliable. See Gen-III. Units like the French Areva’s EPR or the Westinghouse AP1000 are examples.
It is too easy to imagine failure modes – what if multiple things go wrong (a la Fukushima)? These plants would be safe against everything but the unexpected.
Even so, had the various corporate managements allowed, these could have been proposed in the 1960’s when we were into nuclear construction; the history of nuclear power might have been much more benign.
The Gen-III discussion website just mentioned compares reactor issued to a car wreck. Are they really similar? The thread through all my posts is that reactors generate a different class of incident. A car wreck might kill one or two families, but a reactor wreck might make Japan uninhabitable … to name a country at random. Reactor incidents are low probability events with consequences that are transcendent to the merely awful ones.
Assessment: Modifications to PWR and BWR designs are too little and much too late.
Many Gen-III proposals are for throw-away reactors (use them up and ditch them). These are mostly small generator modules (< 300MWe) meant for sites (A) located away from the power grid, (B) that have small but needed power demands, (C) with many parallel units to provide high overall output power (GWe) with good reliability, or all three. No one mentions what exactly will happen to the cores when they are dumped. I suspect they do not plan to put these in some farmer’s ditch or in a municipal dump, but afterwards, what?
Assessment: Throw-away reactors do not help the overall issue of long-term safety.
Gen-III also has proposals for at least two kinds of the high temperature helium cooled reactor, outgrowths of the 1970’s HTGR design. These are (A) the the gas cooled modules reactor with encapsulated fuel pellets loaded in graphite blocks (like the old HTGRs), and (B) the pebble bed which uses ping-pong sized fuel capsules that are inserted into the top of the funnel shaped core, flow down to the bottom drain port, then out for reuse or replacement.
One of the (A) types is the GT-MHR designs (Gas Turbine Modular Helium Reactor). The idea probably grows from General Atomics’ analysis of the success with its small Peach Bottom reactor and the issues that kept its large Fr. St. Vrain unit from full success. These are proposed as clusters of small modules (250 MWe generators). They would be highly cost competitive due to the high build-volume envisioned. There is no inefficient intermediate coolant loop and the turbine is driven by the coolant at 850ºC; very high thermal efficiencies are expected.
Follow-on Gen-IV designs are also being evaluated by a panel of the 13 signatories to the Gen IV International Forum (GIF). Machines from these deliberations might not enter service much before 2030. these should be high efficiency naturally safe reactors.
Both Gen II (ended in the US in 1979) and Gen III (currently under construction) have designs that are intrinsically safe and cost effective. Power company management and the NRC regulators have just not bothered with them, yet.
No excuses: Fuel melt due to loss of coolant accidents ought to be a thing of the past.
• Fuel waste storage or disposal scenarios were examined in Decisions-3. Fuel sequestration was identified as false security; disposal techniques would probably work and include fusion or accelerator neutron generators for enhanced transmutation.
The most common “solution” is permanent immersion in continuously chilled and circulating water. These are disasters waiting for release.
Fukushima, for example, had over a million rods in its spent fuel storage pools when the tsunami and LOCA events occurred. This is the background for the catastrophe that still unfolds as this is written.
Most reactor fuel pellets are enriched uranium with small ad-mixture of plutonium; These pellets become spent (poisoned for fission) with 97% of the original fuel left intact. Spent fuel rods are an attractive nuisance, sort of like putting poisoned candy out – If you leave it out, you might destroy more than pests. There is a lot of usable stuff in spent rods which people must handle, move about, maybe reprocess. Where there be humans, be there the threat of diversion. So we have the double danger of release into the environment and diversion to terrorists. Waste handling really is a tough issue.
There is nothing we can compare with a waste storage breaching problem; it is an event without peer. The handling of nuclear waste must be treated more rigorously than mining ore or pumping petroleum which might only cause severe local environmental damage and with only occasional widespread losses of life.
Sequestration is the top choice of many people and attractive methods have been proposed.
All fail either in the delivery phase (during transit to the sequestration location) or in the long term storage phase (during the 100 thousand to 10 million year interdiction period).
We must eradicate the threat. Our only current choices are to use dirty chemical reprocessing (potential for diversion of weapons grade material and environmental spills), or to use fast breeder reactors (which have proven hugely dangerous and where, again, the material must be processed by humans), or to look seriously at transmutation schemes to burn nuclear waste into simpler atoms thereby cutting short the interment.
Decision-III argued that we must not choose sequestration. We cannot obligate God to keep our poisons safe and must not expect nature to do so (too many zeros in the sequestration times).
What is it worth?
The US chose the short term safety of not undertaking the danger of reprocessing techniques. As of now, underground storage has proven to have unacceptable risks, refer t0 the Yucca Mountain discussion.
On May 13, 2011, the President’s review committee made the unwise decision to use above ground dry cask isolation and putting this at a site, yet unselected.
I really have only one question: How do the manufacturers of these casks plan to reimburse the locals for leaks 100,000 years from now?1
How much natural Uranium are we discussing?
When asking how much waste must be sequestered, we have to ask: how much uranium can we find to use? This is like asking how much oil can I buy at 40 US$/bbl? (1 bbl is 1 barrel). To answer the petroleum question, we are flat out of oil at that price. The point is that the price of anything will rise as demand tries to exceed supply. For a finite reservoir like the petroleum reserves, when about half the stored amount has been used, demand will outpace supply and cause very high prices, indeed.
Rising Demand:: In the last couple decades, China, India and others have been busy building their manufacturing economy, but especially their nuclear armaments. The demand for U has risen dramatically just since the turn of this new century.
Fuel Data: Uranium occurs naturally in the Earth’s crust as U3O8 (natU). About 2/3 of a percent of natU is 235U called fissile, because it fissions into smaller daughter products and releases a lot of energy. For a fuel pellet, uranium must be separated from oxygen and 235U concentration enriched to a couple percent in concentration. This is LEU, low enriched uranium. The rest is 238U
Concentration Data: NatU has a concentration of about 2.8 ppM, similar to tin and nearly 600× that of gold. Some exists in mineable deposits and some is weakly diffused everywhere. Bricks, stones, seawater … it is all around us. Radon in people’s basements comes from radioactive decay of the U in cement and mortar. Most would be hard to get and expensive to extract. Consider the mine-able deposits.
Material Data: The RAR (Reasonable Assured Reserves same as proven reserves) for natural Uranium is shown in the table for both 2005 and 2009. Assumption: ultimately, we will have RAR =19 Mt. We also see the 10:1 relationship between natural Uranium and low enriched uranium, and the energy generated by that 1 t of LEU.
Mt means million metric tons. We drop the metric distinction because one metric ton only 10% more than one English ton.
kWh is kilo Watt hour. Monthly home energy bills are stated these units.
Usage Data: Information for 2008 from U.S. EIA . As a whole, the world used 144 T kWh of electrical energy. Nuclear power contributed about 1.9% of that. U.S. numbers are as shown, nuclear provided about 3.7%.
T means trillion (US) or tera (ISO).
How many tons of natU were required in 2008?
Ore = (2.8 T kWh/yr) · (1 t LEU/400 M kWh) · (10 t natU/t LEW) = 70,000 t natU/yr
How long will natU last at the 2008 rate but with RAR=19 M t?
Time at current usage rate = 19 M t /(0.07 M t/yr) = 270 years.
If you have read any of our Peak Oil posts, you will know that it is very likely that we are at the peak of oil production; the world’s fields will not continue to match demand. We need something to replace petroleum as the power source of choice.
Suppose we replace all power devices by rechargeable batteries. No kerosene, gasoline, etc. It makes sense to ask: If we try to make up for petroleum loss by total reliance on uranium, how long would mineable resources last?
How long will natU last at the 2008 rate but with triple RAR?
Inverse relation: If at 2% of total, the uranium will last 260 years, then increasing the fractional usage must decrease the total lifetime of the ore deposits … fraction-used times lifetime is a constant number. ( f T )A = ( f T )B for any two rates A and B
Lifetime if sole power = (fraction of total) × (Lifetime if at fraction)
0.019 × 270 y = (1) × T … sole power means f = 1.
Lifetime of natural Uranium if sole source of power T = 5.1 years.
Shift to total nuclear dependance, use up natU ore in less than 5 years.
To summarize the results: the fuel melt issue – We could build reactors safe from fuel meltdown, if we so choose.
The nuclear waste issue – storage, transmutation or reuse. We have two options.
Assume no reuse of spent fuel: We maintain current U.S. policy of sequestering spent fuel, or we decide to transmutate it to assure safety to our progeny. We must recognize that mine-able fuel represents no more than 5 years of world energy supply. Keeping our reactors running doing this is a truly stupid policy that just builds the future danger. It is ridiculous to consider nuclear power to be worth continued build up of deadly residue if availability is so short (nuclear needed for all power uses).
Under this set of rules, we should shift the investment in nuclear power into some other power source that can deliver much more than a 5 year reserve.
Oil is at the halfway depletion point, after 150 years after its beginning. I would expect inexorable price rises over the coming years, accompanied by large fluctuations. Even so, gasoline will be available at least another 20 to 50 years; but will grow increasingly unaffordable, but it will be available. This means we still have a short interval for smooth transition to another energy source.
Assume we decide to reuse the spent fuel: The US policy whose idea originated in 1957 and began implementation in 1976 (see previous posts) is wrong. We must reuse the 97% good fuel we are throwing out, and invest in using other reactor technologies. If we do this we could assure high levels of power for many hundreds of years (perhaps thousands).
This is not a call for a return to Fermi I, Dounreay, Phénix or any of the other fast breeder reactors that were frightening and very dangerous.
- The CANDU heavy water reactors can generate power using our current volume of spent fuel after some reprocessing. This is demonstrated technology with decades of evolutionary development. The history with India may indicate that it could be used to make weapons grade fuel, however.
- Innovative Gen-III reactors like GT-HTR and PB-HTR designs are also “fast” units that are intrinsically safe. These high temperature helium cooled reactors are also demonstrated successful technology. The diversion capability is unclear with these units.
If governments are willing to provide secure facilities, these reactors are a stupendous opportunity for a massive extension of the reservoir lifetime. General Atomics leads a consortium for small-module, very high-efficiency reactors. Because they use fast neutrons, they are able convert spent fuel into second generation fuel sources. and other meterials such as thorium (which is more abundant than uranium). This way, nuclear energy could last for more years than can be intelligently predicted.
Preferred waste disposal: Even if we were to reject these as primary power plants (and begin the closure of our nuclear plants), as waste burners, they still are superior to either accelerator or fusion neutron sources.
At The End
Those final paragraphs sound good, but I am very discouraged. The cartoon says most of what I think, and in only 14 words. We need charismatic leadership to take us to secure energy; we had such to take us to the moon. Nowhere do I see even one charismatic political or scientific leader to step forward. Certainly not on the President’s Commission, which did only what it was told to do: it suggested a “new” sequestration technique.
Here, as throughout the history of nuclear power, we see the spectrum of human motivations. Almost all human motivations are present in our nuclear energy processes: intense professional fear, high levels of financial gain, the urge for self protection, desire for personal aggrandizement or to minimization of criticism, certainly for professional advancement. For decades these have trumped the need for our civilization to survive.
Thus the core thrust of this blog site. We must act decisively to keep our technical society in existence. Do we have the will to succeed?
Charles J. Armentrout, Ann Arbor
2011 May 15, Addendum, 2011 Jun 3
Listed under Technology … Technology > Fission
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1 I am not certain where this cartoon came from. I clipped it from a magazine many decades ago and I cannot read the artist’s signature. It has served as my icon for the nuclear industry since. I wish I could locate its source, and would appreciate being told its origin. It is a gracefully drawn, bitingly clear statement of my own personal feelings about US society as it has existed for most of my life.
Update: 2013 Mar 31 This week I discovered the cartoonist Ed Fisher (not Ed Fischer) used the signature shown on our dinosaur cartoon, it is in his style, and I now believe it was published in the Saturday Review of Books (defunct), mid to late 1960s . It is hard to find information about him, but I believe his first name is Edwin and he died in the early 2000’s. This is not from the New Yorker magazine, and is not included in any of Fisher’s cartoon sets. There is no website about Mr Fisher to validate creative authorship.