Is Nuclear Energy Safe After Fukushima?

“Is Nuclear Energy Safe after Fukushima?”

By Dr. Michael Natelson

Ideal Taxes Association, Working Paper #4

Originally delivered as an Osher Lecture

CarnegieMellonUniversity Lifelong Learning Lecture Series

November 9, 2011

“In the beginning” there was Einstein’s land mark 1905 paper on Special Relativity. He was primarily concerned with putting the laws of electricity and magnetism on the same bases as the laws of mechanics. They should be the same in all inertial frames of reference. (In an inertial reference frame an object at rest stays at rest, and an object moving with at constant velocity maintains that velocity.) Einstein succeeded making use of the assertion (resulting from the Michelson-Morley experiments (1887)) that the speed of light c (300 million meters/second in vacuum) is the same in all inertial reference frames. The key result in Einstein’s paper relative to “Nuclear Energy” is E=Mc2 , the most widely known equation to the educated public. To see how it applies to energy release it is better written as E=Mc2 , the change in kinetic energy of participants in an inelastic collision (as apposed to an elastic (billiard ball) collision) is equal to the change in mass of the participants times the speed of light squared. Given the magnitude of the speed of light, it is easy to imagine a collision that resulted in a modest loss of mass would yield a huge increase in kinetic energy of the final constituents. When Einstein published his papers on this result no such collision (reaction) had been identified, but this did not inhibit people from imagining such a reaction and its possible consequences.

In early 1914, H. G. Wells published his novel The World Set Free. He wrote that in1932 we would discover a means of controlling the rate of radioactive decay of heavy elements, thus releasing large quantities of “atomic energy”. This abundant, and cheep, new energy source would revolutionize the world economy. Not all for the good, massive unemployment of manual laborers would result. Also, “atomic bombs” could be constructed, and with economic/social unrest a cataclysmic “atomic” world war between nation states would take place in the 1950s. As a result of this terrible war, Wells envisioned that the surviving leaders would see that a world governing process was an absolute necessity for mankind’s survival, and that wars between nation state having these weapons would be an anathema.

All Wells’ predictions are not right on the money, but in the large they are remarkable. Einstein’s “equation” did lead to an abundant (if not “cheap) new energy source. And, this “energy source” could yield terrible weapons, which having been used in war once, has led to some international institutions devoted to world peace and controlling these weapons. Wars between nation states having these weapons have been avoided. One could assume, as I believe Wells would, that this is because of mutual recognition of the horrible consequences of their use (by design or accident).

It is a remarkable coincidence that Wells chose 1932 for the breakthrough development of the mechanism of “atomic” energy release. For in fact James Chadwick discovered the neutron in1932. In 1911 Chadwick’s mentor and colleague Ernest Rutherford had determined that most of the mass of atoms was concentrated in a compact positively charged nucleus surrounded by a cloud of much smaller negatively charged electrons. The make up of the nucleus was not initially understood, which is easily seen by noting that: The lightest atom (element), hydrogen, has one electron. It’s positively charged nucleus is called a proton. The next lightest atom, helium, has two electrons. But it’s nucleus, with twice the positive charge of a proton, has approximately four times the mass of a proton. Chadwick’s neutron has no charge and is slightly more massive than the proton. With a short range, attractive force it can be part of an atomic nucleus, aiding in holding the protons together (At distances larger than the diameter of an atomic nucleus positively charged protons repel, but like the neutron at small distances they also exert an attractive force.). Thus, in the above example, the helium nucleus (referred to as an alpha particle) has two protons and two neutrons.

Now why is the discovery of the neutron the “breakthrough development”? The Hungarian physicist and friend of Einstein, Leo Szilard first saw the answer to this question. A neutral, uncharged, neutron should be able to readily penetrate a nucleus in an inelastic collision, cause the nucleus to split, fission, with a loss of mass and a release of much energy and possibly additional neutrons so as to cause more fissions, i.e. to initiate a chain reaction. Even though fission had not been observed in the early thirties, Szilard prepared a patent based on this idea for a nuclear reactor and assigned it the British government in 1936. (Rutherford had speculated about an energy liberating fission reaction, but with knowledge of only positively charged protons and alpha particles as initiators, he thought these particles would need so much kinetic energy to penetrate a positively charged nucleus that the net energy release would not be of practical use.)

With the discovery of the neutron, the Italian physicist Enrico Fermi began experiments bombarding naturally occurring heavy elements (e.g. Uranium) with neutrons to produce new heavy (transuranic) elements. He received a Nobel prize for this work in 1938. However, the German chemists Hahn and Strassman determined that Fermi had produced lighter elements. Hahn’s long time associate Lisa Meitner and her nephew Otto Frish identified Fermi’s process as fission, and reconciled it with a physics model of a heavy element nucleus absorbing a neutron and becoming unstable, splitting into high kinetic energy lighter elements (fission products), additional neutrons (2 or 3) , high energy electromagnetic radiation (gamma rays) and electrons/anti-electrons (beta particles).

News of Meitner’s work reached the USA in 1939, where Szilard, Einstein and Fermi had all emigrated to escape Fascism. Einstein was urged to write President Roosevelt to pursue nuclear research and stockpile Uranium, and so began the Manhattan Project. Niels Bohr, the eminent Danish physicist, was visiting the USA at the time, and informed his US colleagues that the most readily fissionable naturally occurring nucleus would be the minority isotope of Uranium, U235 (92 protons, 143 neutrons, .711 weight % of total U). (Various elements have more than one atomic weight, i. e. more than one isotope, depending on the number of neutrons in their nuclei.)

The Manhattan Project’s prime objective was to produce nuclear weapons as quickly as possible, before Germany or Japan. (Both countries had outstanding physicists.) But, as a key part of this effort nuclear reactors were developed. Fermi and Szilard led the design and construction of the first, a low power Critical Pile (CP-1) located under the stands of the University of Chicago’s Stag field.

With a mustering of talent and resources that no technology has ever received, the Manhattan Project succeeded. The most terrible war was ended, but nuclear energy was destined to be associated with “the bomb”. The first large reactors were built in HanfordWashington to produce the transuranic element Plutonium, a key component of more advanced “bombs”. (The bomb dropped on Hiroshima used Uranium enriched in the isotope U235). It was not until December of 1953 with President Eisenhower’s Atoms for Peace speech to the United Nations, that the development of nuclear reactors for electrical energy production got its big push.

By the end of WWII work was under way on reactor concepts for powering submarines. This effort was ultimately centered at Westinghouse’s Bettis Atomic Power Laboratory in Pittsburgh. The design for the first nuclear submarine, USS Nautilus (commissioned September 1954) was a pressurized water reactor, PWR. Water at ~ 2000LB/square inch and ~600o F is pumped through the reactor “core”, made up of fuel elements (some form of Uranium clad in corrosion resistant metal), the through heat exchangers (steam generators) and back through the core, this is called the primary loop(s). On what is called the secondary side of the heat exchangers, water is turned to steam which drives turbines, the steam exhausted from the turbines enters another heat exchanger (a condenser) where it is cooled to liquid and pumped back to the ”steam generators”, this is called the secondary loop. In the condenser “waste” heat is transferred to an ultimate heat sink, in the case of a submarine, the ocean.

Gwilym Price, the post war president of Westinghouse, met with Captain Hyman Rickover, the point man on the Navy’s nuclear submarine effort, and agreed to found and staff the Bettis Lab. (1948). Price saw a future for commercial nuclear energy and supported Bettis’ work (under Rickover’s direction) in conjunction with the utility, Duquesne Light, to design and build the nation’s first commercial nuclear power plant at Shippingport PA(1957). This plant was based on PWR technology. During the same time period an alternate “water’’ reactor was being developed at the Argonne National Laboratory. It is referred to as a boiling water reactor, BWR. In this case there is a single “loop.” Water (at ~1000 lbs/in2 , ~550 OF ) is pumped through the core where it boils. The liquid-steam mixture leaves the core and passes through baffles (separators) which direct the liquid back to the inlet to the care, and allows the steam to be piped directly to a turbine. As in a PWR the steam exhausted from the turbine is directed to a condenser and cooled to liquid. In a BWR the cooled water is pumped back to the inlet of the core. General Electric followed up on the Argonne work and commercialized BWR technology.

See below simple schematics for PWR and BWR electric power plants.

PWR(figure 1)

BWR(figure 2)______

BWR schematic.

By 1960 Westinghouse had established a commercial Atomic Power Division and with their licensees, e.g. Mitsubishi (Japan), Framatone (France), proceeded to build PWR plants in the US, Europe and Asia. Other industrial corporations, B&W, Combustion Engineering and Siemens, have also designed and built PWR plants. General Electric and its licensees, Hitachi and Toshiba, have built BWR plants in the US and Asia.

It obviously took more than President Eisenhower’s urging to get these corporations and their utility customers to embark on the risky enterprise of building and operating new technology plants. Economic gain, profit, was the primary motive, but contrary to what some critics have claimed, early industry leaders did not believe that this would be easy. The first Chairman of the US Atomic Energy Commission has often been quoted as saying that “nuclear power will be too cheap to meter.” He was in fact referring to an expectation he had for energy from fusion, not fission. When a young engineer at Foster-Wheeler Corp.(1954),Theodore Stern, eventually a Westinghouse Senior VP for commercial nuclear power, wrote an exhaustive report on how difficult the competition with fossil fuels would be for nuclear power. So what factors provided the optimism to undertake this enterprise?

ENERGY INTENSITY Fission has produced the enormous energy release envisioned from E=MC2. Note below the comparison (in the favorite energy units of nuclear physicists, electron volts) between fission of U235 and “combustion” of Carbon.

There is a factor fifty million, which is reflected in how little fuel is needed for a nuclear as apposed to a comparable fossil fuel power plant. This is well illustrated by comparing the yearly fuel requirement for the large power stations near Pittsburgh.

Mansfield on the left burns six million metric tons of coal per year in its three 835 megawatt electric (MW(e)) plants. The two BeaverValley nuclear plants (892 MW(e) and 846 MW(e)) add ~39 metric tons Uranium Oxide(in fuel elements) per year. The elements reside in the reactors for about four and a half years and are then removed. They still contain Uranium, but also fission products and transuranic elements (e.g. Plutonium isotopes). These “spent” fuel elements are initially stored in water filled pools. After a few years as their high radioactivity and attendant energy release decreases they can be stored in dry shielded canisters.

MINIMUM WASTE DISPOSAL While much is made today about the “problem” of nuclear waste disposal, the fact is that almost all the spent fuel generated at the US plants operating today is stored at the plant sites. The technology exists to reprocess spent fuel, extracting usable materials (Uranium, fission products with medical and industrial application and Plutonium to be recycled as power reactor fuel) and reducing the amount of highly radioactive waste that should ultimately be placed in a geologically isolated repository. Perspective on the magnitude of this “waste” is provided in the following table.

Table 1

From this data one can appreciate why the initiators of commercial nuclear power did not view waste disposal as a significant inhibitor. The handling of highly radioactive material cannot be taken lightly, but is not a difficult technical challenge. In the US it has, however, become a political problem, i.e. YuccaMountain. By law the Department of Energy (DoE) is to take ownership and dispose of spent fuel from the Nation’s commercial nuclear power plants. The utilities that own and operate these plant contribute to a fund to pay for the DoE’s efforts. In the US, spent fuel is not “reprocessed” (to be discussed below). The DoE had planned to transport spent fuel elements to Nevada, put them in highly corrosion resistant containers and place the containers in drifts (tunnels) under YuccaMountain(a desert geologic formation). Senator Harry Reid of Nevada has been able to stifle this plan. Reid withheld DoE funds for completing a licensing review of the YuccaMountain repository by the Nuclear Regulatory Commission. At present the DoE is considering a new study to reconsider the entire issue, but the legality of halting the licensing review is being decided in the courts.

Reprocessing of spent fuel is being done in some countries (e.g. France), but in the US availability of Uranium at reasonable cost is expected to meet the requirements of existing plants (104), and those to be built in the next ten years (~6), for decades. An acceleration of plant construction in the US and in the rest of the world will make reprocessing economically attractive. But as was evident to the pioneers of nuclear power, fuel resources should not be limiting to the growth of nuclear power.

RESOURCE ABUNDANCE.Uranium is common in the earth’s crust, see the table below. As noted previously it has a readily fissionable isotope, U235, referred to as fissile) and a majority fertile isotope U238 . Fertile, in that if it absorbs a neutron it has a high probability of transmuting into a fissile isotope. In the case of U238 the result is the fissile isotope of Plutonium, Pu239. The major isotope of Thorium,Th232, is also fertile. Here neutron absorption can yield the fissile Uranium isotope U233. The energy potential of fertile isotopes can be exploited in power reactors. In today’s PWRs and BWRs ~ a third of the energy produced is from fission of Pu239. Use of Thorium, which is more plentiful than Uranium, will most likely await the economic viability of reprocessing.

Table 2ppm is parts per million. ppb is parts per billion.

The bottom line is that Uranium, and ultimately Thorium, fueling reactors could supply the bulk of humanity’s electrical energy needs for several thousand years. A further motivation for pioneers of nuclear power is the fact that Uranium and Thorium have negligible substitution-value. They have no other significant economic application. This is not true for other sources of electrical energy. Obviously, coal, oil and natural gas are excellent chemical feed stocks. It is already clear that it makes no sense to burn oil to generate electricity. It is much more valuable as an energy source for transportation.

Burning gas in combined cycle turbine generators with thermal efficiencies of~60% is attractive at today’s gas prices, but with modern home heating furnaces at better than 90% efficient this use might be a better choice if we are to burn this finite resource. One can also think about “substitution-value” as applied to the resources needed for electrical energy generation from “renewable” sources. The land needed per Watt for solar, biomass and wind farms could have other uses.

Table 3

Having reviewed the origins of nuclear power and the motivations for its wide spread application, 104 plants in the US (20% of electricity generation), 433 plant total (~13% of electricity generation), we address the “questions” raised by the tragic events of March 11, 2011 in Japan.

First, how should we view the safety of nuclear energy relative to:

The health and welfare of the public?

Data says that it is “safe” when compared to other major sources of electric power.

Table 4 OECD is the Org. for Economic Cooperation and Development(34 European and North American Countries, plus Japan),does not include Russia, China and India.