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Dr. Digby MacDonald compares damaging cracks in nuclear reactor pressure vessels to Ebola or measles. He is professor in the Departments of Material Science, Engineering, and Nuclear Engineering at UC Berkeley. He is also affiliated with Penn State. He has written more than 930 academic papers; holds at least 10 patents; was Nobel Prize in Chemistry Nominee in 2011. He is an expert in corrosion science and electro-chemistry with a Ph.D in Chemistry. In short he is one of the foremost, and perhaps the foremost expert in the field. Thus, his warnings should be taken seriously. [1]

Unfortunately, outside of Belgium, his concerns appear to have gotten little attention. From a recent interview with Dr. MacDonald, Ph.D on the nuclear reactor cracks in Belgium:
(16 sec) “Ultimately if these voids become large enough, it will compromise the mechanical integrity of the system. It is vital that there be a surveillance program that continually monitors these flakes to see if they are growing….
[…]
(1.50) “At this point I would assume that this is a widespread illness, of reactors. This is like the measles or Ebola, ok.
[…]
(2.06) “Well, the importance could range from it being inconsequential to being so severe that it would shut down all of the reactors.
[…]
(2.49) “The phenomenon is basically the entry of hydrogen from water, which is on the inside of the reactor pressure vessel. The water is in contact with the stainless steel sheath, but hydrogen can go through and the stainless steel sheath corrodes – injects hydrogen into the stainless steel and then into the carbon steel. And, what happens is the hydrogen is injected as hydrogen atoms. They are small and they easily move through the lattices, like having a marble move through a pile of billiard balls.
billiard balls by Tmv23, CC-BY-SA-3.0, modified to illustrate radiation hydrogen damage
[Schematic image not in the original; photo credit at bottom.]
(3.25)
[…]
(3.58) “So the hydrogen pressure due to the hydrogen molecules builds up and will blister the steel.
[…]
(4.18) “Analyses have taken only a mechanical viewpoint of what’s happening, when, in fact, the fundamental root causes of this is most likely a corrosion problem, a corrosion issue and unless we deal with the root cause phenomena we are never likely to understand the phenomena at all
[…]
(4.47) “The consequences could be very severe, yes, fracture of pressure vessel, loss of coolant accident this would be a leak before break scenario. In which case before a fracture of pipe occurred or pressure vessel occurred you would see a jet of steam coming out through the insulation.
[…]
(5.35) “My advice is that all reactor operators under the guidance of their regulatory commissions or agencies, whatever they are, should be required to do an ultrasonic survey of their pressure vessels.

The reporter then asks “ALL 430 nuclear power stations, all over the world?
Dr. MacDonald responds “All of them“.
[From the Terzake-Redactie. be (13-2-15, 21.09) show on the Belgian Nuclear Reactor cracks-interview with Dr. MacDonald. The Terzake report continues with interesting interviews-discussion with experts in Flemish. The […], above, is additional information, commentary in Flemish. We transcribed Dr. MacDonald’s interview for those who may not understand Dr. MacDonald’s accent, for those who have no patience for the Flemish part, and because the interview may not stay online forever. It is literally critically important. For students or speakers of Germanic languages, the Flemish part appears almost more interesting. Original video found here: http://deredactie. be/cm/vrtnieuws/videozone/programmas/terzake/2.37612

The Terzake commentator notes, in Flemish, that this problem could involve nuclear submarines, as well. He also noted, in Flemish, that this is a well-known problem in the petrochemical industry. However, we note that the problem is much worse in nuclear reactors due to radiolysis, although one cannot exclude radiolysis in the petrochemical industry due to NORM (Naturally Occurring Radioactive Materials). Thus, we probably should not be surprised that the best general description of hydrogen damage is found at a Saudi Arabia university web site. It is short, clear, to the point with great visuals: http://faculty.kfupm.edu.sa/ME/hussaini/Corrosion%20Engineering/04.07.03.htm

Forgotten in this interview seems to be the role of neutrons in contributing to damage. See: https://miningawareness.wordpress.com/2014/08/15/neutrons-in-nuclear-reactors-bombs-make-non-radioactive-materials-radioactive-accelerate-reactor-degradation/

No discussion is made of the fact that these reactors used MOX, at least in the 1990s. More details on this are found below and the link to an extensive study by another Material Science expert is found at endnote. [2]

Some of the complex issues involved in degradation of nuclear reactors are outlined in the following computer models discussed in the dissertation of one of Dr. MacDonald’s Ph.D. students, Dr. Han Sang Kim, Ph.D.
FOCUS model of nuclear reactor damage from A Study for Modeling Electrochemistry in Light Water Reactors, by Han Sang Kim, 2007
A Study for Modeling Electrochemistry in Light Water Reactors, by Han Sang Kim, 2007, P-ECP model
From “A Study for Modeling Electrochemistry in Light Water Reactors“, by Han Sang Kim, 2007.

Dr. Kim, 2007 explains: “Using the frame of FOCUS, a new simulation code for the Pressurized Water Reactor (PWR) was developed in this study. In order to simulate the PWR, different radiological and chemical models for the calculation of individual chemical species concentrations were developed and equipped in this new code for PWRs. This new code was named P-ECP. Also, the pH model capable of calculating pH values with variations of temperatures and concentrations of the boric acid and lithium hydroxide was developed.” (p.iii)

Dr. Kim explains increased corrosion dangers due to high burn-up fuel and power uprates of nuclear reactors: “the uranium enrichment level is being increased to extend the cycle operation period, as a result, the capacity factor also increases. The cycle operation period which was 12 months a decade ago, now been extended to 18 months. With the increase in the uranium enrichment level, a high borate concentration is needed to control reactivity. In addition to the extension of the fuel burnup, most of the utilities are trying to increase the electrical power of the NPP, through power uprates. This requires higher coolant temperature and higher thermal outputs. The corrosive impact of these factors is significant in most situations, and may be critical in other cases“. (Kim, 2007, pp. 103-104)
[…]
Dr. Kim, 2007, explains that whereas the role of hydrogen in primary water stress crack corrosion is well known, there is still not an adequate hydrogen embrittlement model.
It is also well known that the dissolved hydrogen in the reactor coolant of PWRs affects the Primary Water SCC (PWSCC) of nickel base alloys such as Alloy 600. When the proper hydrogen embrittlement model is developed, that model could be included into the P-ECP code to calculate the crack growth rate.” (Kim, 2007, p. 119) (Emphasis added).
Dr. Kim’s Ph.D. studies at Penn State were funded by his employer, Korea Hydro & Nuclear Power Co., so he cannot be “accused” of anti-nuclear activism, on the contrary.

Further unknowns, such as the possibility of sub-standard steel entering the process, and defects which enter during the production of the reactor pressure vessel or other metal parts (e.g. cheating in the cooling process), make it almost impossible to predict the rate of cracking. High burn-up of fuel, which increases the corrosion of the zirconium, and which leads to higher likelihood of cracks in the fuel rods, which in turn leads to exit of radioactive metals (e.g. cesium, uranium, plutonium), which themselves can corrode, and lead to more hydrogen gas formation adds to the problem of evaluation of crack rate, as mentioned by Dr. Kim. Hydrogen gas (H2) is actually added to some water cooled reactors to reduce corrosion rate, but would apparently increase hydrogen damage, as radiolysis of the hydrogen gas could allow it to move through the steel, as single atoms. Pressurized reactors often add Boric acid which can speed up corrosion and production of hydrogen. Lithium is now known to pose previously unknown corrosion hazards. The problems of boric acid and lithium are discussed in Dr. Kim’s dissertation.

Hydrogen damage has been noted since at least 1875. However, radiolysis speeds the process up. This has been long known – probably for at least the 70 years since the start of the nuclear age, possibly longer due to earlier experiments with x-rays and radionuclides. Then, of course, there is neutron damage too.

Digby MacDonald discusses corrosion in cars from road salt, in this video. He explains that corrosion is attempts by refined metals to return to their natural state. http://youtu.be/ah_Y3Z5rRvc

Digby MacDonald on his development of a corrosion damage-fracture model, to “calculate the crack growth rates in stainless steels in nuclear reactors…as accurately as you can measure them“: http://youtu.be/9DJi_sWNnr8 He points out that naysayers said it could not be done, because “corrosion is too complex“. He says that “you can describe the pheonomena and damage fraction analysis as a result“. Is he eating crow about now? He may not be wrong in that he can “describe the phenomena“, in an ideal situation of nuclear reactor knowns, “as accurately as you can measure them.” This last is the crux. While it is interesting to try, the risks of depending on a model for nuclear reactors is too great. (Models need to be used, in conjunction with testing, for nuclear waste, however.) There are too many nuclear reactor input and operating unknowns. We suspect that some, or all, in the nuclear industry are manipulating these models to get the result which they want. After all, they have almost no liability in the event of an accident. In this interview, however, we see a bit of the dangerous optimistic arrogance, which has helped to perpetuate the nuclear industry. Science has been described as a continuum from physical science as hard science, to social science as soft science. However, in real life the number of variables, and intervening variables, which can enter into physical science, appear to be as problematic as those in the social sciences and generally with far more dangerous repercussions, exacerbated by an arrogant belief in the precision of scientific knowledge. A computer model is only as good as the input. One cannot speak of science as knowns, but only unknowns. That is both the challenge and the danger in the hands of arrogant men and women. In short, scientific method, yes. Science as truth, no. The world is too multivariate. And, there are intervening variables too.

Damaging effects of hydrogen in metallic materials have been known since 1875 when W. H. Johnson reported[1] ‘some remarkable changes produced in iron by the action of hydrogen and acids’. During the intervening years many similar effects have been observed in different structural materials, such as steel, aluminium, titanium, and zirconium. Because of the technological importance of hydrogen damage, many people explored the nature, causes and control measures of hydrogen related degradation of metals. Hardening, embrittlement and internal damage are the main hydrogen damage processes in metals.http://en.wikipedia.org/wiki/Hydrogen_damage

Another Materials Expert discusses possible causes of the cracks:
2.2.1 Radiation effects
During the operation of a nuclear power plant neutrons are emitted from the reactor core and reach the reactor pressure wall. Neutrons (with energies above about 0.5 MeV) cause atomic displacements in the RPV materials, creating interstitials and vacancies (so-called Frenkel defects) that can diffuse through the lattice, recombine or agglomerate forming larger defects. These defects impede dislocation movement causing embrittlement of the material. This radiation embrittlement results in an increase of the ductile-brittle transition temperature (DBTT) to higher temperatures and a reduction of toughness/ductility. The DBTT has to be far below the operational temperatures of the RPV otherwise there is a risk of brittle fracture of the component. Radiation reaching the RPV wall without displacing atoms in the materials lattice structure, can enhance diffusion of impurities by the deposited energy, the so-called radiation-enhanced diffusion (RED). Hydrogen diffusion in the material can also be supported by radiation.
‘The effects of neutron irradiation will lead, in the core area, to an embrittlement of the material and the generation of heat sources by γ-radiation. Heat sources caused by the absorption of γ-radiation are a special type of thermal loading.’ 37
Another effect originating from radiation impact on materials is the radiation-induced segregation (RIS), defined as a radiation-induced redistribution of alloy constituents and impurities at point defect sinks. 38

Radiation effects are complicated processes due to the simultaneous influence of temperature causing thermal diffusion of the produced defects. This diffusion can cause recombination of interstitials and vacancies, but can also induce the formation of vacancy or interstitial clusters. A consequence is for instance a reduced radiation embrittlement at higher irradiation temperatures39…” (p. 15)

In both Doel 3 and Tihange 2 NPPs MOX 43 fuel elements were used instead of pure UOX 44 -fueling during the 1990ies 45.

The consequence of MOX-fuelled reactor cores is a shift of the neutron spectra and the neutron flux for the impinging neutrons at the RPV wall depending on the core configuration 46. There is not much known on the effect of these changes with respect to radiation embrittlement of the RPV wall materials.
[…]
2.2.3 Fatigue
LCF (low-cycle fatigue) of RPV materials is caused by the thermo-mechanical cycling during the startup and shutdown procedures; an influence of the LCF on the microstructure (for instance hydrogen-related defects) and radiation-induced material degradation has to be expected.[2]
” (p. 17) From “Flawed Reactor Pressure Vessels in Belgian Nuclear Plants Doel-3 and Tihange-2, Some Comments“, by Ilse Tweer, Materials Scientist, Consultant, January 2013 Commissioned by Rebecca Harms, President of The Greens/EFA Group in the European Parliament http://www.greens-efa.eu/fileadmin/dam/Documents/Studies/Flawed%20Reactor%20Pressure%20Vessels%20in%20Belgian%20Nuclear%20Plants%20Doel-3%20and%20Tihange-2.pdf

Boric Acid Use
Boric acid is used in some nuclear power plants as a neutron poison. The boron in boric acid reduces the probability of thermal fission by absorbing some thermal neutrons. Fission chain reactions are generally driven by the probability that free neutrons will result in fission and is determined by the material and geometric properties of the reactor. Natural boron consists of approximately 20% boron-10 and 80% boron-11 isotopes. Boron-10 has a high cross-section for absorption of low energy (thermal) neutrons. By increasing boric acid concentration in the reactor coolant, the probability that a neutron will cause fission is reduced. Changes in boric acid concentration can effectively regulate the rate of fission taking place in the reactor. Boric acid is used only in pressurized water reactors (PWRs) (boiling water reactors (BWRs) use Sodium Pentaborate for the same purpose). Boric acid may be dissolved in spent fuel pools used to store spent fuel elements. The concentration is high enough to keep neutron multiplication at a minimum. Boric acid was dumped over Reactor 4 of the Chernobyl Nuclear Power Plant after its meltdown to prevent another reaction from occurring.http://en.wikipedia.org/wiki/Boric_acid

[1] Dr. MacDonald “Research Areas:
Electrochemistry, corrosion science, battery science and technology, thermodynamics, chemical kinetics, high temperature aqueous chemistry, nuclear power technology, energy conversion technology, and physical chemistry
Education:
1969 Ph.D., University of Calgary, Chemistry
1966 MSc, University of Auckland, Chemistry
1965 BSc, University of Auckland, Chemistry

Nominated for the Nobel Prize in Chemistry, 2011
http://www.mse.berkeley.edu/ourfaculty/macdonaldd

[2] “Flawed Reactor Pressure Vessels in Belgian Nuclear Plants Doel-3 and Tihange-2, Some Comments“, by Ilse Tweer, Materials Scientist, Consultant, January 2013
Commissioned by Rebecca Harms , President of The Greens/EFA Group in the European Parliament http://www.greens-efa.eu/fileadmin/dam/Documents/Studies/Flawed%20Reactor%20Pressure%20Vessels%20in%20Belgian%20Nuclear%20Plants%20Doel-3%20and%20Tihange-2.pdf

Photo credits: “Pool billiard balls with three chalk cubes,” by Tmv23, CC-BY-SA-3.0, original modified with addition of hydrogen, etc. Modifications based on our understanding-interpretation of the MacDonald interview, and the explanation of hydrogen damage found here, which is the best illustration and explanation which we found online: http://faculty.kfupm.edu.sa/ME/hussaini/Corrosion%20Engineering/04.07.03.htm However, it is not regarding radiolysis per se. Nonetheless, it explains that only hydrogen atoms can enter the metal, not the molecule. Once the hydrogen atoms enter they join to form the H2 molecule and exert pressure on the metal. Also very useful for basics: http://www.personal.psu.edu/staff/m/b/mbt102/bisci4online/chemistry/chemistry4.htm

[Emphasis added by us, throughout, even where not noted.]