aging nuclear power stations, aging nuclear reactors, chemical attack, concrete, corrosion, degradation, environmental degradation, NRC comment period, nuclear containment structures, nuclear power plant, nuclear power plants, Nuclear Power Stations, Portland cement concrete durability, radiological attack, rust, Seabrook Nuclear Power Station, water, water transport
While the deadline for writing in support of the proposed rule for “Improved Identification Techniques Against Alkali-Silica Reaction Concrete Degradation” at US Nuclear Power Stations is past, the problem of aging concrete in nuclear facilities remains. This is especially true for spent fuel pools and the dry cask storage of nuclear waste. While containment should be an issue, at Fukushima style nuclear reactors, the US NRC has decided to have venting in the event of a nuclear disaster, with no radiation filter. Still, concrete failures within the nuclear power station could lead to other failures (e.g. broken pipes), leading to nuclear disaster.
The rule was proposed by those concerned about concrete degradation at the Seabrook Nuclear Power Station in New Hampshire, but just up the coast from Boston Mass. It is suffering from serious concrete degradation. Just looking at it common sense says that this is a non-brainer. Almost all nuclear power stations are on water. As we have discussed for several days, salt speeds up corrosion.
View of Seabrook Nuclear Power Station. Note bridge corrosion. The chloride in sea salt accelerates corrosion of metals by removing the protective oxide layer.
In this obviously watery context, it is interesting to read parts of what the inane Dan Naus, who is paid by the US taxpayer to spout a weird savvy or stupid combination of truths and pro-nuclear distortions-lies, has to say about water in Naus (2006) of ORNL: “Primer on Durability of Nuclear Power Plant Reinforced Concrete Structures – A Review of Pertinent Factors” for the US NRC. He states that “Water is the single most important factor controlling the degradation processes of concrete (i.e., the process of deterioration of concrete with time is generally dependent on the transport of a fluid through concrete), apart from mechanical deterioration.“. With the transport of water comes salt and other things, including bacteria, which degrade concrete. Water itself swells concrete. Then, of course, drying-lowering of water tables can lead to cracking. Water itself, the universal solvent, degrades concrete over time.
These excerpts are of what seem to be truthful portions of his document. He fails to mention the impact of radiation on the concrete, however, it falls under “environmental influences”. It has aspects of physical and chemical attack, but he should add radiological attack.
From Naus-NRC (2006):
“As concrete ages, changes in its properties will occur as a result of continuing microstructural changes (i.e., slow hydration, crystallization of amorphous constituents, and reactions between cement paste and aggregates), as well as environmental influences….
Concrete, however, can suffer undesirable changes with time because of improper specifications, a violation of specifications, or adverse performance of its cement paste matrix or aggregate constituents under either physical or chemical attack.
Portland cement concrete durability is defined as its ability to resist weathering action, chemical attack, abrasion, or any other process or deterioration.2 A durable concrete is one that retains its original form, quality, and serviceability in the working environment during its anticipated service life. The materials and mix proportions specified and used should be such as to maintain concrete’s integrity and, if applicable, to protect embedded metal from corrosion.3 The degree of exposure anticipated for the concrete during its service life together with other relevant factors relating to mix composition, workmanship, and design should be considered.4… Serviceability of concrete has been incorporated into the codes through strength requirements and limitations on service load conditions in the structure (e.g., allowable crack widths, limitations on mid-span deflections of beams, and maximum service level stresses in prestressed members). Durability generally has been included through items such as specifications for maximum water-cement ratios, minimum cementitious materials contents, type cementitious material, requirements for entrained air, and minimum concrete cover over reinforcement. Requirements are frequently specified in terms of environmental exposure classes (e.g., chloride and aggressive ground environments). Specifications in terms of service life requirements…have only recently been developed, primarily through European standards.6
Water is the single most important factor controlling the degradation processes of concrete (i.e., the process of deterioration of concrete with time is generally dependent on the transport of a fluid through concrete), apart from mechanical deterioration. … The rate, extent, and effect of fluid transport are largely dependent on the concrete pore structure (i.e., size and distribution), presence of cracks, and microclimate at the concrete surface. The primary mode of transport in uncracked concrete is through the cement paste pore structure (i.e., its permeability). The dominant mechanism controlling rates of water penetration into unsaturated or partially saturated concrete is absorption caused by capillary action of the concrete’s pore structure. Absorption is referred to as the sorptivity of concrete, with sorptivity defined as the rate of movement of water through a porous medium under capillary action. To improve the durability of concrete, generally the capillary and pore size within the concrete matrix should be reduced to a minimum.
Although the coefficient of permeability for concrete depends primarily on the water-cement ratio and maximum aggregate size, it is influenced by the curing temperature, drying, cementitious materials content, and addition of chemical or mineral admixtures as well as the tortuosity of the path of flow.
However as the nuclear power plants age, degradation incidences are starting to occur at an increasing rate, primarily due to environmental-related factors. One-fourth of all containments have experienced corrosion, and nearly half of the concrete containments have reported degradation related to either the reinforced concrete or post-tensioning system.
Portland cements are composed primarily of four chemical compounds: tricalcium silicate (C3S), dicalcium silicate (C2S), tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF). The type of portland cement produced (e.g., general purpose, moderate sulfate resistance and heat of hydration, high early strength, low heat of hydration, and sulfate resistant) depends on the relative amounts of the four basic chemical compounds and fineness (high early strength). The calcium silicate hydrates (C-S-H) constitute about 75% the mass. The C-S-H gel structure is made up of three types of groups that contribute to bonds across surfaces or in the interlayer of partly crystallized tobermorite material: calcium ions, siloxanes, and water molecules. Bonding of the water within the layers (gel water) with other groups via hydrogen bonds determines the strength, stiffness, and creep properties of the cement paste.
…” (Naus-NRC, 2006)
It would be helpful to everyone if everyone would use the proper chemical notation for the concrete, instead of the so-called “cement chemist notation”. This bogus notation keeps people from properly examining the sorts of chemical transformations which are undergone by concrete. It is apparently in the short-term interests of the concrete industry and in the interest of the nuclear industry- of which the US NRC and DOE and ORNL are clearly a wing – for people not to understand chemical degradation of concrete.
Here are the chemical compounds written in proper notation, as well as improper:
“Alite is a name for tricalcium silicate, Ca3SiO5, sometimes formulated as 3CaO·SiO2 (C3S in cement chemist notation, CCN). It is the major, and characteristic, mineral phase in Portland cement.” http://en.wikipedia.org/wiki/Alite
“Belite is an industrial mineral important in Portland cement manufacture. Its main constituent is dicalcium silicate, Ca2SiO4, sometimes formulated as 2 CaO · SiO2 (C2S in cement chemist notation)“. http://en.wikipedia.org/wiki/Belite
“Tricalcium aluminate Ca₃Al₂O₆, often formulated as 3CaO·Al₂O₃ to highlight the proportions of the oxides from which it is made, is the most basic of the calcium aluminates.” http://en.wikipedia.org/wiki/Tricalcium_aluminate
“Calcium aluminoferrite (Ca2(Al,Fe)2O5) is a dark brown crystalline phase commonly found in cements. In the cement industry it is termed ferrite. It also exists in nature as the rare mineral brownmillerite.” http://en.wikipedia.org/wiki/Calcium_aluminoferrite
“The type of portland cement produced (e.g., general purpose, moderate sulfate resistance and heat of hydration, high early strength, low heat of hydration, and sulfate resistant) depends on the relative amounts of the four basic chemical compounds and fineness (high early strength). The calcium silicate hydrates (C-S-H) constitute about 75% the mass. The C-S-H gel structure is made up of three types of groups that contribute to bonds across surfaces or in the interlayer of partly crystallized tobermorite material: calcium ions, siloxanes, and water molecules. Bonding of the water within the layers (gel water) with other groups via hydrogen bonds determines the strength, stiffness, and creep properties of the cement paste.” (Naus-NRC, p. 10)
On the first pages of this document, Naus’ distortion-lie is “These changes do not have to be detrimental to the point that concrete will not be able to meet its functional and performance requirements. When specifications covering concretes production are correct and are followed, concrete will not deteriorate.1“(Naus-NRC, 2006) Over time concrete degrades, period. We live in a real world, not a hypothetical one. The concrete at nuclear power stations is to protect in the case of an accident, as well as for day to day function. The concrete standards were weaker when the nuclear power stations were licensed in the US. As we saw yesterday, these standards were not followed or wood and gloves would not have been found. The statement by Naus was apparently taken, somewhat out of context, from B. Mather, “Concrete Need Not Deteriorate,” pp. 32–37 in Journal of American Concrete Institute, 1(9), Detroit, Michigan, September 1979.
It seems to be more of a senseless hypothetical statement of the sort found in the 2013 document by William et. al. where they state that water in concrete should increase shielding against radiation, but adding water to concrete weakens the concrete and weakens shielding by making it more porous. Then they make some inane statement about needing to do research.
Looking at this interview with Mather, it appears that is statement is more hypothetical: http://epdweb.engr.wisc.edu/AEC_Articles/07_Concrete_Repair_text.html
Furthermore, Mather is from the US Army Corps of Engineers, which apparently isn’t always as competent as one would hope. Their incompetence contributed to the levee failure- destruction of New Orleans during Hurricane Katrina: http://en.wikipedia.org/wiki/U.S._Army_Corps_of_Engineers_civil_works_controversies_(New_Orleans)
Naus’ idea appears to be that people should go scout for damage to the old concrete where it can be seen in the old nuclear power stations and patch them. However, patching is not a good solution for something as dangerous as a nuclear power station.
Maybe if people still read the Bible and tested it against what they see in everyday life, they would have more common sense. The Bible says in Mark 2: 21 “No man also seweth a piece of new cloth on an old garment: else the new piece that filled it up taketh away from the old, and the rent is made worse.” Rent means a tear. What it means is the strength of the new and old material are not the same. And, of course, the seam is a weak point too. Same thing for concrete. Common sense, no brainer for people who live in the real world and pay attention to their surroundings. (NB: That’s not what the Bible verse is really about, as it’s a parable. The parable refers back to common sense knowledge, which is now lost.)
Naus whopper distortion-lie is regarding the Roman Colosseum which is NOT concrete as he alleges. The stones did not even have mortar. It has been repaired many times, is under repair on google street-view and is not fit-safe for much use. It is open air and certainly not fit for nuclear containment. As Wikipedia explains: “The outer wall is estimated to have required over 100,000 cubic metres (3,531,467 cubic feet) of travertine stone which were set without mortar; they were held together by 300 tons of iron clamps. However, it has suffered extensive damage over the centuries, with large segments having collapsed following earthquakes. The north side of the perimeter wall is still standing; the distinctive triangular brick wedges at each end are modern additions, having been constructed in the early 19th century to shore up the wall. The remainder of the present-day exterior of the Colosseum is in fact the original interior wall.” http://en.wikipedia.org/wiki/Colosseum The French version of wikipedia also states that it was stone with no mortar. Some sources seem to suggest that cement mortar may have been used with brick in arches (this is not certain) and some concrete or cement paste-stucco was visibly added over the years, (visible within the colosseum). However, the cement-concrete used in Rome used special volcanic ash and has nothing to do with the modern cement-concrete used in nuclear power stations. They found another source which was water resistant for ports. We suspect that some terms related to masonry and mortar are getting mistranlated-misinterpreted. Furthermore, multistory housing collapsed in Roman times due to typical cost-cutting. There were concerns and Senate hearings, if I recall correctly from Roman History class.
Primer on Durability of Nuclear Power Plant Reinforced Concrete Structures – A Review of Pertinent Factors
Manuscript Completed: November 2006 Date Published: February 2007
Prepared by D.J. Naus
Oak Ridge National Laboratory Managed by UT-Battelle, LLC P.O. Box 2008 Oak Ridge, TN 37831-6283
H.L. Graves, III, NRC Project Manager
Prepared for Division of Fuel, Engineering and Radiological Research Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 NRC Job Code N6002”