JPH0843586A - Method for decreasing occurrence or growth of crack in surface of metal part - Google Patents

Abstract

PURPOSE: To provide a method of reducing generation or growth of a crack on a surface of a metal part in a water cooling type nuclear reactor or its related equipment. CONSTITUTION: A method includes a step for filling solution or suspension of a pH adjusting compound in reactor water. The pH adjusting compound is added by amount so that pH in a tip of a crack or in a portion where the crack tends to be generated is within a range of about 6.5-8.0 unrelated to electrochemical potential (at high temperature). The compound is resolved under temperature condition of the nuclear reactor and emits S or atom for adjusting pH of the reactor water. pH of thus adjusted reactor water is within 6.5-8.0.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for inhibiting stress corrosion cracking of metal parts exposed to high temperature water. As used herein, "hot water" refers to water, steam, or condensate produced therefrom that has a temperature of greater than or equal to about 150 ° C. Hot water is found in a variety of known devices such as water deaerators, nuclear reactors and steam driven generators.

[0002]

BACKGROUND OF THE INVENTION Nuclear reactors are used for power generation, research and propulsion applications. In the reactor pressure vessel, reactor coolant (ie, water) to remove heat from the core
It is included. Each tubing system carries heated water or steam to a steam generator or turpin and returns recycled water or feedwater to the pressure vessel. The operating pressure and temperature of the pressure vessel are about 7 MPa and 288 ° C. for a boiling water reactor (BWR), and about 15 MPa and 32 for a pressurized water reactor (PWR).
0 ° C. The materials used in both BWRs and PWRs must be able to withstand various load, environmental and radiation conditions.

Examples of materials exposed to high temperature water include:
Carbon steel, alloy steel, stainless steel, nickel base alloys, cobalt base alloys and zirconium base alloys can be mentioned. Despite the careful selection and treatment of these materials used in water-cooled nuclear reactors, corrosion of materials exposed to high temperature water occurs. Such corrosion includes stress corrosion cracking, crevice corrosion, wear corrosion, pressure relief valve sticking, and γ
It causes various problems such as the accumulation of ⁶⁰ Co isotopes that emit rays.

Stress corrosion cracking (SCC) is a known phenomenon that occurs in nuclear reactor components (eg, structural components, piping, fasteners and welds) exposed to high temperature water. As used herein, "SCC" means a crack that grows due to a combination of static or dynamic tensile stress and corrosion at the crack tip. Reactor components may have, for example, differences in coefficient of thermal expansion, operating pressures required to contain the reactor cooling water, and other causes such as residual stresses associated with welding, cold working and other asymmetric metal treatments. ) Are susceptible to various stresses. Furthermore, water chemistry, welding, interstitial geometry, heat treatment and radiation may increase the susceptibility of component metals to SCC.

It is well known that SCC occurs at a faster rate when oxygen is present in the reactor water at a concentration of about 1-5 ppb or higher. There is also a further increase in SCC in the high flux of radiant flux that produces oxidative species such as oxygen, hydrogen peroxide and short-lived radicals due to radiolysis of reactor water. Such oxidizing species increase the electrochemical corrosion potential (ECP) of the metal.
Electrochemical corrosion is caused by the flow of electrons from the anode region to the cathode region on the metal surface. E
CP is a measure of thermodynamic tendency indicating the likelihood of corrosion phenomena, and is a basic parameter in determining, for example, SCC, corrosion fatigue, corrosion film thickening, and general corrosion rate.

In the BWR, as a result of radiolysis of the primary cooling water in the core, a small amount of water is decomposed into H ₂ and H ₂ .
_It produces products such as ₂ O ₂ , O ₂ , oxidizing radicals and reducing radicals. Under steady-state operating conditions, the concentrations of O ₂ , H ₂ O ₂ and H ₂ present in the recirculating water and steam sent to the turbine reach equilibrium. Such concentrations of O ₂ , H ₂ O ₂ and H ₂ are oxidative, which may result in conditions that promote intergranular stress corrosion cracking (IGSCC) of sensitive structural materials. . One of the methods used to reduce the IGSCC of sensitive materials is the use of hydrogen water chemistry (HWC) technology, which changes the oxidizability of the BWR environment to a more reducing state. Such an effect is achieved by adding hydrogen gas to the water supply to the reactor. When such hydrogen reaches the pressure vessel, it reacts uniformly with the oxidizing species produced by radiolysis on the metal surface to regenerate water, thereby dissolving the oxidizing chemistry dissolved in the water near the metal surface. Reduce the concentration of seeds. The rate of such recombination reactions depends on the local radiation field, the water flow rate and other variables.

The injected hydrogen reduces the level of oxidizing species (eg, dissolved oxygen) in the water, and consequently the ECP of the metal in the water. However, due to factors such as fluctuations in the flow rate of water and the irradiation time and intensity of neutrons and γ rays, the amount of oxidizing species produced differs depending on the reactor. Therefore, IGSC in high temperature water
The amount of hydrogen required to reduce the level of oxidizing species to a sufficient extent to keep the ECP below the critical potential to prevent C was not constant. As used herein, the term "critical potential" means a corrosion potential within the range of about -230 to -300 mV when expressed on the standard hydrogen electrode (she) scale. In a system where ECP is higher than the critical potential, IGSCC progresses at a fast rate, and in a system where ECP is lower than the critical potential, IGSCC progresses at a substantially slow rate or does not progress at all. Whereas water containing oxidizing species such as oxygen raises the ECP of metals exposed to it above the critical potential,
Water containing little or no oxidizing species is E
CP is lowered below the critical potential.

Thus, SCC susceptibility in BWRs is significantly influenced by the corrosion potential. FIG. 1 shows 0.
2 with a solution conductivity in the range of 1-0.5 μS / cm 2
FIG. 3 shows observed and predicted crack growth rates as a function of corrosion potential for 304 stainless steel sensitized in the furnace at 27.5-30 MPa√m in 88 ° C. water. The data points at high corrosion potential and crack growth rate correspond to irradiated water chemistry conditions in test or commercial reactors. Reducing corrosion potential is the most widely pursued means to reduce SCC in existing plants. The fundamental importance of corrosion potential compared to (for example) the dissolved oxygen concentration itself is shown in FIG. The figure shows that once excess hydrogen conditions are achieved, the crack growth rate of Pd coated CT specimens is dramatically reduced despite the presence of relatively high oxygen concentrations. Figure 2 shows Pd of sensitized 304 stainless steel.
3 is a graph plotting crack extension versus time for coated CT specimens, about 0.1 μM H ₂ SO ₄ in 288 ° C. water containing about 400 ppb oxygen.
It is shown that the promotion of crack growth occurs in the presence of.
Since the CT specimens were coated with Pd, the change to excess hydrogen conditions resulted in a decrease in corrosion potential and crack growth rate.

By the way, as our understanding of SCC progresses, the focus shifts from controlling dissolved oxygen to the corrosion potential (which is a more basic parameter) and then to the crack tip (which is an even more basic parameter). Moved to chemistry. Dissolved oxygen determines the corrosion potential (along with other oxidants and reducing agents and other factors (eg, flow rate)), and the corrosion potential alters crack chemistry by concentrating anions and changing pH. Let Therefore, controlling the pH of the crack tip constitutes the most basic way to control the environmental components of SCC. If suitable means for limiting the change in pH within the cracks were identified, it would be possible to significantly reduce SCC regardless of the dissolved oxygen concentration or corrosion potential.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to the root cause of environment-enhanced crack growth in hot water (ie, solution pH within the crack).
To prevent stress corrosion cracking of metal parts. With the progress of our understanding of SCC, the emphasis has moved from the dissolved oxygen itself to the corrosion potential (which governs the sensitivity to SCC). At constant oxygen levels, high flow rates tend to increase the corrosion potential, while precious metal coatings can decrease the corrosion potential. Increasing the corrosion potential leads to concentration of anions within the crack and changes the pH within the crack. However, it is not the corrosion potential itself that promotes SCC, but the pH of the crack tip.
Experiments have shown that it is the effect of the corrosion potential on the. Therefore, the method of limiting the change in pH within the crack is SCC regardless of the dissolved oxygen concentration or corrosion potential.
Can be significantly reduced. According to a preferred embodiment, the change in solution pH in hot water is about 6.5-.
SCC is suppressed by limiting it to within the range of 8.0.

Means for limiting changes in pH include the use of chemical buffers to adjust the water chemistry [ie,
Depending on the anionic species in the water, an acid or base (eg Z
controlled addition of nO)]. Ideally, such species would have only a small effect on low temperature conductivity (so that radioactive waste does not increase significantly with increasing desalination load), while at the same time increasing the temperature of hot water. It is necessary to preferentially dissociate in.

The advantages of such comprehensive means include (1)
No need for consideration of corrosion potential and related oxidizing species, and (2) importance of anionic impurities because the effect of anionic impurities on the chemical conditions (pH) in the crack is directly controlled. And (3) that the flow rate in the reactor water purification system (which typically accounts for 1 to 3% of the reactor water flow rate and affects the overall thermal efficiency) can be reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with a preferred embodiment of the present invention, crack growth in metal parts immersed in high temperature water can be reduced by adjusting the solution pH inside the crack. . In the case of water-cooled reactors (eg BWR), to adjust the pH inside the crack, pour the circulating water (eg by injection into the feed water).
An H regulator may be added. Such pH adjusters can consist of chemical buffers, acids or bases, depending on the magnitude and direction of the pH change required.

The susceptibility of metal parts in hot water to SCC correlates with an increase in corrosion potential. The increase in corrosion potential causes the concentration of anions and changes the pH within the crack. The effect of corrosion potential on crack tip pH increases SCC. Based on the following logic, the basic importance of the crack tip pH is confirmed. The corrosion potential (at the outer surface) and the conductivity of the solution (body) interact to produce specific intra-crack chemistry. Therefore, constant in-crack chemistry may result from different combinations of corrosion potential and conductivity. That is,
High corrosion potential and moderate conductivity can theoretically result in the same chemical conditions in a crack as low corrosion potential and high conductivity. Although analytical and experimental modeling exists to demonstrate such basic interactions, the exact relationship over the entire range of corrosion potential and conductivity level (and type) is analytically also. It has not been fully quantified or confirmed experimentally. 1 and 3 illustrate the difference in susceptibility to, for example, conductivity as a function of corrosion potential.

Specifically, FIG. 3 is a graph plotting crack extension versus time for a Pd coated CT specimen of sensitized 304 stainless steel. This figure shows 400
If a low corrosion potential (excess hydrogen, ie 78 ppb of H ₂ ) is maintained despite the presence of ppb oxygen, then at 33 MPa√m a high impurity level (0.1
It shows increased tolerance to μM or 0.863 μS / cm H ₂ SO ₄ ). At 6124 hours, changing to an excess of oxygen dramatically increases the corrosion potential and crack growth rate. Also, when the state of hydrogen excess is restored at 6244 hours, the corrosion potential and the crack growth rate decrease again.

FIG. 3 shows that at low corrosion potentials (which occur under excess hydrogen and moderate oxygen conditions on Pd coated CT specimens), the tolerance for impurities is dramatically higher than at higher corrosion potentials. It is shown that. However, even at low corrosion potentials, the crack growth rate increases if a sufficient amount of impurities are added (see FIGS. 4-6). FIG. 4 shows degassed 2 which gives φ _c = −0.6 V _she in the slow strain rate experiment of 1 × 10 ⁻⁶ sec ^−1.
Shows the effect of addition _of H ₂ SO ₄ for crack growth rate of the sensitizing 304 stainless steel tested in water at 89 ° C.. FIG. 5: Sensitization 3 tested in degassed 289 ° C. water containing 0.3-10 ppm H ₂ SO ₄ during a slow strain rate experiment of 1 × 10 ⁻⁶ sec ^−1.
4 shows the effect of the borate / sulfate molar ratio on the crack growth rate of 04 stainless steel. FIG. 6 relates to stainless steel and Alloy 82, 28
Figure 3 shows the correlation between corrosion potential and solution conductivity in determining anion activity at the crack tip by comparing the crack growth rates in aerated and degassed solutions at 8 ° C. If the crack growth rates under the two conditions are similar, it can be inferred that the chemical conditions at the crack tip are also similar. Each point represents a pair of data obtained under similar crack growth rates and loading conditions for stainless steel and alloy 82 in 288 ° C water. Since complete data pairs showing identical crack growth rates under aerated and degassed conditions were generally not available,
The ratio of the crack growth rate in the aerated solution to the crack growth rate in the degassed solution is indicated by the label (eg 2.9x). The arrow indicates the direction in which the points move when the crack growth rates are perfectly matched. In the degassed solution, p of anion at the solution body and crack tip is
pm are almost equal.

The crack growth rate is controlled by the chemical conditions within the crack, not by the external potential itself, for example. While some crack growth models rely on cathodic reduction of oxygen at the crack openings, high corrosion potentials are not needed. The best data to demonstrate this point is the paper by Shack et al., "Environmentally Accelerated Cracking in Light Water Reactors" (Semi-Annual Report, April 1985-9).
Mon, NUREG / CR-4667, Volume 1) slow strain rate test, and Andresen
"Modeling the Effects of Water and Material Chemistry on Crack Tip Chemical Conditions and the Dynamics of Crack Growth Obtained From It" (Proceedings of the Third International Conference on Material Degradation in the Nuclear Industry, Michigan). Traverse City, August 31-September 4, 1987). The data of Shack et al. Are shown in FIGS. 4-6 in their paper and the data of Andresen are shown in FIGS. 6 and 7 in their paper. These data clearly show that a large crack growth rate is achieved at -0.5 V _she when the acidic additive is added at a level of about 10 μS / cm. Shack et al. Showed this for sensitized and non-sensitized stainless steels, and Andresen showed it for sensitized and non-sensitized stainless steels and Alloy 82 weld metal. Such an increase in crack growth rate is not so small that a crack growth rate as high as that in aerated water may be obtained.

Cracking responds to changes in solution pH at the crack tip, rather than, for example, the sulfate ion activity itself. According to Andresen, the increase in crack growth rate for sensitized stainless steels was changed to low pH (see data in Figures 4-6 and 7-9) and to high pH (see data in Figure 10). (However, for NaOH, H ₂
It is shown that a larger pH change than in the case of SO ₄ is required)]. In addition, according to a test conducted by Shack et al. And Andresen (see data in FIGS. 4 to 6 and FIGS. 7 to 9), in sufficiently degassed water, an increase in crack growth rate is caused by an acidic additive. It has also been shown to occur for (H ₂ SO ₄ ) but not for more neutral additives such as Na ₂ SO ₄ (which becomes slightly basic in 288 ° C. water). ing. Shack et al. Also use borate and H ₂ SO
Tests with a mixture of ₄ were also performed and showed that the crack growth rate increased only when the buffer capacity of the borate was exceeded (see data in Figures 7-10).

FIGS. 7 and 8 are graphs plotting the relationship between crack extension and response time to changes in water chemistry for unsensitized 304L stainless steel and Alloy 82 weld metal, respectively. It shows that under conductivity, the crack growth rate of non-sensitized material increases even in degassed water. This illustrates the correlation between solution conductivity and corrosion potential in producing a particular chemical condition at the crack tip and thus a particular crack growth rate. The straight line segments represent the predicted crack growth rate results for the various conditions shown. FIG. 9 is a graph plotting the relationship between crack extension and time for a Pd-coated CT test piece of sensitized 304 stainless steel. If a sufficient amount of H ₂ SO ₄ is added, [complete degassing will occur]. That accelerated crack growth can be achieved even at the lowest thermodynamically corrosive potential, which is characteristic of the catalyst surface in the presence of excess hydrogen (ie, 78 ppb H ₂ ) with water or 400 ppb O ₂ generated. Is shown. This is also
It is also shown that a low corrosion potential gives a large tolerance for impurities, as the effect of about 0.1 μM H ₂ SO _{4 on} crack growth at high corrosion potential is readily seen. FIG. 10 is a graph plotting the amount of crack extension with respect to sensitized 304 stainless steel in water at 288 ° C., showing the effect of various concentrations of OH ⁻ derived from, for example, NaOH.

In degassed water there is no acidification mechanism (and therefore the gradient of corrosion potential within the crack)
Note that acidic impurities must be used. In aerated water, Na ₂ SO ₄ acidifies within the cracks to form H ₂ SO _4, which is described in Taylor et al., “High Temperature Aqueous Crevice Corrosion in Alloy 600 and 304L Stainless Steel”. (Proceedings of the conference on the chemistry of localized cracks and the dynamics of environmentally accelerated cracks, AIM
E. Philadelphia, October 1983). Taylor et al. Also show that in pure water, NaOH-added water, etc., a pH change to the higher side occurs.

While cracks may occur when the pH rises and falls,
A larger pH change is required on the basic side than on the acidic side in order to increase the crack growth rate. This was obtained for sensitized stainless steel under NaOH addition, as reported in Andresen's paper "Effect of specific anionic impurities on environmental cracking of austenitic materials in water at 288 ° C". It is based on the data. However, it should be noted that at high pH, the formation of sulfide ion (S ²⁻ ) by reduction of sulfate ion, sulfite ion, etc. becomes important. Sulfide levels above about 100 ppm have been shown to cause depassivation and increased crack growth rates (see Figures 11 and 12). FIG.
1 and 12 show the effect of sulfide concentration on excess anodic current density (metal dissolution rate) and slow strain rate behavior of Alloy 600, respectively. It has been shown that there is a steep boundary at the position of the sulfide concentration of about 100 ppm. The test conditions are 7500 ppm B, pH = 7, 29
It was 0 ° C. For Figure 11, the strain rate is 2 x 1
It was 0 ^-3 sec ^-1 . For Figure 12, the applied potential was -720 mV _she .

Thus, by controlling the pH in the crack, it is possible to achieve the smallest possible crack growth rate for a given material, load and temperature. Andresen's paper "Effect of aqueous impurities on intergranular stress corrosion cracking of sensitized 304 stainless steel" (EPRI NP-33).
84, Final Report, November 1993), an intermittent slow strain rate crack initiation test performed on smooth specimens revealed that a larger strain cracked with basic impurities. Whereas, for acidic impurities, smaller strains have been shown to cause cracking. FIG. 13 shows 200 ppb of O ₂
Strain rate test of sensitized 304 stainless steel in water containing 288 ° C (3.3 × 10 ^-7 sec ^-1 )
8 shows the effect of impurities of 10 μS / cm on crack initiation, measured by repeated interruptions. These results do not show a good correlation to impurity levels (or solution conductivity), but to (roughly) pH at the test temperature. Andressen et al. Also reported in their article “Short Crack Behavior in Stainless Steel at 288 ° C.” (Article No. 495, Corrosion 9
0, NACE, Las Vegas, NV). According to it, short cracks are 20-50μ
When a depth of m is reached and multiple cracks coalesce to form a larger crack, short cracks behave like long cracks (ie, internal degassed and anion concentration at the tip). Is higher).
It should be noted that the problem of how extremely small cracks behave when exposed to oxygen-containing water (a problem closer to the "generation" of cracks) is more complicated. Thus, the benefits of pH control can also be applied to "smooth" surfaces, very short cracks, and long cracks.

It is not enough to add sufficient levels, for example NaOH, to produce neutral water. Because, due to the acidification mechanism driven by the electric potential, H
_This is because the titration reaction from ₂ SO ₄ to Na ₂ SO ₄ is reversed in the crack. However, Na ⁺ ions dominate over H ⁺ (so that Na ⁺ does not induce acidification by supplying charge to the remaining anions in the crack) and OH ⁻ is SO ₄ ²⁻ , Cl ^- becomes superior with respect to such, and (for example, by hydrolysis of the metal ion) H ⁺ generated in the crack OH ^- and to a point such that the pH in the crack remains in a proper value in order to recombine , NaO
It is clearly possible to raise the H (or KOH or LiOH) level.

The beneficial effect of ZnO addition is probably partly related to its dissociation to produce Zn ²⁺ and OH ⁻ . Obviously, Zn also has another effect on film properties, but it would probably be impossible to link it to changes in pH. Nevertheless, some of the beneficial effects of ZnO on crack growth rate may be pH related. In addition, other oxides and a practical pH buffer may be present as long as they have equivalent effects.

In summary, the idea of the present invention is to limit changes in solution pH in hot water (ie solution pH).
Is limited to the range of about 6.5 to 8.0) to suppress SCC. This appears to correspond to the pH range where the solubility of iron oxide and nickel oxide is minimal. The present invention addresses more fundamental problems with SCC than controlling dissolved oxygen concentration or corrosion potential. This is because the dissolved oxygen concentration and the corrosion potential react with the impurities contained in the entire solution to produce a pH change in the crack. Such pH
Is controlled, the SCC can be significantly reduced regardless of the dissolved oxygen concentration or the corrosion potential. Means for limiting pH changes include chemical buffers (eg, NH
Adjustment of the water chemistry from the use of ₄ OH, Na _x H _(3-x) PO ₄ and H ₃ BO ₃ [ie acid depending on the anionic species in the water (eg H ₃ PO ₄ , C ₂ H ₄ O
OH, CH ₂ OOH, H ₃ BO ₃ or H ₂ CO ₃ ) or base (eg ZnO, NaOH, LiOH or K)
OH) under controlled addition].

Species that do not need to be present in high concentrations or that dissociate little in hot water (hence,
It is desirable to select chemical species that are not efficiently removed by the desalinator or that do not shorten the operating life of the desalinator, but to reduce the proportion of reactor water purified in the reactor water purification system. Is also possible. Because if the pH in the crack is controlled, impurities (like corrosion potential)
This will no longer affect the SCC. Further, for example NH instead of H ⁺ form with respect to cation
It is also _{possible 3} ⁺ -type become so the desalter to "conversion".

The above method is disclosed for purposes of illustration. It will be apparent to those skilled in the art of water chemistry that various changes and modifications can be made to such methods. It is to be understood that all such changes and modifications are covered by the appended claims.

[Brief description of drawings]

FIG. 1 is a graph in which observed and predicted crack growth rates are plotted against corrosion potential for in-reactor sensitized 304 stainless steel in 288 ° C. water.

FIG. 2: Approximately 400 ppb oxygen and 0.1 μM H ₂ S
FIG. 3 is a graph in which the amount of crack extension is plotted against time for a Pd-coated CT specimen of sensitized 304 stainless steel in water containing O ₄ at 288 ° C.

FIG. 3 is a graph of crack extension plotted against time for a Pd coated CT specimen of sensitized 304 stainless steel.

FIG. 4 H ₂ S vs. crack growth rate of sensitized 304 stainless steel tested in degassed 289 ° C. water.
O ₄ is a graph showing the effect of addition.

FIG. 5 is a graph showing the effect of the borate / sulfate molar ratio on the crack growth rate of sensitized 304 stainless steel tested in degassed 289 ° C. water containing H ₂ SO ₄ .

FIG. 6 is a graph showing the correlation between corrosion potential and solution conductivity in determining crack tip anion activity by comparing crack growth rates in aerated and degassed solutions. is there.

FIG. 7 is a graph plotting the relationship between crack extension and response time to changes in hydrogen water chemical conditions for unsensitized 304L stainless steel.

FIG. 8 is a graph plotting the relationship between crack extension and response time to changes in hydrogen water chemistry conditions for Alloy 82 weld metal.

FIG. 9 is a graph plotting the relationship between crack extension and time for a Pd-coated CT specimen of sensitized 304 stainless steel, thermodynamically if a sufficient amount of H ₂ SO ₄ is added. It shows that promotion of crack growth can be achieved even at the lowest corrosion potential.

FIG. 10 is a graph plotting the amount of crack extension against time for a sensitized 304 stainless steel in water at 288 ° C.

FIG. 11 is a graph showing the effect of sulfide concentration on excess anode current density (metal dissolution rate) of Alloy 600.

FIG. 12 is a graph showing the effect of sulfide concentration on the slow strain rate behavior of Alloy 600.

FIG. 13 is a graph showing the effect of impurities on crack initiation as measured during the slow strain rate test of sensitized 304 stainless steel in 288 ° C. water containing 200 ppb O ₂ .

Claims (6)

[Claims] 1. A method for reducing the occurrence or growth of cracks on the surface of a metal part in a water-cooled reactor or related equipment, comprising: (a) measuring the pH of water in the reactor; and (b) A method comprising adjusting the pH of the water to be in the range of 6.5 to 8.0. 2. The pH adjusting step (b) is performed so that the electrochemical potential at the tip of the crack or at the site where the crack is likely to occur is lower than the critical electrochemical potential required for the initiation or growth of the crack. The method of claim 1, which is carried out by adding a conditioning compound. 3. The method according to claim 1, wherein the compound has a property of decomposing under a temperature condition of a nuclear reactor to release an ion or an atom for adjusting the pH of the water. 4. The method of claim 1, wherein the compound is a buffer. 5. The method of claim 1, wherein the compound is a base. 6. The method of claim 1, wherein the compound is an acid.