Early construction and operation of highly contaminated water treatment system in Fukushima Daiichi Nuclear Power Station (I) – Ion exchange properties of KURION herschelite in simulating contaminated water

To support the design and operation of the decontamination system using KURION media for the treatment of highly contaminated water accumulated in Fukushima Daiichi Nuclear Power Station, Central Research Institute of Electric Power Industry has urgently carried out many kinds of research and development programs to support the operation of the decontamination system using columns filled with three kinds of KURION media (H, AGH and SMZ). Since the contaminated water at Fukushima Daiichi Nuclear Power Station contained seawater and oil, the effects of sea salt and dissolved oil on Cs adsorption behavior were examined closely by batch type. The concentration of sea salt in the solutions was varied between 0.0 and 3.4 wt%. The Cs adsorption capacity of KURION herschelite in seawater decreased to nearly 1/10th of that in pure water, but it was still concluded that herschelite has sufficient adsorption capacity to remove Cs from the contaminated water. The effect of dissolved oil could be ignored because of its low solubility in seawater. Langmuir-type adsorption isotherm equations, which can be applied for estimating Cs adsorption in sea salt containing water, were developed.     

Transmission of scattered γ-radiation in water

Measurements have been made of the attenuation of doses of scattered-photons from Au¹⁹⁸, Co⁶⁰, and Na²⁴ sources as a function of the distance between the source and the detector for various collimation angles, thereby eliminating the possibility of primary-radiation from entering the detector. The measurements were carried out at distances ranging from 3 to 4 and 8 to 12 mean-free-paths for the-photons. The collimation angles were varied from 30 to 80. The experimental data which were obtained are compared with the results of calculations based on an assumption which allows the problem to be reduced to the calculation of a triple integral rather than the direct solution of the kinetic equation. Satisfactory agreement is found between the experimental and theoretical results.In conclusion the authors wish to express their gratitude to Dr. Phys.-Math. Sciences A. K. Krasin for setting up the problem and for illuminating discussions on the results of the measurements, to Dr. Phys.-Math, Sciences G. I. Marchuk for a number of remarks concerned with the calculation and also to V. A. Tolstikov for participating in the present series of experiments.     

Demonstration test on purification systems of contaminated water using liquid–solid settling technology by flocculants (decontamination technology using high-pressure water)

For the purpose of decontaminating residential buildings, roads, rubble, and so on, the high-pressure water washing decontamination system had been developed, which are composed of a recovery system for contaminated washing water and mobile purification system of liquid–solid settling technology by flocculants. The high-pressure washing technology applied in this demonstration test can be used for both high- and ultrahigh-pressure washing decontamination and water surface chipping, by changing pumps and attachments. These systems were applied to decontaminate pools, concrete floor and side ditch around the pool in an elementary school located at Motomiya, Fukushima Prefecture as a demonstration test. Additionally, to compare decontamination effects, the tests, to chip and decontaminate surfaces of outer concrete and asphalt pavement had been conducted. From the results, high-pressure water jet decontamination systems have been practically proven.     

A study of radiation induced reactions in super critical water

It is known that water exists in supercritical state above 374℃ and 22.1MPa, where gas phase and liquid phase are merged into a single phase. In the supercritical state, the density is controllable by changing the pressure. The properties such as the ionic product, solubilities of salts, gas and organic compounds, and dielectric constant of supercritical water are very different from those of water at room temperature.     

Angle-energy distribution ofγ radiation scattered in water and iron

In this paper we investigate the detailed characteristics of multiple scattering of rays, in particular the angle-energy distribution, a knowledge of which allows us to calculate the attenuation of radiation in complex geometries. Measurements have been made of the angle-energy distribution of rays from a Co⁶⁰ source in water and iron for a semiinfinite geometry and it has been established that these distributions have a maximum close to the energy corresponding to single scattering at the minimum angle. It is shown that the angular distributions are exponential and that the exponential factor is a linear function of the atomic number of the medium. The energy distributions are compared with calculations carried out by Goldstein and Wilkins [1].In conclusion the author wishes to thank I. I. Bondarenko and V. I. Kukhtevich and S. G. Tsypin for discussion of the present work; the author is also indebted to A. N. Voloshin and V. I. Popov for help in carrying out the experiments.     

Determining factors for anodic polarization curves of typical structural materials of boiling water reactors in high temperature – high purity water

In order to examine the anodic polarization characteristics of typical structural materials of boiling water reactors (BWRs), the anodic polarization curves of type 316L stainless steel (316L SS) and Alloy 182 were measured in deaerated high purity water at 553 K using the previously reported measurement method which was confirmed suitable for high temperature – high purity water. In order to specify which constituent element determines the dissolution characteristics of these materials, the anodic polarization curves of pure iron, pure nickel, and pure chromium were also surveyed. The anodic polarization curve of 316L SS was determined to have active, passive, and transpassive states which were the same as type 304 SS (304 SS) showed. But, Alloy 182 had different polarization characteristics especially near the corrosion potential as it had no active state. From comparison results of the polarization characteristics of these materials and their constituent elements, the corrosion characteristics of these materials were concluded to be mainly determined by the corrosion characteristics of chromium.     

Track structure and energy deposition distribution of heavy ions in liquid water

Progress in theoretical research into track structure and energy deposition distribution of heavy ions in introduced,and some research results are given,such as a Monte Carlo model of heavy ion track structure calculation,frequency distribution of energy deposition inside a electron track and radial dose distribution around a heavy ion path.Moreover,research direction in future is also analysed.     

Cathodic polarization curves of the oxygen reduction reaction on various structural materials of boiling water reactors in high temperature–high purity water

Cathodic polarization curves of the O₂ reduction reaction were measured by using electrodes made from typical structural materials of boiling water reactors (BWRs) to evaluate the effects of kind of material on the electrochemical corrosion potential (ECP) calculation. To estimate ECPs at any region in the BWRs on the basis of the BWR environmental conditions, anodic and cathodic polarization curves should be obtained in advance under relevant conditions. The concentration of oxidants such as O₂ and H₂O₂ in coolant changes depending on the region in which they exist. As well, reduction reaction rates might differ depending on the kind of materials. In this work, the cathodic polarization curves of type 316L stainless steel (316L SS) and Alloy 182 were measured in high purity water at 553 K with different O₂ concentrations and compared with those of type 304 SS (304 SS). The results showed that the cathodic polarization curves differed depending on the kind of materials at the activation-controlled region. But, the difference in the ECP vs. O₂ concentration relationship was small when the ECPs were calculated by using both anodic and cathodic polarization curves measured on the objective material.     

Early construction and operation of the highly contaminated water treatment system in Fukushima Daiichi Nuclear Power Station (III) – a unique simulation code to evaluate time-dependent Cs adsorption/desorption behavior in column system

A simulation code was developed to evaluate the performance of the cesium adsorption instrument operating in Fukushima Daiichi Nuclear Power Station. Since contaminated water contains seawater whose salinity is not constant, a new model was introduced to the conventional zeolite column simulation code to deal with the variable salinity of the seawater. Another feature of the cesium adsorption instrument is that it consists of several columns arranged in both series and parallel. The spent columns are replaced in a unique manner using a merry-go-round system. The code is designed by taking those factors into account. Consequently, it enables the evaluation of the performance characteristics of the cesium adsorption instrument, such as the time history of the decontamination factor, the cesium adsorption amount in each column, and the axial distribution of the adsorbed cesium in the spent columns. The simulation is conducted for different operation patterns and its results are given to Tokyo Electric Power Company (TEPCO) to support the optimization of the operation schedule. The code is also used to investigate the cause of some events that actually occurred in the operation of the cesium adsorption instrument.     

Experimental investigation on pressure-buildup characteristics of a water lump immerged in a molten lead pool

Motivated to understand the pressure-buildup characteristics in a circumstance of a water droplet immerged inside a heavy liquid metal pool, which is a key phenomenon during a Steam Generator Tube Rupture accident of Lead-cooled Fast Reactor,many experiments have been conducted by injecting water lumps into a molten lead pool at Sun Yat-sen University. In order to deepen the understanding of the influence of melt material, this lead experiment was compared with a Lead–Bismuth-Eutectic(LBE) exper...     

Development of unstructured mesh-based numerical method for sodium–water reaction phenomenon in steam generators of sodium-cooled fast reactors

When pressurized water or vapor leaks from a failed heat transfer tube in a steam generator of sodium-cooled fast reactors, a high-velocity and high-temperature jet with sodium–water chemical reaction may cause wastage on the adjacent tubes. For safety assessment of the steam generator, a computational fluid dynamics code called SERAPHIM calculating compressible multicomponent multiphase flow with sodium–water chemical reaction has been developed. The original SERAPHIM code is based on the finite difference method. In this study, unstructured mesh-based numerical method for the SERAPHIM code was developed to advance a numerical accuracy for the complex-shaped domain including multiple heat transfer tubes. Numerical analysis of an underexpanded jet experiment was performed as part of validation of the unstructured mesh-based SERAPHIM code. The calculated pressure profile showed good agreement with the experimental data. To investigate the effect of the introduction of the unstructured mesh and to confirm applicability of the numerical method for the actual situation, water vapor discharging into liquid sodium was analyzed. The calculated behavior of the reacting jet agreed with the previous experimental knowledge. It was demonstrated that the proposed numerical method could be applicable to evaluation of the sodium–water reaction phenomenon.     

Influence of water content on the inactivation of P. digitatum spores using an air–water plasma jet

In order to investigate whether an air–water plasma jet is beneficial to improve the efficiency of inactivation, a series of experiments were done using a ring-needle plasma jet. The water content in the working gas(air) was accurately measured based on the Karl Fischer method. The effects of water on the production of OH(A~2Σ~+–X~2Π_i) and O(3p~5P–3s~5S) were also studied by optical emission spectroscopy. The results show that the water content is in the range of 2.53–9.58 mg l~(-1), depending on the gas/water mixture ratio. The production of OH(A~2Σ~+–X~2Π_i) rises with the increase of water content, whereas the O(3p~5P–3s~5S) shows a declining tendency with higher water content. The sterilization experiments indicate that this air–water plasma jet inactivates the P. digitatum spores very effectively and its efficiency rises with the increase of the water content. It is possible that OH(A~2Σ~+–X~2Π_i) is a more effective species in inactivation than O(3p~5P–3s~5S) and the water content benefit the spore germination inhibition through rising the OH(A~2Σ~+–X~2Π_i) production. The maximum of the inactivation efficacy is up to 93% when the applied voltage is -6.75 kV and the water content is 9.58 mg l~(-1).     

A new approach to analysis of water chemistry indicators in the first loop of reactor installations in nuclear power plants with VVÉR reactors

A new approach is developed for analyzing a complex of data reflecting the state of the coolant in the first loop of reactor installations of nuclear power plants with VVéR reactors. The method is based on the treating the measurements of the concentration of the components of the coolant during a run as nonuniform time series and desribing them using a flicker-noise model or continuous wavelet analysis. It is shown that this method can be used to obtain objective information about the relations between the physicochemical processes leading to the transformation of various components of the coolant (hydrogen, ammonia, hydrazine, metal ions—products of corrosion) in the technological regime without using any speculative models. 8 figures, 1 table, 3 references. Special Design Office “Gidropress”. Translated from Atomnaya énergiya, Vol. 87, No. 3, pp. 194–199, September, 1999.     

Simulation of the inhibition of water α-radiolysis via H2 addition

The continuous formation of H₂, O₂, and H₂O₂ observed in water during α-radiolysis may be suppressed by the addition of H₂ above the threshold hydrogen concentration (THC). Using the FACSIMILE simulation code, water radiolysis was reproduced in order to determine the THC and clarify the mechanism at room temperature. Using the reaction set and rate constants reported by Ershov and Gordeev together with the primary yields for water decomposition products generated using 12 MeV α-particles, the THC was found to be 165 μM. Further simulation results clearly showed that the value of THC is strongly dependent on the reaction set and rate constants. In addition, a possible mechanism involving a chain reaction governed by the two reactions OH + H₂ → H + H₂O and H + H₂O₂ → OH + H₂O was proposed. Furthermore, the same inhibition effect was found when a high-temperature simulation (300 °C) was performed, but the concentration range and THC were much smaller than the values obtained at room temperature. The importance of the reverse reaction OH + H₂ → H + H₂O was also investigated.     

In situ measurement of corrosion of type 316L stainless steel in 553 K pure water via the electrical resistance of a thin wire

A system for the in situ monitoring of corrosion depth via electrical resistance measurements was applied to study the corrosion rate of type 316L stainless steel at 553 K in pure water. Corrosion depth was measured using a 50 μm diameter wire probe mounted axially in the tube. Measurements were in good agreement with literature data for both the hydrogen water chemistry (HWC) condition and the normal water chemistry (NWC) condition. Oxide film analyses by scanning electron microscopy and laser Raman spectroscopy on the wire probe and the tube showed no effects from shape of the test specimens or the application of electric current. Corrosion kinetics was evaluated by fitting equations to the measurements. Data for the HWC condition could be fitted by a two-step logarithmic–parabolic law. A single-step logarithmic law fitted data for the NWC condition. Changes in corrosion rate by the water chemistry changes were readily detected with the technique. Corrosion depth change could be observed for the water chemistry change from the NWC condition to the HWC condition with electrochemical corrosion potential (ECP) of ?0.56 V vs. standard hydrogen electrode, which is lower than the ECP that the phase of iron oxide changes from α-Fe₂O₃ to Fe₃O₄.     

Improvement of Taihu water quality by the technology of immobilized nitrogen cycle bacteria

Experimental studies were carried out on the purification of eutrophic Taihu Lake water by dynamic experiment using immobilized nitrogen cycle bacteria (INCB).The results showed that the eutrophic water of Taihu Lake can be purified effectively as it passes through the experimental reactor into which some immobilized nitrogen cycle bacteria were put.The removal efficiencies for Total N(TN),NH4^ -N with immobilized nitrogen cycle bacteria were 72.4% and 85.6%,respectively.It was found that the immobilized nitrogen cycle bacteria also have purificatory effect on eutrophic water of Taihu Lake at winter temperature(7℃) ,and that the removalm efficiencies for Total N(TN),NH4^ -N were 55.6%,and 58.9%,respectively.The removal efficiencies for TN and NH4^ -N depend on the time the water stays in the experimental reactor.