Formation of Local, Transient “Acid Spikes” in the Fast Neutron Radiolysis of Supercritical Water at 400 °C: A Potential Source of Corrosion in Supercritical Water-Cooled Reactors?

2020 ◽  
Vol 6 (3) ◽  
Author(s):  
Md Mohsin Patwary ◽  
Sunuchakan Sanguanmith ◽  
Jintana Meesungnoen ◽  
Jean-Paul Jay-Gerin
Keyword(s):  
Fast Neutron ◽  
Supercritical Water ◽  
Reactor Core ◽  
Radiation Chemistry ◽  
Operating Conditions ◽  
Monte Carlo Simulation Study ◽  
Proper Understanding ◽  
Gen Iv ◽  
Reactor Operating

Abstract The use of supercritical water (SCW) in GEN IV reactors is a logical approach to the ongoing development of nuclear energy. A proper understanding of the radiation chemistry and reactivities of transients in a reactor core under SCW conditions is required to achieve optimal water chemistry control and safety. A Monte Carlo simulation study of the radiolysis of SCW at 400 °C by incident 2 MeV monoenergetic neutrons (taken as representative of a fast neutron flux in a reactor) was carried out as a function of water density between ∼150 and 600 kg/m3. The in situ formation of H3O+ by the generated recoil protons was shown to render the “native” track regions temporarily very acidic (pH ∼ 1). This acidity, though local and transitory (“acid spikes”), raises the question whether it may promote a corrosive environment under proposed SCW-cooled reactor operating conditions that would lead to progressive degradation of reactor components.

scholarly journals Temperature Dependence of Primary Species G(values) Formed from Radiolysis of Water by Interaction of Tritium β-Particles

2017 ◽  
Vol 19 (1) ◽  
pp. 17
Author(s):  
Sofia Loren Butarbutar ◽  
Sriyono Sriyono ◽  
Geni Rina Sunaryo
Keyword(s):  
Temperature Dependence ◽  
Nuclear Power ◽  
Reactor Core ◽  
Cooling Water ◽  
Radiation Chemistry ◽  
Operating Conditions ◽  
Water Radiolysis ◽  
Direct Measurements ◽  
Temperature Ranges ◽  
Reactor Operating

TEMPERATURE DEPENDENCE OF PRIMARY SPECIES G(VALUES) FORMED FROM RADIOLYSIS OF WATER BY INTERACTION OF TRITIUM β-PARTICLES. G(values) are important to understand the effect of radiolysis of Nuclear Power Plant (NPP) cooling water. Since direct measurements are difficult, hence modeling and computer simulation were carried out to predict radiation chemistry in and around reactor core. G(values) are required to calculate the radiation chemistry. Monte Carlo simulations were used to calculate the G(values) of primary species , H•, H2, •OH dan H2O2 formed from the radiolysis of tritium β low energy electron. These radiolytic products can degrade the reactor components and cause corrosion under the reactor operating conditions. G(values) prediction can indirectly contribute to maintain the material reliability. G(values) were calculated at 10-8, 10-7, 10-6 and 10-5 s after ionization at temperature ranges. The calculation were compared with the G(values) of g-ray 60Co. The work aimed to understand temperature effect on the water radiolysis mechanism by the tritium β electron. The results show that the trend similarity was found on the temperature dependence of G(values) of tritium β electron and g-ray 60Co. For tritium β electron, G(values) for free radical were lower than g-ray 60Co, but higher for molecular products as temperature raise at 10-8 and 10-7. The significant differences for these two type of radiations were on G(H2), G(•OH) and G(H•) at 10-6and 10-5 s above 200 oC.

“Acid spike” formation in the fast neutron radiolysis of supercritical water at 400 °C studied by Monte Carlo track chemistry simulations

2019 ◽  
Vol 97 (5) ◽  
pp. 366-372 ◽  
Author(s):  
Md Mohsin Patwary ◽  
Sunuchakan Sanguanmith ◽  
Jintana Meesungnoen ◽  
Jean-Paul Jay-Gerin
Keyword(s):  
Monte Carlo ◽  
Fast Neutron ◽  
Supercritical Water ◽  
Recoil Proton ◽  
Early Time ◽  
Operating Conditions ◽  
Acidic Ph ◽  
Ph Response ◽  
Time Required ◽  
Reactor Operating

A reliable understanding of radiolysis processes in supercritical water (SCW) cooled reactors is required to ensure optimal water chemistry control. In this perspective, Monte Carlo track chemistry simulations of the radiolysis of pure, deaerated SCW at 400 °C by 2 MeV mono-energetic neutrons were carried out as a function of water density between 0.15 and 0.6 g/cm3. The yields of hydronium ions (H3O+) formed at early time were obtained based on the G values calculated for the first three generated recoil protons. Combining our calculated G(H3O+) values with a cylindrical track model allowed us to estimate the concentrations of H3O+ and the corresponding pH values. An abrupt, transient, and highly acidic pH response (“acid spikes”) was observed at early times around the “native” fast neutron and recoil proton trajectories. This intra-track acidity was found to be strongest at times of less than a few tens to a hundred of picoseconds, depending on the value of the density considered (pH ∼ 1). At longer times, the pH gradually increased for all densities, finally reaching a constant value corresponding to the non-radiolytic, pre-irradiation concentration of H3O+, due to the autoprotolysis of water. Interestingly, the lower the density of the water, the longer the time required to reach this constant value. Because many in-core processes in nuclear reactors critically depend on the pH, the present work raises the question whether such highly acidic pH fluctuations, though local and transitory, could promote or contribute to corrosion and degradation of materials under proposed SCW-cooled reactor operating conditions.

Study of the Influence of Microstructure and Intergranular Carbides on the Oxidation Behavior of a Nickel Base Alloy 690 TT in Supercritical Water Nuclear Reactor Conditions

2020 ◽  
Author(s):  
Alberto Sáez-Maderuelo ◽  
María Luisa Ruiz-Lorenzo ◽  
Francisco Javier Perosanz ◽  
Patricie Halodová ◽  
Jan Prochazka ◽  
...  
Keyword(s):  
Supercritical Water ◽  
Nuclear Power ◽  
Power Plants ◽  
Oxidation Behavior ◽  
Nuclear Reactor ◽  
Base Alloy ◽  
Nuclear Industry ◽  
Operating Conditions ◽  
Alloy 690 ◽  
Reactor Operating

Abstract Alloy 690, which was designed as a replacement for the Alloy 600, is widely used in the nuclear industry due to its optimum behavior to stress corrosion cracking (SCC) under nuclear reactor operating conditions. Because of this superior resistance, alloy 690 has been proposed as a candidate structural material for the Supercritical Water Reactor (SCWR), which is one of the designs of the next generation of nuclear power plants (Gen IV). In spite of this, striking results were found [1] when alloy 690 was tested without intergranular carbides. These results showed that, contrary to expectations, the crack growth rate is lower in samples without intergranular carbides than in samples with intergranular carbides. Therefore, the role of the carbides in the corrosion behavior of Alloy 690 is not yet well understood. Considering these observations, the aim of this work is to study the effect of intergranular carbides in the oxidation behavior (as a preliminary stage of degenerative processes SCC) of Alloy 690 in supercritical water (SCW) at two temperatures: 400 °C and 500 °C and 25 MPa. Oxide layers of selected specimens were studied by different techniques like Scanning Electron Microscope (SEM) and Auger Electron Spectroscopy (AES).

scholarly journals Patchy nuclear chain reactions

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Eric Dumonteil ◽  
Rian Bahran ◽  
Theresa Cutler ◽  
Benjamin Dechenaux ◽  
Travis Grove ◽  
...  
Keyword(s):  
Nuclear Reactor ◽  
Reactor Core ◽  
Rensselaer Polytechnic Institute ◽  
Operating Conditions ◽  
Chain Reactions ◽  
Branching Random Walks ◽  
Stochastic Fluctuations ◽  
Nuclear Chain ◽  
Reactor Operating ◽  
Experimental Findings

AbstractStochastic fluctuations of the neutron population within a nuclear reactor are typically prevented by operating the core at a sufficient power, since a deterministic (i.e., exactly predictable) behavior of the neutron population is required by automatic safety systems to detect unwanted power excursions. In order to characterize the reactor operating conditions at which the fluctuations vanish, an experiment was designed and took place in 2017 at the Rensselaer Polytechnic Institute Reactor Critical Facility. This experiment however revealed persisting fluctuations and striking patchy spatial patterns in neutron spatial distributions. Here we report these experimental findings, interpret them by a stochastic modeling based on branching random walks, and extend them using a “numerical twin” of the reactor core. Consequences on nuclear safety will be discussed.

Various Design Aspects of the Canadian Supercritical Water-Cooled Reactor Core

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Metin Yetisir ◽  
Rui Xu ◽  
Michel Gaudet ◽  
Mohammad Movassat ◽  
Holly Hamilton ◽  
...  
Keyword(s):  
Supercritical Water ◽  
Thermal Efficiency ◽  
Nuclear Reactor ◽  
Reactor Core ◽  
Operating Conditions ◽  
Stress Distributions ◽  
Light Water Reactors ◽  
Core Components ◽  
Water Reactors ◽  
Supercritical Water Cooled Reactor

The Canadian Supercritical Water-Cooled Reactor (SCWR) is a 1200 MW(e) channel-type nuclear reactor. The reactor core includes 336 vertical pressurized fuel channels immersed in a low-pressure heavy water moderator and calandria vessel containment. The supercritical water (SCW) coolant flows into the fuel channels through a common inlet plenum and exits through a common outlet header. One of the main features of the Canadian SCWR concept is the high-pressure (25 MPa) and high-temperature (350°C at the inlet, 625°C at the outlet) operating conditions that result in an estimated thermal efficiency of 48%. This is significantly higher than the thermal efficiency of the present light water reactors, which is about 33%. This paper presents a description of the Canadian SCWR core design concept; various numerical analyses performed to understand the temperature, flow, and stress distributions of various core components; and how the analyses results provided input for improved concept development.

Design of Reverse Flow Blockage Device for Reactor Coolant Pumps

2016 ◽  
Vol 852 ◽  
pp. 489-497
Author(s):  
S. Aravindan ◽  
Bhagwana Ram Manda ◽  
K.V. Sreedharan ◽  
S. Athmalingam ◽  
V. Balasubramaniyan
Keyword(s):  
Cylindrical Shell ◽  
Reverse Flow ◽  
Reactor Core ◽  
Operating Conditions ◽  
Coolant Fluid ◽  
Reactor Coolant ◽  
The Core ◽  
Time Operation ◽  
Reactor Operating ◽  
Tie Rods

Future Sodium cooled Fast Reactors (SFR) in India, are being designed with 3 Reactor Coolant Pumps (RCP). Reactor Coolant Pumps (RCP) are used in pumping the coolant fluid through the reactor core. As the RCPs are operating in parallel, failure of one pump will result in a significant portion of the pumped coolant to bypass the core via tripped RCP. Thus, the reactor has to be shut down and the tripped RCP has to be replaced, which results in down time. Operation of reactor with only two RCP (2/3 mode) will supplement the power generation. Henceforth, if the flow path through the tripped RCP is made highly resistant as compared to the core, then eventually, flow from the two operating RCPs will go through reactor core. Such a flow blocking/resisting arrangement can also provide the flexibility during reactor startup. A cylindrical shell is designed for closing the suction passage of the pump and the shell is raised or lowered from above the roof slab with the help of tie-rods. The cylindrical shell (sleeve shell) is designed to withstand water hammer shock due to inadvertent sudden closure of the suction passage. To determine the shell thickness, pump performance curves are developed based on reactor operating conditions. The sleeve shell will not be able to perfectly close the suction passage as space is required for movement of sleeve shell over the pump shell, thus a study is performed on incorporating a labyrinth to minimize the leakage.

Viewport Influence on Optical Pyrometry and Deposition Process in Mocvd Vertical Rotating Disc Reactors

1999 ◽  
Vol 588 ◽  
Author(s):  
Anton Prokopenko ◽  
Alexander Gurary ◽  
Vadim Boguslavskiy ◽  
Jeffrey Ramer ◽  
Matthew Schurman
Keyword(s):  
Deposition Process ◽  
Operating Conditions ◽  
Flow Dynamics ◽  
Monitoring And Control ◽  
Rotating Disc ◽  
Process Monitoring And Control ◽  
Purge Flow ◽  
Reactor Operating ◽  
And Control

AbstractOptical access to the wafer for the in-situ process monitoring and control is a requirement for the advanced MOCVD equipment. Depending on their location and design, viewports can affect the reactor flow dynamics and temperature distribution inside the growth chamber thus ultimately affecting the deposition process. Furthermore, deposition on the viewport can influence the accuracy of in-situ measurements.We have investigated viewport influence on the MOCVD vertical rotating disc reactors manufactured by EMCORE Corporation. Viewport transmittance was established for different conditions and viewport types. Computational fluid dynamics was utilized to establish conditions at which viewport has no considerable influence on deposition results. The validity of model predictions was verified by examining the results of actual deposition runs on the reactor. We have demonstrated that under typical EMCORE reactor operating conditions, viewports presence on the reactor inlet flange and a purge flow through it have minimal effect on the reactor flow dynamics and ultimately on material growth rate and thickness uniformity.

Cathodoluminescence of Catalyst Crystallites

1982 ◽  
Vol 40 ◽  
pp. 664-665
Author(s):  
E.D. Boyes ◽  
P.L. Gai ◽  
D.B. Darby ◽  
C. Warwick
Keyword(s):  
Defect Density ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Semiconductor Materials ◽  
Environmental Cell ◽  
High Resolution Structure ◽  
Commercially Important ◽  
Crystallographic Defects ◽  
Resolution Structure

The extended crystallographic defects introduced into some oxide catalysts under operating conditions may be a consequence and accommodation of the changes produced by the catalytic activity, rather than always being the origin of the reactivity. Operation without such defects has been established for the commercially important tellurium molybdate system. in addition it is clear that the point defect density and the electronic structure can both have a significant influence on the chemical properties and hence on the effectiveness (activity and selectivity) of the material as a catalyst. SEM/probe techniques more commonly applied to semiconductor materials, have been investigated to supplement the information obtained from in-situ environmental cell HVEM, ultra-high resolution structure imaging and more conventional AEM and EPMA chemical microanalysis.

Identification of Bearing Coefficients of Flexible Rotor-Bearing Systems

2000 ◽  
Author(s):  
Tachung Yang ◽  
Wei-Ching Chaung
Keyword(s):  
Industrial Applications ◽  
Operating Conditions ◽  
Least Square ◽  
Flexible Rotor ◽  
Fem Modeling ◽  
Identification Method ◽  
Reaction Forces ◽  
Manufacturing Assembly ◽  
Stiffness And Damping

The accuracy of stiffness and damping coefficients of bearings is critical for the rotordynamic analysis of rotating machinery. However, the influence of bearings depends on the design, manufacturing, assembly, and operating conditions of the bearings. Uncertainties occur quite often in manufacturing and assembly, which causes the inaccuracy of bearing predictions. An accurate and reliable in-situ identification method for the bearing coefficients is valuable to both analyses and industrial applications. The identification method developed in this research used the receptance matrices of flexible shafts from FEM modeling and the unbalance forces of trial masses to derive the displacements and reaction forces at bearing locations. Eight bearing coefficients are identified through a Total Least Square (TLS) procedure, which can handle noise effectively. A special feature of this method is that it can identify bearing coefficients at a specific operating speed, which make it suitable for the measurement of speed-dependent bearings, like hydrodynamic bearings. Numerical validation of this method is presented. The configurations of unbalance mass arrangements are discussed.

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