bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of a Model for Prediction of Atmospheric Corrosion in Tropical Environments
Authors: Tidblad J , Mikhailov AA , Kucera V
Published: April 2008

Based on analysis of data from field exposure programs within, e.g., UN ECE and ISO CORRAG a model describing atmospheric corrosion of common technical metals has been developed. The model uses environmental parameters that are easily available on different geographical scales. The combination of temperature and relative humidity can be used to express the time of wetness based on a probability model for the prediction of time of wetness from annual temperature and relative humidity data. The sulfur dioxide air concentration and the chloride deposition are included in different parts of the model and these two parts contain separate expressions for the combination of temperature and relative humidity (or temperature and time of wetness). This makes it possible to apply the model in marine areas with different deposition of chlorides and different pollution levels. The development of the model has contributed to a better understanding of the conditions for atmospheric corrosion, including tropical regions. The individual terms of the model have been adapted using physical and chemical principles. This makes the model useful for predictions also in regions outside those defining the original data set. Examples of independent data from field exposures not included in the model development are shown and discussed.
Aerosol Model Aids Interpretation of Corrosivity Measurements in a Tropical Region of Australia
Authors: Klassen R , Hinton B , Roberge P
Published: April 2008

The corrosivity pattern near the tropical coastal city of Townsville, Australia is of interest because of concerns related to the corrosion of RAAF aircraft. The corrosivity at seven sites near Townsville was characterized over a four-year period with bimetallic specimens (CLIMAT units) and salt candles. The CLIMAT results highlight the effects of elevation above the ground and topography on local corrosivity. The increase in corrosivity due to elevation at the same site is readily explained by the increase in aerosol deposition. The flow pattern around objects that significantly obstruct wind is very complicated but one clear conclusion is that the wind flow speed and turbulence are highest near the top. Thus aerosol deposition, and therefore corrosion, rates are higher near the top of obstructions to wind such as hills and buildings. The main conclusion is that the principles of salt aerosol transport and deposition offer a physical framework for understanding and predicting patterns of aerosol deposition and consequently the patterns of corrosivity.
Thirty-Eight Years of Atmospheric Corrosivity Monitoring
Authors: Phull BS , Pikul SJ , Kain RM
Published: April 2008

The marine atmospheric test site at Kure Beach, North Carolina, has long been recognized for its corrosion severity. It represents a benchmark for testing materials' resistance to marine atmospheric corrosion. The two test areas at the site have often been referred to as the 80-foot and 800-foot test lots (or the 25-meter and 250-meter lots), respectively. For over 38 years the amount of airborne chlorides from the sea spray have been monitored monthly. Chloride deposition is only one of several environmental factors which can contribute to atmospheric corrosion. Some of the other important factors include relative humidity, time of wetness, temperature, prevailing wind direction, and rainfall—which are all also monitored routinely. Corrosivity is monitored more directly by determination of mass loss for two reference materials, carbon steel and zinc.

Because of a number of recent changes, the 25- and 250-meter test locations have now been designated as the “oceanfront” and the “near-ocean” lots. Continued monitoring of these sites will benefit existing and future marine atmospheric test programs, including those of various ASTM subcommittees. Examples of materials on continuous exposure in the “museum areas” of the oceanfront and the near-ocean lots are reviewed for the purpose of educating new corrosion engineers on the importance of long-term testing in natural environments.
Atmospheric Corrosion in Marine Environments along the Gulf of México
Authors: Cook DC , Van Orden AC , Reyes J , Oh SJ , Balasubramanian R , Carpio JJ , Townsend HE
Published: April 2008

Atmospheric corrosion in México is creating significant structural problems in the tropical marine regions of the Gulf of México. This is especially true along the southern Gulf coast where increasing petrochemical pollution is present with the extremely high chloride concentrations resulting from strong onshore winds, and the ever-present high time-of-wetness. The climatic and environmental parameters have been measured, between 1993 and 1998, at 12 coupon exposure sites at marine locations around the Gulf of México. Corrosion classifications for iron, aluminum, copper and zinc have been calculated for each site using mean values of the time-of-wetness, chloride and sulfur dioxide concentrations. The theoretically predicted corrosion rates have been determined from the site classification data, and compared to the 12-month corrosion rates measured by coupon mass loss for the four metals exposed at the same sites. The data show that all sites have at least a C4 classification with most having C5 even though many are located over 1 km from the shoreline. The measured corrosion rates of different metals are often not in good agreement with those predicted using the environmental parameters, providing evidence that other climatic factors such as frequency of precipitation can modify the corrosion rates and distort the correlation with theoretical corrosion predictions and models. Spectroscopic analysis of corrosion products from exposed carbon steel coupons shows that large fractions of akaganeite form in high chloride environments, along with lepidocrocite and goethite. The oxides form in distinct layers on the steel surface. The amount of akaganeite formed is related to some extent by the precipitation frequency which controls if pollutants are regularly flushed from the steel surfaces.
Electrochemical Evaluation of the Protective Properties of Steel Corrosion Products Formed in Ibero-American Tropical Atmospheres
Authors: Uruchurtu-Chavarín J , Mariaca-Rodriguez L , Micat G
Published: April 2008

The purpose of the MICAT project (Ibero-American Map of Atmospheric Corrosiveness) was to foster collaborative ventures between groups conducting research on atmospheric corrosion. Overall 14 Ibero-American countries, including Spain and Portugal were involved with a network of 75 test stations distributed throughout the region and on 3 continents, and many of them were set within tropical regions representing a broad spectrum of climatological and atmospheric pollution conditions. The general objective of the MICAT electrochemical studies was to characterize the electrochemical and protective properties of the corrosion products formed during different periods of atmospheric exposure (1 to 4 years). The particular objective of the present work is to present electrochemical results associated to the protective properties of steel corrosion products formed in test sites with tropical atmospheres. After atmospheric exposure, pre-rusted mild steel specimens were immersed in a sodium sulfate solution and electrochemically evaluated. Linear polarization resistance (LPR) and electrochemical potential noise (EPN) measurements were performed after one hour of immersion. Electrochemical measurements were related to the presence of the atmospheric oxides formed and associated to climatological and atmospheric pollution data; its protective properties reflected in the weight loss data obtained during exposure. For specimens rusted in marine atmospheres, the presence of chlorides promotes localized corrosion. The electrochemical measurements were able to characterize and evaluate the protective properties of oxides according to the nature and environmental conditions to which specimens were exposed.
A Methodology for Quantifying the Atmospheric Corrosion Performance of Fabricated Metal Products in Marine Environments
Authors: King GA , Norberg P
Published: April 2008

In Australia a long-term project is studying the marine atmospheric corrosion performance of several metals and alloys, and a range of generic classes of coatings and finishes (metallic and organic) on steel and aluminum. Specimens have been exposed for over nine years at three marine sites, both in the open and under a specially designed glass shelter which has greatly accelerated deterioration. The sheet product test pieces include a range of features designed to simulate the types of distress introduced during manufacture and building, and at which corrosion defects initially manifest. A methodology is described for the development of quantitative performance indices for these formed specimens. The general philosophy involves using the collected data to determine appropriate weighting to different types of defects on features, or to the relative contribution of different features to overall defect indices and in turn their relative contribution to a total performance index. A rigorous mathematical procedure was followed to calculate defect indices and total performance indices for all products. Some results for the two-year specimens are discussed.
The Moisture Effect on the Diffusion of Chloride Ion in Hydrated Cement Paste
Authors: Guimarães ATC , Helene PRL
Published: April 2008

Previous research [1] showed high chloride concentrations (2% / cement) on the outside surface of reinforced concrete structures in the mist zone of marine environments. However, the chloride penetration reaches low depths for the concrete class used. Observed data have raised suspicions as to the effect of moisture content on the diffusion of chlorides. A test method was developed to assess the changes in the chloride diffusion coefficient with changes in moisture content in cement paste. It was concluded that the saturation degree (SD) (percentage of moisture content in the cement paste in relation to maximum water absorption of the cement paste) has a large influence in the chloride diffusion properties of the hardened cement paste, and this factor must be taken into consideration when predicting the service life of a reinforced concrete structure.
Model Solutions of Concrete Environment and Effect of Chloride Ions on the Electrochemical Corrosion Behavior of Reinforcing Mild Steel
Authors: Véleva LP , Cebada MC
Published: April 2008

Two model solution have been used in this study in order to simulate the corrosion behavior of mild steel rebars in the pore concrete environment. The first one is based on saturated calcium hydroxide (Ca(OH)2, pH 12.7± 2) and cement (portland Type I) extract solution (pH 12.7± 2) in open air, at room temperature (24± 1°C). The effect of chloride ions (5g/l and 10g/l NaCl) was studied in both model solutions. Electrochemical techniques such as potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) have been performed in a classical three-electrode cell. Also additional information was obtained by SEM and EDAX analysis. It seems that there is a difference in the way each solution simulates the behavior of steel, because the passive films formed show dissimilar topography, composition and anticorrosion protectiveness. The presence of chloride ions allows one to see more clearly the difference between the model solutions and the way each one interacts with the reinforcing steel. In this case the cement solution provides a more protective film for the reinforcing steel.
Degradation of Fiber Reinforced Mortar in a Marine Environment
Authors: de Gutiérrez R , Calderón LA , Delvasto S
Published: April 2008

Concrete is a brittle material with a relatively low tensile strength compared to its compressive strength. Reinforcement with randomly distributed short fibers could improve the ductility and tensile strength of concrete and permits the stabilization of the crack system. These products could be used in marine applications, but several chemical reactions must be controlled to generate durable materials. Sulfates and chlorides presented in seawater are especially dangerous ions for the concrete and the reinforcing steel.

The main objective of this research was to determine the effects of a marine environment on the properties of fiber reinforced mortars. Different types of natural and synthetic fibers such as sisal (S), fique (F), coconut (C), glass (G), polypropylene (PP) and steel (St) were used. The physical, mechanical and durability properties of the mortar made with each type of fiber were determined. The mortar matrix included additions such as silica fume (SF), and a superplasticizer (SP). Durability properties under marine environments were evaluated by measuring chloride ion penetration and water absorption.

The test results indicate an increase in the matrix porosity due to fiber application, but the blended cement matrix showed superior performance compared to the portland cement under marine service conditions. The utilization of mineral additions and additives in fiber reinforced mortars under severe environments was recommended.
Cathodic Protection of Structures in Coral Sands in the Presence of Salt Water
Authors: Dreyman EW
Published: April 2008

This paper covers the use of cathodic protection in saline muds and soils to protect steel and aluminum structures such as tanks and piping. The history of this type of corrosion control in the Carribean Islands is covered, as well as developments over time in this part of the world. The conditions encountered with saline muds and sands are unique to these areas and lend themselves to specialized application of galvanic and impressed current corrosion control.
Features of SRB-Induced Corrosion of Carbon Steel in Marine Environments
Authors: Videla HA , Swords C , Edyvean RGJ
Published: April 2008

Sulfate reducing bacteria (SRB) growth induces several important features in the steel/seawater interface such as changes in pH, redox potential, ion concentrations and structure and composition of corrosion product films. These features, absent in abiotic media, produce drastic changes in the corrosion behavior of the metal. In addition to pitting and crevice corrosion, conditions conductive to the enhancement of corrosion-fatigue crack growth and of hydrogen embrittlement can be generated by the metabolic production of hydrogen sulfide by SRB. While SRB produces more hydrogen entry into susceptible metals when compared with similar levels of abiotic sulfides, corrosion fatigue crack growth rates are slower in biological environments than in similar abiotic conditions. Moreover, bacteria also decrease the performance of cathodic protection of steel and protective coatings in marine environments. A review of the literature and recent results from our laboratories involving the use of electrochemical techniques for corrosion assessment, surface analyses and different types of microscopy also are briefly described.
Why Do We Need Dosimetry?
Authors: Gérard R , Zaritsky SM
Published: April 2008

Dosimetry plays a key role in the context of reactor pressure vessel surveillance and lifetime assessment. Uncertainty in the fluence estimate has a direct impact on the integrity assessment and on the operating limits of the reactors, and must be limited. The required precision is discussed in the light of practical examples. The review concludes that the fast neutron fluence statistical accuracy of 15 to 20% is sufficient and can be achieved in most important cases, at least in “Western” PWRs. Regarding VVER reactors, there are situations when such accuracy is not achieved, systematic biases are expected and careful benchmarking is necessary.
ASTM Standards for Reactor Dosimetry and Pressure Vessel Surveillance
Authors: Griffin PJ
Published: April 2008

The ASTM standards provide guidance and instruction on how to field and interpret reactor dosimetry. They provide a roadmap towards understanding the current “state-of-the-art” in reactor dosimetry, as reflected by the technical community. The consensus basis to the ASTM standards assures the user of an unbiased presentation of technical procedures and interpretations of the measurements. Some insight into the types of standards and the way in which they are organized can assist one in using them in an expeditious manner. Two examples are presented to help orient new users to the breadth and interrelationship between the ASTM nuclear metrology standards. One example involves the testing of a new “widget” to verify the radiation hardness. The second example involves quantifying the radiation damage at a pressure vessel critical weld location through surveillance dosimetry and calculation.
Assessment of Neutron Fluence Uncertainty and its Impact on Safety Issues
Authors: Lippincott EP
Published: April 2008

Exposure to fast neutron fluence causes damage to reactor vessels, and this damage must be constrained within limits for safe operation. Therefore, the fluence becomes an important quantity when such limits are approached. This paper discusses some impacts of fluence uncertainty on where these limits are set. Improvements in fluence assessment in recent years may indicate that fluence margins can be reduced, but detailed probabilistic considerations that take into account how well uncertainties are known may play an important part in quantifying safety margins.
Review of Problems and Requirements in VVER Reactor-Type Pressure Vessel Dosimetry
Authors: Zaritsky SM , Platonov PA , Nikolaev YA , Ošmera B , Valenta V
Published: April 2008

The main tasks and problems of VVER reactor pressure vessel (RPV) dosimetry are reviewed taking into account the RPV metal characteristics, the peculiarities of surveillance programs and some features of irradiation embrittlement of VVER-440 and VVER-1000 RPV materials. The problems of dosimetry of VVER-1000 surveillance program are discussed separately. The experimental dosimetry programs, which are carried out in this time, are briefly summarized. It's concluded that there are the serious reasons for improvement of VVER dosimetry.
Improved Evaluation of the Atucha-I Ex-Vessel Dosimetry
Authors: Albornoz AF , Blaumann H , Lopasso EM , Blanco A , Gennuso G , Serra O
Published: April 2008

A re-evaluation of the first ex-vessel dosimetry experiment at CNA-I was performed. The activation dosimeters were irradiated at the cavity behind the RPV during 1994–1995. This study differs from the previous one [1] in the calculation tools employed, as well as in some of the input data needed to perform the calculations. As a result, consolidated neutron spectra at the dosimeters' position were obtained. The possible reasons of disagreement in the calculated C/M ratios were analyzed and their impact was quantified. Lessons learned from this study were used to design a new ex-vessel experiment that will be developed next year.
Integrity Assessment for Aging Reactor Vessel of Japan's First Generation PWR Plants
Authors: Sato T , Kusuki A , Shiota S
Published: April 2008

Integrity assessment was performed for the reactor vessel of Mihama-1, which started operation early among Japan's PWRs, in view of neutron irradiation Bembrittlement to be undergone after 60 years of operation. Reference temperature RTNDT and upper shelf energy after 60 years of operation was estimated based on the results of surveillance tests. It was confirmed that the fracture toughness evaluation based on the surveillance tests and speculated reference temperature exceeded the stress intensity factor K1 which occurred in the event of pressurized thermal shock, and the decreased upper shelf energy evaluated in accordance with the elasto-plastic fracture mechanics would not lead to the growth of an assumed crack followed by fracture after 60 years of operation. The results of evaluations have demonstrated that the integrity of the Mihama unit No. 1 reactor vessel could be maintained after 60 years of operation.
Measurement of Neutron Flux Distribution for Decommissioning in Tokai Power Station
Authors: Shirakawa M , Yamamoto T , Nakazawa M
Published: April 2008

This document outlines the measurement of neutron flux distribution for decommissioning in the Tokai Power Station. An activation foil method and direct measurement using a gas filled neutron detector were used for this purpose. A wide range of data could be obtained before stopping its commercial operation, from areas to be controlled as radioactive waste to areas that do not require treatment as radioactive waste. From the viewpoint of practical use, it was confirmed that these types of detection methods were sufficiently effective.
Impact of the ENDF/B-VI Cross Sections on the RPV Fluence Determination
Authors: Remec I
Published: April 2008

The calculations with the broad-group cross-section library Bugle-96, and atom displacement (dpa) cross sections for iron, both derived from ENDF/B-VI data, result in higher calculated fast neutron fluxes, better agreement of calculations with radiometric dosimeter measurements, and significantly slower dpa rate attenuation through pressure vessel walls relative to the results with their predecessors: the Sailor library and ASTM iron dpa cross sections.
Factors Affecting Predicted Neutron Dose Rates to Steel Pressure Vessels of Magnox Plant
Authors: Thornton DA
Published: April 2008

Monte Carlo radiation transport calculations have been performed in order to determine the factors affecting predicted neutron dose rates to steel reactor pressure vessels (RPV) of Magnox reactors. The AEA Technology Monte Carlo radiation transport code MCBEND has been used to create a model of a notional Magnox reactor representing the main features of the presently operating Magnox reactors with steel RPVs. It was developed with the single purpose of improving understanding and was created so as to facilitate making the perturbations required in sensitivity calculations. A comprehensive series of sensitivity studies has been performed identifying influential factors and investigating the dominant pathways for the transmission of neutrons between the active core and RPV.

This study has confirmed the current calculational methodology for the provision of Magnox RPV doses. It has increased understanding of the neutron transport mechanisms and now provides a sound basis for the assessment of modelling uncertainties.
Establishment of Fe-Filtered Neutron Beam Facility and Measurement of the Filtered Neutrons
Authors: Kobayashi K , Yoshimoto T , Fujita Y , Utsuro M , Utsumi H
Published: April 2008

Thick Fe-filters have been installed at the beam tube No.1 (B-1) facility of the Kyoto University Reactor (KUR) at the Research Reactor Institute, Kyoto University (KURRI). By making reactor neutrons penetrate through Fe-filters of 45 cm in thickness mixed with Al-filters of 35 cm in total thickness, the Fe-filtered neutron beam at 24 keV has been established. In order to characterize the B-1 Fe-filtered neutron beam facility, following experiments/ analyses have been performed; (1) the Fe-filtered neutrons at 24 keV have been measured with a proton recoil gas counter, (2) the neutron energy spectrum of the Fe-filtered neutrons has been obtained by analyzing the activation foil data using the NEUPAC code, and (3) the neutron flux at 24 keV also has been determined to be 6.7 × 106 n/cm2/s by the sandwiched gold foils using the 197Au(n, γ)198 Au reaction. It has been found that the neutron fluxes at 24 keV obtained above are in general agreement with each other. Finally, (4) the absorbed doses at the B-1 facility also have been measured with thermoluminescence dosimeters (TLDs) and tissue-equivalent pair chambers.
Dosimetry of a GeV Proton-Driven Spallation Neutron Field by the Activation Method
Authors: Kasugai Y , Takada H , Ikeda Y
Published: April 2008

In order to meet the requirement from the high energy neutron dosimetry application, we have examined potential reactions for the neutron activation detector at spallation neutron fields, which were provided by driving protons with energies of 1.6, 12 and 24 GeV into a mercury target. The experiments were carried out using AGS accelerator at Brookhaven National Laboratory. Metal foils of In, Nb, Al, Co, Ni, Ti, Y and Bi were selected as dosimeters. Thirty-one reactions with threshold energies between 0.3 and 60 MeV were identified. Foils were irradiated at different locations around the mercury target. After the irradiation gamma-ray from the activation foils were measured with HPGe detectors. Using the 115In(n,n’)115mIn reaction with the threshold energy of 0.3 MeV, the spatial distribution of the neutron flux around the spallation target was obtained, and the neutron spectrum was determined by means of multiple-foil activation unfolding method.
The Irradiation Characteristics of the KUR Heavy Water Facility — Neutron Energy Spectra for Several Irradiation Modes
Authors: Kobayashi T , Sakurai Y , Kobayashi K
Published: April 2008

The Heavy Water Neutron Irradiation Facility of Kyoto University Reactor was remodeled in March 1996 mainly for neutron capture therapy. The remodeled facility can supply neutron energy spectra from almost pure thermal to mainly epithermal, using the heavy water spectrum shifter, and the thermal neutron filters of cadmium and boral. We will report the evaluation of the neutron energy spectra at the normal irradiation position with the multi-activation foil method for the three irradiation modes; i.e. the non-filtered, the cadmium-filtered and the boral-filtered modes. Gold foil for thermal neutrons, four kinds of resonance foils (such as gold, indium, etc.), and nine kinds of threshold foils (such as indium, aluminum, etc.), were used. The initial neutron energy spectra were calculated using a two-dimensional transport code “DOT 3.5,” and the adjustment was performed using the code “NEUPAC.” The evaluation repeatability was thought to be within about 20%.
Fatigue and Fracture Mechanics: 30th Volume
Authors: Jerina KL , Paris PC
Published: April 2008

Description

STP 1360 provides advanced state-of-the-art techniques for predicting fracture and fatigue, as well as applications and engineering problem solving in a number of key industries. Over 30 comprehensive, peer-reviewed papers from the world's leading experts address topics in fracture mechanics, fatigue, and applications.

Areas of fracture mechanics covered include:

• Effects of geometry

• Specimen size on fracture behavior

• Toughness in the transition region

• Loading effects on fracture

• Innovative crack solutions

• Analysis techniques in analytical fracture mechanics

Areas of fatigue include:

• Effects of crack closure, stress ratio, residual stress and loading on fatigue

• Novel test methods and data analysis

Applications include:

• Predicting and measuring fatigue performance

• Fracture mechanics applications

• Finite element modeling of cracks and crack growth

This is a critical resource for mechanical, materials, and structural engineers involved with structural parts design and analysis; regulatory and investigative organizations and national laboratories.
Measurement of Neutron Spectrum at HANARO
Authors: Hong U , Kang HD , Seo CG , Kang YH
Published: April 2008

For the use of the accurate element analysis in materials, the energy spectrum of neutrons in the NAA3 hole of the HANARO has been measured by the multi-wire activation method. The experimental results have been compared with the spectrum calculated by the MCNP code. In the MCNP calculation, the hole is the farthest hole from the core, so energy splitting and geometry splitting techniques are used to reduce the statistical errors. The results show that the neutron flux is proportional to 1/E1+β in the energy region from about 1eV to a few hundred keV, where β is equal to 0.12. The comparison of adjusted neutron spectrum and calculated one shows a good agreement, however, the measured fast neutron flux is a little higher than calculated one. The difference is within the uncertainties in the MCNP calculation and the measurement.
Combining Measurements and 3D Neutron Transport Calculations — A Powerful Tool in Detailed Neutron Dosimetry and Damage Analysis
Authors: Voorbraak WP , Freudenreich WE , Ketema DJ
Published: April 2008

This document shows that the combination of 3D neutron transport calculations with the results from activation foil measurements at a limited number of locations in a materials testing irradiation experiment can provide information at any position in the experiment for detailed neutron dosimetry and damage analysis.
Characterization of Neutron Field for Stainless Steel Irradiation Experiments in JMTR
Authors: Shimakawa S , Nagao Y , Fujiki K
Published: April 2008

A series of spectral tailoring irradiation tests for type 304 stainless steel (304SS) has been completed in the Japan Materials Testing Reactor (JMTR). The purpose of the experiments is to study the material property changes by irradiation with different neutron energy spectrum. A new procedure of neutron dosimetry and the verification results of neutronics calculation are described here. According to the procedure, the detailed estimation with neutron spectrum uncertainties at an actual neutron field is made possible to determine accurate dpa rate and helium production rate.
Assessment of the Fission Power Level in Fuel Rods Irradiated in the High Flux Materials Testing Reactor BR2 with the Aid of Fluence Dosimetry and Comparison with Other Methods
Authors: De Raedt C , Malambu E , Bodart S , Wéber M , Willekens M
Published: April 2008

To determine the fission power in fuel targets irradiated in BR2, various methods are applied. The three most commonly used are the thermal balance method, the non-destructive gamma-spectrometry of the irradiated fuel rods, and the destructive post-irradiation measurements. A fourth method, called here the fluence-dosimetry method, combines the measurement of fluence dosimeters with the calculation of the flux chart inside the irradiation device, and in particular of the flux and the fission density in the fuel. The various factors influencing the accuracy of the latter method will be analysed.
Estimation of Low Level Neutron Doses Based on Neutron Spectra in the Vicinity of a Nuclear Reactor
Authors: Urabe I , Sagawa H , Ogawa Y , Ohsawa T , Kobayashi K , Yoshimoto T , Tsujimoto T
Published: April 2008

For the improvement of dosimetric methods for low intensity neutrons, a highly sensitive multi-moderator neutron spectrometer was constructed and applied for the determination of neutron energy spectra in the vicinity of the Kinki University Reactor, UTR-KINKI. It became clear from the measured spectra that relatively high intensity fast neutrons were observed around the electrical connection panel of the reactor, while the 1/E neutrons and low intensity fast neutrons were usually observed in the vicinity of the nuclear reactor. These neutron energy spectra were obviously changed by the beam emission upward from the top shield of the reactor; especially, the intensity of low energy neutrons was very much increased by the interaction of neutrons with the ceiling of the reactor building. The neutron doses, which could not be precisely determined by a neutron sievert (Sv) counter, could be estimated on the basis of these neutron spectra.
Conceptual Neutronics Design of “Neutron Factory” as a Future Plan on Neutron Source in Kyoto University Research Reactor Institute (KURRI)
Authors: Shiroya S , Unesaki H , Kawase Y , Moriyama H , Inoue M
Published: April 2008

A synergetic system of a high energy proton accelerator and a spectrum controlled type research reactor is considered to be a main candidate of a future neutron source in Kyoto University Research Reactor Institute (KURRI). A study on a conceptual neutronics design has been performed for an accelerator driven subcritical reactor, which is expected to be a main facility for the joint use program as a substitute of the 5 MW research reactor (KUR). The neutron flux levels in several irradiation or experimental ports in the research reactor were examined through neutronics calculations when the reactor is operated either independently or in combination with the accelerator. In addition, preliminary studies were conducted to get information concerning the neutron pulse shape, the neutron multiplication and the power distribution in the accelerator driven system (ADS).
Results from the NIST Round Robin Test of Fissionable Dosimeters in a Reactor Leakage Spectrum
Authors: Adams JM
Published: April 2008

The National Institute of Standards and Technology has completed a round robin test of 237Np and 238U fissionable dosimeters. The objective of the test was to demonstrate the utility of the Materials Dosimetry Reference Facility for performing neutron metrology testing for applications in fast-neutron dosimetry for reactor pressure vessel surveillance monitoring. For this test, 237Np and 238U fission dosimeters were irradiated to a certified fluence in the Facility, and then distributed to the test participants for determination of the fast-neutron fluence, principally by radioassay of long-lived 137Cs fission product activity. In the present paper are reported the results obtained from this test, showing that the 237Np results are, on the average, within 2.9 % of the certified values, and that the 238U results are within 4.6 %, both based on 137Cs radioassay. These results are well within limits acceptable for neutron surveillance monitoring for determining the fast-neutron exposure in commercial nuclear power reactors.
New NEA Benchmarks for Calculating Fast Neutron Fluence in the Reactor Pressure Vessel
Authors: Hehn G , Na BC
Published: April 2008

For proving the precision achievable today in predicting the neutron fluence for reactor pressure vessels, the OECD/NEA initiated a new international benchmark exercise as a blind test, where the measured results are not known in advance. To validate two- and three-dimensional radiation transport codes, high precision measurements at the VENUS critical facility of SCK.CEN, Mol in Belgium were used representing the pressure vessel internals of a Westinghouse three loop reactor. About 20 independent calculations were contributed world-wide for the two-dimensional benchmark VENUS-1. The most challenging task was the validation of the newest versions of three-dimensional transport codes like TORT, PENTRAN and MCNP. 14 calculations were contributed for the complex 3D-benchmark VENUS-3 and compared with about 400 local measurements. In conclusion, the results of the three-dimensional benchmark VENUS-3 were in general much closer to the experimental values than for the two-dimensional benchmark VENUS-1, which shows inherent deficiencies of two-dimensional transport calculations that suffer on approximations like diffusion based axial buckling or improper averaging of axial sources and shielding layers.
Adjustment of the 235U Fission Spectrum
Authors: Griffin PJ , Williams JG
Published: April 2008

The latest nuclear data are used to examine the sensitivity of the least squares adjustment of the 235U fission spectrum to the measured reaction rates, dosimetry cross sections, and prior spectrum covariance matrix. All of these parameters were found to be very important in the spectrum adjustment. The most significant deficiency in the nuclear data is the absence of a good prior covariance matrix. Covariance matrices generated from analytic models of the fission spectra have been used in the past. This analysis reveals some unusual features in the covariance matrix produced with this approach. Specific needs are identified for improved nuclear data to better determine the 235U spectrum. An improved 235U covariance matrix and adjusted spectrum are recommended for use in radiation transport sensitivity analyses.
Development of Calibration Fields of Intermediate Neutrons by Using Several Sources
Authors: Takeda N , Kudo K , Fujishiro M , Okamoto K , Kobayashi K , Yoshimoto T
Published: April 2008

Intermediate neutron Fields were developed using three different neutron sources, i.e., a 124Sb-Be photoneutron source, an iron filtered neutron beam from the Kyoto University Reactor (KUR), and a Sc(p,n)Ti reaction using an electrostatic accelerator at the Electrotechnical Laboratory (ETL). Neutron fluences of the iron filtered neutron beam and the neutron generated by Sc(p,n)Ti reaction were measured by a 3He or hydrogen gas proportional counter. Neutron emission rate of the 124Sb-Be source was measured by a manganese bath method developed at the ETL. Neutron energy spectra were simulated by MCNP-4 code. Field properties were then studied and compared.
A Study on 14 MeV Neutron Beam Characteristics and its Applications
Authors: Sakane H , Uno Y , Maekawa F , Kasugai Y , Konno C , Kaneko J , Ikeda Y
Published: April 2008

A collimator system for extracting 14 MeV-neutron beam has been devised by utilizing a shield assembly for the streaming experiment at Fusion Neutronics Source (FNS) facility at JAERI. The collimator consists of a 500 mm pre-collimator and a 1.2 m iron bulk shield followed by 400 mm polyethylene and 200 mm lead layer, at the center of which a hole of 20 mm in diameter penetrates along the horizontal line from a 14 MeV source. The collimated beam's characteristics are experimentally studied in terms of beam on/off ratio, neutron flux spectrum at the exit of collimator hall by using an imaging plate, activation foils, and NE213 scintillator. It was found that the background level at an off-neutron-beam is low enough to make an in-beam experiment effective. Using the collimated beam, a series of secondary gamma-ray production cross section measurements were conducted without pulse mode operation.
Production of a Dosimetry Cross Section Set Up to 50 MeV
Authors: Maekawa F , von Möllendorff U , Wilson PPH , Wada M , Ikeda Y
Published: April 2008

For the dosimetry of high-energy accelerator neutron sources such as spallation neutron source facilities and the International Fusion Material Irradiation Facility, a dosimetry cross section set up to 50 MeV was produced by means of integral activation experiments. Activation foil samples of Al, Mn, Fe, Co, Ni, Y, Nb, In, Tm, Au, and Bi were irradiated in d-Li and d-Be neutron fields of which maximum energy was 55 MeV, and reaction rates were measured. Cross sections for 27 dosimetry reactions including (n,n'), (n,p), (n, α) and (n,2n) through (n, 6n) reactions and neutron flux spectra at the irradiation fields were adjusted simultaneously with the SAND-II code so as to be consistent with the measured reaction rates. The adjusted cross sections were found to be consistent with each other for the typical broad neutron spectra produced by the d-Li and d-Be sources.
Measurement of Differential Neutron-Induced Charged-Particle Emission Cross Sections for 5 – 75 MeV Neutrons
Authors: Baba M , Sanami T , Nauchi Y , Hirasawa Y , Hirakawa N , Nakashima H , Meigo S , Tanaka S
Published: April 2008

Differential cross sections have been measured for the 16O(n,xα) reaction between 11.5 and 15 MeV using a gridded-ionization chamber with gas samples, and the Fe, Ni(n,xp), (n,xd), (n,xα) reactions at 55 and 75 MeV using a 7Li(p,n) source and multiple counter telescopes. The results were favorably compared with ENDF/B-VI, JENDL-3.2, and LA-150 library, but in marked disagreement in some cases.
Fast Neutron Yields Generated from Deuteron Break-up in Low Energy Reactions of Light Nuclei
Authors: Bém P , Burjan V , Cvachovec F , Götz M , Kroha V , Nikolskii EY , Šimečková E , Štursa J , Vincour J
Published: April 2008

Investigation of neutron production by break-up processes in light-nuclei reactions is described. The energy spectra of neutrons emitted by thick deuterium and helium targets at 0° angle irradiated by a beam of 15.8 MeV protons, 14.1 MeV and 17.1 MeV deuterons, respectively, were measured in an open geometry with stilbene and NE 213 scintillators and with a two-dimensional n-γ discrimination technique. Obtained spectral yields were compared with those of p+Be and d+Be reactions at corresponding energies. This comparison shows that the D- and 4He- targets spectra are substantially harder having lower relative contribution of low-energy neutrons. The p+D reaction looks to be the most effective reaction for producing fast neutrons on low energy cyclotrons.
PV-Surveillance Dosimetry and Adjustment: Review of Several Significant Oral Laws
Authors: Perel RL , Wagschal JJ , Yeivin Y
Published: April 2008

We elaborate on several topics related to the adjustment formalism, of which LEPRICON is a particular application. The latter is a most reliable way for estimating the fluence in pressure vessels of reactors from given iron cross-section data and surveillance-dosimetry measurements. New insights of adjustment should hopefully also enhance a deeper understanding of dosimetry. Our review includes the following: (a) Adjustment for pedestrians — an even more elementary derivation of the comprehensive prescriptions, based on geometric considerations in the parameter space and on arguments relating to dimensions of vectors and matrices; (b) the iteration of adjustment, is it worth its while? and (c) absolute and relative uncertainties and sensitivities.
Physically Constrained Adjustment of Calculated Neutron Spectra for Dosimetry and Vessel Locations
Authors: Williams JG , Griffin PJ
Published: April 2008

Modal (eigenvector) decomposition has been performed on the published neutron spectrum covariance matrices for Arkansas Nuclear One, Unit 1. The largest eigenvalue of the 15×15 correlation matrix is 10.97, and only five others exceed 0.15 (1% of the trace). The remaining nine eigenvalues are extremely small. Small values imply that some linear combinations of the fluences are almost invariant under any permissible adjustment. The invariance was enforced by setting the corresponding eigenvalues to zero. The non-zero eigenvalues that remain in this example represent the variances of the fluence within the vector space where adjustment can occur. It is shown that this procedure produces physically meaningful adjustments, without the need for complete prior covariance information. Included is consideration of the propagation of adjustments from the dosimetry location to the T/4 position within the reactor pressure vessel.
Three Dimensional Neutron Analysis in the Baffle-Former Area of PWR Plant
Authors: Kitagawa H , Yamagiwa N , Yamashita K
Published: April 2008

Three dimensional (3-D) neutron flux distributions are usually obtained by synthesizing the results from the two dimensional (2-D) calculations. However, 3-D neutron flux synthesis is inadequate in a complex geometry like the baffle-former plate area of a PWR plant because it spreads out along another axis that can not be expressed in 2-D geometry. 3-D neutron analyses for geometry with former plate were done with the three dimensional discrete ordinates code TORT [1]. Neutron spectra were obtained at the former plate area and various locations within the reactor vessel. These results were compared for energy above 0.1 MeV and 1.0 MeV with those of 2-D analyses.
Performance of A3MCNP™ for Calculation of 3-D Neutron Flux Distribution in a BWR Core Shroud
Authors: Haghighat A , Hiruta H , Petrovic B
Published: April 2008

This paper analyzes the performance of the A3MCNP™ (Automated Adjoint Accelerated MCNP) for determination of neutron fluence in a BWR core shroud. A3MCNP™ automatically prepares variance reduction parameters based on the CADIS (Consistent Adjoint Driven Importance Sampling) methodology that uses a 3-D energy dependent “importance” function. A3MCNP™ prepares necessary input files for performing adjoint transport calculations using the TORT Sn code. Using A3MCNP™, we have calculated DPA (displacement per atom) values (with a lσ uncertainty) at the H4 weld of a BWR core shroud in less than 5 CPU hour. For the same calculation, an analog Monte Carlo simulation requires about one month of CPU time. The trade-off between the accuracy of the adjoint function calculation and overall computation cost is examined. It is demonstrated that even for a very approximate adjoint function distribution, A3MCNP™ yields significant speedup over an analog Monte Carlo calculation.
Development of Induced Activity Estimation Method for PWR Containment
Authors: Nakata M , Muramatsu T
Published: April 2008

This document shows the development of the induced activity estimation method and confirmation of the accuracy of this method for activated concrete estimation. As a result of comparison, the calculated value to the measured value (C/E) for 60Co was about 1.7 and the C/E for 152Eu was about 0.9. According to the comparison, it was shown that the calculated activity for 60Co was moderately conservative and 152Eu was in good agreement.
Comparative Analysis of DPA Processed from Current Evaluated Nuclear Data Libraries
Authors: Chang J , Gil C-S , Cho YS , Kim J-D
Published: April 2008

Recent pressure vessel surveillance reports contain DPA rates as an exposure parameter. In order to assess the reliability of the DPA data, it is useful to inter-compare available DPA data processed from current evaluated nuclear data libraries. We generated the damage energy production cross sections for elements in a RPV of a PWR and a core barrel of a LMR, with NJOY 97 code system from the currently available evaluated nuclear data libraries, ENDF/B-VI.5, JEF-2.2, JENDL-3.2, BROND-2.2, and CENDL-2.1. The DPA rates using the neutron spectra from the surveillance test of Korean PWR Ulchin Unit 1 and the design of KALIMER LMR were inter-compared. The results show a maximum relative difference of 22% for carbon steel in a PWR. The effect of partial damage cross sections such as elastic scattering, inelastic scattering and disappearance reaction has been analyzed as well as status of iron, chrome and nickel.
A Study of Displacement Cross Section in Medium-Energy Region
Authors: Iga K , Takada H , Ikeda Y
Published: April 2008

Nucleon-Meson Transport Code of Japan Atomic Energy Research Institute version (NMTC/JAERI) was revised by implementing Lindhard-Robinson model and updating nucleon-nucleus total and non-elastic cross sections above 1 GeV so as to calculate displacement cross sections in the medium energy region of 20 MeV to 3.5 GeV. The displacement cross sections of Cr, Fe, Ni, and type 316 stainless steel were studied with the revised NMTC/JAERI. It is found that accurate treatment of the angular distribution with the optical model potentials gives reasonable displacement cross sections at tens of MeV. The applicability of the revised NMTC/JAERI code for the estimation of the radiation damage by medium-energy nucleons was supported by the comparison between the NMTC/JAERI and the LAHET calculation. The results of the NMTC/JAERI, however, were 20 % smaller than the values of Japanese Evaluated Nuclear Data Library (JENDL) PKA File at 20 MeV.