Eishi Ibe

Impact of Scaling on Neutron-Induced Soft Error in SRAMs From a 250 nm to a 22 nm Design Rule

Trends in terrestrial neutron-induced soft-error in SRAMs from a 250 nm to a 22 nm process are reviewed and predicted using the Monte-Carlo simulator CORIMS, which is validated to have less than 20% variations from experimental soft-error data on 180-130 nm SRAMs in a wide variety of neutron fields like field tests at low and high altitudes and accelerator tests in LANSCE, TSL, and CYRIC. The following results are obtained: 1) Soft-error rates per device in SRAMs will increase x6-7 from 130 nm to 22 nm process; 2) As SRAM is scaled down to a smaller size, soft-error rate is dominated more significantly by low-energy neutrons (<; 10 MeV); and 3) The area affected by one nuclear reaction spreads over 1 M bits and bit multiplicity of multi-cell upset become as high as 100 bits and more.

Terrestrial neutron-induced soft errors in advanced memory devices

Terrestrial Neutron Spectrometry and Dosimetry Irradiation Test in the Terrestrial Field Neutron Irradiation Test Facilities Review of Experimental Data and Discussions Monte Carlo Simulation Methods Simulation Results and Their Implications International Standardization of Neutron Test Method Summary and Challenges.

Radiolytic Aspects in Boiling Water Reactor Primary Systems: Results from Numerical Simulations and Statistical Regression Analyses

Dependencies of radiolytic aspects on geometric and operational conditions of boiling water reactor (BWR) primary systems were studied for normal operation or for hydrogen alternate water chemistry (HAWC) by using a computer simulation code AQUARY. Statistical regression analyses were applied to those calculated results and a great many close correlations were found among radiolytic concentrations. In the course of the study, it was discovered that residence time and energy deposition rate in th downcomer had a critical effect on HAWC. A set of simple estimation formulas for radiolytic conditions was proposed for normal BWR operation, and the following prediction formulas were proposed for the oxygen gas release rate and oxygen concentration in the recirculation line under HAWC: R0 = R0 exp (-0.00985 C* /SUB H/ ) and C02 = 191.3 exp (-0.0483 C /SUB H/ ).

A Novel Feature of Neutron-Induced Multi-Cell Upsets in 130 and 180 nm SRAMs

Bit-multiplicity of neutron-induced single event upsets (SEU) in CMOS SRAMs formed with 130 and 180 nm technologies was analyzed using mono-energetic, quasi-mono-energetic, and spallation neutron sources in various accelerator facilities. The energy dependence of the ratio of multi-cell upsets (MCUs) to the total number of upsets can be described by a Weibull-type function with the threshold energy of the MCU. The 130 nm SRAMs show a novel feature of multi-cell upsets (MCUs) including frequency distribution of the multiplicity of error bits. In the case of the 130 nm SRAM, the probability function of the MCU can be expressed as a sum of exponential and Lorentzian functions of the multiplicity of error bits. According to previous results of 3-dimensional device simulation, the Lorentzian component can be due to bipolar action.

Formation and dissolution of oxide film on zirconium alloys in 288°C pure water under γ-ray irradiation

Laboratory corrosion tests for zirconium alloys which were based on Zircaloy-2 were performed in 288°C oxygenated pure water for 100 days both with and without60Co γ-ray irradiation. No nodular oxide was observed. Corrosion weight gains of the alloy which had the lowest nodular corrosion resistance were lower for the irradiated condition than the non-irradiated condition. On the other hand, the alloys which had higher nodular corrosion resistances showed almost the same weight gains for both conditions. Differences of weight gain with and without irradiation were attributed to dissolution of the oxide film in the high temperature water. Dissolution tests of single crystal yttria-doped ZrO2 indicated that 30–40% larger amounts dissolved into water under the γ-ray irradiation. Low angle incident X-ray diffraction analysis showed that the tetragonal-ZrO2 fraction in the oxide film was lower with irradiation than without it, especially for the near surface area. The water radiolysis species accelerated the dissolution of the oxide film, especially film on the alloy with lower nodular corrosion resistance. This dissolution led to the lower tetragonal-ZrO2 fraction and was considered to be one of the factors causing a localized breakdown of the barrier oxide film to make the nodular oxide.

A water radiolysis model in a circulating flow system with a boiling region and its application to hydrogen alternate water chemistry of boiling water reactors

A gaseous mass transfer model has been proposed for quantitative evaluation of the chemical chain-back reaction system with volatile species in a boiling channel. Theoretical expression for concentration transients in liquid and vapor phases were obtained. The model was applied to water radiolysis in a boiling water reactor core channel with Bankoffs two-phase flow treatment. Hydrogen injection tests in the Oskarshamn-2 and Dresden-2 units were simulated. The calculated results showed that gas release and absorption rates in the boiling channel were not consistent with Henrys law. By using optimized parameters related to the gaseous mass transfer, calculated results agreed within a factor of 2 for lower hydrogen injection rates at the two plants. It was determined that more exact treatments are needed to determine the radiation level in the downcomer and catalytic decomposition rate of hydrogen peroxide in order to provide better evaluations of water radiolysis phenomena.

Threshold energy of neutron-induced single event upset as a critical factor

The physical modeling of neutron-induced SEU (single event upset) is usually described by high energy neutrons above a few tens MeV. In JESD89 it is assumed that the sensitivity of the concerned device to neutrons with energies less than 10 MeV is low enough to be ignored. The scaling of semiconductor devices can cause their higher susceptibility even to neutrons of several MeV, where the flux of terrestrial neutron is relatively high enough to affect SER (soft error rate) -estimation from data acquired by accelerated test. Although the information on the threshold energy of neutron-induced SEU becomes more important, the definition of the threshold energy of neutron-induced SEU is not still an obscure issue. This work focuses on importance of the threshold energy of neutron-induced SEU. It is demonstrated how the threshold energy of neutron-induced SEU affects SER-estimation by accelerated test with (quasi-) mono energy neutrons.

Application of Hydrogen Water Chemistry to Moderate Corrosive Circumstances around the Reactor Pressure Vessel Bottom of Boiling Water Reactors

Many efforts to preserve the structural integrity of major piping, components, and structures in a boiling water reactor (BWR) primary cooling system have been directed toward avoiding intergranular stress corrosion cracking (IGSCC). Application of hydrogen water chemistry (HWC) to moderate corrosive circumstances is a promising approach to preserve the structural integrity during extended lifetimes of BWRs. The benefits of HWC application are (a) avoiding the occurrence of IGSCC on structural materials around the bottom of the reactor pressure vessel (RPV) and (b) moderating the crack growth rate, even if microcracks are present on the structural materials. Several disadvantages caused by HWC (e.g., turbine dose rate increase, 60 Co radioactivity buildup, and effects on fuel cladding) are evaluated to develop suitable countermeasures prior to HWC application. The advantages and disadvantages of HWC are quantitatively evaluated based on both BWR plant data and laboratory data shown in unclassified publications. Their trade-offs are discussed, and suitable applications of HWC are described. It is concluded that an optimal amount of hydrogen injected into the feedwater can moderate corrosive circumstances, in the region to be preserved, without serious disadvantages. The conclusions have been drawn by combining experimental and theoretical results. Experiments in BWR plants - e.g., direct measurements of electrochemical corrosion potential and crack growth rate at the RPV bottom - are planned that would collect data to support the theoretical considerations

Picosecond diffusion in a thermal spike during ion mixing

Abstract The thermodynamic process in a thermal spike during bilayer ion beam mixing was examined using a numerical diffusion model for times of a few picoseconds. Parameter identification by the model suggested that the amount of bilayer system mixing depended equally on the intrinsic diffusion coefficients and the heat of mixing. Direct applications of the numerical model, however, to actual Au/Ti, Au/Cu, Au/Cr, and Au/Co bilayer systems were unsuccessful. Extensive study is required for analysis of diffusion-like processes in the thermal spike at excessively high temperatures and pressures.

Radiolytic Environments in Boiling Water Reactor Cores

Radiolytic, environments in the BWR primary system were evaluated by using a theoretical model. Reactor core was divided into two regions, boiling and by-pass (non-boiling) channels. The major findings are summarized as follows: (1) Under normal operation without hydrogen addition, dissolved hydrogen and oxygen concentrations had their maximum values at the height where boiling started. Their concentrations in the boiling channel were lower than those in the by-pass channel because of hydrogen and oxygen release from liquid phase to gas phase. (2) The most efficient oxygen suppression by hydrogen addition was expected in the non-boiling regions of the reactor core where injected hydrogen was confined in the liquid phase. (3) When the bulk decomposition of water in the reactor core is represented by the coefficient decreased as hydrogen injection rate increased, but B hardly changed at a low hydrogen addition rate.