Japan

Fatigue crack growth (FCG) tests for compact tension (CT) specimens of an annealed low-carbon steel JIS-SM490B were performed under various combinations of hydrogen pressures ranging from 0.1 to 90 MPa test frequencies from 0.001 to 10 Hz and test temperatures of room temperature (RT) 363 K and 423 K. In the hydrogen pressures of 0.1 0.7 and 10 MPa at RT the FCG rate increased with a decrease in the test frequency; then peaked out. In the lower test frequency regime the FCG rate decreased and became nearly equivalent to the FCG rate in air. Also in hydrogen pressure of 45 MPa at RT the hydrogen-assisted FCG acceleration showed an upper limit around the test frequencies of 0.01 to 0.001 Hz. On the other hand in the hydrogen pressure of 90 MPa at RT the FCG rate monotonically increased with a decrease in the test frequency and eventually the upper limit of FCG acceleration was not confirmed down to the test frequency of 0.001 Hz. In the hydrogen pressure of 0.7 MPa at the test frequency of 1 Hz and temperatures of 363 K and 423 K the stress intensity factor range ΔK for the onset of the FCG acceleration in hydrogen gas was shifted to a higher ΔK with an increase in the test temperature. The laser-microscope observation at specimen surface revealed that the hydrogen-assisted FCG acceleration always accompanied a localization of plastic deformation near crack tip. These results infer that the influencing factor dominating the hydrogen-assisted FCG acceleration is not the presence or absence of hydrogen in material but is how hydrogen localizes near the crack tip. Namely a steep gradient of hydrogen concentration can result in the slip localization at crack tip which enhances the Hydrogen Enhanced Successive Fatigue Crack Growth (HESFCG) proposed by the authors. It is proposed that such a peculiar dependence of FCG rate on hydrogen pressure test frequency and test temperature can be unified by using a novel parameter representing the gradient of hydrogen concentration near crack tip.

‟How crack growth is prevented” is key to improve both fatigue and monotonic fracture resistances under an influence of hydrogen. Specifically the key points for the crack growth resistance are hydrogen diffusivity and local ductility. For instance type 304 austenitic steels show high hydrogen embrittlement susceptibility because of the high hydrogen diffusivity of bcc (α´) martensite. In contrast metastability in specific austenitic steels enables fcc (γ) to hcp (ε) martensitic transformation which decreases hydrogen diffusivity and increases strength simultaneously. As a result even if hydrogen-assisted cracking occurs during monotonic tensile deformation the ε-martensite acts to arrest micro-damage evolution when the amount of ε-martensite is limited. Thus the formation of ε-martensite can decrease hydrogen embrittlement susceptibility in austenitic steels. However a considerable amount of ε-martensite is required when we attempt to have drastic improvements of work hardening capability and strength level with respect to transformation-induced plasticity effect. Since the hcp structure contains a less number of slip systems than fcc and bcc the less stress accommodation capacity often causes brittle-like failure when the ε-martensite fraction is large. Therefore ductility of ε-martensite is another key when we maximize the positive effect of ε-martensitic transformation. In fact ε-martensite in a high entropy alloy was recently found to be extraordinary ductile. Consequently the metastable high entropy alloys showed low fatigue crack growth rates in a hydrogen atmosphere compared with conventional metastable austenitic steels with α´-martensitic transformation. We here present effects of metastability to ε-phase and configurational entropy on hydrogen-induced mechanical degradation including monotonic tension properties and fatigue crack growth resistance.

The aim of this study is to provide a quantification of the internal pressure contribution to the SSRT properties of H-charged Type-316L steel tested in air at room temperature. Considering pre-existing penny-shaped voids the transient pressure build-up has been simulated as well as its impact on the void growth by preforming JIc calculations. Several void distributions (size and spacing) have been considered. Simulations have concluded that there was no impact of the internal pressure on the void growth regardless the void distribution since the effective pressure was on the order of 1 MPa during the SSRT test. Even if fast hydrogen diffusion related to dislocation pipe-diffusion has been assessed as a conservative case the impact on void growth was barely imperceptible (or significantly low). The effect of internal pressure has been experimentally verified via the following conditions: (I) non-charged in vacuum; (II) H-charged in vacuum; (III) H-charged in 115-MPa nitrogen gas; (IV) non-charged in 115-MPa nitrogen gas. As a result the relative reduction in area (RRA) was 0.84 for (II) 0.88 for (III) and 1.01 for (IV) respectively. The difference in void morphology of the H-charged specimens did not depend on the presence of external pressure. These experimental results demonstrate that the internal pressure had no effect on the tensile ductility and void morphology of the H-charged specimen.

The effects of different mole fractions of hydrogen and carbon dioxide on the combustion characteristics of a premixed methane–air mixture are experimentally and numerically investigated. The laminar burning velocity of hydrogen-methane-carbon dioxide-air mixture was measured using the spherically expanding flame method at the initial temperature and pressure of 283 K and 0.1 MPa respectively. Additionally numerical analysis is conducted under steady 1D laminar flow conditions to investigate the adiabatic flame temperature and dominant elementary reactions. The measured velocities correspond with those estimated numerically. The results show that increasing the carbon dioxide mole fraction decreases the laminar burning velocity attributed to the carbon dioxide dilution which decreases the thermal diffusivity and flame temperature. Conversely the velocity increases with the thermal diffusivity as the hydrogen mole fraction increases. Moreover the hydrogen addition leads to chain-branching reactions that produce active H O and OH radicals via the oxidation of hydrocarbons which is the rate-determining reaction.

This study aimed to identify the impact of achieving the 1.5 ◦C target on the petroleum supply chain in Japan and discuss the feasibility and challenges of decarbonization. First a national material flow was established for the petroleum supply chain in Japan including processes for crude petroleum refining petroleum product manufacturing plastic resin and product manufacturing and by-product manufacturing. In particular by-product manufacturing processes such as hydrogen gaseous carbon dioxide and sulfur were selected because they are utilized in other industries. Next the outlook for the production of plastic resin hydrogen dry ice produced from carbon dioxide gas and sulfur until 2050 was estimated for reducing petroleum consumption required to achieve the 1.5 ◦C target. As a result national petroleum treatment is expected to reduce from 177048.00 thousand kl in 2019 to 126643.00 thousand kl in 2030 if the reduction in petroleum consumption is established. Along with this decrease plastic resin production is expected to decrease from 10500.00 thousand ton in 2019 to 7511.00 thousand ton by 2030. Conversely the plastic market is expected to grow steadily and the estimated plastic resin production in 2030 is expected to be 20079.00 thousand ton. This result indicates that there is a large output gap between plastic supply and demand. To mitigate this gap strongly promoting the recycling of waste plastics and making the price competitiveness of biomass plastics equal to that of petroleum-derived plastics are necessary

Hydrogen produced without carbon emissions could be a useful fuel as nations look to decarbonize their electricity transport and industry sectors. Using the iodine–sulfur (IS) cycle coupled with a nuclear heat source is one method for producing hydrogen without the use of fossil fuels. An economic dispatch model was developed for a nuclear-driven IS system to determine hydrogen sale prices that would make such a system profitable. The system studied is the HTTR GT/H2 a design for power and hydrogen cogeneration at the Japan Atomic Energy Agency’s High Temperature Engineering Test Reactor. This study focuses on the development of the economic model and the role that input data plays in the final calculated values. Using a historical price duration curve shows that the levelized cost of hydrogen (LCOH) or breakeven sale price of hydrogen would need to be 98.1 JPY/m3 or greater. Synthetic time histories were also used and found the LCOH to be 67.5 JPY/m3 . The price duration input was found to have a significant effect on the LCOH. As such great care should be used in these economic dispatch analyses to select reasonable input assumptions.

An integrated system to harvest efficiently the energy from the waste of pulp mill industry which is black liquor (BL) is proposed and evaluated. The proposed system consists of the supercritical water gasification (SCWG) of BL syngas chemical looping and power generation. To minimize the exergy loss throughout the system and to optimize the energy efficiency process design and integration is conducted by employing the principles of exergy recovery and process integration methods. Hydrogen is set as the main output while power is produced by utilizing the heat generated throughout the process. Process simulation is conducted using a steady state process simulator Aspen Plus. Energy efficiency is defined into three categories: hydrogen production efficiency power generation efficiency and total energy efficiency. From process simulation both of the integrated systems show very high total energy efficiency of about 73%.

The major demand of energy in today’s world is fulfilled by the fossil fuels which are not renewable in nature and can no longer be used once exhausted. In the beginning of the 21st century the limitation of the fossil fuels continually growing energy demand and growing impact of greenhouse gas emissions on the environment were identified as the major challenges with current energy infrastructure all over the world. The energy obtained from fossil fuel is cheap due to its established infrastructure; however these possess serious issues as mentioned above and cause bad environmental impact. Therefore renewable energy resources are looked to as contenders which may fulfil most energy requirements. Among them hydrogen is considered as the most environmentally friendly fuel. Hydrogen is clean sustainable fuel and it has promise as a future energy carrier. It also has the ability to substitute the present energy infrastructure which is based on fossil fuel. This is seen and projected as a solution for the above-mentioned problems including rise in global temperature and environmental degradation. Environmental and economic aspects are the important factors to be considered to establish hydrogen infrastructure. This article describes the various aspects of hydrogen including production storage and applications with a focus on fuel cell based electric vehicles. Their environmental as well as economic aspects are also discussed herein.

After the Fukushima Daiichi nuclear power plant (NPP) accident new regulatory requirements were enforced in July 2013 and a backfit was required for all existing nuclear power plants. It is required to take measures to prevent severe accidents and mitigate their radiological consequences. The Regulatory Standard and Research Department Secretariat of Nuclear Regulation Authority (S/NRA/R) has been conducting numerical studies and experimental studies on relevant severe accident phenomena and countermeasures. This article highlights fission product (FP) release and hydrogen risk as two major areas. Relevant activities in the S/NRA/R are briefly introduced as follows: 1. For FP release: Identifying the source terms and leak mechanisms is a key issue from the viewpoint of understanding the progression of accident phenomena and planning effective countermeasures that take into account vulnerabilities of containment under severe accident conditions. To resolve these issues the activities focus on wet well venting pool scrubbing iodine chemistry (in-vessel and ex-vessel) containment failure mode and treatment of radioactive liquid effluent. 2. For hydrogen risk: because of three incidents of hydrogen explosion in reactor buildings a comprehensive reinforcement of the hydrogen risk management has been a high priority topic. Therefore the activities in evaluation methods focus on hydrogen generation hydrogen distribution and hydrogen combustion.

The strength against fracture nucleation from an interface free-edge of silicon-nitride (SiN)/copper (Cu) micro-components is evaluated. A special technique that combines a nano-indenter specimen holder and an environmental transmission electron microscope (E-TEM) is employed. The critical load at the onset of fracture nucleation from a wedge-shaped free-edge (opening angle: 90°) is measured both in a vacuum and in a hydrogen (H₂) environment and the critical stress distribution is evaluated by the finite element method (FEM). It is found that the fracture nucleation is dominated by the near-edge elastic singular stress field that extends about a few tens of nanometers from the edge. The fracture nucleation strength expressed in terms of the stress intensity factor (K) is found to be eminently reduced in a H2 environment.