Flow separation at inlet causing transition and intermittency in circular pipe flow

Ogawa, Masuro*

JAEA-Technology 2019-010, 22 Pages, 2019/07

JAEA-Technology-2019-010.pdf:1.5MB

Transition phenomena from laminar to turbulent flow are roughly classified into three categories. Circular pipe flow of the third category is linearly stable against any small disturbance, despite that flow actually transitions and transitional flow exhibits intermittency. These are among major challenges that are yet to be resolved in fluid dynamics. Thus, author proposes hypothesis as follows; "Flow in a circular pipe transitions from laminar flow because of vortices released from separation bubble forming in vicinity of inlet of pipe, and transitional flow becomes intermittent because vortex-shedding is intermittent." Present hypothesis can easily explain why linear stability theory has not been able to predict transition in circular pipe flow, why circular pipe flow actually transitions, why transitional flow actually exhibits intermittency even due to small disturbance, and why numerical analysis has not been able to predict intermittency of transitional flow in circular pipe.

Study on reduction of potential radiotoxicity for spent fuel by using HTGR

Fukaya, Yuji; Kunitomi, Kazuhiko; Ogawa, Masuro

Nihon Genshiryoku Gakkai Wabun Rombunshi, 14(3), p.189 - 201, 2015/09

https://doi.org/10.3327/taesj.J14.037

A study on reduction of potential radiotoxicity for spent fuel by using High Temperature Gas-cooled Reactors (HTGRs) have been performed. Unlike Partitioning and Transmutation (P&T), the reactor concept is investigated from the viewpoint of reduction of the radiotoxicity generation itself. To reduce the radiotoxicity, U, which generates Pu, Am and Cm, should be excluded. Therefore, we proposed HTGR fueled by new concept fuels with alternative fuel matrix instead of U. Those are Yttria Stabilized Zirconia (YSZ) and thorium, and the fissile material is Highly Enriched Uranium (HEU) with the enrichment of 93%. With the HEU, the radiotoxicity can be significantly reduced, and the cooling time to decay to a natural uranium level can be shorted down to approximately 800 years. Fuel integrity and proliferation resistance can be remained by the dilution using YSZ, and neutronic characteristics of self-regulation is remained by the loading of erbium. The fuel can generate heat as same amount as ordinary uranium fuel. The electricity generation cost is as cheap as ordinary GTHTR300. It is concluded that the proposed reactor concept can reduce the cooling time less than 1% from 100 thousand years to a 800 years without additional technology development.

Process evaluation of use of HTGRs to an ironmaking system based on active carbon recycling energy system (iACRES)

Hayashi, Kentaro*; Kasahara, Seiji; Kurihara, Kohei*; Nakagaki, Takao*; Yan, X.; Inagaki, Yoshiyuki; Ogawa, Masuro

Tanso Junkan Seitetsu Kenkyukai Saika Hokokusho; Tanso Junkan Seitetsu No Tenkai, p.42 - 62, 2015/02

Reducing coking coal consumption and CO emissions by application of HTGRs (high temperature gas-cooled reactors) to iACRES (ironmaking system based on active carbon recycling energy system) was investigated using process flow modeling. Two systems were evaluated: a SOEC (solid oxide electrolysis cell) system using CO electrolysis and a RWGS (reverse water-gas shift reaction) system using RWGS reaction with H produced by IS (iodine-sulfur) process. Coking coal consumption was reduced from a conventional BF (blast furnace) steelmaking system by 4.3% in the SOEC system and 10.3% in the RWGS system. CO emissions were decreased by 3.4% in the SOEC system and 8.2% in the RWGS system. Remaining H from the RWGS reactor was used as reducing agent in the BF in the RWGS system. This was the reason of the larger reduction of coking coal consumption and CO emissions. Electricity generation for SOEC occupied most of HTGR heat usage in the SOEC system. H production in the IS process used most of the HTGR heat in the RWGS system. Optimization of the SOEC temperature for the SOEC system and higher H production thermal efficiency in the IS process for the RWGS system will be useful for more efficient heat utilization. One typical-sized BF required 0.5 HTGRs and 2 HTGRs for in the SOEC system and RWGS system, respectively. CO emissions reduction per unit heat input was larger in the SOEC system. Recycling H to the RWGS will be useful for smaller emissions per unit heat in the RWGS system.

Economic evaluation of HTGR IS process hydrogen production system

Iwatsuki, Jin; Kasahara, Seiji; Kubo, Shinji; Inagaki, Yoshiyuki; Kunitomi, Kazuhiko; Ogawa, Masuro

JAEA-Review 2014-037, 14 Pages, 2014/09

JAEA-Review-2014-037.pdf:8.84MB

Thermochemical iodine-sulfur (IS) process is one of the promising technologies, which harnesses heat energy of high temperature gas-cooled reactors (HTGRs). An economic estimation of hydrogen production by a future commercial HTGR-IS process hydrogen production system was performed on the basis of economic evaluation data of an existing commercial hydrogen production plant using fossil fuel as a raw material. Hydrogen production cost was estimated at 25.4 JPY/Nm under this estimation conditions. Capital cost and energy cost account for 13% and 78% of the total hydrogen production cost, respectively. To decrease HTGR construction cost, to increase HTGR availability, to improve hydrogen production thermal efficiency are important for cost reduction of hydrogen. The cost will be competitive with estimated costs by fossil fuel hydrogen production methods. It is appropriate that the hydrogen production cost is set for a goal of present R&Ds.

Process flow sheet evaluation of a nuclear hydrogen steelmaking plant applying very high temperature reactors for efficient steel production with less CO emissions

Kasahara, Seiji; Inagaki, Yoshiyuki; Ogawa, Masuro

Nuclear Engineering and Design, 271, p.11 - 19, 2014/05

https://doi.org/10.1016/j.nucengdes.2013.11.002

Nuclear hydrogen steelmaking (NHS) system was evaluated by flow sheet analysis using very high temperature reactors (VHTRs) and thermochemical hydrogen production IS process. Heat input and CO emissions including material production, material transportation, and power generation were evaluation criteria. Though total heat input to the NHS system was 130-142% of a conventional blast furnace steelmaking system, CO emissions were 13-21%. Pre-heating of hydrogen by coal combustion before blowing to a shaft furnace was effective to decrease heat input although CO emissions increased. Direct nuclear pre-heating was also effective without increase of CO emissions if close location of the nuclear reactor to the steelmaking plant was publicly accepted. Hydrogen production thermal efficiency had a significant influence on the heat input. Conceptual design of a plant unit of the NHS system producing steel of 1.47 10 t/y with 2 VHTRs of 600MW heat and one shaft furnace and electric arc furnace was proposed. This article is revised from a proceeding presented in HTR2012.

Inherently-safe high temperature gas-cooled reactor for hydrogen production

Ogawa, Masuro; Kunitomi, Kazuhiko; Sato, Hiroyuki

Keynote Lecture for International Conference of PM2.5 & Energy Security 2014 (PMES 2014), p.72 - 74, 2014/03

The present paper reviewed the overview of HTGR technologies as well as excellent characteristics, such as environmental friendliness, safety, minimum waste, economic competitiveness, sustainability, usability and proliferation resistance, suitable for an energy supply system to be deployed in the field of heat utilization.

Thermochemical water-splitting hydrogen production iodine-sulfur process

Kubo, Shinji; Ogawa, Masuro

Nihon Enerugi Gakkai-Shi, 92(11), p.1041 - 1045, 2013/11

no abstracts in English

Inherently-safe high temperature gas-cooled reactor

Ogawa, Masuro

Zero-Carbon Energy Kyoto 2012, p.183 - 194, 2013/00

http://link.springer.com/chapter/10.1007/978-4-431-54264-3_20

High temperature gas-cooled reactor (HTGR), also known as VHTR, is one of the six Generation-IV nuclear energy systems. It can generate electricity at 50% thermal efficiency, and also produce hydrogen and supply high-quality process heat. Its production remains highly economical and safe even at as small as 600 MWt plant size. In this report, a new concept of inherently-safe HTGR is proposed never to compromises the safety of the public, society and environment for any accidents. It is designed so that any accident will be self-controllable to safe state only with physical phenomena but without reliance on active and/or passive devices and systems. Some inherent-safety characteristics of the inherently-safe HTGR have already been confirmed by test of the HTTR. The balance of the inherent safety characteristics required to establish the inherently-safe HTGR concept is analyzed. These results of the inherently-safe HTGR are presented, here.

Process flow sheet evaluation of a nuclear hydrogen steelmaking plant applying high temperature gas-cooled reactors for efficient steel production with less CO emissions

Kasahara, Seiji; Inagaki, Yoshiyuki; Ogawa, Masuro

Proceedings of 6th International Topical Meeting on High Temperature Reactor Technology (HTR 2012) (USB Flash Drive), 8 Pages, 2012/10

Nuclear hydrogen steelmaking (NHS) system was evaluated by flow sheet analysis using High Temperature Gas-cooled Reactors (HTGRs) and thermochemical hydrogen production IS process. Heat input and CO emissions of the system including material production, material transportation, and power generation were evaluation criteria. The result was compared with that of a conventional blast furnace steelmaking (BFS) system. Though total heat input to the NHS system was 141-159% of the BFS system, CO emissions were 9-17%. Pre-heating of hydrogen by coal combustion before blowing to the shaft furnace was effective to decrease heat input although CO emissions increased a little. Direct nuclear pre-heating was expected to be less heat input without increase of CO emissions if the problems with nearby location of the nuclear reactor to the steelmaking plant would be solved. Influence of hydrogen production thermal efficiency on heat input of the NHS was great. A conceptual design of a plant unit of the NHS system producing steel of 7.4310 t/y with a HTGR of 600 MW heat and a shaft furnace and an electric arc furnace was proposed.

Technical examination on high temperature gas-cooled reactor as energy source of active carbon recycling energy system for steelmaking

Kasahara, Seiji; Sato, Hiroyuki; Inagaki, Yoshiyuki; Ogawa, Masuro

Zairyo To Purosesu (CD-ROM), 25(2), p.647 - 650, 2012/09

Application of ACRES (Active Carbon Recycling Energy System) to steelmaking process is proposed for reduction of CO emission and security of fossil fuel supply. ACRES is the concept of reuse of carbon element in CO from fossil fuel usage by reducting to CO using non-fosssil primary energy. Selection of the primary energy and CO reduction technology is important for the usability evaluation. High temperature gas-cooled reactor is a candidate of the energy, which can supply electricity, hydrogen and high temperature heat usable for CO reduction. Technical examination on high temperature gas-cooled reactor as energy source of ACRES for steelmaking was carried out. Renewable solar energy is an also promising energy source. Here, ability of HTGR to follow load change was investigated and validated for parallel use of HTGR and solar energy.