Japan Atomic Energy Research Institute/United States Integral Neutronics Experiments and Analyses for Tritium Breeding, Nuclear Heating, and Induced Radioactivity

Abdou, Mohamed; Maekawa, Hiroshi; Oyama, Y.; Youssef, M.Z.; Ikeda, Yujiro; Kumar, Anil; Konno, Chikara; Maekawa, Fujio; Kosako, Kazuaki; Nakamura, Tomoo; Bennett, E.F.

doi:10.13182/fst95-a30399

Cited by 7 publications

(6 citation statements)

References 44 publications

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“…Based on this prior work, the best estimate of the achievable TBR for the most detailed blanket system designs available is 1.15. There is uncertainty of ∼10% between integral experiments and calculations [56,63] that cannot be resolved until we build and operate a practical blanket system.…”

Section: Tablementioning

confidence: 99%

Blanket/first wall challenges and required R&D on the pathway to DEMO

Abdou

Morley

Smolentsev

et al. 2015

Fusion Engineering and Design

274

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a b s t r a c tThe breeding blanket with integrated first wall (FW) is the key nuclear component for power extraction, tritium fuel sustainability, and radiation shielding in fusion reactors. The ITER device will address plasma burn physics and plasma support technology, but it does not have a breeding blanket. Current activities to develop "roadmaps" for realizing fusion power recognize the blanket/FW as one of the principal remaining challenges. Therefore, a central element of the current planning activities is focused on the question: what are the research and major facilities required to develop the blanket/FW to a level which enables the design, construction and successful operation of a fusion DEMO? The principal challenges in the development of the blanket/FW are: (1) the Fusion Nuclear Environment -a multiple-field environment (neutrons, heat/particle fluxes, magnetic field, etc.) with high magnitudes and steep gradients and transients; (2) Nuclear Heating in a large volume with sharp gradients -the nuclear heating drives most blanket phenomena, but accurate simulation of this nuclear heating can be done only in a DT-plasma based facility; and (3) Complex Configuration with blanket/first wall/divertor inside the vacuum vessel -the consequence is low fault tolerance and long repair/replacement time.These blanket/FW development challenges result in critical consequences: (a) non-fusion facilities (laboratory experiments) need to be substantial to simulate multiple fields/multiple effects and must be accompanied by extensive modeling; (b) results from non-fusion facilities will be limited and will not fully resolve key technical issues. A DT-plasma based fusion nuclear science facility (FNSF) is required to perform "multiple effects" and "integrated" experiments in the fusion nuclear environment; and (c) the Reliability/Availability/Maintainability/Inspectability (RAMI) of fusion nuclear components is a major challenge and is one of the primary reasons why the blanket/FW will pace fusion development toward a DEMO.This paper summarizes the top technical issues and elucidates the primary challenges in developing the blanket/first wall and identifies the key R&D needs in non-fusion and fusion facilities on the path to DEMO.Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

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Section: Tablementioning

confidence: 99%

Blanket/first wall challenges and required R&D on the pathway to DEMO

Abdou

Morley

Smolentsev

et al. 2015

Fusion Engineering and Design

274

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“…A comprehensive analysis of the many aspects of the achievable TBR was made by Abdou et al in reference [1]. Subsequently, a large number of integral experiments for fusion blanket neutronics was conducted using DT neutrons at the fusion neutronics source facility as part of a 10 years collaborative program between the Japanese Atomic Energy Institute and USA [34]. These integral experiments enabled quantitative evaluation of the uncertainties in predicting the achievable TBR due to calculation methods, codes, and nuclear data.…”

Section: The Achievable Tritium Breeding Ratiomentioning

confidence: 99%

“…Additional detailed neutronics calculations of the impact of various materials, design options, and physics and technology choices on the achievable TBR were reported in reference [3]. There have been many calculations of tritium breeding by many authors over many years, but references [1,3,34] represent the stateof-the art evaluation of the achievable TBR and associated uncertainties, which we will summarize brie y below. Further advances in the state-of-the-art will not be possible prior to performing experiments in DT fusion facilities, as we will also explain below.…”

Section: The Achievable Tritium Breeding Ratiomentioning

confidence: 99%

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Physics and technology considerations for the deuterium–tritium fuel cycle and conditions for tritium fuel self sufficiency

et al. 2020

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The tritium aspects of the DT fuel cycle embody some of the most challenging feasibility and attractiveness issues in the development of fusion systems. The review and analyses in this paper provide important information to understand and quantify these challenges and to define the phase space of plasma physics and fusion technology parameters and features that must guide a serious R&D in the world fusion program. We focus in particular on components, issues and R&D necessary to satisfy three ‘principal requirements’: (1) achieving tritium self-sufficiency within the fusion system, (2) providing a tritium inventory for the initial start-up of a fusion facility, and (3) managing the safety and biological hazards of tritium. A primary conclusion is that the physics and technology state-of-the-art will not enable DEMO and future power plants to satisfy these principal requirements. We quantify goals and define specific areas and ideas for physics and technology R&D to meet these requirements. A powerful fuel cycle dynamics model was developed to calculate time-dependent tritium inventories and flow rates in all parts and components of the fuel cycle for different ranges of parameters and physics and technology conditions. Dynamics modeling analyses show that the key parameters affecting tritium inventories, tritium start-up inventory, and tritium self-sufficiency are the tritium burn fraction in the plasma (f b), fueling efficiency (η f), processing time of plasma exhaust in the inner fuel cycle (t p), reactor availability factor (AF), reserve time (t r) which determines the reserve tritium inventory needed in the storage system in order to keep the plant operational for time t r in case of any malfunction of any part of the tritium processing system, and the doubling time (t d). Results show that η f f b > 2% and processing time of 1–4 h are required to achieve tritium self-sufficiency with reasonable confidence. For η f f b = 2% and processing time of 4 h, the tritium start-up inventory required for a 3 GW fusion reactor is ∼11 kg, while it is <5 kg if η f f b = 5% and the processing time is 1 h. To achieve these stringent requirements, a serious R&D program in physics and technology is necessary. The EU-DEMO direct internal recycling concept that carries fuel directly from the plasma exhaust gas to the fueling systems without going through the isotope separation system reduces the overall processing time and tritium inventories and has positive effects on the required tritium breeding ratio (TBRR). A significant finding is the strong dependence of tritium self-sufficiency on the reactor availability factor. Simulations show that tritium self-sufficiency is: impossible if AF < 10% for any η f f b, possible if AF > 30% and 1% ⩽ η f f b ⩽ 2%, and achievable with reasonable confidence if AF > 50% and η f f b > 2%. These results are of particular concern in light of the low availability factor predicted for the near-term plasma-based experimental facilities (e.g. FNSF, VNS, CTF), and can have repercussions on tritium economy in DEMO reactors as well, unless significant advancements in RAMI are made. There is a linear dependency between the tritium start-up inventory and the fusion power. The required tritium start-up inventory for a fusion facility of 100 MW fusion power is as small as 1 kg. Since fusion power plants will have large powers for better economics, it is important to maintain a ‘reserve’ tritium inventory in the tritium storage system to continue to fuel the plasma and avoid plant shutdown in case of malfunctions of some parts of the tritium processing lines. But our results show that a reserve time as short as 24 h leads to unacceptable reserve and start-up inventory requirements. Therefore, high reliability and fast maintainability of all components in the fuel cycle are necessary in order to avoid the need for storing reserve tritium inventory sufficient for continued fusion facility operation for more than a few hours. The physics aspects of plasma fueling, tritium burn fraction, and particle and power exhaust are highly interrelated and complex, and predictions for DEMO and power reactors are highly uncertain because of lack of experiments with burning plasma. Fueling by pellet injection on the high field side of tokamak has evolved to be the preferred method to fuel a burning plasma. Extrapolation from the DIII-D penetration scaling shows fueling efficiency expected in DEMO to be <25%, but such extrapolations are highly uncertain. The fueling efficiency of gas in a reactor relevant regime is expected to be extremely poor and not very useful for getting tritium into the core plasma efficiently. Gas fueling will nonetheless be useful for feedback control of the divertor operating parameters. Extensive modeling has been carried out to predict burn fraction, fueling requirements, and fueling efficiency for ITER, DEMO, and beyond. The fueling rate required to operate Q = 10 ITER plasmas in order to provide the required core fueling, helium exhaust and radiative divertor plasma conditions for acceptable divertor power loads was calculated. If this fueling is performed with a 50–50 DT mix, the tritium burn fraction in ITER would be ∼0.36%, which is too low to satisfy the self-sufficiency conditions derived from the dynamics modeling for fusion reactors. Extrapolation to DEMO using this approach would also yield similarly low burn fraction. Extensive analysis presented shows that specific features of edge neutral dynamics in ITER and fusion reactors, which are different from present experiments, open possibilities for optimization of tritium fueling and thus to improve the burn fraction. Using only tritium in pellet fueling of the plasma core, and only deuterium for edge density, divertor power load and ELM control results in significant increase of the burn fraction to 1.8–3.6%. These estimates are performed with physics models whose results cannot be fully validated for ITER and DEMO plasma conditions since these cannot be achieved in present tokamak experiments. Thus, several uncertainties remain regarding particle transport and scenario requirements in ITER and DEMO. The safety standard requirements for protection of the public and release guidelines for tritium have been reviewed. General safety approaches including minimizing tritium inventories, reducing tritium permeation through materials, and decontaminating material for waste disposal have been suggested.

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“…Presently, the only place in which tritium is artificially produced for ITER and other D-T fusion reactors is in CANDU reactor type with about 1.7 kg/year production rate [2]. One of the important characteristics of ITER is its tritium ''self-sufficiency'' [3][4][5][6][7]. In other words, tritium is produced in it, at least for its own consumption.…”

Section: Introductionmentioning

confidence: 99%

Tritium Breeding Ratio Calculation for ITER Tokamak Using Developed Helium Cooled Pebble Bed Blanket (HCPB)

Soltani

Habibi

2015

J Fusion Energ

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In this paper, neutronic calculations were performed to obtain tritium breeding ratio (TBR) for ITER device using developed helium cooled pebble (HCPB) blanket. The designed blanket module has the following combinations; natural lithium, Li 4 SiO 4 (20 %), beryllium moderator and neutron multiplier. To ensure tritium selfsufficiency, the calculated achievable TBR should be equal to or greater than the required TBR. Simulations have been performed by means of Monte Carlo MCNP-4C code using END/B-VII.1 data library. Results show that TBR of 1.14 is obtained for this new HCPB.

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Japan Atomic Energy Research Institute/United States Integral Neutronics Experiments and Analyses for Tritium Breeding, Nuclear Heating, and Induced Radioactivity

Cited by 7 publications

References 44 publications

Blanket/first wall challenges and required R&D on the pathway to DEMO

Blanket/first wall challenges and required R&D on the pathway to DEMO

Physics and technology considerations for the deuterium–tritium fuel cycle and conditions for tritium fuel self sufficiency

Tritium Breeding Ratio Calculation for ITER Tokamak Using Developed Helium Cooled Pebble Bed Blanket (HCPB)

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