Neutronics aspects of the FESS-FNSF

Davis, Andrew; Harb, M.; El-Guebaly, L.; Wilson, Paul P. H.; Marriott, E.P.

doi:10.1016/j.fusengdes.2017.06.008

Cited by 35 publications

(5 citation statements)

References 6 publications

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“…Here, the 14.1 MeV maximum neutron energy peak is evident, but the FW and regions behind it will experience a broad neutron energy spectrum. In order to show the nuclear impacts, the dpa, He and H production rates through the radial depth of an FNSF blanket modelled using F82H steel are shown in figure 25 [436]. The neutron dose is at a maximum at the FW and decreases with the radial distance into the backend outboard breeding zone.…”

Section: Design Challenges For Fusion Reactors Including Fnsfmentioning

confidence: 99%

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Irradiation damage concurrent challenges with RAFM and ODS steels for fusion reactor first-wall/blanket: a review

et al. 2022

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Reduced activation ferritic-martensitic (RAFM) and oxide dispersion strengthened (ODS) steels are the most promising candidates for fusion first-wall/blanket (FW/B) structures. Performance of these steels will deteriorate in-service due to neutron damage and transmutation-induced gases like helium/hydrogen at elevated operating temperatures. Here, after highlighting the operating conditions of fusion reactor concepts and a brief overview, the major irradiation-induced degradation challenges associated with RAFM/ODS steels are discussed. Their long-term degradation scenarios such as (i) low temperature hardening-embrittlement (LTHE) - including dose-temperature dependent yield stress, tensile elongations, necking ductility, test temperature effect on hardening, Charpy impact ductile to brittle transition temperature and fracture toughness, (ii) inter-mediate temperature cavity swelling, (iii) the effect of helium on LTHE and cavity swelling, (iv) irradiation creep and (v) tritium management issues are reviewed. The potential causes of LTHE are discussed that highlights need for advanced characterization techniques. Mechanical properties including tensile/Charpy impact of RAFM and ODS steels are compared to show that current generation of ODS steels also suffer from LTHE, and they can show irradiation hardening up to high temperatures, ~400-500 °C. To minimize this, future ODS steel development for FW/B specific application should target materials with lower Cr concentration (to minimize α’) and minimize other elements that could form embrittling phases under irradiation. RAFM steel designing activities targeting improvements in creep and LTHE are reviewed. The need to better understand synergistic effects of helium on thermo-mechanical properties in the entire temperature range of FW/B is highlighted. Because fusion operating conditions will be complex including stresses due to magnetic field, primary loads like coolant pressure, secondary loads from thermal gradients, and due to spatial variation in damage levels and gas production rates, an experimentally validated multi-scale modelling approach is suggested as a pathway to future reactor component designing such as for the fusion neutron science facility

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Section: Design Challenges For Fusion Reactors Including Fnsfmentioning

confidence: 99%

“…Radial distribution of dpa, He and H production versus depth into the outboard (OB) blanket of FNSF, in F82H steel, showing the strong gradient in production rate of these quantities. FPY = full power year, FW = first wall, BZ = breeding zone.Reprinted from[436], copyright (2018), with permission from Elsevier. CC BY-NC-ND 4.0.…”

mentioning

confidence: 99%

Irradiation damage concurrent challenges with RAFM and ODS steels for fusion reactor first-wall/blanket: a review

et al. 2022

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“…39 With the current module and feeder design having roughly 6-mm thickness and a 20% to 30% FW coverage fraction (depending on waveguide route), a conservative estimate would reduce the TBR by 0.018. Thus for the FNSF, the calculated TBR of 1.07 from previous work 13 might decrease to 1.05. The impact to TBR of tungsten in the FW is complex, plus the antenna and waveguides have complicated geometry so an accurate estimate must be done using a detailed 3-D model.…”

Section: Wallace Et Al • Steady-state Lower Hybrid Current Drive Antmentioning

confidence: 67%

“…The PAM antennas do not achieve the same power density averaged over the entire area of the antenna (as opposed to the active waveguide area) as compared with the FAM antennas, and consequently require ~2× more area on the wall of the tokamak, thus impacting neutron shielding and the tritium breeding ratio (TBR) to a larger degree. The FNSF design point is for full tritium breeding self-sufficiency 13 and benefits greatly from any change to the design that increases the TBR.…”

Section: Introductionmentioning

confidence: 99%

Multiphysics Simulations of a Steady-State Lower Hybrid Current Drive Antenna for the FSNF

Wallace

Bohm

Kessel

2021

Fusion Science and Technology

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The Fusion Nuclear Science Facility (FNSF) is a proposed tokamak reactor with the mission to investigate operation of a fusion reactor in a nuclear environment. The high neutron fluence component of the FNSF mission requires steady-state operation for extremely long pulses (t pulse , months) at full power. Plasma sustainment and current drive will be critical components of a successful FNSF. COMSOL Multiphysics® software is used for combined radiofrequency (RF) and thermal simulations of the lower hybrid current drive antenna system. These simulations consider the resistive RF losses in the antenna including realistic surface roughness and a range of potential materials. The thermal analysis adds volumetric nuclear heating, plasma heat flux on leading edges, and electromagnetic radiation from the plasma to the RF heating calculated by COMSOL. Additional neutronics calculations have been performed to determine the impact of these antenna designs on activated waste disposal for the materials considered. The simulations show that it is technically feasible to implement a fully active multijunction (FAM) rather than a passive-active multijunction (PAM) style of antenna if the septum between adjacent waveguides is sufficiently wide and the thermal conductivity of the structural material is sufficiently high. The FAM has the benefit of higher achievable power density with respect to the PAM, which results in a more compact antenna with potentially lower impact on neutron shielding and tritium breeding. These considerations point to tungsten rather than steel as the preferred structural material in constructing the antenna.

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“…The analysis of the blanket region has been carried out in great detail by the FNSF team [22][23][24][25][26]. It requires a substantial effort.…”

Section: • Minimum Blanket Region Thicknessmentioning

confidence: 99%

A steady state vs pulsed fusion neutron science facility

Guazzotto

Freidberg

2022

Nucl. Fusion

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Two major modifications to the existing steady state Fusion Neutron Science Facility (FNSF) concept [1] are investigated with the aim of determining whether or not its predicted performance can be improved. The modifications are high magnetic field and pulsed operation. We find that high field leads to major economic improvements in a steady state FNSF, although at the expense of lowering the engineering gain. Pulsed operation replaces the problems associated with low current drive efficiency, with hopefully more manageable engineering problems. Here, however, high toroidal field (TF) is not helpful, and a lower TF field is more desirable economically. Pulsed FNSFs also have a reduced engineering gain. Further modifications lead to FNSF designs satisfying the additional constraint of engineering gain equal to unity. For these designs there is a large cost penalty for the steady state FNSF but only a modest penalty for the pulsed FNSF. All of our modified designs show modest to large potential economic improvements over the existing design. Overall, our conclusion is that it may be desirable to carry out a more detailed analysis of one of our improved designs, the choice depending upon which issue in the existing design is most important.[1] C.E.Kessel, J.P.Blanchard, A.Davis, L.El-Guebaly, L.M.Garrison, N.M.Ghoniem, P.W.Humrickhouse, Y.Huang, Y.Katoh, A.Khodak, E.P.Marriott, S.Malang, N.B.Morley, G.H.Neilson, J.Rapp, M.E.Rensink, T.D.Rognlien, A.F.Rowcliffe, S.Smolentsev, L.L.Snead, M.S.Tillack, P.Titus, L.M.Waganer, G.M.Wallace, S.J.Wukitch, A.Ying, K.Young, and Y.Zhai, Fusion Engineering and Design, 135 (2018), 236-270

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Neutronics aspects of the FESS-FNSF

Cited by 35 publications

References 6 publications

Irradiation damage concurrent challenges with RAFM and ODS steels for fusion reactor first-wall/blanket: a review

Irradiation damage concurrent challenges with RAFM and ODS steels for fusion reactor first-wall/blanket: a review

Multiphysics Simulations of a Steady-State Lower Hybrid Current Drive Antenna for the FSNF

A steady state vs pulsed fusion neutron science facility

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