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Journal Articles

Release and transport behaviors of non-gamma-emitting fission products and actinides in steam and hydrogen atmospheres

Miwa, Shuhei; Ducros, G.*; Hanus, E.*; Bottomley, P. D. W.*; Van Winckel, S.*; Osaka, Masahiko

Nuclear Engineering and Design, 326, p.143 - 149, 2018/01

 Times Cited Count:2 Percentile:30.45(Nuclear Science & Technology)

The release and transport behaviors of 13 non-gamma-emitting fission products (FPs) and actinides in steam and hydrogen atmospheres were investigated based on the chemical analysis of their deposits on the components of VERCORS test loops. The new findings were obtained; strontium release was significantly enhanced in hydrogen atmosphere and a part of released strontium was transported towards the lower temperature region, uranium release was enhanced in steam atmosphere but most of released uranium deposited at high temperature region.

Journal Articles

Upgrading the experimental database of fission products and actinides release behaviour in the VERCORS program through chemical analysis

Miwa, Shuhei; Ducros, G.*; Hanus, E.*; Bottomley, P. D. W.*; Van Winckel, S.*

Proceedings of 7th European Review Meeting on Severe Accident Research (ERMSAR 2015) (Internet), 11 Pages, 2015/03

The release behaviour of $$alpha$$-ray emitters, $$beta$$-ray emitters and stable nuclide from the degraded fuel in the fission product (FP) and actinide release and transport tests, VERCORS tests, were investigated based on the chemical analysis of their deposits on the components of VERCORS test loops. The release of Sr which has a significant public impact shows the possibility to be enhanced in reducing atmosphere. The release of U was significantly enhanced in steam atmosphere, but almost all the released U remained near the fuel. The release behaviour of other non-$$gamma$$-ray emitters such as Rb, Pd, Tc and Pu shows the good consistency with the expectation based on the previous VERCORS tests results. The experimental database of the FP and actinide release behaviour was upgraded through the chemical analysis in terms of the effects of atmosphere on the release behaviour of $$alpha$$-ray emitters, $$beta$$-ray emitters and stable nuclide.

Journal Articles

Fuelling characteristics of supersonic molecular beam injection in JT-60U

Takenaga, Hidenobu; Miyo, Yasuhiko; Bucalossi, J.*; Marty, V.*; Urano, Hajime; Asakura, Nobuyuki; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi

Nuclear Fusion, 50(11), p.115003_1 - 115003_10, 2010/11

 Times Cited Count:19 Percentile:58.9(Physics, Fluids & Plasmas)

The supersonic molecular beam injection (SMBI) was successfully operated in JT-60U. Frequent density jumps were clearly observed in the main plasma against the SMBI pulses with the background gas pressure ($$P$$$$_{rm BK}$$) of 2-6 bar. Fuelling efficiency exhibited weak dependence on $$P$$$$_{rm BK}$$ and the injection direction (high- and low-field-side injections). The amount of the fuelling necessary for achieving the same density level is much smaller for the SMBI than for the gas-puffing. It is comparable for the SMBI and the pellet injection even with shallower penetration of the SMBI as discussed below. The SMBI ionization area was estimated based on emission measured using the fast TV camera with a time resolution of 0.167 ms. The estimations indicated similar penetration position for $$P$$$$_{rm BK}$$ = 6 and 2 bar, although the ionization area was larger for 6 bar. This result supports the weak $$P$$$$_{rm BK}$$ dependence of the fuelling efficiency. The front of the ionization area moved between first and second frames of the fast TV camera and it reached just inside the separatrix in the second frame. The ionization area was significantly expanded from the expected SMB size and the expansion was also enhanced between two frames. These relatively slow changes between two frames suggest that interaction between SMB and plasma significantly influences the fuelling characteristics.

Journal Articles

The Characteristics of the internal transport barrier under reactor relevant conditions in JT-60U weak shear plasmas

Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Asakura, Nobuyuki; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; et al.

Nuclear Fusion, 49(7), p.075012_1 - 075012_11, 2009/07

 Times Cited Count:9 Percentile:34.22(Physics, Fluids & Plasmas)

Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature (T$$_{i}$$) in the central region inside the ITB decreased due to cold pulse propagation even with edge fuelling. By optimizing the injection frequency and the penetration depth, the decreased central T$$_{i}$$ was recovered and good ITB was sustained with enhanced pedestal pressure. The T$$_{i}$$-ITB also degraded significantly with electron cyclotron heating (ECH), when stiffness feature was strong in the electron temperature (T$$_{e}$$) profile. The ion thermal diffusivity in the ITB region increased with the electron thermal diffusivity, indicating existence of clear relation between ion and electron thermal transport. On the other hand, T$$_{i}$$-ITB unchanged or even grew, when stiffness feature was weak in the T$$_{e}$$ profile. Density fluctuation level at ITB seemed to be unchanged during ECH, however, correlation length became longer in the T$$_{i}$$-ITB degradation case and shorter in the T$$_{i}$$-ITB unchanging case.

Journal Articles

Particle control study towards burning plasma control in JT-60U

Takenaga, Hidenobu; JT-60 Team

Journal of Nuclear Materials, 390-391, p.869 - 875, 2009/06

 Times Cited Count:9 Percentile:53.48(Materials Science, Multidisciplinary)

Particle control is important for burning plasma control, because fuel density is one of a few controllable parameters in a burning plasma. First, mechanisms responsible for determining density profiles and dependence of impurity transport on density profiles were investigated. Peakedness of density profiles increased with decreasing collisionality, which is consistent with ITG/TEM turbulence theory. However, other hidden parameters, such as toroidal rotation, existed. Metal impurity accumulation was observed with peaked density profile, while light impurity accumulation was not. Next, effects of fuelling on confinement was investigated using newly installed supersonic molecular beam injection (SMBI). SMBI directly affected the plasma parameters at r/a 0.8 as similar as pellet injection. However, confinement degraded with constant pedestal pressure in contrast to pellet injection. Using the burning plasma simulation scheme, it was demonstrated to reduce the simulated a-heating with SMBI due to confinement degradation and flattening of pressure profile.

Journal Articles

Characteristics of internal transport barrier under reactor relevant condition in JT-60U weak shear plasmas

Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature ($$T_{i}$$) in the central region decreased even with edge fuelling. The $${it T}_{i}$$ decrease with edge fuelling was larger inside the ITB than that outside the ITB, which can be described by cold pulse propagation using the ion thermal diffusivity ($$chi_{i}$$) estimated from power balance analysis in the SMBI case. By optimizing the injection frequency and the penetration depth, the decreased $$T_{i}$$ was recovered and good ITB was sustained with enhanced pedestal pressure. The $$T_{i}$$-ITB also degraded significantly when stiffness feature was strong in the electron temperature ($$T_{e}$$) profile against electron cyclotron heating (ECH). The value of $$chi_{i}$$ in the ITB region increased with the electron thermal diffusivity ($${it chi}_{e}$$), indicating existence of clear relation between ion and electron thermal transport. On the other hand, $$T_{i}$$-ITB unchanged or even grew, when stiffness feature was weak in the $$T_{e}$$ profile. Density fluctuation level seemed to be unchanged during ECH, however, correlation length became longer in the $${it T}_{i}$$-ITB degradation case and shorter in the $$T_{i}$$-ITB unchanging case.

Oral presentation

Development of supersonic molecular beam injection system for JT-60U

Miyo, Yasuhiko; Nishiyama, Tomokazu; Kaminaga, Atsushi; Takenaga, Hidenobu; Urano, Hajime; Sasajima, Tadayuki; Masaki, Kei; Bucalossi, J.*; Marty, V.*

no journal, , 

no abstracts in English

Oral presentation

Solidification test of B-C-Fe-O melt in the PLINIUS/VITI facility

Ikeuchi, Hirotomo; Piluso, P.*; Fouquart, P.*; Bailly, J. S.*; Brackx, E.*; David, C.*; Domenger, R.*; Excoffier, E.*

no journal, , 

In order to clarify chemical forms of boron after the solidification of the B-C-Fe-O melt with low oxygen concentration, small-scale experiments were performed at the PLINIUS/VITI facility in CEA-Cadarache under the framework of JAEA-CEA collaboration in 2015FY. The overview of the experiment will be presented briefly during the SARNET annual meeting.

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