In-Reactor Measurement of Neutron Absorber Performance

Hollenberg, G.W.; Jackson, J.L.; Basmajian, J.A.

doi:10.13182/nt80-a32510

Cited by 15 publications

(14 citation statements)

References 4 publications

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“…In their study, they heated B 4 C neutron irradiated samples (7 x 10 +18 n.cm -2 , and ~0.02 mol.% He in average) at different heating rates and deduced from the temperature difference of the maximum release rates an activation energy of 1.73 and 2.15 eV for sintering temperature of 1200 and 2400°C, respectively. Next Hollenberg et al 7,12 , Kovyrshin 13 and Bespalov and Pavlinov 17 also published E a values. However these works should all be discarded according to the following reasons: _ Hollenberg wrongfully assumed that 1) once a helium atom reached a grain boundary it would be released out of the material, which is never experimentally observed (on the contrary, it has been shown that helium gets trapped at the grain boundaries) and 2) that in their experimental conditions bubble traps were not quantitatively formed again in contradiction with numerous works, see Motte and reference therein 8,8 .…”

Section: Discussionmentioning

confidence: 96%

“…With this setup, we were able to accurately measure effective diffusion rates from ~10 -17 m².s -1 . Considering the literature results 7,8,10 , this experimentally limited the plateau measurements to temperature greater or equal to 800°C.…”

Section: Thermo-desorption Spectroscopy (Tds)mentioning

confidence: 99%

“…Moreover its characteristics make it a serious candidate for neutron absorption application in future Gen-IV reactors 2 . When submitted to a neutron flux, 10 B atom mostly undergoes the (n,α) absorption reaction leading to the formation of 7 Li and 4 He. As a consequence, in fast neutron reactors, a spent B 4 C would accumulate up to ~10 mol.% of He 3 .…”

Section: Introductionmentioning

confidence: 99%

“…Experimentally, aggregation of He in the form of intra-and/or intergranular bubbles is commonly reported above 500°C, inducing anisotropic grain swelling and microcracking at both grain and grain boundaries scale. [4][5][6][7] As recently reminded by Motte et al 8 , knowledge of the diffusion mechanisms and kinetics of He in B 4 C is still scarce, even though considerable works were made [8][9][10][11][12][13][14][15][16][17] because of the numerous parameters to account for (reactor irradiated B 4 C vs. He implanted B 4 C vs. numerical simulations, B 4 C microstructure, He concentration and so on).…”

Section: Introductionmentioning

confidence: 99%

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Experimental determination of intragranular helium diffusion rates in boron carbide (B4C)

Horlait

Gosset

Jankowiak

et al. 2019

Journal of Nuclear Materials

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Boron carbide, B 4 C, is widely used as a neutron absorber in nuclear reactors. Since neutron absorption by 10 B leads to 4 He production, it appears necessary to study He behavior and its possible effects on the B 4 C ceramic. In this study, the diffusion characteristics of ion-implanted He in B 4 C (500 keV, fluences from 1 x 10 +13 to 2 x 10 +15 He.cm-2) were investigated mainly by Thermo-Desorption Spectroscopy (TDS) from 600°C up to B 4 C melting point. The experiments were done on dense B 4 C samples having large grains (30-60 µm) to render grain boundaries effects on He outward diffusion ineffective and thus to access intragranular He diffusion kinetics. From controlled temperature ramp experiments, it was notably observed that He release was realized in two main stages. A first He population was able to exit the material at moderate temperatures by interstitial diffusion. Then a second population was quantitatively released only over 1150°C. This was attributed to He atoms that, in their initial interstitial diffusion course at moderate temperatures from their implantation sites, got trapped in defect aggregates and/or He bubbles. As the nucleations of both these traps are expected to be related to helium and irradiation defect concentrations, the ratio of the two He populations was indeed found to be correlated with the implantation fluence. From the obtained He release curves, the apparent activation energies (E a) of He intragranular diffusion in B 4 C was determined (2.6-3.1 eV) in the 800-1100°C temperature range. This value appears slightly higher than the one determined at lower temperatures, hinting that a change in diffusion mechanism may occur around 800°C. The apparent E a of He detrapping from He bubbles (~2.5 eV) and from defect aggregates (~4 eV) were also determined for temperatures within 1200-1500°C.

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Section: Discussionmentioning

confidence: 96%

Section: Thermo-desorption Spectroscopy (Tds)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental determination of intragranular helium diffusion rates in boron carbide (B4C)

Horlait

Gosset

Jankowiak

et al. 2019

Journal of Nuclear Materials

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“…Although there is a large scatter in the swelling data, 4 Burnup dependence of pellet swelling the sivclling of B4C pellets tends to linearly increase. For irradiation temperature below l,OOO°C, the average value of the swelling rate was 3.5% per IOOX lo2' cap/m3 up to about SOX lo2' cap/m3.…”

Section: Swellingmentioning

confidence: 99%

Effect of Fast Neutron Irradiation on the Properties of Boron Carbide Pellet.

Maruyama¹,

Onose²,

Kaito³

et al. 1997

J. Nucl. Sci. Technol.

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Boron carbide pellets were irradiated in the experimental fast reactor "JOYO" to log burnup of up to 1 7 0~1 0~~ cap/m3, fluences of 2x102'/m2 (E>0.1 MeV), and maximum temperatures of about 1,200"C. Post irradiation examinations were made of microstructural changes, helium release, swelling, and thermal conductivity.Boron carbide pellets irradiated to high burnups developed extensive cracking. Helium release from the pellets was initially low, but enhanced helium release was observed at high burnups and high temperatures. The swelling linearly increased with burnup, and when boron carbide was irradiated at high temperatures, the swelling rate began to decrease corresponding to the beginning of enhanced helium release. The correlation between swelling and the helium release was studied and the swelling was interpreted in terms of accumulation of helium in the boron carbide pellet. The thermal conductivity of the boron carbide pellets decreased rapidly by neutron irradiation accompanied with loss of temperature dependence.

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LMFBR Core Materials

Roberts

1981

Structural Materials in Nuclear Power Systems

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In-Reactor Measurement of Neutron Absorber Performance

Cited by 15 publications

References 4 publications

Experimental determination of intragranular helium diffusion rates in boron carbide (B4C)

Experimental determination of intragranular helium diffusion rates in boron carbide (B4C)

Effect of Fast Neutron Irradiation on the Properties of Boron Carbide Pellet.

LMFBR Core Materials

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