Compaction in optical fibres and fibre Bragg gratings under nuclear reactor high neutron and gamma fluence

Remy, Laurent; Cheymol, G.; Gusarov, A.; Morana, Adriana; Marin, Emmanuel; Girard, Sylvain

doi:10.1109/animma.2015.7465627

Cited by 6 publications

(9 citation statements)

References 15 publications

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“…The two levels of neutron fluence were selected by taking the previous compaction measurements into consideration. At 3x10 19 n fast /cm 2 compaction should have reached saturation according to Primak work [8], and our SAKE 1 results [7] that showed no significant difference between the compactions measured at 3 or 5 x10 19 n fast /cm 2 . A smaller fluence of 10 19 n fast /cm 2 was chosen as we expected that at this level the changes are not saturated yet and the FBGs response should be clearly different.…”

Section: Kinet and P Mégret Are With The Electromagnetism Andsupporting

confidence: 54%

“…Not only FBG, but also bare fibre samples were irradiated during the SAKE 2 experiment. Then compaction was measured on SMF28e samples (same fibre as used for FBG sample A1-A3); with similar procedure as described in [7]. The compaction was measured at 0.29% ± 0.05% in capsule 1 and 0.57% in capsule 2.…”

Section: Discussionmentioning

confidence: 99%

“…The predicted variation direction agrees with the observation of the negative BWS. During SAKE 1 we irradiated [7] some gratings similar to samples C, which were not annealed. They were erased after irradiation.…”

Section: Discussionmentioning

confidence: 99%

“…The experiments involved few centimetres long fibre samples, functionalized or not. The results of SAKE 1 were reported in [7]. Beside the fact that Study of Fibre Bragg Grating samples exposed to High Fast-Neutron Fluences A A #102 uncoated fibre samples irradiated in the MTR core could be successfully handled to perform post-irradiation measurements and give appreciated results, the main conclusion was that the mean value of the obtained compaction after exposition to 3 to 5x10 19 n fast /cm², at 290 °C, for the pure silica core fibre used in the FPSs, was less than what could be expected from the measurements on bulk silica samples made by Primak [8] in the sixties: 0.27% instead of 1%.…”

Section: Kinet and P Mégret Are With The Electromagnetism Andmentioning

confidence: 99%

“…Structural modifications associated with neutron induced compaction are supposed to affect drastically the Bragg peak. As the compaction tends to saturate at about 3x10 19 n fast /cm 2 [7][8], writing a FBG in a pre-irradiated fibre was considered of interest in order to obtain a rad-hard FBG. LabHC wrote two FBGs in uncoated pure-silica SM fibre samples previously irradiated at 5x10 19 n fast /cm 2 during SAKE 1 campaign [7].…”

Section: A Tested Fibre Bragg Gratingsmentioning

confidence: 99%

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Study of Fiber Bragg Grating Samples Exposed to High Fast Neutron Fluences

Cheymol

Remy

Gusarov

et al. 2018

IEEE Trans. Nucl. Sci.

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Abstract-Fibre Bragg Grating (FBG) sensors are expected to provide valuable data in extreme radiation environments associated with nuclear research reactors. However, when the fast neutron fluence reaches 10 18 to 10 19 n/cm², the radiation induced changes in the material density and refractive index may drastically bias the measurements. The present study evaluates the radiation effect on the FBG performances by comparing their properties before and after their exposure to fast neutron fluences exceeding 10 19 n/cm² (E > 1 MeV). We studied responses of FBGs manufactured by three different laboratories in the same single-mode optical fibre but using different inscription conditions. The Bragg wavelength and the reflectivity were measured before and after irradiation thanks to a dedicated mounting. For nearly all FBGs, the Bragg peak remains visible after the irradiation while the radiation-induced Bragg wavelength shifts (RI-BWS) vary from a few pm (equivalent temperature error < 1°C) to nearly 1 nm (~100°C error) depending of the FBG inscription conditions. Such high RI-BWSs can be explained by the huge refractive-index variation and compaction observed for bare fibre samples through other experimental techniques. Our results show that by using specific hardening techniques the FBG-based temperature measurements in a nuclear research reactor experiment may become feasible.

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Section: Kinet and P Mégret Are With The Electromagnetism Andsupporting

confidence: 54%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Kinet and P Mégret Are With The Electromagnetism Andmentioning

confidence: 99%

Section: A Tested Fibre Bragg Gratingsmentioning

confidence: 99%

See 3 more Smart Citations

Study of Fiber Bragg Grating Samples Exposed to High Fast Neutron Fluences

Cheymol

Remy

Gusarov

et al. 2018

IEEE Trans. Nucl. Sci.

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Online optical refractive index measurement in research reactor core

Fourneau¹,

Agoyan

Chemol³

et al. 2021

EPJ Web Conf.

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There is a growing interest in fiber optic measurements for applications in radiation environments. Optical fiber sensors and diagnostics can monitor many parameters of interest inside a research reactor core. For some applications, fiber optics are combined with an optical system that collects or focuses the light beam. The Radiation-Induced-Refractive-Index-Change (RIRIC) of the used glasses appears then as major phenomenon as it is a determining value for the sensor optical function. In the framework of the development of a radiation hardened confocal chromatic sensor, we implemented an on-line refractive index measuring device in order to test in a reactor core various glasses, candidates to be implemented into the sensor. The measurement relies on interferometry, which is a challenge because of the small volume available, the impossibility to make optical adjustments once installed, and the high temperature of operation. Precisely, the quantity retrieved is the optical path (product of the length L by the optical refractive index n), when L is well known, we can deduce n. But under high neutron fluence, some variation in density can be observed. The targeted online measurement of the refractive index therefore becomes an optical path measurement. We will present the device, the principle of measurement, and the first results of some index change measurement, produced by a temperature ramp from 20 °C and 350 °C. We have obtained original data for most of the candidate glasses used to design the optical system.

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