Fuel Irradiation Devices Test of Feedthroughs Equipped With Optical Fibers in support of the development of innovative instrumentation

¹ CEA, DES, IRESNE, Nuclear Technology Department
² CEA, DES, IRESNE, Reactors Studies Department
³ CEA, DES, ISAS, Chemical & Physical Department
^1,2 CEA, French Alternative Energies and Atomic Energy Commission, Division of Energies, CEA Cadarache. 13108 Saint Paul lez Durance. France.
³ Université Paris-Saclay, CEA, Service d’Études Analytiques et de Réactivité des Surfaces, 91191, Gif-sur-Yvette, France

^* stephane.gaillot@cea.fr

Published online: 21 November 2023

Abstract

As part of the activities for developing experimental devices for research reactors and associated test loops, some concern the development and qualification of instrumentation.

The on-board instrumentation makes it possible to monitor online the evolution of physical parameters of samples and/or components subjected to different stresses (thermal, hydraulic, chemical and nuclear, etc.).

In addition to the so-called “classic” instrumentation implemented in this type of equipment (pressure, temperature, flow, elongation), R&D actions are in progress in order to propose innovative instrumentation, able to improve the experimental offer and describe the physical phenomena with more accuracy.

This is the case of optical measurements which present many advantages (compactness, insensitivity to EM waves, complex measurements by optical interrogation of a single fiber).

In addition, actions are underway for the selection of optical fibers that can be used for applications in a nuclear reactor (in particular resistance to the irradiation).

The tests presented in this paper relate to the behavior of sealed feedthroughs for optical fibers to the thermal hydraulics conditions of light water reactors.

These tests are part of the safety demonstration in so-called degraded operating cases i.e. corresponding to a configuration where the optical fiber is placed directly in the process fluid (pressurized water). One note that in normal operation, the optical fiber is isolated from the process fluid by a jacket consisting of a metal capillary.

After an introduction and a brief presentation of the use of optical fibers in experimental equipment, the paper describes the tightness feedthroughs used, the tests carried out, indicate the main results obtained and opens up some perspectives for future development phases.