Radiation-Resistant Optical Fibres
Development of Production Technology and Investigation of Radiation-Resistant Optical Fibres for Civil Nuclear Industry and Nuclear Physics
Tech Area / Field
- FIR-INS/Nuclear Instrumentation/Fission Reactors
- ENV-MIN/Monitoring and Instrumentation/Environment
3 Approved without Funding
TRINITI, Russia, Moscow reg., Troitsk
- Institute of General Physics named after A.M. Prokhorov RAS / Fiber Optical Research Center, Russia, Moscow
- EURATOM-Ciemat, Spain, Madrid\nSCK-CEN, Belgium, Mol
Project summaryThe range of promising uses of fibre optics in the civil nuclear industry and nuclear physics is wide: systems of optical diagnostics of plasma in the International Thermonuclear Experimental Reactor (ITER), systems for transmission of images from nuclear installations, optoelectronic sensors, including intra-reactor sensors at nuclear power plants (NPPs), optoelectronic remote handling systems etc. However, insufficient radiation resistance of commercially available optical fibres prevents their application in these areas. Thus, this Project is aimed at developing technologies of such radiation-resistant optical fibres.
This Project is in essence an extension of successfully completed ISTC Project # 1472 "Research and Development of Radiation-Hardened Optical Fibers Intended for Use in the Civil Nuclear Industry". The main results of Project # 1472 were the development of a laboratory technology of radiation-resistant optical fibres at FORC and comparison reactor tests of such fibres and those produced by the world's leading companies. These tests were performed at SRC RF TRINITI and demonstrated record high radiation resistance of the fibres developed at FORC. Record high radiation resistance of these fibres was confirmed by independent investigations at the SCK•CEN Belgian Nuclear Research Centre.
The fibres developed in the framework of Project # 1472 have a hermetic (e.g. aluminum) coating and contain molecular hydrogen dissolved in the fibre's silica. The hermetic coating of such fibres plays a two-fold role: 1) ensures mechanical strength at high temperature and in the presence of nuclear radiations and 2) prevents molecular hydrogen outdiffusion from the fibre glass. Under nuclear radiation exposure, hydrogens make bonds at the site of any radiation-disrupted bonds in glass network. In this way radiation colour centres, both absorbing and luminescent, are suppressed to lead to radical enhancement of radiation resistance.
The objectives of this Project are as follows: to optimize the technology of radiation hardening of optical fibres with the help of molecular hydrogen, which foundation was laid in Project # 1472, to apply this technology to other promising optical fibre types (microstructured and communication fibres), to investigate the possibility to improve fibre radiation resistance with this radiation hardening technology not only in the visible spectral region (as we demonstrated earlier), but also in the near-UV and near-IR regions.
To achieve these objectives, the following tasks are to be performed:
- Optimization of the technological regimes of the new equipment (gasostat) created at SRC RF TRINITI as a result of the Russian-European cooperation under support of EFDA. The gasostat is meant for radiation hardening of large-diameter optical fibres via H2 loading of the glass of hermetically coated fibres.
- Determination of the optimal type of silica in the core of radiation-resistant hermetically coated optical fibres fabricated by the POD-technology and containing a high H2 concentration in the glass.
- Determination of the optimal diameter of the radiation-resistant POD-fibres with a hermetic coating and a high H2 concentration in the glass, investigation of radiation resistance of such optimized POD-fibres in the near-UV region, conclusions regarding the possibility to use not only the visible region, but also the near-UV region for fibre-based ITER plasma diagnostics.
- Investigation of radiation resistance of microstructured (holey) optical fibres in the conditions of supply of H2 gas into the longitudinal holes of the fibre in the process of its irradiation (this is expected to lead to virtually complete suppression of radiation colour centres in the fibre's glass and to significant prolongation of the fibre's life-time in installations and technologies associated with intense fluxes of ionizing radiation). Estimation of the life-time of microstructured fibres in radiation fields, comparison with the optimized all-solid fibres (including radiation resistance in the near-UV range), conclusion regarding the prospects for application of microstructured (holey) fibres in ITER plasma optical diagnostic systems, development of microstructured fibre technology providing a large 'filling factor' (a large ratio of the cladding and core diameters).
- Application of the radiation-hardening techniques that we developed in the framework of Project # 1472 to single-mode fibres intended for operation at the wavelengths of ~ 1.30 and 1.55 μm, conclusions regarding the prospects for application of such radiation-hardened fibres in ITER remote handling systems, in nuclear reactors of NPPs and other nuclear installations.
Thus, in the framework of this Project, technologies of radiation-resistant optical fibres will be developed and optimized, applied research on radiation resistance of optical fibres of different types will be carried out, three radiation-resistant optical fibre prototypes (an optimized POD-fibre, a microstructured fibre, and a single-mode communication fibre) will be fabricated and demonstrated to the international nuclear community.
Tasks 1-3 will set the stage for small-lot production of radiation-resistant optical fibres for European and Russian ITER plasma diagnostic systems. This production is projected to be implemented by the two institutions participating in the Project.
Two Russian institutes will join forces to fulfill the Project: The State Research Centre of the Russian Federation "Troitsk Institute for Innovation and Fusion Research" (SRC RF TRINITI) and The Fibre Optics Research Centre at the A.M.Prokhorov General Physics Institute of the Russian Academy of Sciences (FORC). FORC will fabricate all the samples of optical fibres for the investigation. SRC RF TRINITI will perform radiation hardening of the fibres by dissolving molecular hydrogen in the fibres' glass with the help of the equipment created at SRC RF TRINITI. Besides, the latter institute will be investigating the fibres in radiation fields.
SRC RF TRINITI possesses wide experience in developing plasma diagnostic systems and neutron diagnostic systems for tokamak reactors, including those based on fibre optics. The Project participants from SRC RF TRINITI and RRC "Kurchatov Institute" have at their disposal IR-8 research nuclear reactor, GUT-200 cobalt gamma-source, radionuclide sources, a neutron generator, and dosimetric equipment. These participants have wide experience in testing optical fibres in gamma and neutron fields. At the IR-8 reactor and the GUT-200 source, an equipment for testing optical fibres is available, which includes a spectroscopic system based on a CCD matrix and some auxiliary devices to stage the experiments. The gamma and neutron fields have been measured at the positions at which the fibres will be irradiated. All the Project participants are carrying out R&D works on radiation-resistant in the framework of the International Thermonuclear Experimental Reactor (ITER) project. The key SRC RF TRINITI participants have experience in working with ISTC under Projects # 1472 "Research and Development of Radiation-Hardened Optical Fibers Intended for Use in the Civil Nuclear Industry" and # 2283 "Research and Development of Diamond Detector Based Spectrometers and Dosimeters". It is worth noting that SRC RF TRINITI has obtained encouraging results on the development of radiation detectors based in radiation-resistant optical fibres.
FORC is one of the world's leading scientific establishments in the field of specialty optical fibres. FORC began R&D works on fibres for the civil nuclear industry in the 90-ies of the last century. These works were devoted to radiation-resistant multimode fibres (including those for ITER plasma optical diagnostic systems) and radiation-resistant fibres for operation in the communication spectral windows, at the wavelengths of ~ 1.30 and 1,55 μm. FORC's R&D works have gained wide international recognition. FORC has taken out a Russian patent and filed another patent application for the techniques of radiation hardening of fibres and the radiation-resistant fibres themselves. It is these techniques and fibres that will be investigated in this Project. FORC has experience in working with ISTC in the framework of Project # 1472.
The Collaborators of this Project – the Belgian Nuclear Research Centre (SCK•CEN) and the CIEMAT of Spain – will carry out independent investigations and tests of all the fibre types developed in this Project. Numerous joint publications of the Collaborators and the Russian Participants bear witness to their experience of collaboration.
This Project does meet the ISTC goals. It will allow the SRC RF TRINITI weapon specialists to continue R&D work in a peaceful science and technology area. The radiation-resistant fibres to be developed in this Project can be applied in NPPs, nuclear-contaminated areas, and nuclear-hazard facilities. Thus, the Project relates to the priority R&D fields of ISTC: energy production, nuclear safety, and environmental monitoring. The Project will make a contribution to the International Thermonuclear Experimental Reactor (ITER) Project.