Title page for ETD etd-05122009-145713


Type of Document Master's Thesis
Author Alfeeli, Bassam
Author's Email Address alfeeli@vt.edu
URN etd-05122009-145713
Title Ionizing Radiation Resistance of Random Hole Optical Fiber for Nuclear Instrumentation and Control Applications
Degree Master of Science
Department Materials Science and Engineering
Advisory Committee
Advisor Name Title
Pickrell, Gary R. Committee Chair
Clark, David E. Committee Member
Wang, Anbo Committee Member
Keywords
  • Nuclear energy
  • Nuclear power generation
  • Microstructured optical fibers
  • Photonic crystals
  • Optical fiber fabrication
  • Optical fiber sensors
Date of Defense 2009-05-04
Availability unrestricted
Abstract
Random hole optical fibers (RHOF) offer advantages over other types of microstructured optical fibers (MOFs). They are inexpensive and easy-to-make when compared to the high cost of ordered hole MOFs. They also have unique characteristics since they contain open and closed holes. The open holes contain ambient air under normal conditions and the closed holes contain residual gases from the fabrication process at certain pressure. The objective of this research work was to investigate the radiation resistance of Random Hole Optical Fibers (RHOF) for possible use as both sensing element and data transmission medium in nuclear reactor instrumentation and control applications.

This work is motivated by the demand for efficient, cost effective, and safe operation of nuclear power plants, which accounts for more than 14% of the world’s electricity production.

This work has studied the effect of gamma irradiation on RHOF fibers by comparing their performance to that of standard solid telecommunication fibers and commercially available specialty solid fiber designed to be radiations hardened fiber. The fibers were evaluated at different absorbed dose levels: 12 mGy(Si), 350 mGy(Si), and 7200 Gy(Si) by measuring their radiation induced absorption (RIA) on-line. In the low dose test, the maximum RIA measured in untreated RHOF was approximately 8 dB while the RIA in the untreated MMF fibers reached a maximum at about 28 dB. In the high dose test, the maximum RIA measured in untreated RHOF was 36 dB while RIA in the methanol washed RHOF was only 9 dB. RHOF also demonstrated superior radiation damage recovery time over all of the other fibers tested. Based on the experimental evaluations, it was deduced that RHOFs used in this work are resistant to gamma radiation. and recover from radiation damage at a faster rate compared to other fibers tested. The radiation induced absorption (RIA) at the 1550 nm window in the RHOF fibers could be attributed to the OH absorption band tail. However, the existence of other mechanisms responsible for RIA is also postulated. Some of these mechanisms include bulk and surface defects which are related to the fabrication process and the influence of the gases confined within the RHOF microstructure.

Gamma radiation resistance of RHOFs can be attributed to the lack of dopants and also possibly the inherent OH and nitrogen content. The behavior of thermally annealed RHOF and their fast recovery is in favor of this hypothesis.

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