Demonstration of long term optical fiber thermometry in the in-core region of a nuclear reactor

Fredrik Jensen, Masaharu Nakazawa, Tsunemi Kakuta, Tatsuo Shikama, Minora Narui, Tsutomu Sagawa

Research output: Contribution to journalConference articlepeer-review

4 Citations (Scopus)


An experimental demonstration of fiber optic temperature sensing in the in-core region of Japan Materials Testing Reactor from 250 to 750 °C is described. Temperature data could be obtained for two full-power weeks with neutron fluxes of ̃1014 n/cm2/s and gamma dose rates of ̃5 × 103 Gy/s. The measurements were based on thermally generated infrared light within the optical fiber itself. The fiber thus served as both signal generator and signal transmitter to the out-of-core region. The fibers utilized in the experiments where of high OH pure-silica-core type and showed good radiation resistance. In the infrared region the transmission of the fibers was only weakly affected by the incident radiation. Radiation induced luminescence and Cerenkov radiation in the optical fibers were found to have small influence on the signal in the infrared window. The high OH content of the fibers used in the present experiment precluded the use of the spectral regions at 945, 1245 and 1390 nm, due to the high intrinsic and radiation induced absorption at these wavelengths. The use of silica fibers limited the maximum temperature to <1000 °C. The present experiments show that optical sensors based on infrared emission can be used to monitor temperature in the in-core region of nuclear reactors for extended periods of time.

Original languageEnglish
Number of pages1
JournalProceedings of SPIE - The International Society for Optical Engineering
Publication statusPublished - 1997 Dec 1
EventOptical Technology in Fluid, Thermal, and Combustion Flow III - San Diego, CA, United States
Duration: 1997 Jul 281997 Jul 28


  • Infrared
  • Nuclear Reactor
  • Optical fiber
  • Radiation
  • Sensing
  • Temperature

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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