Development of in-core monitoring system using optical fiber for advanced fission reactor

A new kind of optical dosimetry such as the in-core power monitoring and gamma ray thermometer using radio luminescence and thermal radiation due to gamma ray in optical fibers was demonstrated. During heavy irradiation in the core region of JMTR fission reactor, optical fiber kept good transmission characteristics and radio luminescence and thermal radiation appeared in the infrared region. Intensities of radio luminescence and thermal radiation were found to be directly proportional to the reactor power. Also, temperatures could be estimated by thermal radiation of Planck's law. The optical measuring method using optical fiber could be used to compose simple and convenient monitoring system of power and temperature as a reactor dosimetry.