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This paper addresses the particular need to develop suitable fabrication techniques of glasses to improve the radiation-resistance and extend the lifetime of optical fibres in high radiation background. Two radiation hardening techniques based on hydrogen and fluorine doping of glass have been applied on step index pure silica core optical fibres. The radiation-induced optical absorption and luminescence have been measured in gamma and fission reactor irradiation conditions at SCKCEN, Mol Belgium. The experimental results show that the lowest optical absorption is achieved in the hydrogen-treated fibre sample. However, the luminescence effect remains significant in any type of fibre and cannot be reduced by the investigated radiation hardening techniques.

Radiation effects in components and materials will be one of the most serious technological issues in nuclear fusion systems realizing burning-plasmas. Especially, diagnostic components, which should play a crucial role in controlling plasmas and understanding the physics of burning-plasmas, will be exposed to high-flux neutrons and gamma rays. Dynamic radiation effects will affect the performance of components substantially from the beginning of exposure to radiation environments, and accumulated radiation effects will gradually degrade their functioning abilities in the course of their service. High-power-density fission reactors will be the only realistic tools to simulate the radiation environments expected to occur in burning-plasma fusion machines such as the International Thermonuclear Experimental Reactor (ITER), at present. Some key diagnostic components, namely magnetic coils, bolometers, and optical fibres, were irradiation-tested in a fission reactor, to evaluate their performances in heavy radiation environments. Results indicate that ITER-relevant radiation-resistant diagnostic components could be developed in time, although there are still some technological problems to be overcome.

Fused silica core optical fibers are expected to play crucial roles especially in the size-reduced International Thermonuclear Experimental Reactor (ITER-FEAT). Several radiation resistant optical fibers have been developed in Japan and the Russian Federation. The task force on radiation effects in diagnostic components in the ITER-EDA (engineering and design activity) promoted international round-robin irradiation experiments on the developed optical fibers. Ten different optical fibers were tested in a cobalt-60 gamma-ray irradiation facility and in the Japan Materials Testing Reactor. The paper reports results obtained on five different optical fibers, which include purified, hydrogen loaded, and fluorine doped ones. Results show that the developed optical fibers could be deployed in remote handling and out-of-vessel applications. But, for the in-vessel diagnostics in the visible range optical spectroscopy, further improvement of the radiation resistance of optical fibers will be needed.

Irradiation tests on many diagnostic components have been carried out as a part of the R&D program of the ITER Engineering Design Activities (EDA). Five kinds of ITER round robin fibers were irradiated in JMTR and60Co γ-rays. Induced transmission loss of those fibers are much smaller than that of pure SiO2 core fiber. Especially, KU-H2G from Russian Federation and F-doped fibers from Japan have rather good radiation hardness even in the visible range. Those fibers might be available in the diagnostic port of ITER. The transmissivity of KU-1 quartz, which is a candidate of the window material for UV and visible spectroscopy in ITER, was measured under the irradiation of 14 MeV neutrons and γ-rays in the UV range (200 - 400 nm). Significant transmission loss was observed in the wavelength range of 200-300 nm. The Mica substrate bolometer was irradiated in JMTR during three irradiation cycles. Total neutron fluence was about 1×1024 n/m2 which was equivalent to 0.1 dpa. Significant increase in the meander resistance was observed, which was causedby the nuclear transmutation of gold into mercury. The use of gold meanders might be problematic in ITER.

As a part of the R&D program of the ITER Engineering Design Activities (EDA), we have carried out irradiation tests on a number of diagnostic components. In this paper the recent results of neutron irradiation tests on diagnostic windows, bolometer substrates and magnetic coils at JAERI are described. UV range transmission losses of a KU-1 quartz glass were measured during 14 MeV neutron irradiation at the Fusion Neutronics Source (FNS) with neutron fluences of up to 7.4×1019 n/m2. Significant transmission losses were observed in the wavelength of 200–300 nm. Mica substrates of bolometers were irradiated at the Japan Material Testing Reactor (JMTR) with neutron fluence between 1×1022 and 2.2×1023 n/m2. The size expansion was found to be only 0.13% at 2.2×1023 n/m2 and 150 °C, which gives us the good prospect of the bolometer in the ITER-FEAT application. Magnetic coils made with four kinds of Mineral Insulated (MI) cables have been irradiated in JMTR up to a fast neutron fluence of 1.1×1024 n/m2. Radiation Induced Electrical Motive Force (RIEMF) of several volts was observed between core inductor and sheath of the MI cable.

Oxyhydrate (OH) doped and fluorine (F) doped fused-silica core optical fibers were irradiated in a fission reactor at 370–380 K with a fast neutron flux of about 5×1016n/m2s and a gamma-ray dose rate of about 500 Gy/s for about 24 days. Oxyhydrate and fluorine dopings improved radiation resistance of optical fibers especially in the visible range. A fluorine doped and heat-treated optical fiber showed best radiation resistance and its radiation induced loss in a visible range is about 20 dB/m after it was irradiated up to a fast neutron fluence of 1×1023 n/m2. Results are implying that fused silica core optical fibers can be used nearer to a burning plasma for plasma diagnostics and remote sensing.

For applying to optical diagnostics for fusion reactor, two types of radiation-resistant optical fibers have been fabricated and their optical phenomena were examined in the JMTR. The optical absorption due to radiation-induced defects and formation of color centers, is concentrated in the wavelengths less than 700 nm. By contrast, the absorption was quite low in the wavelength range from 700 to 1500 nm. The optical fibers appeared to have good radiation resistance and survived neutron irradiation up to 2 × 10 24 n/m 2 . During JMTR irradiation, strong optical emission from 400 to 1400 nm with a sharp peak intensity at 1270 nm was observed. The peak value at 1270 nm is directly proportional to the reactor power. The results of absorption and fluorescence phenomena suggest the possibility of multi-parameter sensing for fusion reactor diagnostics.

Several kinds of optical diagnostics are planned in a fusion reactor. Complicated optical systems such as periscopes are thought to be primary candidates for optical measurements, especially for visible wavelengths. However, optical fibers have several advantages over such optical systems. Also, the optical fibers could be a far better transmission line for signals under a high electromagnetic field. However, they have been considered vulnerable to heavy irradiation. In this study, several kinds of optical fibers were irradiated in the Japan Material Testing Reactor (JMTR). The optical transmissivity in fibers was measured in situ during fast neutron and gamma irradiation, up to doses of 2×1024 n m−2 and 5×109 Gy, respectively. The irradiation temperature ranged from 300 to 700 K. For pure ionizing irradiation environments, some methods for improving the radiation resistance of optical fibers were indicated. The results showed that effects of the irradiation associated with fast neutrons would be different from the effects of pure ionizing irradiation. Some fibers were found to withstand the heavy irradiation, especially in an infrared wavelength range.

As an R&D task of the ITER engineering design activities (EDA), we carried out the irradiation tests on the basic materials of transmission components such as ceramics, windows, fiber optics and mirrors, and in-vessel diagnostics sensors such as magnetic probes and bolometers. Ceramics will be used as general insulating materials. Here we investigated the radiation induced conductivity (RIC) of ceramics for 14 MeV neutrons. Optical elements are the most sensitive to radiation damages among the transmission components. Radiation induce transmission loss of window materials and fiber optics have been measured in the Japan material testing reactor (JMTR). Off line irradiation tests were carried out for molybdenum corner cube reflector (CCR) and gold coated mirrors in JMTR also. Fourteen MeV-neutron-induce luminescence of window material was evaluated in the fusion neutronics source (FNS). Bolometers should be installed inside the vacuum vessel to measure the radiation losses in the infra red to soft X-ray range. We demonstrated the performance of the JT 60 type bolometer under 60Co gamma-rays.

Pure, OH-doped and F-doped silica core optical fibers were irradiated in a fission reactor at 400 ± 10 K using an electric heater at a reactor power greater than 10 MW (20% of the full power). The temperature was not controlled well at the early stage of the reactor startup, when the temperature was about 320-340 K. The optical fibers were irradiated with a fast neutron (E> 1 MeV) flux of 3.2 x 10 17 n/cm 2 s and a gamma dose rate of 3 x 10 3 Gy/s for 527 h. Optical transmission loss at 850 nm was measured in situ during irradiation, A prompt increase in optical transmission loss was observed as irradiation started, which was probably due to dynamic irradiation effects caused by short-lived and transient defects and is probably recoverable when irradiation ceases. After the prompt increase in optical transmission loss, a so-called radiation hardening was observed in fibers containing OH. Radiation hardening was also observed in 900 ppm OH-doped fiber at the second startup. The optical transmission loss increased linearly with irradiation dose, denoted as the accumulated loss, which we believe is due to irradiation-induced long-lived defects. Accumulated loss dominates radiation-induced optical transmission loss in a fission reactor irradiation.

Two types of pure-silica-core fibers (one low-OH, Al-jacketed, one medium-OH, polyimide jacketed) suitable for use as sensing fibers for Raman-scattering-based temperature measurements in nuclear environments have been subjected to gamma and fission reactor irradiation tests. Spectral attenuation measurements were performed between 500 and 1500 nm with samples kept at room temperature, 80 and 300/spl deg/C. The Al-jacketed fiber was developed for use under ionizing radiation and showed lower loss compared with the polyimide-jacketed fiber at room temperature under gamma irradiation. Both fiber types showed similar spectra at room temperature with the main part of the loss originating from a band tail extending from the ultraviolet. Thermal bleaching of the radiation-induced defects was found to be effective in both fiber types. At 80/spl deg/C the loss in both fibers was compounded of a band at 625 nm together with the band tail from the ultraviolet, which now had a strength several times lower compared with room-temperature irradiations. At 300/spl deg/C, both fibers exhibited similar low-loss spectra, except for the band at 625 nm which reached levels of approximately /spl sim/2000 dB/km at an accumulated dose of 2.8/spl times/10/sup 4/ Gy(SiO/sub 2/). In light of the experimental spectral findings, selection of suitable Raman-distributed temperature sensors for nuclear plants can be made.

A nuclear pumped laser is attractive as a self-powered and visible radiation sensor which is capable of processing information with coherent light signals. The development of highly efficient and low-threshold nuclear pumped lasers was advanced in an 3He/Ne/Ar gas mixture. This paper presents the analytic results of the lasing mechanisms of the 3He/Ne/Ar nuclear pumped laser through numerical simulations and reactor experiments.

The effects of irradiation on the performance of optical fibers with silica core were examined during irradiation in a fission reactor, JMTR. The fibers performed well in terms of their radiation characteristics up to the fast neutron fluence of 1.06 × 10 20 n/cm 2 and the gamma ray dose rate of 4.3 × 10 9 Gy at 460 K. Three kinds of optical radiation induced by the reactor irradiation were observed during irradiation. Origins of these optical radiations were studied. Broad optical radiations centered at 0.45 and 0.73 μm are thought to be Cherenkov radiation. The sharp optical radiation at 1.27 μm was thought to be generated in the silica core by the gamma-ray irradiations in the reactor.

Two kinds of optical fibers were irradiated in a fission reactor, JMTR (Japan Materials Testing Reactor), up to a 1.55 × 10 19 n/cm 2 fast neutron fluence and a 3.3 × 10 9 Gy ionizing dose at 370 K. Optical transmission spectra were measured in the wavelength range of 450–1750 nm, in situ. Growth of strong optical absorption bands and a peak were observed in the range of wavelength shorter than 750 nm. In the meantime, the fibers showed good radiation-resistance in the range of wavelength larger than 750 nm. Some optical radiation from the fibers was observed. The main cause of the optical radiation is thought to be so-called Cherenkov radiation.

Radio-luminescence from the sapphire was detected in-situ under the reactor irradiation using the silica core optical fiber. The radio-luminescence peaks at 420, 690, and 860 nm, and broad band in 700--1200 nm were identified. However, these radio-luminescence peaks and band became obscure as the reactor power went up, due to the increase of the specimen temperatures and to the interference of the strong radio-luminescence from the silica core optical fiber itself. The effect of the applied electric field on the radio-luminescence was studied. Change was observed due to the electric field but it was very small. Further study and a better-controlled experiments will be needed to clarify the effect.

Applicability of fused silica core optical fibers to in-reactor dosimetry was demonstrated at elevated temperatures and a special irradiation rig was developed for realizing high-temperature optical dosimetry in a High Temperature Test Reactor (HTTR) in Oarai Research Establishment of JAERI (Japan Atomic Energy Research Institute). The paper will describe present status of preparation for the high temperature dosimetry in HTTR, utilizing radiation-resistant optical fibers and radioluminescent materials. Temperature measurement with a high-speed response is a main target for the present optical dosimetry, which could be applied for monitoring transient behaviors of the HTTR. This could be realized by measuring intensity of thermoluminescence and black body radiation in infrared region. For monitoring reactor powers, optical measurements in visible region are essential. At present, measurement of intensity of Cerenkov radiation will be most promising. Other possibilities with radio-luminescent materials having luminescent peaks in visible region are under survey. One of the candidates will be silica, which has a robust radioluminescent peak at 450 nm.

Radioluminescence from rare earth oxide materials was measured in the visible wavelength range and the range from 1000 to 3000 nm in an ion beam accelerator and a fission reactor of Japan Materials Testing Reactor (JMTR). In erbium oxide, peaks at 560, 660, and 1540 nm were observed by the proton beam irradiation, and the complicated luminescence peaks around 1800 and 2000 nm were observed by the proton beam irradiation and at the reactor full power operation of 50 MW. The peaks at 560, 660, and 1540 nm are attributed to the electron transition between the energy levels of Er3+ ions. The complicated luminescences observed in JMTR were quenched with the irradiation time elapsed, though the intensity was not changed by the irradiation of the proton beam of 2.6 x 1013 p/cm2s. It was considered that the precursors for the complicated luminescent peaks around 1800 and 2000 nm disappeared under the neutrons irradiation.

With the aim to develop new in-core monitoring system using optical techniques, studies have been started on heavy neutron irradiation effects on optical fibers. Two types of highly radiation resistant optical fibers. Pure silica (SiO/sub 2/) with OH content core and SiO/sub 2/ with fluorine doped core fibers were irradiated in the core region of JMTR. The fibers were irradiated under fast neutron flux (E>1.0 MeV) of about 1/spl times/10/sup 17/ n/m/sup 2/ s and gamma-ray dose rate of 2/spl times/10/sup 3/ Gy/s. The optical absorption and the light emission spectrum change were measured in-situ along the irradiation. As a result, the following effects have become clear. Large absorption loss at wavelength of shorter than 700 nm and loss peak of 630 nm were appeared. However, the increase in absorption was quite low in the wavelength from 700 to 1700 nm. The SiO/sub 2/ fibers were survived up to 3/spl times/10/sup 23/ n/m/sup 2/. During irradiation, the induced light emission in the wavelength from 400 to 1700 nm and light peak at about 1200 nm were observed. Induced light emission was directly proportional to the neutron yield. >

When optical fiber radiation measurements are applied for a high dose rate area, there has been a problem of radiation induced loss in the optical fibers. In this study, red and near infrared (IR) fluorescence from rare earth ions has been used to reduce the problem. From continuous measurements using Gd/sub 2/O/sub 2/S:Pr/sup 3+/, the superiority of using long wavelength emission has been shown from the view point of radiation hardness. Linear relation between dose rate and peak counts was confirmed and it shows the possibility of using the long wavelength emission for radiation measurements. For calibration of the radiation induced loss, the optical time domain reflectometry (OTDR) technique has been applied. It has been shown that this method can broaden the dose rate limit of the optical fiber based measurements. Also, glass samples doped with rare-earth ions have been made and irradiated by gamma rays. Emission at a longer wavelength than 700 nm has been observed for Eu/sup 3+/ ions doped into silica, fluorophosphate and ZBLAN glass samples. Considering that it is easy to make silica glass and to connect it to usual silica glass optical fiber, silica glass doped with Eu/sup 3+/ is thought to be the most promising material for new scintillating fibers with high radiation resistivity.

Since the nuclear pumped laser technique can be applied to the optical detection of neutrons, numerical simulations and demonstration experiments have been carried out for He-Ne-Ar mixtures. Test cells filled with /sup 3/He gas (1140 torr), Ne gas (540 torr) and Ar gas (208 torr) were irradiated with a thermal neutron flux up to about 10/sup 12/ n/cm/sup 2//s at JRR-4 reactor, JAERI. In these experiments, an optical output of 585.3 nm from Ne 3p-3s transitions was clearly observed. Its intensity was almost proportional to the thermal neutron flux, and these results agree with those of the numerical simulation. This system can be applied to optical neutron detection. The simulation results show that the population inversion between 3p'[1/2]/sub 0/, and 3s'[1/2]/sub 0//sup 1/ levels of neon atom for the cell can be achieved at the thermal neutron flux of much higher than 10/sup 12/ n/cm/sup 2//s. It is also estimated that the threshold thermal neutron flux for the population inversion is about 3/spl times/10/sup 12/ n/cm/sup 2//s for the gas cell filled with optimized gas mixtures.

To promote development of radiation-resistant core optical fibers, the ITER-EDA (International Thermonuclear Experimental Reactor-Engineering Design Activity) recommended carrying out international round-robin irradiation tests of optical fibers to establish a reliable database for their applications in the ITER plasma diagnostics. Ten developed optical fibers were irradiation-tested in a Co-60 gamma cell, a Japan Materials Testing Reactor (JMTR). Also, some of them were irradiation tested in a fast neutron irradiation facility of FNS (Fast Neutron Source), especially to study temperature dependence of neutron-associated irradiation effects. Included were several Japanese fluorine doped fibers and one Japanese standard fiber (purified and undoped silica core), as well as seven Russian fibers. Some of Russian fibers were drawn by Japanese manufactures from Russian made pre-form rods to study effects of manufacturing processes to radiation resistant properties. The present paper will describe behaviors of growth of radiation-induced optical transmission loss in the wavelength range of 350-1750nm. Results indicate that role of displacement damages by fast neutrons are very important in introducing permanent optical transmission loss. Spectra of optical transmission loss in visible range will depend on irradiation temperatures and material parameters of optical fibers.

Strong radioluminescence band and peaks were observed in fused silica core optical fibers under irradiation in fission reactors of Japan Materials Testing Reactor (JMTR) and in gamma-irradiation facility. A broad band in 400-1700 nm could be attributed to Cerenkov radiation, whose intensity was proportional to inverse of the third power of wavelength. The optical intensity of the peak at 450 nm, that was considered to be generated by oxygen vacancies, was proportional to the reactor power under the electronic excitation dose rate up to 5.0 x 10 3 Gy/s, and the dynamic range was at least more than five orders of magnitude. The peak intensity depends on details of silica microstructures and became twice after annealing at 773K. By using these radioluminescence peak and band, wide range dosimetry could be actualized in heavy radiation environments.

Retention and thermal release behavior of hydrogen isotopes in fused silica, synthesized silica and optical fibers were investigated by ion beam analysis technique. Initially contained H in the interior of the specimens is about 0.1~0.2 at.% at room temperature, irrespective of the nominal value of OH concentration. Besides, H atoms more than 1 x 1016H/cm2 was found at the surface. The thermal release of the H atoms from the interior was affected by re-trapping at the near surface. During 5 keV ion injection, the retained D in the implanted layer was quickly saturated with a concentration of about 1 x 1021D/cm3. Under the subsequent D injection to doses above 1 x 1018D/cm2, D atoms were trapped with a concentration about 1 at.% in the depth far beyond the projected ranges of D ions. Thermal release of D in the injected layer started at lower temperature than that from the larger depth for lower implantation dose, while the two release curves close to each other for the higher dose. Irradiation of 10 keV He ion into the fused silica caused H up-take in the He implanted depth, where no He atoms were retained.

Optical transmission properties of optical fibers with a purified and undoped fused-silica core were investigated under irradiation by 14 MeV fast neutrons in the temperature range from room temperature to 573 K at a fast neutron irradiation facility of Fast Neutron Source (FNS). Growth of optical absorption in the wavelength range of 420-630 nm, which includes a well-known absorption peak called Non-Bridging-Oxygen-Hole-Center (NBOHC), took place due to the neutron irradiations. Change of the optical absorption depended strongly on the irradiation temperature. Particularly, growth rate of the radiation-induced optical absorption at the wavelength of 630 nm decreased with increase of the irradiation temperature up to 473 K, because of the dynamic recovery of the initial structural imperfections and the radiation-induced defects.

Nine different fused silica core optical fibers were irradiated in a fission reactor up to an ionizing dose of 10 9 Gy and a fast neutron fluence of 10 23 n/m 2 at 400 K. One specimen, fluorine doped and specially sintered and annealed, showed good radiation resistance in the wavelength range of 300 - 1850 nm. Results showed that the fibers can be applied in a neutron associated heavy radiation environments.

Radiation resistant fused silica core optical fibers, 900 ppm OH doped with their hydrogen treated fibers with a plastic jacket, 18000 ppm OH doped one having very low optical transmission loss with a carbon jacket, and a fluorine doped fiber with a plastic jacket, were irradiated in a JMTR fission reactor, at 400 +/- 10 K with a fast neutron (E > 1 MeV) flux of 3.2 X 10 17 n/cm 2 s and a gamma dose rate of 3 X 10 3 Gy/s for 527 hours. Their optical transmission loss at 850 nm was measured in- situ during irradiation.

An experimental demonstration of fiber optic temperature sensing in the in-core region of Japan Materials Testing Reactor from 250 to 750 degrees C is described. Temperature data could be obtained for two full-power weeks with neutron fluxes of approximately 1014 n/cm2/s and gamma dose rates of approximately 5 X 103 Gy/s. The measurements were based on thermally generated IR 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 IR 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 IR 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 degrees C. The present experiments show that optical sensors based on IR emission can be used to monitor temperature in the in-core region of nuclear reactors for extended periods of time.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A distributed temperature sensor based on Raman scattering in optical fibers has been tested for use as coolant loop monitor in nuclear power plants. Different types of pure- silica-core, polyimide-coated fibers have been subjected to 60Co-gamma-ray and fission-reactor irradiation at varying temperatures. 60Co-gamma-ray irradiations at dose rates from 4.8 kR/h up to 1 MR/h were done. Simultaneous gamma-ray and high temperature experiments up to 300 degrees Celsius have also been performed. The induced loss of the tested fibers was found to saturate with increasing dose at the anti-Stokes and Stokes wavelengths. This feature was then made use of to develop a model for radiation induced loss which was used to make system lifetime predictions. It has also been demonstrated that the induced loss of the optical fibers is favorably affected by high-temperature use. A 10-fold decrease in the radiation- induced loss levels when the system was operated at 300 degrees Celsius was observed, as compared with room- temperature operation. The experiments have shown that with a pure-silica-core, polyimide-coated fiber the temperature sensing capabilities of the RDTS will not be degraded excessively if used at primary coolant loops with an expected upper radiation level of 200 R/hr.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The numerical simulation of a nuclear pumped 3He–Ne–Ar gas laser (λ=585.3 nm) has been made to estimate the optimal gas mixtures. The calculation shows that the optimization is established under a condition of He pressure of 2280 Torr, Ne pressure of 24 Torr, and Ar pressure of 8 Torr. The oscillation is expected to occur at a thermal neutron flux density of 3.3×1014 cm-2 s-1 when the cavity length is 50 cm and the mirror reflection coefficient is 99%. On the other hands, the energy efficiency does not exceed 0.33% under the same condition.

Gamma thermometers have been in routine use in nuclear power plants for power distribution monitoring for more than 35 years. These instruments depend upon the heating of a metal block by gamma rays. The generated heat is proportional to the specific power of nearby fuel rods. Usually heat is allowed to escape to a sink through a controlled heat path and the temperature drop is measured by thermocouples. If the heat sink is at a known temperature, a single thermocouple may be employed to measure the temperature of the metal block.

In order to fabricate an optical fiber with an excellent radiation resistance characteristic, we have investigated the radiation resistance characteristics of various types of optical fibers. As a result, two kinds of fiber were found to have an excellent radiation resistance characteristic which can be sufficiently used in the practical application under large doses exceeding 1 \times 10^{8} R.

The heat and radiation resistant cable for the use on the liquid metal cooled fast breeder reactor (LMFBR) has been newly developed. Stainless steel sheathed mineral insulated type cable has been usually used in the vinicity of the primary cooling circuit of LMFBR because of the harsh environmental condition in this area. Sometimes, this type of cable causes problems for its inflexibility in terms of installation. This newly developed cable (named M. Flex cable) consists of inorganic materials such as mica and glass, and the heat and radiation resistant organic materials such as polyimide for the insulation and stainless steel wire braid for the protection layer. Such tests as gamma irradiation test up to total dose of 1.4 × 1010R, flexibility test, and other tests, have been performed and results show that M. Flex cable has been satisfactory for the LMFBR applicaltion. And also, these results implied the applicability of this cable to the other fields than nuclear plants.

(社)大阪ニュークリアサイエンス協会では,耐放射線性機器・材料に関する成果を集約整理するために,データベースの構築を目的として,昭和61年度より各分野の専門家からなる委員会を設置し,活動を開始した。研究開発の動向および今後の利用価値等の展望から,データの収集分野を有機材料,光ファイバ,半導体素子,化合物半導体とした。昭和62年度までには,プロトタイプデータベース構築を目指し,システム構成,集録データの項目と属性に関するフォーマットの作成,システムの動作試験等を行なった。

The influence of the kinds of impurities in the core and manufacturing process of the core on the radiation resistance was investigated for 6 kinds of pure silica core optical fibers. We have obtained the following results: 1. The radiation resistance of OD doped fiber was good and the initial loss before irradiation was low also although the total hydroxide molecule content was low. on doped fiber will be promising as the radiation resistant optical fiber in a future. 2. The induced loss characteristic varied very much according to the kinds of impurities and the manufacturing processes even in the pure silica core fiber: The induced loss characteristic of each kind of fiber was much different especially according to the difference in photo power. The photobleaching effect of fiber No. 4 manufactured by the MCVD method was quite low, but fiber No. 5 and 6 manufactured by the plasma method was rather high. To put it more concretely, the induced loss of No. 5 had the difference of 20db/100m and 2db/100m respectively according to the different measurement condition of 0.14 µ w and l4 µ w. Measurement conditions should be standardized for the measurement of the radiation resistance of optical fibers, especially with respect to photo power etc, because of photobleaching effect.