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Journal Articles

Degradation of cable insulation material by accelerated thermal radiation combined ageing

Seguchi, Tadao*; Tamura, Kiyotoshi*; Kudo, Hisaaki*; Shimada, Akihiko; Sugimoto, Masaki

IEEE Transactions on Dielectrics and Electrical Insulation, 22(6), p.3197 - 3206, 2015/12

 Times Cited Count:27 Percentile:76.91(Engineering, Electrical & Electronic)

The degradation of ethylene propylene rubber (EPR) sheets as a cable insulation material for nuclear power plants (NPP) was studied by accelerated thermal ageing, radiation ageing and thermal - radiation combined ageing. The oxidation of EPR proceeded with ageing and the decay of mechanical property was closely related to the content of oxidation products. The antioxidant as a stabilizer in EPR was effective for the thermal oxidation, but not for the radiation oxidation. For the thermal and radiation combined oxidation, the mechanical property and the content of oxidation products were different among the treatment sequences due to the decay of antioxidant. The lifetime of EPR cable is closely related to the remaining content of antioxidant, and the lifetime evaluation would be recommended by the reverse sequential combination (thermal ageing after radiation ageing).

Journal Articles

Degradation mechanisms of Silicone Rubber (SiR) by accelerated ageing for cables of nuclear power plant

Shimada, Akihiko; Sugimoto, Masaki; Kudo, Hisaaki*; Tamura, Kiyotoshi*; Seguchi, Tadao*

IEEE Transactions on Dielectrics and Electrical Insulation, 21(1), p.16 - 23, 2014/02

The thermal and radiation ageing behaviors and degradation mechanisms of SiR for the cable insulation of nuclear power plants were studied. The thermal ageing and radiation ageing in air were conducted up to 235$$^{circ}$$C and 195$$^{circ}$$C, respectively. The dose rate of radiation ageing is 1 kGy/h. Thermal ageing in vacuum as well as in air was also conducted. The degraded SiR is evaluated by tensile test, gel fraction measurement, swelling ratio measurement and weight measurement, and then the results are analyzed. It is appeared that the radiation degradation of SiR at high temperature is much more severe than that of SiR at low temperature at the same dose. Focusing on the molecular structure, it is supposed that crosslinking reagents which are included in SiR are removed, oxygen atom is attached instead of the reagents and new crosslinking is foamed. Their behaviors are different from the polymer of hydrocarbon.

Journal Articles

Degradation distribution in insulation materials of cables by accelerated thermal and radiation ageing

Shimada, Akihiko; Sugimoto, Masaki; Kudo, Hisaaki*; Tamura, Kiyotoshi*; Seguchi, Tadao*

IEEE Transactions on Dielectrics and Electrical Insulation, 20(6), p.2107 - 2116, 2013/12

 Times Cited Count:37 Percentile:83.07(Engineering, Electrical & Electronic)

The degradation of cables by the accelerated thermal and radiation ageing for nuclear power plant was studied. The thermal oxidation of crosslinked polyethylene (XLPE) as a cable insulation showed the heterogeneous features along the depth of sheet specimens. The degree of oxidation was closely related to the distribution of antioxidant content due to the decay of antioxidant content by the evaporation and radiation decomposition during accelerated ageing. The specific relations were observed between the tensile properties and the yield of oxidation products and also between the oxidation products and antioxidant content in XLPE specimens. The yields and the content and their distribution were detected by FTIR. The oxidation of XLPE containing antioxidant of enough content proceeded proportionally with ageing time or radiation dose at any ageing conditions. When the antioxidant content decreased less than a limited content by thermal and/or radiation ageing, the oxidation rate by thermal ageing increased sharply with ageing time. Therefore, the oxidation at surface of XLPE was much accelerated when the antioxidant decreased to result the heterogeneous oxidation. The mechanical properties depend closely on the degree of oxidation at the surface. The behavior of oxidation was also affected by the types of antioxidant.

Journal Articles

Temperature dependence of gas evolution from polyolefins on irradiation under vacuum

Seguchi, Tadao*; Haruyama, Yasuyuki; Sugimoto, Masaki

Radiation Physics and Chemistry, 85, p.124 - 129, 2013/04

 Times Cited Count:5 Percentile:40.63(Chemistry, Physical)

The yields of gas evolution from various types of polyethylene and ethylene-propylene copolymer by radiation were precisely measured after $$gamma$$ ray irradiation under vacuum at the wide range of temperatures (-196 $$sim$$ 200$$^{circ}$$C). For all polymers the major gas was H$$_{2}$$ and the minor products were C$$_{1}$$, C$$_{2}$$, C$$_{3}$$ hydrocarbons and oxidation compounds as CO$$_{2}$$ and CO. The total gas yield increased with the increase of irradiation temperature. The yield of total gas increased with irradiation temperature, and the behavior was closely related to the molecular motion of polymer matrix during irradiation.

Journal Articles

Product analysis for polyethylene degradation by radiation and thermal ageing

Sugimoto, Masaki; Shimada, Akihiko; Kudo, Hisaaki*; Tamura, Kiyotoshi; Seguchi, Tadao*

Radiation Physics and Chemistry, 82, p.69 - 73, 2013/01

 Times Cited Count:56 Percentile:97.83(Chemistry, Physical)

The oxidation products formed by thermal and radiation ageing of crosslinked polyethylene for cable insulation were analyzed by FTIR-ATR spectrometry. The most of products were composed of carboxylic acid, carboxylic ester, and carboxylic anhydride. The carboxylic acid was the primal product, and the others were the secondary products by the thermal reaction of carboxylic acids. The carboxylic acid as the primal oxidation product supports the proposed new oxidation mechanisms that the main chain scission should occur directly by oxidation of polyethylene radicals.

JAEA Reports

Study of cable ageing mechanism for nuclear power plant (Contract research)

Seguchi, Tadao*; Tamura, Kiyotoshi*; Watashi, Katsumi; Suzuki, Masahide; Shimada, Akihiko; Sugimoto, Masaki; Idesaki, Akira; Yoshikawa, Masahito; Oshima, Takeshi; Kudo, Hisaaki*

JAEA-Research 2012-029, 158 Pages, 2012/12


The degradation mechanisms of ethylene-propylene rubber (EPR), crosslinked polyethylene (XLPE), polyvinylchloride (PVC), and silicone rubber (SiR) as the cable insulation materials were investigated for the cable ageing research of the nuclear power plant. The materials as same insulations for the practical cable (practical formulation) and as the model formulation containing specific additive were selected. They were exposed to the accelerated radiation and thermal environments. The mechanical properties, the crosslinking and chain scission, and the distribution of antioxidant and of oxidative products were measured and analyzed.

Journal Articles

Mechanism of antioxidant interaction on polymer oxidation by thermal and radiation ageing

Seguchi, Tadao*; Tamura, Kiyotoshi; Shimada, Akihiko; Sugimoto, Masaki; Kudo, Hisaaki*

Radiation Physics and Chemistry, 81(11), p.1747 - 1751, 2012/11

 Times Cited Count:37 Percentile:93.51(Chemistry, Physical)

The mechanism of polymer oxidation by radiation and thermal ageing was investigated for the life evaluation of cables installed in radiation environments. The antioxidant as a stabilizer was much effective for thermal oxidation with a small content in polymers, but was not effective for radiation oxidation. The ionizing radiation induced the oxidation to result chain scission even at low temperature, because the free radicals were produced and the antioxidant could not stop the oxidation of radicals with the chain scission. A new mechanism of antioxidant effect for polymer oxidation was proposed. The effect of antioxidant was not the termination of free radicals in polymer chains such as peroxy radicals, but was the depression of initial radical formation in polymer chains by thermal activation. The antioxidant molecule was assumed to delocalize the activated energy in polymer chains by Boltzmann statics (distribution) to result decrease the probability of radical formation at a given temperature. The interaction distance (delocalization area) by one antioxidant molecule was estimated to be 5-10 nm in polymer matrix, though the value would depend on the chemical structure of antioxidant.

Journal Articles

Radiation ageing technique for cable life evaluation of nuclear power plant

Shimada, Akihiko; Sugimoto, Masaki; Kudo, Hisaaki*; Tamura, Kiyotoshi; Seguchi, Tadao*

IEEE Transactions on Dielectrics and Electrical Insulation, 19(5), p.1768 - 1773, 2012/10

 Times Cited Count:14 Percentile:60.25(Engineering, Electrical & Electronic)

The life of cables installed in nuclear power plant was evaluated by the accelerated ageing tests of thermal and radiation degradation. For radiation degradation, the dose rate was the important points, because the oxidation distribution in the insulation was much affected by dose rate due to oxygen penetration limitation during irradiation. The oxidation distribution was observed by FTIR for crosslinked polyethylene (XLPE) and ethylene propylene rubber (EPR) of cable insulation degraded at various irradiation conditions and compared with the mechanical degradation. The oxidation profile was almost same between a low dose rate at room temperature and a high dose rate at elevated temperature (100 $$^{circ}$$C), and the degradation was same for both irradiations. By increasing the irradiation temperature the oxygen penetration rate increased exponentially and the thermal degradation during irradiation was negligible at around 100 $$^{circ}$$C. Therefore, the dose rate could be increased by 15 times by irradiation at 100 $$^{circ}$$C instead of the irradiation at room temperature for the adequate oxidation throughout insulation. The experimental result was coincident with the theoretical analysis.

JAEA Reports

Ageing research of cable insulation materials

Seguchi, Tadao*; Tamura, Kiyotoshi; Kudo, Hisaaki*; Shimada, Akihiko; Sugimoto, Masaki; Idesaki, Akira; Oshima, Takeshi; Yoshikawa, Masahito

JAEA-Review 2012-027, 46 Pages, 2012/08


The research on cable degradation mechanisms was conducted for 5 years in 2006 - 2010 as the project research of plant life management for nuclear power plant by NISA (Nuclear and Industrial Safety Agency) of METI (Ministry of Economy, Trade, and Industry). At the finish of above research, the degradation mechanisms were reviewed on the analysis of many reports on cable degradation. The reports published after 1970 were mainly surveyed and the facts or data containing the experimental accuracy were selected. The verified facts, the reasonable interpretation of the facts, unresolved aspects were checked on the view points of recent techniques or analysis, and proposed the new model of degradation mechanisms was proposed.

Journal Articles

The Effect of antioxidants on degradation mechanism of cable insulation material for nuclear power plant

Shimada, Akihiko; Kudo, Hisaaki*; Idesaki, Akira; Sugimoto, Masaki; Yoshikawa, Masahito; Tamura, Kiyotoshi; Seguchi, Tadao*

Proceedings of 12th International Conference on Radiation Curing in Asia (RadTech Asia 2011) (Internet), p.244 - 247, 2011/06

Journal Articles

Degradation mechanisms of cable insulation materials during radiation-thermal ageing in radiation environment

Seguchi, Tadao*; Tamura, Kiyotoshi; Oshima, Takeshi; Shimada, Akihiko; Kudo, Hisaaki*

Radiation Physics and Chemistry, 80(2), p.268 - 273, 2011/02

 Times Cited Count:62 Percentile:97.74(Chemistry, Physical)

The cables applied in radiation facility such as a nuclear power plant degrade by radiation and thermal combined ageing. The degradation of polymers for cable insulation is induced by oxidation, and the oxidation is accelerated by synergism of radiation and thermal oxidation. The degradation mechanisms were studied at accelerated degradation for various cable insulation materials. The distribution of degradation in film samples was investigated with various techniques. It was found that the antioxidant agent for stabilizer of insulation materials is closely related to the synergism. With progress of ageing, the concentration of effective antioxidant decreases by radiation decomposition and also by evaporation in thermal ageing. When the concentration of antioxidant is reduced to a limited value, the thermal oxidation is progressing.

Journal Articles

Irradiation condition on accelerated ageing test of cable designed for nuclear power plants

Shimada, Akihiko; Kudo, Hisaaki*; Idesaki, Akira; Oshima, Takeshi; Tamura, Kiyotoshi; Seguchi, Tadao*

Proceedings of International Conference on Condition Monitoring and Diagnosis 2010 (CMD 2010), Vol.2, p.705 - 708, 2010/09

The lifetime evaluation of cable insulation used in nuclear power plants is very important for their safety running. In the present, the evaluation of cable lifetime is performed under the higher dose rate of radiation and elevated temperatures compared to actual conditions. In that case, we need to select the reasonable dose rate. One of the important points is the homogeneous oxidation throughout insulation polymer materials during irradiation for the equivalent oxidation with the real ageing condition. The oxidation depth of polymer material depends on the dose rate and oxygen diffusion coefficient into polymer material. Then, the dose rate could be increased if the diffusion coefficient was increased by increasing the irradiation temperature. The relations between dose rate and irradiation temperature were studied on XLPE, EPR, PVC and SiR for cable insulation. These materials are irradiated with cobalt 60 $$gamma$$-rays at dose rates up to 1 kGy/h under elevated temperature. The irradiation effects were analyzed by tensile test, change of swelling ratio and gel fraction, SEM-EDS, and FT-IR.

JAEA Reports

Radiation resistance of polymer materials; Degradation evaluation by accelerated testing for application condition

Seguchi, Tadao*; Sorimachi, Masami*; Tamura, Kiyotoshi

JAEA-Data/Code 2009-018, 123 Pages, 2010/02


The radiation resistance of 25 type polymer materials as plastics and rubbers applied in practical environments was evaluated by the accelerated testing of $$gamma$$-ray irradiation under oxygen pressure, and compared with the radiation resistance determined from the traditional testing by irradiation with a high dose rate in air. The polymer materials were formulated to be similar or equivalent to practical materials, and the most of formulation (chemical compounds and quantities) were disclosed. For all materials, the tensile properties (elongation at break, ultimate strength, 100% or 200% modulus), electric resistivity, gel-fraction, and density were measured after irradiation in oxidation conditions and non-oxidation conditions. The data of relations between each properties and total dose at various conditions were compiled, and the relations among the changes of mechanical properties, electrical properties, and radiation induced chemical reactions were discussed.

Journal Articles

Development of SiC/SiC composite from precursor polymer by radiation application

Sugimoto, Masaki; Morita, Yosuke; Tanaka, Shigeru; Seguchi, Tadao; Ito, Masayoshi*; Okamura, Kiyohito*

IAEA-SM-365/7, p.35 - 40, 2003/09

no abstracts in English

JAEA Reports

Gas evolution of polyethylene by radiolysis and the application to dosimeter

Haruyama, Yasuyuki; Sunaga, Hiromi; Arakawa, Kazuo; Seguchi, Tadao

JAERI-Tech 2002-084, 105 Pages, 2002/11


no abstracts in English

Journal Articles

New material synthesis by radiation processing at high temperature; Polymer modification with improved irradiation technology

Seguchi, Tadao; Yagi, Toshiaki; Ishikawa, S.*; Sano, Y.*

Radiation Physics and Chemistry, 63(1), p.35 - 40, 2002/01

 Times Cited Count:65 Percentile:96.21(Chemistry, Physical)

no abstracts in English

Journal Articles

Fine SiC fiber synthesized from organosilicon polymers; Relationship between spinning temperature and melt viscosity of precursor polymers

Idesaki, Akira; Narisawa, Masaki*; Okamura, Kiyohito*; Sugimoto, Masaki; Tanaka, Shigeru; Morita, Yosuke; Seguchi, Tadao; Ito, Masayoshi*

Journal of Materials Science, 36(23), p.5565 - 5569, 2001/12

 Times Cited Count:37 Percentile:77.35(Materials Science, Multidisciplinary)

A very fine silicon carbide (SiC) fiber with diameter of 6 $$mu$$ m, about a half of that of a commercially available SiC fiber, was synthesized from a polymer blend of polycarbosilane (PCS) and polyvinylsilane (PVS). The fine SiC fiber was obtained by optimizing the composition and the spinning temperature of PCS-PVS polymer blends. In order to determine these optimum conditions, the relationship between temperature and melt viscosities of the polymer blends was investigated. As a result, it was found that the optimum spinning temperature range was within a temperature range where the melt viscosity is 5-10Pa$$cdot$$s. Moreover, by blending PVS with PCS, the spinning temperature of the polymer blends was lowered, the spinnability of polymer system was improved, and finer polymer fiber was obtained compared with PCS. The optimum content of PVS in the polymer blend was 15-20wt%.

Journal Articles

Mechanisms and kinetics of hydrogen yield from polymers by irradiation

Seguchi, Tadao

Nuclear Instruments and Methods in Physics Research B, 185(1-4), p.43 - 49, 2001/12

 Times Cited Count:18 Percentile:51.16(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Recovery system for uranium from seawater with fibrous adsorbent and its preliminary cost estimation

Sugo, Takanobu; Tamada, Masao; Seguchi, Tadao; Shimizu, Takao*; Uotani, Masaki*; Kashima, Ryoichi*

Nihon Genshiryoku Gakkai-Shi, 43(10), p.1010 - 1016, 2001/10

 Times Cited Count:16 Percentile:73.78(Nuclear Science & Technology)

The cost of uranium recovered from seawater was estimated by using the amidoxime adsorbent of polymer fibers synthesized by radiation modification, and the technical problems in the recovery system were extracted. The cost of adsorbent materials, storage in seawater for uranium absorption, and the uranium detachment from the adsorbent was estimated respectively in three different systems of the storage in seawater as a buoy, floating body, and chain binding system. The recovery cost of uranium from seawater was estimated to be 8$$sim$$10 times of that from mine uranium. More than 80% of the total cost was occupied by the cost for storage in seawater, which is owing to a weight of metal cage for the holding of adsorbents. The cost can be attained to half by the reduction of the weight to 1/4. One of facing research subject is the improvement of adsorbent ability, since the cost directly depends on the adsorbent performance.

Journal Articles

Electron spin resonance study on chemical-crosslinking reaction mechanisms of polyethylene using a chemical agent, 6; Effect of $$alpha$$-methyl styrene dimer

Yamazaki, Takanori*; Seguchi, Tadao

Journal of Polymer Science, Part A; Polymer Chemistry, 39(13), p.2151 - 2156, 2001/05

no abstracts in English

301 (Records 1-20 displayed on this page)