Project Subjects
Deterioration Diagnosis of Instrumentation and Electrical Equipment
Background and Objective
For long-term operation of nuclear power plants, the ageing of equipment, pipe and instrumentation andelectrical equipment is one of the important issues that should be taken into account. It has been expected todevelop diagnosis method to detect their ageing.
In case of SCC crack appearance, continuous operation or repair of component is selected, following theJSME code “Rules on Fitness-for-Service for Nuclear Power Plants”. Phased array UT was applied to measure
the defect depth sizing on several components such as pipes and shrouds, etc. However, it was difﬁcult to measure
the defect depth sizing on nickel based alloy welds by conventional UT. Therefore, the development of advanced
phased array UT technique is required for nickel based alloy welds.
Long-term integrity of cable insulation is conﬁrmed by tests based on the Technical Report publishedby the Institute of Electrical Engineers of Japan. Especially, the conﬁrmation of integrity (evaluation of material
deterioration) of mechanical properties such as strength and elongation of cable insulation is important sincecable insulation is deteriorated due to thermal stress and radiation. Therefore, it is required to establish the effective index to evaluate the combined radiation-thermal deterioration of cable insulating materials.
The objectives of this project are to develop the phased array UT technique for measurement of highaccuracy for defect depth sizing and to establish an analysis method to evaluate quantitatively radiation-thermaldeterioration of cable insulating materials.

Main results
1. Application of phased array UT for crack depth sizing on nickel based alloy weldAt ﬁrst, phased array UT examination was carried out to select the UT condition using by side drilledholes specimen. The UT conditions were optimized on phased array probe aperture, focal depth of ultrasound andso on. Phased array UT technique was applied to nickel based alloy weld specimen with EDM notches. Defectdepth could be measured up to 5mm by phased array UT and the relation between actual and measured EDM
notch depth showed a good agreement (defect depth accuracy approximately equal to 1mm) (Fig.1). From theexperimental results, the superior performance of phased array UT technique for inside inspection was shown.
2. Study of deterioration diagnosis index of radiation-thermal deterioration of cable insulation materials
To ﬁnd useful analysis tools to detect radiation-thermal deterioration through changes in material characteristics and microscopic structures of cable insulating materials, we applied chemical luminescence analysis,
micro Fourier transform infrared spectroscopy, the X-ray diffraction method and the nano indentation method,and evaluated changes of material characteristics. As a result, it was found that the micro Fourier transform infrared spectroscopy was one of the useful methods to evaluate oxidation (Fig. 2) and the X-ray diffraction method
was one of the most useful methods to evaluate microscopic structure change. Also, it was conﬁrmed that chemical luminescence analysis and positron annihilation spectroscopy were new methods that were highly sensitive indetecting oxidation and microscopic structural changes, respectively.

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Nuclear Technology
EDM
notch
人工欠陥
d=20mm
深さ20mm

超音波探傷による測定結果(mm)
Me asured depth by UT (mm)Defect
欠陥開口部

欠陥先端
Defect Tipcorner302520

表 Surface
面1510

開口部エコーCornerecho

5Tip echo
先端部エコー

00510152025
人工欠陥深さ(mm)EDM no tch depth (mm)30

Fig.1 EDM notch depth sizing result
Good accuracy is evaluated for defect depth sizing by phased array UT.
(Average error: 0.92mm, RMS error: 1.58mm)

1.0

1.0

0.8

0.8

0.6

0.6

0.4

0.4

0.2

0.2

002

468

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Normalized Aging Index

Normalized Mechanical Property

Aging index
Mechanical property

012

Accelerated Aging Time (x1000 hr)

Fig. 2 Mechanical property (elongation) and deterioration index (oxidation degree) of cable insulation
as a function of accelerated aging time
Elongation of cable insulation with accelerated radiation-thermal deterioration and its oxidation degree measured by themicro Fourier transform infrared spectroscopy show dependence on accelerated aging time, and the increase in the oxidation degree and the decrease in elongation show a similar tendency. Therefore, the integrity of mechanical strength can beevaluated with the aging index on the basis of the oxidation degree.

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