講演番号をこちらに

05pD15P
IFMIFターゲットアセンブリの健全性評価の進め方
ターゲットアセンブリの健全性評価の進め方
A Study on the Assessment Procedure for a Structural Integrity in IFMIF TA伊藤 譲，若井栄一
Yuzuru Ito, Eiichi Wakai（独）日本原子力研究開発機構
Japan Atomic Energy Agency
1. Introduction and Background
The International Fusion Materials Irradiation Facility (IFMIF)
is a plant to test effects of neutron irradiation on candidate
materials for fusion reactors. The lithium target facility provides
a neutron field for testing the materials in the IFMIF plant,
which consists of lithium target, i.e. Target Assembly (TA), anda lithium loop. One of the most critical components among theIFMIF in terms of reliability and availability is the Target
Section [1]. Therefore, the structural integrity of TA should beensured to obtain a safety operation of IFMIF. In this study, thestructural integrity assessment of IFMIF TA is focused andproposed the possible procedure for Non DestructiveEvaluation (NDE) and sampling specimen from TA as a workof engineering design under IFMIF/EVEDA (EngineeringValidation and Engineering Design Activity) project.

2. Non Destructive Evaluation (NDE)
Applicable technique: NDE would be necessary to assure thestructural integrity of TA and to verify the welded area on a lip
flange. The evaluation at the Back Plate (BP) in TA is especially
important because the results of the evaluation are relevant withspecimen sampling under Post Irradiation Examination (PIE)
activity. Inspection items contain the identification of crack andits shape and size, the hardness distribution and the wall thickness
at the BP. A Radiation Transmission (RT) test is widely usedtechnique of NDE to identification of crack and its shape. The RT
test, however, would not be applicable since the BP would beactivated by neutron irradiation because of IFMIF operation.
Therefore, the Penetrate Test (PT) or potential drop techniquewould be more appropriate instead of the RT test. Although RT
test would be applicable to the welded area on a lip flange where
the neutron irradiation would not be so severe, it is desirable tocommoditize the testing machine in order to utilize the Test Cell(TC) space and to prepare a spare testing machine. On theother hand, it is well known an Ultrasonic Testing (UT) is
widely employed to maintain the hardness and thickness of
the welded area by using the portable tester and/or portablegage [2]. Thus, UT is reasonable to estimate the hardness
distribution and the wall thickness at the BP as well as thewelded area on a lip flange.
BP at TA: Not only identification of a crack but measurementof the crack shape and size should be necessary. And then, it
is important to evaluate a crack growth through analyzing theidentification and measurement data obtained by NDE. The
hardness distribution and the wall thickness at the BP shouldbe also measured. The inspection before annual TA
replacement will be performed in order to check thesoundness of the TA and to sample specimens for PIE activity.

The in-service inspection (ISI) of TA will be also performed
with appropriate interval. The inspection after new TA
installed in TC wouldn’t be required because a quality
certification of new TA is enough.
Welded area on a lip flange: Identification of porosity, i.e. acrack, at the welded area on a lip flange will be evaluated. Thehardness distribution and the thickness at the welded area
should be also measured. The inspections before and after
in-service will be performed at the welded area on a lip flange.
Namely, the validity of welding and cutting will be checked
during each inspection to assure the soundness of lip seal
flange. That is, all over the welded area will be evaluatedbefore in-service, while Heat Affected Zone (HAZ) will beevaluated after in-service.

3. Sampling specimen from BP in TA
Although liquid lithium is not considered to be very
corrosive, some elements in the liquid lithium, such as
nitrogen, oxygen and hydrogen,are regarded as impurities. It isreported that high nitrogencontent in the liquid lithium isenhanced forming nitride
ternary compounds [3]. Thus,
BP at TA is exposed tocorrosive environment byimpurities such as nitrogen as
well as centrifugally-stress bylithium flow. Also beamfootprint area where neutron
irradiates at BP would be mostserve region for the structural
material. Therefore, it is betterto sample a specimen from BP
after the TA replaced.

4. Summary

Fig.1 BP area and lip seal
flange area

The structural inspection andintegrity assessment of IFMIF TA is focused in this study.
The possible procedure for NDE at TA and sampling
specimen cut out from TA is proposed in a design work.

References[1] IFMIF, Plant Design Description Document.
[2] Taketo Yamakawa, Journal of the Japan Welding Society,Vol. 59 (1990) No. 8, pp. 585−589.
[3] O.K. Chopra and D.L. Smith, Journal of Nuclear Materials,
Vol. 141−143 (1986), pp. 584−591.