変形燃料束流力振動試験(第2報) : Porosity/Ringの影響

Flow induced vibration of a deformed fuel pin bundle (2); Effect of porosity/ring on pin vibration

大坪 章*; 阿部 定好*; 井口 達郎*

not registered; Abe, Sadayoshi*; Iguchi, Tatsuro*

「常陽」MK―1燃料被履管に発生したウェアマーク(擦り痕)の発生原因の主因子の一つとして,燃料ピンの流力振動が考えられている。本試験では,流力振動に及ぼす燃料束のPorosity/Ringの影響を調べるため,「常陽」MK―1燃料束の2倍のPorosity/Ringをもつ試験体を用いた。「常陽」MK―1燃料束体系での第一報の試験結果と比較して,次のような事が明らかとなった。炉内照射中の燃料束の周辺ピンの熱湾曲を模擬した変形ピンを用いた変形燃料束では,Porosity/Ringの影響よりも変形ピンの拘束効果の方が大きく,燃料ピンの振動は今回の試験でも観測されなかった。変形ピンを含まない正常燃料束試験では,Porosity/Ringを2倍にした影響は大きく,前報にくらべて大きい燃料ピン振動が観測された。

The flow induced vibration of a fuel pin bundle is considered to be one of the major factors causing wear marks observed on "JOYO" MK-I fuel claddings. This experiment was performed by using a fuel pin bundle having porosity/ring of twice as large as that of "JOYO" MK-I fuel assembly, in order to study the effect of porosity/ring on the flow induced vibration of pins. The following was clarified from the comparison between the results of this experiment and the previous one using the test bundle of porosity/ring equal to that of "JOYO" MK-I fuel assembly. Any significant fuel pin vibration was not observed in the deformed bundle test in which the deformed pins were lined up on the outermost row simulating thermal bowing of the fuel assembly irradiated in reactor, because the restrain effect of the deformed peripheral pins was larger than that of porosity/ring. The similar result ,had been obtained in the previous experiment. In the test of normal bundle without any deformed pin, the fuel pin vibration was much larger in this experiment than the previous one. This experimental result showed that the effect of porosity/ring on the vibration was significant in the normal bundle.