SWAT-1放出系非予熱条件下での熱過渡試験 : 大リーク・ナトリウム-水反応試験(第13報)

Thermal transient tests of non-preheated pressure relief line of SWAT-1; Large leak sodium-water reaction test (No.13)

田辺 裕美*; 高橋 憲二郎*; 綿見 正和*; 大後 美道; 佐藤 稔*

not registered; not registered; not registered; Daigo, Yoshimichi; not registered

高速増殖炉の蒸気発生器内で大リーク・ナトリウム-水反応事故が発生した場合,予熱されていない放出系配管で生じる可能性のある熱衝撃・配管閉塞の問題について,大リーク・ナトリウム-水反応試験装置SWAT-1を用いて実証試験を行なった。以下にその結果を示す。注水試験は4回実施し,"もんじゅ"SGとSWAT-1反応容器との内径比換算で伝熱管破断数DEG以上の大注水率のもの2回,同1DEG以下の小注水率のもの2回であった。放出系配管内での流動様相は,大注水率の場合,初期にナトリウム単相流に近い低ボイド率流が0.20.3秒続いてその後ボイド率0.9程度の高ボイド率流に変わる。これに対し低注水率の場合は,初期12秒にナトリウムの層状流が見られ,その後水素ガス単相流となる。大注水率の場合,極く初期を除けば熱流束の最大値は1106〔kcal/m2・h〕,熱伝達率の最大値は3104〔Kcal/m2・h・〕である。小注水率の場合は更に小さい値となる。熱応力による歪量は,大注水率の場合8001,500Strain程度で上記熱伝達率を用いた計算結果と良く一致する。ナトリウム凍結によって配管閉塞の起こり得る可能性はSWAT-1試験装置の体系ではほとんど考えられない。

When a large leak sodium-water reaction accident occurs in a steam generator of LMFBR, pressure relief piping might be received thermal shock or blocked by frozen sodium, if it is not preheated. Then, the thermal transient tests were performed using the large leak sodium water reaction test rig SWAT-1. The results are summarized as follows; (1)Four tests were executed. The water injection rate of two tests was equivalent to that of several DEG (double-ended guilotine) failure of heat transfer tubes considering the difference of evapourator inner diameters between "Monju" and SWAT-1, and in other two tests the injection ratio was equivalant to less than that of 1 DEG. (2)Flow pattern in the pressure relief piping of two large injection rate tests was as follows, void fraction was as low as that of sodium single-phase flow in its early stage of 0.20.3 sec., and rapidly increased to about 0.9. In case of the small injection rate tests, the stratified flow had continued for 23 sec., it was followed by hydrogen gas single-phase flow. (3)In the large injection rate tests the maximum value of heat flux was about 110[kcal/(mh)], and that of heat transfer coefficient was 310[kcal/(mhC)] except in its very initial stage. In case of the small tests, they were lower. (4)In the large injection rate tests, stain of outer piping surface was about 8001,50010, which agrees with the calculation using above value as heat transfer coefficient. (5)Possibility of blockage by frozen sodium is seemed to be very little in SWAT-1 test rig.