As　an　important　means　of　removing　decay　heat　from　containment,　whether　the　existing　water　film　coverage　design　could　meet　integrity　requirements　needs　to　be　determined.　An　integral　experiment　is　carried　out　to　validate　this　by　adjusting　the　cooling　water　flow　and　film　coverage　associated　with　the　DEGB　LOCA　scenario.　The　results　show　that　the　current　design　could　ensure　the　residual　heat　removal,　inhibit　the　temperature　and　pressure　rise　in　the　containment,　even　the　cooling　water　flow　and　film　coverage　as　low　as　50%　of　design　values.　The　energy　balance　analysis　shows　that　the　energy　in　the　current　test　is　derived　from　the　＇condensation-conduction-evaporation＇　path　at　the　containment　shell,　which　undertakes　1/3–2/3　energy　removal　in　the　initial　stage　and　almost　all　rest　energy　removal　in　the　long-term　stage.　That　is,　the　condensation　and　evaporation　heat　transfer　process　on　the　shell　is　the　dominant　factor　affecting　the　long-term　cooling　of　the　containment　incorporated　steel　internal　containment　and　its　passive　cooling　system　via　external　surface.　©　2022