放ほう射しゃ線せん分ぶん解かい

• 放ほう射しゃ線せん

  放射線 means 'radiation' itself, while 放射線分解 refers specifically to the decomposition caused by radiation.

• 分ぶん解かい

  分解 is a general term for 'decomposition' or 'disassembly'; 放射線分解 specifies decomposition induced by radiation.

Compound of 放射線 (radiation) and 分解 (decomposition).