主题：起个头：核电站事故与我们的对策 -- 王二狗

My mistake, 238Pu is not a good nuclear fission material, therefore it is not used in nuclear weapons.

One big difference between 238Pu and 239Pu is that 238Pu does not emit significant amount of gamma ray. Due to alpha-ray's weak penetrating ability, it is suited for being used as power source of radioisotope thermoelectric generators or heaters for spacecrafts.

Thanks for the correction!