The radio isotope used to control blood Cancer (leukaemia) is

Phosphorus-32 is a radioactive isotope of phosphorus. It is used in the treatment of leukemia. It is also used to diagnose leukemia.

Cobalt-60 is a radioactive isotope of cobalt. It is used in the treatment of cancer. It is also used to sterilize medical equipment.

Iodine-131 is the most commonly used radioisotope for the treatment of blood cancer (leukaemia). It is a beta emitter, which means that it emits beta particles when it decays. Beta particles are high-energy electrons that can damage cancer cells. Iodine-131 is taken up by the thyroid gland, which is located in the neck. The thyroid gland is a target for leukaemia cells, so Iodine-131 can be used to kill these cells.

Sodium-24, phosphorus-32, and cobalt-60 are also radioactive isotopes that can be used to treat cancer. However, they are not as commonly used as Iodine-131.