KI + K2S2O8 reaction?

When solutions of KI and K₂S₂O₈ are mixed, a redox reaction occurs. I⁻ ions in KI are oxidized to I₂ solution, while S₂O₈²⁻ ions are reduced to SO₄²⁻ ions. The solution turns brown due to the formation of brown I₂ solution.
2 I⁻(aq) + S₂O₈²⁻(aq) → I₂(aq) + 2 SO₄²⁻(aq)

However, the rate of the above reaction is slow, and it needs a period of time to complete. When the reaction mixture is pure in 100 mL of water with ice in it, the reaction is practically stopped. This is because the reaction mixture is well diluted and the temperature is low (0°C).

My best guess is a thermo nuclear explosion