You could overlay a circular texture over the screen centred over the explosion.
Use additive blending mode and starting at alpha 0.0 increase the alpha and the size of the texture so the effect would be a circle of light which whites out more and more of the scene as the explosion occurs.
Use additive blending mode and starting at alpha 0.0 increase the alpha and the size of the texture so the effect would be a circle of light which whites out more and more of the scene as the explosion occurs.