Yes, China has 40 GWe of nuclear power coming on-line in the next 5 years. The United States currently has 97 GWe of nuclear capacity, and China currently has 13 GWe.
But China is also building 40 GWe of coal plants each year.
This is what happens when you take 500 million peasants and turn them into urban factory workers within a period of 30 years. Demand grows so quickly that even the world's largest nuclear plant construction program will only account for a fraction of demand growth.
So, not that that matters for the absolute pollution, but if that >50% is correct, their mix will improve.
Also, they try to build those plants far away from cities. That, hopefully, will spread pollution.
That PDF also states that those plans may not be implemented, as a) coal companies lose money in China because the government fixed electricity prices and b) the public doesn't want their pollution.
On the negative side, their absolute pollution will likely go up, and the gap with the western world will go up even more (elsewhere, new coal plants will often replace older, more polluting ones)