The existing regulatory structure was designed specifically to stop nuclear power plants from doing things like running all the sets of redundant control and monitoring wiring through a single narrow space, filling that wiring space with flammable foam, and then testing the foam for air leaks with a candle when the plant was in operation. (This is not a hypothetical example - it actually happened in the US during the golden era of nuclear power, indeed I think it may have even been standard practice across multiple plants, and it very nearly caused a serious accident when the inevitable happened.)

I know the Trump administration has tinkered with adding more flexibility to the regulations covering fire protection and safety in nuclear plants in order to try and encourage more economical new nuclear power plants with modernized designs, but it hasn't really helped because the tradeoff for being able to deviate from the rigid rules is that the companies building them have to do a bunch of work to show that their new designs achieve the same safety goals.