Produced nuclear power is simply stored as electric power. Building corporations that supply other corporations is a tricky exercise with two pitfalls. One, corporations are most optimal when using the right quality of supplies. I have posted, with supporting data, that supplies around 215 will make your corporations the most profitable. Supplying yourself some of the supplies, rather than allowing the corporation to pick and choose on the market, means that your corporations are often either overpaying for supplies or not receiving sufficiently high quality supplies to make a more profitable product.
The other pitfall is that diverting production to support other corporations often means producing a product that is in oversupply on the market. Producing a product yourself that you can readily find cheaply on the market is inferior to simply purchasing that product and producing a product that is more consistently in demand on your world and has a