EROI isn't as important as the energy budget over time
EROI being a single number derived from a lot of data, doesn't reflect everything you need to know about the energetics of a particular technology. One critical factor is time - not only how much energy needs to be spent, but also WHEN it has to be spent compared to when you get your Energy Return.
Ten years or so before a nuclear plant is commissioned, you have to build a large office and fill it with planners, engineers, lawyers, etc, desks, computers, lights, air-conditioning, etc. Some years later when construction starts, you need to buy lots of concrete and steel (both energy-intensive materials), and the usual load of trucks and bulldozers and construction workers (with their cars). As construction gets more advanced, the need for copper, aluminium and a whole host of exotic materials comes to the fore.
Meanwhile somebody has to be digging up uranium ore and processing it into fuel rods, and that means finding twice as much Zirconium as Uranium for the tubes, and removing the Hafnium contamination from it.
Eventually you get your reactor running and it produces a lot of energy, but it will still takes X years to repay the energy used to build it, so some of that energy has been spent (10+X) years before it gets repaid. Only then does the nuclear plant turn into an energy-positive project.
But in the meantime, you have had to make a start on several other nukes, and they will still be in their energy-negative phase, so the industry as a whole is still energy-negative. And if you go on building more new plants, as you would have to do to scale up, there is a danger that you will NEVER reach the industry-wide energy-positive stage, before the general lack of energy collapses the economy.
This applies whatever the technology, but affects low EROI and "long building phase" technologies most. More at www.peakoil.org.au/news/index.php?energy_profit.htm
