Yes, and we've done calculations to look at the incremental costs of having the nuclear island completely underground. For a two-unit plant, which would be 360 megawatts at $5,000 a kilowatt, you're talking about an overall investment of about $1.8 billion. The extra cost for digging that hole is about $9 million, so it's not much. It isn't just a straight-down hole, but it necks down.
The key here is to ensure the safety performance of this thing against extreme events and extreme threats without having to have a lot of infrastructure around it, and having a high degree of confidence that the technology and the reactor are protected in a very good way.