Hacker News Reader

Comment by corty | Hacker News Reader

The containment isn't the most expensive part, the pressure vessel is. Single forged part of some magic stainless steel alloy able to withstand 300bar at 500K and high neutron flux costing a billion or more. Gen4 reactor designs try to do without that by having the actual core non-pressurized, e.g. in molten-salt reactors or pebble-bed reactors. The other idea is making a loss-of-coolant-accident harmless, thereby getting rid of the necessity to have too many redundant ultra-expensive cooling systems (current EPRs are at quadruple-redundant...). The problem with regulation there is that those novel designs are currently still regulated based upon the aforementioned PWR/BWR reactor designs (so your coolant system has to have X amount of redundancy, the reactor vessel must withstand Y amount of pressure, ...), forcing unnecessary cost that isn't necessary because the possible accidents and conditions are completely different.

View on HN

> The containment isn't the most expensive part, the pressure vessel is.

I was referring to the expense introduced due to regulations. Or are you saying that one could make a much cheaper pressure vessel without those pesky regulators?

Gen IV reactors have the property that they aren't available now, and won't be available and matured anytime soon. Many also have aggressive operating profiles that will stress materials. No one is going to want to buy a MSR only to discover corrosion limits its lifespan to 20 years. So, getting them to a state that customers would be comfortable with will take a long time.

Gen4 reactors are an active area of research, but it isn't like there are none. Some concepts go back decades, as do prototypes like THTR-300 that actually produced power for a few years.

That stress will limit the lifetime of a reactor is true for any reactor. Any BWR or PWR has a maximum lifetime set by the pressure vessel, because that is the one single component you can neither fix nor exchange. As soon as mechanical stress, neutron embrittlement and temperature gradients have done a certain amount of damage, the plant is finished. But even for currently operating reactors, we are still exploring how long that will take exactly, by regularly checking the materials in the running reactors, because no one ran a prototype for 40 or 60 years. And you cannot compare with other models of reactors, because they are usually very different in operating parameters, materials and design.

We currently do not know what a few decades of operation will do to a MSR vessel, but the point is that trying it out has been hindered for a long time by regulations that are not fit for that type of reactor. So you arrive at a costly chicken and egg problem, where a regulator asks for a proof (ideally a proof by pointing at a working prototype with a few decades of maturity) just to allow you building a prototype.

THTR-300 is an example why there's a large gap between concept and commercially proven reactor design. The THTR-300 was a huge disappointment, with major, showstopping design flaws. The Gen IV concepts being bandied about now will have to go through a long, drawn out process of technical maturation before any large scale deployment can occur.

The companies doing serious work on molten salt right now, are mostly in Canada because of regulatory structure. They had to develop their project with very limited funds and totally uninterested governments (until recently in Canada).

Yes they are not available now but they could be available in this decade and by the 2040 you can build 100s if you really actually put some resources behind it.

These designs are infinity easier to scale then what France did.

Of course that kind of planning is not really how the US does things but at least they could seriously get behind a few prove of concept projects. Currently its not even possible to get a non PWR reactor regulated at all.

2040 is 19 years away. In the last 19 years PV module cost per W (adjusted for inflation) declined by a factor of 25.

I think the potential for cost reduction in nuclear is far bigger.

There is no inherent reason why a small reactor couldn't be mass produced. In a perfect world you would have a factory spitting out finished nuclear reactor every day.

Transport it to a site, drop it into a concrete hole, connect the salt loop and plug in the refiling pipe.

It really shouldn't need much operation other then planning how much to refuel.

We have gotten used to thinking of nuclear reactors as these civil engineering projects with large costume one of designs, but there is no inherent reason why you can't produce them at comparable to speeds other items of that size are built. Really once you have the material qualified a nuclear reactor is in some ways simple then a rocket engine or an airplane.

The problem in days world is that you need to get threw regulation (in the US factually not possible, and requires complex engagement with every countries regulatory scheme) and then you need enough costumers that you can actually invest in the assembly line.

Reply on news.ycombinator.com