Why does the US (and Japan) refuse to build true fail-safe nuke plants?

A knowledgeable reader writes:

Looks to me like the nuclear industry is set for another 25 year set back. The fundamental problem here is not the technology, its the lying.

All told I spent six years in nuclear physics and high energy physics labs, and discussed nuclear power with many of the physicists.

As for the current situation in Japan, depending on who you believe there is no problem or we are on the verge of a meltdown. The fundamental problem is that the Japanese nuclear authorities have lied in the past (as have the UK authorities).

So it comes down to what the source of the hydrogen that was vented is. Whether it is the water molecules disassociating or the zirconium casing round the rods reducing the water. In other words a metal fire. They burn under water as most metals are above hydrogen in the reactivity series.

That in turn will depend on whether they have managed to fully insert the control rods or not. That should be easy in normal operation, but what if the earthquake damaged the core?

As an engineer I know that the Japanese designs are not 'fail safe' as the term is understood outside the nuclear field. If the designs were in fact fail safe the loss of the cooling system would not cause a safety problem. What they have is a fundamentally unsafe designs with a series of safety controls intended to allow a shutdown. Despite redundancy, the controls have a common failure mode (vulnerable to earthquake) so there is a major crisis.

There are nuclear designs that are genuinely fail safe. The Canadian CANDU system that uses a heavy water moderator is fail safe, If the reactor overheats, the glass tubes containing the moderator crack and the moderator drains away - failsafe.

Unfortunately and rather predictably, the designs being proposed for new nuclear stations are more of the same, the light water designs that the US power companies know how to build and operate. These are described as failsafe to gain approval, but like the Japanese system this is a convenient lie.

20% of US power comes from nuclear. The plants are old and dilapidated. The choices on offer now are to continue to operate unsafe plants, to build new unsafe plants or to stop using nuclear and burn more carbon fuels.

Wouldn't it make more sense to build some prototype reactors of genuinely failsafe designs?