On: Germany shuts down seven reactors‎ because of Foku...

[ErrantX]

But evidently, the water is not the only moderator they use.

Where did you get that assumption from? Water is definitely the only moderator in this form of LWR (based on the published design specs).

[mironathetin → ErrantX]

I consulted Wikipedia about the design of german light water reactors. Bor is used in addition to water. It enables regulation of the power (in some limits). Makes sense to do that. I don't know if this is done in Japan too. It could explain, why the reaction does not stop after the water is gone.

[ErrantX → mironathetin]

Oh I see.

This is a Boiling Water Reactor, a variant of LWR's, it does not use Bor (in any form) as a day-to-day moderator.

However in this incident Boric acid is being added to the water to help with the process.

Pressurized Water Reactors use Boric acid, which is a different variant.