Hmm, wikipedia (and the ASN used as source) seems to describe this incident a bit differently. I didn't see anything about core temperature rising uncontrollably, it's slightly inaccurate to say that control of the rods themselves was interrupted (only a positioning indicator; they could've emergency shut down the reactor with the rods if they needed to; not sure why you say the control rod failsafe didn't work), and the "emergency flood" of boron which "luckily worked" was standard operating procedure. Do you have a better source?

https://en.wikipedia.org/wiki/Fessenheim_Nuclear_Power_Plant...