"That fantastic old machine is really near the end of its incredibly good and loyal service life,"
Yes, it has sprung a leak! Can you imagine running a dangerous reactor with 7000 litres a day gushing out. Yet, such is the need for isotopes, that they keep the bailing buckets going full blast. An on-going leak makes the seismic risk that much higher, since who knows whether the bailing buckets are on seismic backup power. Besides, falling apart things always fall more apart in an earthquake.