I'm a retired professional interested in Fukushima, and I've read and quoted your postings about nuclear-instrument limitations ("Lessons Learned," May, July, Sept. 2011; pgs. 16, 14, 38, respectively, and available online at www.controlglobal.com).
I agree in part with your analysis about Fukushima's core meltdowns, although I'm not as judgmental regarding the actions under chaotic conditions.
There is a now-expired patent "for the detection of in-core level" using a method "to correlate gamma radiation distribution inside and outside the reactor pressure vessel with the water level." Filed in 1984 and awarded in 1987, its title is "Monitoring System for a Liquid-Cooled Nuclear Fission Reactor." Regrettably, no action has been taken in the past 25 years that would have initiated retrofit for operating water-cooled reactors.
The patent was based on decades of relevant nuclear-diagnostic R&D at Argonne National Laboratory, and that work included studies involving Idaho reactors TREAT and LOFT using neutron/gamma hodoscope systems.
The Fukushima crisis has drawn me out of California retirement, and I've been active writing articles and stimulating revitalization of gamma water-level instrumentation studies at Argonne. I've also filed a provisional patent specific to the present circumstances at Fukushima, which I believe can be improved if they retroactively install a gamma-hodoscope monitoring system for determining water levels and fuel redistribution based on correlated decay gamma radiation—even more than a year after shutdown.
Ialso hope to reach responsible DOE and NRC officials with regard to helping the Japanese at Fukushima, and considering retrofit to operating light-water power reactors.