An article posted at http://www.ohio.com/mld/beaconjournal/3011068.htm
.....says that "regulators said they recommended as early as 1990 that the Davis-Besse reactor vessel head be modified to allow for easier inspection and cleaning, but the modifications were never performed" ......but then quotes plant spokesman Richard Wilkins as saying that the "NRC-recommended modifications weren't done to the Davis-Besse reactor vessel head in large part because that would have meant exposing plant workers to significant amounts of radiation....the cost of making the modifications was not a factor."
It seems possible that the difficult inspections themselves "meant exposing plant workers to significant amounts of radiation," and were therefore deferred for far too long (?).
We hear all sorts of blame being heaped on plant operator FirstEnergy and on the Nuclear Regulatory Commission. But isn't a (small ?) part of the root-cause of this incident due to radiation paranoia and the strong incentive for operators to minimise total worker exposures and therefore keep such inspections to a minimum ?
How about apportioning some of the blame to those responsible for driving this radiation paranoia ? I have found from personal experience, in interacting with plant personnel, that the radiation paranoia mind-set is virtually universal (and supported by a daunting radiation monitoring and dose record keeping bureaucracy, along with all its paraphernalia).
The only difference between the public and NPP employees is that the latter think that anything over ~60 mrem is a "significant amount of radiation." This, while large populations - men, women and children - live entirely healthy, long lives in areas of the world where their annual doses of natural background radiation are in the thousands of mrem (one of which - Kerala, India - is a popular "tropical paradise" tourist destination for westerners and Indians alike...).
No doubt this state of affairs is a tribute to the success of antinuke propaganda.
Of course it does NOT excuse failure to act on the tell-tale sign of rust clogging filters inside the plant....
The situation in Europe (France) seems to be somewhat different, according to reports (see below), but I have no personal knowledge of it.
Comments anyone ?
Jaro
PS.: According to an article in last week's Nucleonics Week, "analyses indicated that the cladding could
have withstood pressures "more than double" the normal operating pressure of 2,155 pounds per square inch. NRC officials have said the maximum accident pressure would have been about 2,628 psi. The analyses, which were done with computer models, will be validated by at least two independent consultants and then provided to the NRC, Wilkins said.
He added that Davis-Besse has release valves and other mechanisms on the head, further reducing the chances that the pressure would have reached rupture-inducing levels.
A broader question is whether the NRC should have responded more aggressively to boric-acid leakage, in light of experience with that issue in France and other European countries a decade ago....
.....EDF [Électricité de France] and vendor Framatome postulated underhead temperature and operating time as the main parameters for crack initiation. But discovery of cracking at Blayais-1, a CP2 unit with a cooler head, in 1992 changed their minds - it was evident that residual stresses from welding of the penetrations also played a role in the stress corrosion cracking of alloy 600 nozzles-and the utility embarked on a program to replace all its vessel heads, using the more stress-resistant alloy 690 for the penetrations. More than half of the 54 heads have now been replaced.
.....
Boric acid was found on vessel heads in two instances, he said: in 1996 at Bugey-3 and in 1998 at Tricastin-4. In both cases, the leak came from outside the reactor vessel, at Tricastin from a flange canopy weld of a CRDM nozzle and at Bugey on a vent nozzle flange. In both cases, he said, the defects were repaired "immediately" and vessel head corrosion was "slight." EDF continues to inspect vessel head penetrations visually at every outage, and has installed detectors based on nitrogen-13 to monitor for leaks between outages, Schmitt said.
.....
French regulators continue to keep a close watch and were ready to share any information the NRC might want.
At this point, SchmJRESitt said, DGSNR considers the vessel head corrosion "above all an American problem."
<end quote>