TO ERR IS HUMAN

The tragedy in Japan reminded me of a glitch at the Diablo Canyon nuclear power plant.  It has two reactors and after it was licensed, a problem was discovered in reactor #1.  From LexisNexis:

'MINOR' CHANGES FORSEEN AS RESULT OF MIXUP AT COAST NUCLEAR PLANT
BYLINE: By ROBERT D. HERSHEY Jr., Special to the New York Times
October 10, 1981, Saturday, Late City Final Edition

Officials of the Pacific Gas and Electric Company said today the company's Diablo Canyon nuclear plant in California required only ''minor'' modifications to remedy a construction error discovered last week and that those were expected to be completed by the end of this month.

The $2 billion plant, which has been under attack by antinuclear groups because it is near an undersea earthquake fault, has been plagued by repeated delays since construction started in 1968. Fuel was being loaded for low-power testing last week when workers found that some piping supports were incorrectly placed so that they might not be able to meet the requirements for withstanding an earthquake.

Company officials disclosed that 691 of the 2,745 pipe supports in the containment area of the No. 1 reactor required study to determine whether they were under strength. As of yesterday 27 needed to be buttressed and company officials estimated that this number would rise to 72 when the review was completed. A spokesman said the repairs would probably be made by welding additional iron bars to the piping support system.

The blunder , which the company said was its fault rather than that of outside consultants, came about when the diagram for the two mirror-image reactors was reversed.

The plans for the No. 1 reactor were used in the No. 2 reactor and vice versa. The mixup was not the result of failing to ''flip'' a single transparent blueprint, as an employee of the utility mistakenly told reporters earlier. Rather, there were separate blueprints for each reactor but the wrong ones were used. Company officials said that the mixup was not noticed because the reactors were built about two years apart.