Quote:
Originally Posted by exitwound
Boba, your description of events matches nearly everything I've read. Indeed, the accidents were failed by the operators, not the technology itself. And it certainly IS tied to fear. The first thing people mention when they talk about nuclear power is Chernobyl, not how efficient it is, or its environmental impacts, or its cost...but what happens when it fails. And of all the plants built worldwide, there have only been two major accidents in 60 years, and ZERO deaths. It's fear of the unknown which is holding back the industry.
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That is not entirely correct the failure on the part of the operators was they didn't trust all of there indications. The technology at the time did fail commercial nuclear construction was not as strict as Navy nuclear tecnology and as a result a situation arose that we trained on as a navy nuke operator, I will try to explain without getting too indepth but here goes the cause was a valve called a pilot operated relief valve malfunctioned and lifted lowering pressurizer pressure and water level as a result and didn't close when it should have, this was due to a loss of feedwater flow and the loss of the steam generators as a heat sink. As this PORV continued to exhaust to a tank called a PRT (pressure relief tank) the hydrogen in the system came out of solution and vented from the tank and collected in the top of containment along with a sizeable steam bubble that was another hazard that could of made this all worse but the safety systems worked properly and that was taken care of. Now what the operators saw in the control room they didn't have at the time reactor vessel level indication they only had pressurizer level indication and that is rendered by having too levels to the transmitter a variable leg which indicates the level in the PZR and a reference leg which is always at a given level to give a set pressure to the transmitter but due to the conditions in containment the ref. leg was not being filled properly and began to lower as it did this the level indication in the control room showed actually a rising level in the PZR, the stuck open valve was not seen and caused the operators to open a manually operated relief valve and compound the problem, lineups were changed that added to the Loss of Coolant Accident (LOCA) and as a result they uncovered the core causing the meltdown. The problem was that there were other indications going on at the time that gave indications of the imminent problem ie. temp. indications and the operators were centered on the levels and disregarding the others. So the cause was a combination of system failure, inadequate indicators in the control room, and a lack of training for the operators. All of these aspects have been address in the industry and were called TMI mods to all the plants in the country.
Chernobyl is a whole nother story.