The Davis Besse event showed what complacency can do, and the ultimate responsibility that operators in a nuclear reactor power plant have. The Davis Besse nuclear facility is built around a PWR (see my prior post on rector types). One of the aspects of a PWR is that a small concentration of boric acid is present in the reactor coolant water. Boron absorbs neutrons readily and thus the boric acid has a similar effect on the reaction as control rods, but in small concentrations will act only to attenuate, rather than to stop, the fission reaction. Boric acid is highly corrosive however. Because of this, the vessel lining is made from Inconel that prevents the boric acid from literally eating away the carbon steel behind it.
During routine inspection during a refueling outage in 2002, it was discovered that boric acid had eaten almost entirely through the 6 1/2 inch thick reactor pressure vessel (RPV) head, as pictured to the right. A breach of the reactor head would have lead to a loss of coolant accident (LOCA), as massive amounts of the reactor coolant system (RCS) water would have partially filled the containment building. Although several safety procedures are in place specifically for such an event, it is a very precarious situation nonetheless.As it turns out, there are nozzles at the top of the RPV that were cracked, allowing some of the borated coolant water to leak past the Inconel lining and eating away at the carbon steel directly. So extensive was the corrosion, that only a 1/4 inch-thick stainless steel cladding, which itself was damaged, prevented a loss of coolant accident. The reactor was taken off-line for 2 years at a huge cost to the utility in addition to $600 million in repairs and upgrades of many systems. But the nuclear industry was not rocked by the material problems of the plant, but rather the underlying cause of the problems.
As it turns out, Davis Besse management had gradually shifted from high-standards of safety to justifying the minimum standards. The result was a lack of management-level oversight, a focus on short-term production over safety, ineffective use of the Operating Experience (see my prior post on this in the "business model" module), lack of sensitivity towards nuclear safety and isolationism. All of the Davis Besse management at all levels were let go as the NRC lost confidence in the utility's ability to run the plant safely. It was this culture of complacency that led to the precarious corrosion incident. In fact, the nozzles at the top of the RPV head, called vessel head penetration, or VHP, nozzles, were slated to be inspected since the NRC had seen cracks in these at other facilities. The inspections were to be done by December 31, 2001 - several months before the refueling shutdown. The management at Davis Besse did not intend to comply, and thus false inspection reports were filed. The company ended up being charged with safety violations by the NRC and paid fines in excess of $30 million. In addition, several employees were indicted for making false statements. 
What was learned at Davis Besse was that the primary focus of nuclear power must be on safety, not on the production of electricity. Procedures, even small ones, cannot be deviated from and for good reason. It is communicated at each nuclear facility throughout training, such as the training that I went through here at Fermi 2, that each of us accepts personal responsibility for the safety of the plant. That must be the first thought in every decision no matter how minuscule. All management personnel are now required to be thoroughly knowledgeable about the Davis Besse incident.Previously:
The Fermi Chronicles - Part 22: Nuclear Events - Chernobyl, 1986
The Fermi Chronicles - Part 21: Nuclear Events - Three Mile Island, 1979
The Fermi Chronicles - Part 20: Nuclear Events - Browns Ferry, Alabama, 1975
The Fermi Chronicles - Part 19: Nuclear Events - Fermi 1, 1966
The Fermi Chronicles - Part 18: Nuclear Events - SL-1 Event, Idaho, 1961
The Fermi Chronicles - Part 17: Nuclear Events - Windscale, UK, 1957
The Fermi Chronicles - Part 16: Nuclear Events - Chalk River, CAN, 1952
The Fermi Chronicles - Part 15: The Nuclear Business Model
The Fermi Chronicles - Part 14: Neutron Moderation
The Fermi Chronicles - Part 13: Nuclear Reactor Types
The Fermi Chronicles - Part 12: Generating Electricity
The Fermi Chronicles - Part 11: Worldwide Uranium Availability
The Fermi Chronicles - Part 10: Utilizing Nuclear Reactions To "Breed" More Fuel
The Fermi Chronicles - Part 9: Nuclear Fission
The Fermi Chronicles - Part 8: Neutron Interaction
The Fermi Chronicles - Part 7: Radioactive Decay and Half-Life
The Fermi Chronicles - Part 6: Atomic Structures
The Fermi Chronicles - Part 5: Nuclear Waste Storage
The Fermi Chronicles - Part 4: Radiation Types and Radiation "Dose"
The Fermi Chronicles - Part 3: Radiation Types
The Fermi Chronicles - Part 2: A week of training
The Fermi Chronicles - Part 1: The alpha post
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