Help. I’ve Fallen and I Can’t Get Up. That’s what we humans face as our structures weaken and organs become fragile with age. Nuclear plants aren’t much different. Bombarded with radiation, their steel structures become brittle over time. Their steam piping needs to be replaced like heart surgery on an old aorta. Their nozzles crack like hip joints. In engineering parlance, this is called the “bathtub” curve. When they’re young, nuke’s kinks aren’t worked out and they are prone to accidents--that’s the high ledge of the tub. As they mature, they tend to run with fewer problems. In middle age, they are at the bottom of the bathtub, running relatively inexpensively along with little input other than maintenance and fuel. When they age, though, they begin to climb the curve of the bathtub--with risks of slipping and falling and not getting up. San Onofre Nuclear Generating Station units 2 and 3 began operation in 1982. Diablo Canyon unit 1 was issued an operating license in 1984; unit 2 in 1985. They received 40-year operating licenses from the Nuclear Regulatory Commission, which expire in 2022 and 2024-2025 respectively. Those operating plants are past middle age in nuke-years. If there was an AARP for nukes, they’d enroll before 40. The melting Japanese reactors are 40 years old. PG&E has a pending application at the Nuclear Regulatory Commission to extend its plant’s life another 20 years, for a total 60 years. Edison’s publicly stated the same, but hasn’t made the formal federal move. Steam generators are just the first on the long list of parts that are failing on aging nuclear plants. In the last couple years, PG&E and Edison spent about $1.6 billion in replacing steam generators at their nukes. (San Diego Gas & Electric owns 20 percent of San Onofre; Edison manages the plant.) Another weak spot on aging nuclear plants are control rod drive mechanism nozzles. Questions about the integrity of these devices came to the NRC’s attention in 1993. The five-foot long nozzles are attached to the control rods in nuclear plants. Control rods are inserted in the reactor to dampen fission and get critical mass under control. Each control rod is a long pole that’s inserted in between uranium fuel rods. Each has a nozzle. This is a weak link in the reactor vessel because in order to insert and withdraw control rods, holes must be drilled into the housing that contains radioactive fission. The nozzles allow the rods to descend and ascend. They are welded in place. Pressure inside the vessel exceeds 2,000 pounds per square inch. That’s like one big colon problem. Unlike an unpleasant gas attack, if these nozzles blow on a nuclear plant--you don’t just stink up the place, you get a “loss of coolant accident.” A loss of coolant accident can result in irradiating the atmosphere. If it gets out of control, it can cause the reactor to melt down. Old nukes’ nightmares include corrosion in difficult-to-see parts of the reactor. I say “difficult to see” because they are in parts of the power plant no one wants to visit, ever--even with a white jump suit and nuclear booties. Workers can only run in and out quickly before their RAD badges show they’re getting too much radiation exposure. For instance, in May 2000, the NRC issued a 20-year license extension to the South Carolina Oconee plant after determining its owner had “aging management” programs in place. Six months later in 2001 Oconee reported that white powder--boron--had accumulated on the reactor vessel as a result of leaking through nozzles. It turns out there was extensive cracking in Oconee’s nozzles. Still, Oconee remains on line. (The biggest issue for the facility now is employees carrying weapons.) Any metal that is supposed to hold the radioactive fission inside the reactor is a general problem. As steel and carbon steel is bombarded with radiation, it becomes brittle like glass. The industry calls it “metal fatigue.” The concrete surrounding the reactor, too, gets stressed out. “As the vessel is embrittled, material toughness decreases and the probability of loss of vessel integrity from pressurized thermal shock increases,” says a feasibility study for Diablo’s license renewal. Losing “vessel integrity” would be a bad thing indeed. But never fear, the ever-cooperative NRC re-evaluated the pressurized thermal shock rule, and relaxed the criteria for screening pressured thermal shock for reactors with 20-year license extensions. A 2003 feasibility study for license extension that’s to determine whether Diablo Canyon can withstand another 20 years of use without accidents was based on equipment fatigue analyses. To carry out those tests, none other than Westinghouse--the maker of nuclear equipment for Diablo Canyon, and many other reactors--decided what stress points the analysts should consider. Westinghouse also made Diablo’s steam generators, the same over $700 million item that had to be replaced 15 years early because the company’s engineers made mistakes. Then there’s spent fuel. Every reactor has a spent fuel pool where uranium--once it’s been though fission and turned into plutonium--goes to die. Those pools are about 40 feet deep and have reinforced concrete walls four to five feet thick. The spent fuel doesn’t suffer a quick death. The spent fuel pool is more like extremely long-term hospice. The problem with spent fuel pools is that in the event they lose the water--say an earthquake ruptures the concrete--it would expose the spent fuel to air and steam. The zirconium cladding on the fuel rods would catch fire at about 1,000 degrees Celsius. It would not be a fire that your local fire department could respond to. The remaining steam feeds such a fire because the zirconium is stripping off the hydrogen from the moisture. It would be a fire that would likely rage for days while the fire department gives it a wide berth waiting for it to burn itself out. The spent fuel/plutonium just keeps coming. For one, it’s yet another design flaw that engineers didn’t make the spent fuel pools big enough to handle waste from the first 40 years of expected operation. It was also a gamble on the part of nuclear power plant owners that a permanent waste storage site would be built by the federal government to off load some of that highly radioactive fuel from the pools in time for more fuel to be crammed in. As the nuclear industry realized that the final resting place at Yucca Mountain, Nevada, isn’t going to be built, the industry began touting “dry cask storage” as an interim solution to all that waste about to burst out of spent fuel pools. Older plants, like Surry and Robinson, ran out of space for spent fuel in the late 1980s. Others, like Point Beach, Nine Mile Point, and Comanche, ran out of space in the 1990s. In California, Diablo Canyon officially ran out of room in 2006. The dry casks being used for offloading spent fuel have walls 18 inches thick. After placing the waste into them, they are planted horizontally on a three-foot thick concrete pad. For a large power plant, like Diablo Canyon, there are well over 100 of these containers. While these aging concerns--as well as seismic influence on California coastal nuclear plants--are in the hands of federal regulators at this point, the state does have influence. The California Public Utilities Commission holds the key to money. The NRC may find that all is well with post-retirement work. The state can respond that it’s simply not worth it to have ratepayers pick up the tab. The state may say that an aging nuclear plant may be a cheaper investment, but if one of those unpredictable earthquakes comes along and rattles its old steel bones, that may be more costly than keeping an old plant in business. My bet is that Japan’s regulators wish they made that “Life Alert” call last year.
