Mar. 28—That is Half 1 of a three-part collection.
Ten years after the March 2011 meltdown of a reactor in Fukushima, Japan, Browns Ferry Nuclear Plant officers say fixed upgrades like these they’re performing now on Unit 2, superior pc modeling and decrease seismic and flooding dangers shield the Limestone County plant from an analogous destiny.
Unit 2 is present process one of many largest building tasks because it went on-line 47 years in the past, the spotlight of which is changing the large generators that convert nuclear-generated steam into electrical energy.
The venture was timed to coincide with a deliberate refueling outage. Unit 2’s outage started 654 days after the final refueling was accomplished. The Tennessee Valley Authority has added 1,500 staff to the 1,400 staff on the plant in the course of the outage.
For the primary time in a decade, the Tennessee Valley Authority this month allowed a tightly managed media tour of the plant. The 9 reporters in attendance wore masks and have been required to have a unfavorable COVID-19 check earlier than attending. In addition they went via a number of steel detectors and have been examined by a mechanical bomb-sniffing system, the identical security procedures used for workers and contractors.
A few third of the gasoline in every of Browns Ferry’s three reactors is changed each two years, and outages are deliberate round that timetable. Through the present outage, TVA is performing an intensive improve geared toward increasing vitality manufacturing by about 7 megawatts, sufficient to energy four,000 houses. Different work in the course of the outage consists of putting in 320 new gasoline assemblies, inspecting reactor elements and conducting 14,800 work actions.
“The work that we’re doing up on the turbine deck is the biggest building venture that we have accomplished at this station on the turbine decks since building within the late ’60s and early ’70s,” mentioned Browns Ferry Web site Vice President Matt Rasmussen. “Plenty of work is occurring.”
Browns Ferry’s three items are boiling water reactors, the identical sort used on the Fukushima plant. Bombarding with neutrons the uranium packed in gasoline rods triggers a series response that generates warmth. The warmth is used to transform water into steam, and pressurized steam turns the generators to energy electrical turbines. The chain response could be stopped or slowed via insertion of neutron-absorbing management rods into the pool holding the gasoline bundles.
Through the outage there might be greater than 600 crane lifts, together with of low-pressure generators that weigh as much as 164 tons. Unit 2, like the opposite two items, has a high-pressure turbine that receives the steam first, and three low-pressure generators that generate electrical energy from steam because it loses strain.
Correctly managing outages each two years is crucial to maximizing energy manufacturing, Browns Ferry Chief Nuclear Officer Tim Rausch defined to The Decatur Each day throughout a break from the media tour, and poorly executed refueling outages trigger some nuclear vegetation to battle to take care of optimum energy manufacturing.
“On refueling, both you take too lengthy to refuel it, otherwise you’re not doing the best work the best means and if you put it again collectively and begin it up it does not run reliably for the subsequent two years,” Rausch mentioned.
Rausch, who has been chief nuclear officer at Browns Ferry for 2 years and held the identical place at non-TVA vegetation for 9 years earlier than that, mentioned a key a part of his function is to generate as a lot energy as doable. Whereas Browns Ferry’s capability has been maxed out at three,954 megawatts — sufficient to energy greater than 2.2 million houses, manufacturing vegetation and companies — he mentioned the three items have room for enchancment by way of sustaining that output between refueling outages.
To perform maximizing output, Rausch mentioned, a nuclear plant wants strong management, expert staff that work as a crew and a system that anticipates tools failures earlier than they occur.
“It’s essential have an analytical system upkeep course of that anticipates put on and tear on tools and prevents failure,” he mentioned. “You utilize your pc system, you utilize information trending, you utilize analytics, distant monitoring, all these kinds of issues.
“It is form of like Disney. You may by no means see a lightbulb burned out at Disney. What they do is that they know the lifetime of the lightbulb they usually know the curve of failure begins at, say, 75% of that lifetime. They’re going to change all lightbulbs at 75% so they do not have an sudden failure. That is the trick right here.”
Redundancy is a part of the key, he mentioned. If two pumps are wanted for a unit to function effectively, there must be 4 in place. That means one could be taken out of operation for upkeep, and even when one other fails, there is a spare. That forestalls any misplaced manufacturing time.
“We run very effectively, however we will run higher,” Rausch mentioned. “And that is our objective.”
Aggressive tools alternative has helped Browns Ferry maximize output, Rasmussen mentioned, and in addition protects it from disasters such because the one in Japan a decade in the past.
Management of river vegetation additionally performs a task in avoiding disruptions in energy manufacturing. Through the tour a helicopter hovered over the Tennessee River, simply exterior Browns Ferry. Rasmussen defined it was monitoring vegetation that had floated downstream from Guntersville. If it appeared to pose a threat to Browns Ferry’s consumption pipes, dams may very well be adjusted to hurry the vegetation’s passage.
Intensive coaching at Browns Ferry is designed to avert issues like people who beset Fukushima earlier than they begin. A lot of that is achieved via a sophisticated simulator that’s an identical to the reactors’ management rooms. Software program is tweaked incessantly to imitate efficiency of the management rooms and to replicate situations of every unit.
“This factor is modeled to look identical to the plant,” mentioned Browns Ferry’s Christopher Baxter, who’s coaching for his operator’s license. “We’ve got a gaggle of engineers and they’re continuously taking a look at information from the plant and tweaking and making changes. … What you are taking a look at is unquestionably a marvel of contemporary expertise.”
A decade in the past, a nuclear catastrophe was unfolding in Japan on the Fukushima Daiichi Nuclear Energy Plant triggered by a March 11, 2011, earthquake and tsunami. A 46-foot tidal wave swamped the turbines that have been designed to proceed pumping coolant water into the spent gasoline swimming pools to forestall warmth from rising. The tip consequence was the meltdown of three reactors, the discharge of radioactive contamination and the evacuation of 154,000 individuals. The boiling water reactors at Fukushima, full with elevated spent gasoline swimming pools, are almost an identical to these at Browns Ferry.
The catastrophe resulted in new laws in the USA.
“Our TVA fleet meets all the necessities post-Fukushima,” Rausch mentioned. “I went to Fukushima a 12 months after it occurred. I spent per week over there. It can by no means go away me.”
Rausch mentioned necessary classes have been discovered from Fukushima, however Browns Ferry doesn’t face the identical dangers because the Japan plant.
“It is superb what number of earthquakes that Japan has each single 12 months if you evaluate it to the USA,” he mentioned. “And its seismic exercise is far more vital by way of magnitude. Then if you look the place they have been constructed, on the ocean, and the way in which they have been constructed, they have been mainly constructed at sea stage.”
He mentioned the Fukushima vegetation additionally did not take acceptable steps to guard the plant from identified dangers, particularly when it got here to the peak of a flood wall designed to dam tsunami-caused tidal waves.
“Over the course of years they’d recalculate the potential tsunami, what its most peak may very well be. Effectively, they constructed the wall for the utmost peak, however then as time went on they really recalculated and mentioned, ‘The tsunami may very well be greater than that.’ However they by no means reconfigured the wall. So that they made some unhealthy technical selections. We’ve got to use all these classes discovered right here.”
Rasmussen mentioned TVA is consistently analyzing dangers primarily based on worst-case fashions, comparable to an assumption of seven straight days of rain and a number of dam failures. These fashions, Rausch mentioned, are included into design modifications.
“So if that (mannequin) resulted in the next most water stage right here due to all these a number of ‘what ifs,’ we must replace the plant in the present day,” Rausch mentioned.
Edwin Lyman, director of nuclear energy security on the nonprofit Union of Involved Scientists, wrote a ebook on Fukushima and not too long ago printed a paper vital of the Nuclear Regulatory Fee’s response to the catastrophe. He mentioned earthquakes and flooding each current dangers to Browns Ferry.
Lyman mentioned Browns Ferry’s location places it within the prime 10 of U.S. websites liable to a seismic meltdown, and since three reactors are situated there the chance is definitely larger.
“The seismic threat is comparatively excessive at Browns Ferry,” Lyman mentioned. “The NRC didn’t take any motion at any nuclear plant within the nation after Fukushima to require seismic or flooding upgrades. The NRC did require vegetation to reevaluate their exterior hazard dangers, like flooding and earthquakes, they usually discovered 96% of the vegetation really had larger flood heights than what they have been designed to guard towards, and Browns Ferry is in that class. However the NRC did not really require any plant to make any modifications.”
He mentioned Browns Ferry has redone its methodology on flooding evaluation, however the NRC hasn’t reviewed it.
“I feel they simply put a Band-Support on the Fukushima drawback with out actually fixing it,” Lyman mentioned of the NRC.
One of many classes of Fukushima is that the failure of turbines could cause catastrophe if typical AC electrical present is disrupted. Put up-Fukishima, a lot effort has been expended to make sure a dependable electrical provide to run the all-important pumps that inject water into the reactor and spent gasoline pool to forestall a meltdown when different programs fail.
Browns Ferry accomplished implementation of a FLEX (for versatile methods) system housed in a separate FLEX constructing in 2018. It comprises high-volume diesel pumps able to drawing water from Wheeler Lake, diesel turbines, batteries and towable tanks containing diesel gasoline.
— firstname.lastname@example.org or 256-340-2435. Twitter @DD_Fleischauer.