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TMI can withstand severe flooding, according to NRC

By Dan Miller


Posted 11/29/17

Three Mile Island has adequate plans and equipment in place to withstand a severe flooding event, according to the Nuclear Regulatory Commission.

TMI and all other nuclear plants in the United …

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TMI can withstand severe flooding, according to NRC


Three Mile Island has adequate plans and equipment in place to withstand a severe flooding event, according to the Nuclear Regulatory Commission.

TMI and all other nuclear plants in the United States in 2012 were ordered to re-evaluate their risk to earthquakes and severe flooding following the disaster that occurred at the Fukushima nuclear power plant in Japan in March 2011.

The agency released the information about TMI on Tuesday morning.

The accident at Fukushima began with an earthquake which was followed by flooding from a tsunami.

The post-Fukushima evaluation of flood risk at TMI was done by TMI owners Exelon and then submitted to the NRC to be evaluated by the commission.

The NRC is “satisfied” with the finding by Exelon that adequate protections are now in place for TMI to “endure a severe flooding situation,” NRC spokesman Neil Sheehan told the Press & Journal on Tuesday, Nov. 28.

Exelon spokesman David Marcheskie emailed this statement to the Press & Journal on behalf of the corporate owner:

“Well before the events of Fukushima, TMI was protected from flooding by watertight doors, elevated equipment and specially engineered flood barriers. Since that time we’ve made significant investments to enhance pumps, hoses, and diesel generator housings to make a safe facility even safer. The recent re-analysis and the NRC’s approval of it confirms that TMI is well protected against flooding.”

TMI has invested nearly $40 million in upgrades and enhancements since Fukushima, Marcheskie added. The various improvements include flood mitigation, but go beyond just that, he noted.

The NRC expected when it ordered the post-Fukushima analysis in 2012 that the entire process would take about five years to complete for all the plants in the country, Sheehan said.

The NRC also required that TMI and all other nuclear plants conduct a similar post-Fukushima analysis to assess their ability to withstand an earthquake.

Exelon conducted an earthquake analysis regarding TMI and submitted its findings to the NRC.

Sheehan in a follow-up email told the Press & Journal that “the NRC staff concluded that no further response or regulatory action was required by the company (Exelon) based on the results of the re-evaluation.” The earthquake assessment is completely separate from the flooding assessment, he noted.

While earthquakes are possible in south central Pennsylvania, Sheehan acknowledged that, historically, flooding poses the far greater risk to structures in this region.

Tropical Storm Agnes — generally considered the benchmark when it comes to a flooding event here — occurred in 1972 and predates TMI.

Unit 1 of TMI came online in September, 1974; and Unit 2 came online in 1978 — not long before Unit 2 was disabled by the March 1979 accident at TMI, Sheehan noted.

Numerous flooding events impacting the Susquehanna River and the Middletown area have occurred since TMI came online, but none of them have affected the plant, Sheehan said.

Nevertheless, what happened at Fukushima prompted the  NRC to conduct a renewed analysis of the risk from flooding to consider factors that had not been considered before.

Regarding TMI for example, Exelon “had to demonstrate that (the plant) could not only withstand a typical flooding on the Susquehanna, but also an upstream dam failing, local intense precipitation, and other conditions. Because of (TMI being) on an island (Exelon) needed to do a more focused evaluation,” Sheehan said.

Separate from this flooding analysis, some changes had already been put in place at TMI since the Fukushima disaster.

A berm has been raised at TMI, and additional plans to cope with flooding are now in place at the plant, Sheehan said.

Additionally, NRC following Fukushima ordered TMI and all other plants to obtain equipment such as emergency diesel generators and batteries so that the plant would have a backup source of electricity in the event of a power loss.

At Fukushima, the earthquake knocked out the power grid around the plant, and the backup power sources were then knocked out by flooding from the subsequent tsunami.

“Fukushima had workers scrounging around the parking lots trying to find batteries” to somehow restore power, Sheehan noted. “We never want to see that in a U.S. plant.”

The loss of power led to meltdowns at three nuclear reactors at Fukushima.

The entire text of NRC’s focused evaluation for the risk of flooding at TMI can be found at the NRC website at https://www.nrc.gov/reading-rm/adams.html