The Three Mile Island Unit 2 reactor, near Middletown, Pa., partially melted down on March 28, 1979. It was the most serious accident in U.S. commercial nuclear power plant operating history. Its aftermath brought about sweeping changes involving emergency response planning, reactor operator training, human factors engineering, radiation protection, and many other areas of nuclear power plant operations.
All of these changes significantly enhanced U.S. reactor safety. The full story is available here.
U.S. NRC Blog 
In case you’ve forgotten the reality of what happened at TMI, here’s a one-hour audio program to mark the 37th anniversary of the nuclear accident, including archival audio, interviews, and an analysis of ongoing health problems that correlate to the radiation release plumes:
Nuclear Hotseat #249 – Three Mile Island nuclear accident Anniversary SPECIAL – the inside story on 1st US commercial nuke reactor meltdown 37 years ago and its ongoing aftermath. Featuring: Eric Epstein of TMI Alert, Arnie Gundersen of Fairewinds, former NCR commissioner Peter Bradford, Middletown resident Mary Stamos, clips of media coverage from Walter Cronkite and the not-yet-coopted mainstream media. bit.ly/1pGEe5b
No Confidence!
Three Mile Island Nuclear Accident – 37 Years Later
Historical Audio - First-Person Accounts
Official Errors – Mutations and Deaths – Lack of Accountability
http://nuclearhotseat.com/2016/03/29/nuclear-hotseat-249-three-mile-island-37th-anniversary-special-eric-epstein-of-tmi-alert/
Yes, TMI was a wakeup call for both the nuclear Industry and the NRC that regulates them. But as we have seen, five years after Fukushima, the nuclear industry has effectively put the NRC back to sleep, thanks to ever more donations to Congress and the President. Now not only has Congress’s oversight of the NRC reduce their effectiveness, but even more R&D money is being spent on new reactors.
Since Fukushima proved that Nature can destroy any land based nuclear reactor and or its Spent Fuel Pool, any place anytime 24/7 we are now really just waiting for the next BAD thing to occur.
Also as the nuclear near miss at San Onofre, CA pointed out, even the NRC is now doing its best to downplay any engineering debacles that occur because they not only make the Operator/Nuclear Industry look bad but also the NRC who is supposed to be regulating them!
#SanOnofreGate The ongoing investigation into the multi-billion $ SCE-CPUC ripoff.
Are you kidding me we still have that mess at
San Onofre
Me, and millions of other public stakeholders in U.S. have already been burned many times over by all the incremental reductions in safety margins which NRC has allowed during the 4 decades since 1979. So whatever the ‘lessons learned’ from Fukishima were, most average citizens in America didn’t ever see the extreme investment and plant upgrades that NRC and utility CEO’s brag about …. (like the new filtered hardened vents) because our regulatory agency backed down to industry complaints about costs and hardships caused by regulatory overreach.
Translates to NRC actions based on decision making metrics applied at NRC, to protect utility/industry profit margins more than public safety margins. Public stakeholders are not stupid, and do not ‘buy the industry party line’ any more.
No disputing the fact that many improvements were made to improve safety at all nuclear power plants. Important changes were made to both prevent a similar accident in the future and to better mitigate an accident should it occur. That’s why it is so shocking and sad to see the NRC in bed with the nuclear industry in response to the devastating nuclear accident just a few years ago in Japan. Get this, the industry talked the NRC out of any actions to “prevent” a similar Fukushima accident here. Only actions to better mitigate a similar accident in the US, when it occurs, were considered. Also, even though are over 30 nuclear plants in the US that are identical to those damaged in Japan, filtered hardened vents now installed on those Japanese plants, were not required to be installed on identical US nuke plants. Today’s NRC is completely in the pocket of those they are supposed to regulate. It is not public safety first with the NRC, it is preserving the viability of the nuclear industry, at any cost, that is now job one!