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The Palisades’ Shutdown Explained

The Palisades nuclear plant in Michigan shut down Sunday after workers noticed steam leaking from a drain valve on the piping from one of the reactor’s two steam generators. The shutdown was uneventful, and the NRC has no immediate safety concerns with this issue.

Here’s what happened: The workers were touring the plant’s auxiliary building when they noticed the leak early on Sunday. The leak was in the “secondary” part of the steam generator, not part of the reactor coolant system.

Because the valve could not be isolated from the rest of the steam generator system, the steam generator had to be declared inoperable. The plant’s technical specifications require the licensee, Entergy, to shut down the reactor within six hours when a steam generator is inoperable. Plant operators completed the procedure by 4:30 p.m., meeting this requirement.

The NRC’s resident inspectors responded to the site, observed portions of the shutdown, and made sure there was no impact on other plant equipment.

As the plant cooled, pressure dropped within the steam system, and that stopped the leak. The steam condensed, and the water was collected. It contained small amounts of radioactive tritium, but at levels far below regulatory limits. It will be disposed of as low-level radioactive waste. After shutting down, plant operators vented steam from the same system into the atmosphere through an established monitored release path. This is a common procedure used to help the plant cool down in order to begin repairs.

Palisades remains in cold shutdown while Entergy workers repair the leaky valve. NRC’s inspectors will monitor and assess the repairs, which are expected to take a few days.

David McIntyre
Public Affairs Officer

8 responses to “The Palisades’ Shutdown Explained

  1. JT November 14, 2012 at 6:39 pm

    That’s nice. What happens if there’s a Carrington Event solar flare?

  2. Ace Hoffman November 7, 2012 at 9:10 pm

    Tritium was disposed of as low level waste? Does that mean “stored in a bucked until it evaporated” or “poured down the drain slowly so it was diluted with other waste water” or what? This was the same fluid that, while hotter, was simply vented as steam elsewhere in the operation? Was THAT also considered to have been diluted to below regulatory concern? How many becquerels got out this time?

  3. Ted Jordanobiwantedj November 7, 2012 at 8:09 am

    I don’t understand disposing of water containing tritium as low-level radioactive waste. Tritium has a half-life of less than 13 days. Most likely, the water will not be radioactive by the time it could be ‘disposed of’.

    • Joffan November 7, 2012 at 11:57 am

      Ted, tritium has a half-life of about 12.3 years. That’s why it is used to power self-illuminating exit signs.

      But I still don’t understand any need for special disposal of the slightly-tritiated water. It could just be put into the lake without any ill-effects to people or environment. Why not indeed, when the trace radioactivity is “at levels far below regulatory limits”.

      • obiwantedj November 7, 2012 at 12:55 pm

        Yes, I just looked it up. It is years not days. My mistake,

      • Moderator November 7, 2012 at 4:32 pm

        Tritium is a radioactive type of hydrogen that occurs both naturally and during the operation of nuclear power plants and has a half-life of 12.3 years. Tritium is regulated like other radioactive materials regardless of the half life. Effluents containing tritium at nuclear power plants are controlled and monitored before releasing to environment. Additionally, the quantities of radioactive material released must be reported. These releases are inspected by the NRC to protect public health and safety.

      • Moderator November 9, 2012 at 10:50 am

        When steam is condensed, contamination levels are concentrated in the resulting water form. The water is collected and stored in the tanks that are part of the radioactive liquid processing system. After water is treated through the radioactive liquid processing system, it is sampled and analyzed. If the samples demonstrate that the concentration is below the regulatory limit the contents of the tank are released through an NRC authorized discharge path that includes in-line radiation detectors as a back-up function to the sampling program. The contents of each radioactive liquid (and gaseous) release is recorded and reported annually. The NRC makes all of the reports available to public. The amount (becquerels) of tritium in this steam release is under review.

  4. James Greenidge November 6, 2012 at 3:12 pm

    Excellent report and heads’ up, but you ought make it a lot plainer and straight that this had NOTHING to do with the reactor, unlike most nuclear biased/science illiterate media outlets which don’t discriminate and throw any nuclear plant malfunction under the same ominous “Nuclear Reactor In Peril” FUD umbrella. What would the equivalent malfunction be in a oil or coal or gas-fired plant? Most people can get a grip on non-techie explanations like that.

    James Greenidge
    Queens NY

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