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View Diary: SONGS: Safety Engineer Blows Whistle (25 comments)

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  •  I can't understand (4+ / 0-)
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    tgypsy, Joieau, randallt, chimene

    this 70% nonsense. Either the damn plant works or it doesn't.

    How will running a plant a partial power overcome the obvious flaws in the steam generator?

    •  The tubes are so damaged, (9+ / 0-)

      and so many of them are plugged, that they're figuring 70% power will be 'easier' on 'em. It shouldn't be allowed, but probably will be. Good luck to those stuck in the danger zone.

    •  An Attempt To Answer Your Question (4+ / 0-)

      At 100% power the flow of steam is maximum producing the maximum amount of turbulence and stress on the tubes. The problem with the Unit 3 Steam Generators is that over the time they ran after SG replacement, the tubes were vibrating so much that they were banging against each other causing the damage.

      Unit 2 operated that entire time at the same power levels with very little damage to the tubes.  Clearly something is different between the two units - something in the construction of the U3 Steam Generators was not right leading to the problems there.

      They believe that U2 does not suffer the same problem that U3 has, but how to verify that?  By lowering power to only 70%, they believe  that damage will not happen to the U2 tubes.  The plan is to run it a few months at 70% and then shut down and go in and inspect to see if damage is occurring.

      The plant is able to be operated safely during this time period.  They do not expect any tubes to fail, but should a tube failure occur, is should not be a big deal unless it happens to a lot of tubes or happens repeatedly.  This is a reasonable approach to verifying that Unit 2 steam generators are fine and do NOT suffer from the same flaw that has beset Unit 3.

      Someday soon Republicans are going to drown Grover Norquist - in a bathtub.

      by nuketeacher on Mon Apr 29, 2013 at 06:27:53 PM PDT

      [ Parent ]

      •  What could possibly go wrong??? (4+ / 0-)
        Recommended by:
        Joieau, Sandino, Creosote, flowerfarmer

        "We refuse to fight in a war started by men who refused to fight in a war." -freewayblogger

        by Bisbonian on Mon Apr 29, 2013 at 06:41:45 PM PDT

        [ Parent ]

      •  This may be helpful (5+ / 0-)

        to get a good overview of the issues -

        NRC: Special Oversight

        Based on the initial 100-percent tube inspections, the licensee completed tube plugging and staking (internal cable support of select plugged tubes) of 192 tubes total: 98 in steam generator 2E088 and 94 in steam generator 2E089.  Of the 192 tubes a total of six tubes, four due to retainer bar wear and two due to anti-vibration bar wear, required plugging because they exceeded the plugging criterion of 35-percent tube wear.  Of the remaining 186 tubes, two tubes were preventatively plugged due to anti-vibration bar wear (<35%) and all tubes adjacent to the "retainer bars" were plugged as a precautionary measure due to unusual wear at that location. As a result of information learned from the Unit 3 cause evaluation and expert panel screening criteria, a total of 323 additional tubes, located in similar areas of tube-to-tube wear in Unit 3 steam generators, were plugged in the Unit 2 steam generators including two tubes with indications of tube-to-tube wear of 15%. The total plugging for Unit 2 was 207 tubes in steam generator 2E088, and 308 in steam generator 2E089.
        Did you catch that? 207 plugged tubes in one, 308 plugged tubes in the other. The SGs for unit 2 are suffering some of the very same "unusual" wear as unit 3's SGs suffered. They've been in operation for all of one [1] cycle. Basically, they're junk.
        •  Context matters (0+ / 0-)
          Physics Forum


          This interim Part 21 is in regard to San Onofre Nuclear Generating Station, Unit 2, Steam Generator replacement.

          "During the first refueling outage following steam generator replacement, eddy current testing identified ten total tubes with depths of 90 to 28 percent of the tube wall thickness. Some of the affected tubes were located adjacent to retainer bars. The retainer bars are part of the floating anti-vibration bar (AVB) structure that stabilizes the u-bend region of the tubes.

          "Other tubes in the two steam generators had detectable wear associated with support points elsewhere in the AVB structure. Each steam generator has 9727 tubes with an 8 percent (778 tubes) design margin for tube plugging.

          So, in Unit 2, there were no tube failures. There were 6 that were plugged due to the criteria for undue wear. The remaining plugged tubes were plugged because they were in locations which had experienced problems in Unit3, not because they showed indications of undue wear themselves - in other words, a preventative measure. The total number of plugged tubes in one SG - 207 - represent 2.1% of the tubes. The total in the other - 308 - represent 3.2% of the tubes. Meanwhile, the number of tubes with problematic wear - 6 of them total - represent 0.03% of the nearly 20,000 total tubes in the two SGs..

          Your claim that they are junk is quite an extreme statement given the actual facts. From the above, it would appear that nuketeacher's description  was accurate. The problems found in Unit 3 were largely NOT found in Unit 2. DESPITE THIS, they plugged hundreds of tubes in Unit 2's SGs as a precaution because they were in the same relative locations as tubes which had problems in Unit 3. And now, you are using their precautionary actions, and associated number of tubes - numbers that sound big and scary when taken out of context -  to proclaim that Unit 2 is suffering the same unusual wear as Unit 3. This is simply not true. Furthermore, regarding their safety to restart, they are still well within their operating margin and could, in fact, plug 3 to 4 times as many tubes and still be within margin.

          Looking at the raw data, (from your NRC link), is more revealing. In Unit 3 there were a total of 134 tubes which had through-wall wear of 50% or greater as compared to 2 tubes in Unit 2. There were an additional 247 tubes in Unit 3 which had between 35% and 50% through-wall wear as compared to 4 tubes in Unit 2. So, 6 bad tubes in Unit 2 versus 381 bad tubes in Unit 3 ... yeah they're about the same. Uh huh.

          Free: The Authoritarians - all about those who follow strong leaders.

          by kbman on Mon Apr 29, 2013 at 10:46:52 PM PDT

          [ Parent ]

          •  Tell me how two identical pieces of equipment (1+ / 0-)
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            manufactured at the same time, in response to the same purchase specifications can have such differing performance results after two years.

            Basically, you are trying to convince us that the Unit 2 steam generator is a sound piece of equipment, while the Unit 3 steam generator was defective.  Please explain how that is possible. Something is rotten at MHI for there to be such differing results.

            And we're supposed to trust MHI that SONGS can run Unit 2 at 70% power as a safe alternative?

            •  First of all, there are four pieces of equipment (0+ / 0-)

              two steam generators per plant. They are not identical. One of the theories regarding the damage has to do with the resonant frequency of the overall system. In Unit 3 they had very tight tolerances for the holes in the stabilizer bars which the tubes pass through.  In Unit 2 the specs were looser. It appears that the tighter specs for Unit 3 "tuned" the tubing system and stabilizing supports to a resonant frequency that responded to the flow of steam when at full power.

              That same resonance is not present in Unit 2. This is likely why there were such dramatic differences between the test results in Unit 2 versus Unit 3. And furthermore, regardless of WHY there were such major differences between the SGs at the two units, those differences exist - 381 to 6. To assert that the unit with 6 problem tubes is identical to the one with 381 problem tubes is highly inaccurate. The fact that they have taken those tubes out of service in Unit 2 which were a problem in Unit 3 means that, even if the same problem appeared in Unit 3, it would not be a risk factor during operations. The fact that the total number of tubes taken out of service is on the order of 1/4 to 1/3 of the number that may be taken out of service strongly suggests that there are no safety concerns with operating the SGs at Unit 2.

              BTW - my sister and her family live in the LA area. If they were to restart SONGS II it would not bother me or concern me in any way regarding their safety - seriously.

              Free: The Authoritarians - all about those who follow strong leaders.

              by kbman on Tue Apr 30, 2013 at 10:50:56 AM PDT

              [ Parent ]

      •  Why would the Unit 2 steam generator... (7+ / 0-)

        ... be any different from the Unit 3 steam generator?  These replacements were both manufactured at the same time by Mitsubishi. Presumably they had near identical purchase specifications.

        If there is a fatal flaw in Unit 3, then it is likely in Unit 2 the same. These pieces of junk failed after less than 2 years of service.  It's insane to operate it at 70% load "as a test".

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