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The basics of how a nuclear power plants works plus a diagram of its radioactive coolant and non-radioactive steam components
Figure 1 – Typical Pressurized-Water Nuclear Power Plant Credit: Enformable
In a Pressurized Water Reactor type nuclear power plant, the energy (in the form of heat) from the reactor is transferred in a two-step process to create steam, which is then transferred by piping where it is used to spin a turbine (bladed shaft), which also turns a generator, which produces electricity.
· In the first step or radioactive loop, core coolant liquid is heated by the radioactive fuel rods inside the reactor vessel. This very hot radioactive coolant is then pumped under very high pressure into the steam generator where it travels through the inside of thousands of separate thin walled steam generator tubes, which lowers the coolant’s temperature before it is pumped back to the reactor to recirculate through the loop all over again. This forms a closed loop system, which contains the majority of the radioactivity of the nuclear power plant.
· In the secondary or non-radioactive loop, water is pumped into the lower portion of the steam generator, which then flows upward around the outside surfaces of all the very hot metallic tubes (called U tubes because of their shape). Nearly 10 thousand tubes are very tightly packed together inside each steam generator. These tubes, each about the diameter of a penny and not as thick as a dime, transfer their heat to the non-radioactive water/steam mixture, turning it into almost pure steam. The steam then exits the top of the steam generator and is transferred by a pipe (called the main steam line) to spin the turbine. Turning the turbine cools the steam back into a water/steam mixture, which is further cooled and condensed with ocean water. The secondary loop water is pumped back to the steam generator to recirculate through the non-radioactive loop all over again.
Important Note: The steam generator’s tubing wall thickness is thinner than a dime (0.043 inches) to help transfer heat, but it also serves as a vitally important boundary between the radioactive coolant circulating inside the tubing which must remain separated from the non-radioactive water/steam mixture which circulates outside the tubing. A leak, crack or worse, a complete failure of one or more of any of the tubes inside the steam generator would allow highly radioactive coolant to mix directly into the non-radioactive water/steam mixture which would then escape into the environment. Additionally, should a main steam line break or other similar problems occur, the rapid loss of core coolant that is needed to constantly cool the radioactive fuel rods in the reactor could lead to a catastrophic meltdown of the entire radioactive reactor core.
SCE’s claims that SONGS Unit 2 Steam Generators are Safe for Restart are Erroneous because they can create a Fukushima-type nuclear meltdown in Southern California
Nuclear Power Accidents
Nuclear power plant accidents include Three Mile Island (1979), Chernobyl (1986), Fukushima Daiichi (2011), and San Onofre Nuclear Generating Station (SONGS) Unit 3’s near miss nuclear disaster (2012). After the SONGS 3 Replacement Steam Generators (RSG’s) tube leakage, additional testing found that 8 tubes failed in-situ testing and could not sustain their structural integrity during a main steam line break (MSLB). Additionally, one RSG tube was discovered with 90% through wall wear in Unit 2 and the structural integrity of thousands of damaged tubes in both SONGS Units 3 and 2 RSG’s has been termed by NRC as a “very serious” safety issue. Now the safety of SCE’s RSG design is being questioned by the public because these almost new SONGS RSG’s now have more damaged and/or plugged tubes than all the rest of the US power plants combined, which is unprecedented in the history of the U.S. Operating Nuclear Fleet. Chart Credit: sanonofresafety.org;
· Unit 3: 1 Tube leaked core coolant/radiation, 8 Tubes then failed in-situ testing, 1600 tubes damaged, 807 tubes plugged - WORST US Record!
· Unit 2: 1 tube found with 90% wear, (almost core coolant/radiation leak/failure), 510 tubes plugged all tubes still not fully examined! 2nd WORST US Record!
Copyright December 12, 2012 by The DAB Safety Team. All rights reserved. This material may not be published, broadcast or redistributed without crediting the DAB Safety Team. The contents cannot be altered without the Written Permission of the DAB Safety Team Leader and or the DAB Safety Team’s Attorneys.
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