Update on California Nuke

Operating a plant less safely than the original design requirements is promoting trouble. Fix it right or shut it down. I'm familiar with the aggressive steam generator tube corrosion issues. Operating at lower power is NOT the same as operating at lower temperatures. It reduces corrosion rate but does not change the corrosion mechanism. The only result of running a crippled plant will be something bad. Ether way this screws the nuclear industry. If nothing immediate happens it set a precedent of allowing any design flaws to be ignored with enough studies. If something does happen......

 

Is there a clear reason why corrosion got bad in the first place?

Back in the day, I took a school field trip to San Onofre and they were proud of the warm-water biota that had colonized their warm-water outflow. Bet those critters are feeling the Humboldt current now!

 

In 1971, I was in the Marine Corps at Camp Pendleton. I remember seeing the domes of San Onofre.

Bob Wilson

 

Here is a quick primer. The inner (primary) loop water heated in the reactor is at high pressure and must be kept as pure as possible to minimize radioactive contamination. (Cobalt leaching from the steel being the major offender). With the exception of Boric acid for neutron control, that is all that is intentionally added. Corrosion is entirely controlled by using materials (mostly stainless steel and zirconium) that do not react with water under any reactor plant conditions. The entire primary loop is contained in the Containment structure. The materials and chemistry has proven itself to be reliable and basically trouble free over many decades (if maintained properly).

This primary loop then boils secondary loop water in a Steam Generator. The concept here is the secondary loop is completely radioactive contamination free, piped as steam outside of the Containment structure and used to power turbines. Often these turbines are outdoors, but do have a roof over them. Since this secondary water is considered "safe", the piping, turbines, condensers, and other water handling equipment uses much cheaper carbon steels. This conventional steel/water combination has proven itself reliable over many decades in conventional power plants. HOWEVER, this requires very exacting pH, buffering, and phosphate chemical control to be put into the secondary water to keep steel corrosion at bay.

Unfortunately, the expected behavior of the pH and phosphate control turned out to not hold at the base of vertically mounted nuclear water based steam generators. The base is where:
1) The hottest water from the primary loop meets the
2) The coldest water from the secondary loop and
3) The "U-Tubes" are mated to the baseplate with very stressed steel components (after welding or press fitting)

It was assumed that gas or coal (air based) boiler behavior would match nuclear steam generator (hot water) boiler behavior. Wrong. What happened is the intense boiling at the base on the secondary side caused all the pH and other chemicals to become super-concentrated in local cells. Instead of suppressing corrosion, it was discovered (long after the plants were finished) that the chemicals were dissolving the tubes. The only (sensible) solution is to replace the steam generators or steam generator internal tubes. Unfortunately, doing this is frightfully expensive and was never planned. In fact, replacing the steam generator at Crystal River Florida was bungled and destroyed the entire nuclear containments facility. That plant is now permanently decommissioned early. Later nuclear plants were able to address this but the early plants were severely affected.

 

Very clear, FL, and not obviously above the level of chemistry / engineering that many people can understand. Makes me wonder why something similar is not in the media?

I think we are at something of a crossroads in the future of nuclear power. Could you pitch this to Scientific American (for example)? I think a semi-technical treatment of how designs and circumstance have gone wrong in the past would be welcomed. Especially in the context of how new designs use the lessons learned.

Too much of our discussions center on who likes them and who doesn't. Or, who pays and is it fair (I have been guilty of that).

 

I have to examine the whole infrastructure of a power technology to realize the true situation. Even the first generation nuclear plants were basically safe when only considering the core plant inside the containment structure. All lessons learned so far about design improvements can be applied retroactively, but oftentimes are not. The danger of nuclear power is really about what is outside of the reactor core. The two most defective things are 1) Utility Management and 2) US Government (lack of) waste regulations and planning. Virtually every serious reactor plant accident worldwide could have been avoided with 1) Competent technical leadership and 2) Competent government regulation and enforcement (even Chernobyl, an stunningly dangerous design). No amount of design brilliance will make up for operational and regulatory incompetence.

With this all said, my big picture view is solar is WAY under harnessed. I'm speaking as an Engineer, not from any environmental or political base. For the same amount of money that can be expended on nuclear, I can see a bigger return implementing solar based systems. Here is why I think that:
1) Solar legislation should focus on allowing home, corporate, co-op, regional, and national generation centers. This intensely scalable and distributable solar aspect where the "sun" is the grid can save huge infrastructure costs. The hurdle here is ENTIRELY mental. (Nuclear requires the extreme opposite--huge plant away from the loads)
2) There is nothing wrong with augmenting solar plants with backup fossil fuel power generation. It may not be aesthetically pleasing to the purist, but what a big step forward. You get the best of both worlds, reliable power and the maximum use of the cheapest fuel. (Nuclear requires long shutdowns every 18 months...if nothing bad happens)
3) Overnight power storage is about the only big technical development needed. My favorite hope is that H2 electrolysis and combining with some of the recently discovered 90+ conversion efficiencies can be scaled to industrial scales. Note this storage can be scaled and distributed just like the solar generation facilities.

Lastly, no subsidies needed, it would be economically self powering if proper legislation for restricting pollution and proper legislation for installing and allowing competition in solar at all scales were implemented.