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  1. Hi Rod,

    I’m looking for information about the possibilities of creating nuclear plants that have improved load-following charateristics. In my discussions with nuclear and antinuclear advocates, the criticism often comes up that nuclear plants cannot load-follow (beyond a small degree), which makes them nothing but an obstacle to integration with intermittent renewables. Natural gas plants then are the better option while intermittent sources are increased and regional interconnectors to reduce the impact of their intermittency are built.

    Leaving the issue of how attractive that plan is aside, and noting that (at least in Europe) utilities are obliged by law to accomodate intermittent renewable power, I wonder if nuclear power plants could not be designed in such a way as to allow better loadfollowing operations, and without reducing the economic viability too much.

    Is there any documentation about this? Could you point me to it, or do a write-up on this question on your (excellent) blog?

    That would greatly help me, as this issue is currently the only one that I cannot easily disarm when it comes up in discussion.


      1. The pebble bed modular reactor as well as most high-temperature reactors can reduce their output to 40% by manipulating coolant flow. Ft. Saint Vrain was also a high temperature reactor.

    1. Since nukes are typically designed for base load operation it is difficult for them to load follow. We may have to concede the point that some gas burners are necessary and point out that the purpose of nukes is to replace dirty sources such as oil(which is also expensive) and coal.

      1. Most nuclear power plants can load follow considerably. It is not done unless really necessary because nuclear power plants are among the lowest cost producers. They’ll outcompete all other generators before throttling down. Considering climate change and air quality, those are extra reasons to keep the nuclear plants running and shut down other generation.

        Ideally, we’d be building enough nuclear power plants to meet peak daily demand and use the excess (mostly during nighttime) to charge electric vehicles. Two birds with one stone.

        1. I just read that the TVA CEO gave his corporation a D for nuclear performance.

          Is it a management issue ?

    2. All of the currently-operating plants are capable of load following, some were even designed to allow the central dispatcher to remotely raise/lower their output, although the NRC never accepted that feature and it has been removed. Generally though, they don’t load follow due to economic and reliability reasons.

      1. While currently operating plants may be able to load follow to some extent, their ramp rates are usually to restrictive to accomodate load variations such as those required to compensate for changes in wind output.

    3. Why would any competent dispatcher want to curtail the use of the least expensive method of producing electricity just to use “Wind Power?” When Wind/Solar power is actually cheaper (with no subsidies) then the designers can re-incorporate this into the nuclear power plants. (I don’t think we will see that in our lifetime.) I say re-incorporate because all B&W plants were designed (and proven during their acceptance testing) to achieve a 10% per minute (normal) power increase/decrease, and often tested out far better. Usually it was steam generator or turbine limited rather than reactor limited. The Rancho Seco B&W NPP vintage also included a 30% emergency run-back that would prevent reactor trip when a sudden power decrease was needed and, all B&W units would withstand a loss of load/turbine without reactor trip. The NRC BWR types that were at TMI after the accident did not like these features and had all PWR reactors remove these features and replace with reactor trips – as it was “Safer” (B/S).

      1. I wonder what portion of these B&W design features resulted from B&W’s involvement with the Naval Reactors? I would guess a substantial amount. Rod and Cal would likely be capable of expounding on that question, but are likely restricted from doing so too much.

    4. Of the plants currently in use, BWRs tend to be the most responsive to load following. This is done by a combination of control rod positions and altering the recirculation flow rate. PWRs in this country typically use chemical shim for reactivity control and thus are more difficult to use in load following. The French have altered the PWR control systems to allow some measure of load following that evidently is fairly responsive (“grey” control rods).

      But, as others have noted, it is usually not economical to use nuclear plants in load following, since they produce the most and lowest (incremental) cost power. Better to load follow using other generating assets, if you have them.

  2. @Joris van Dorp

    Load following is not terribly difficult – I cut my nuclear teeth on submarines and a land based prototype for a surface ship reactor. I cannot provide any technical details, but suffice it to say that both reactor designs I have operated were quite responsive to changes in power demand.

    I have written about load following several times on Atomic Insights.

    1. Oh yeah? Were you at Dig or A1W? Either way we have a little more in common, then. I did S5G for prototype (riding that bus for nine months) and D2G on CGN-36.

      And gosh I hate the LNT, having been intimately involved in Operation Tomogachi, seeing so many people suffer needlessly. Not just there, but also for want of power in the rest of the world. Applebaum, Caldicott, Jacqzco, that RMI guy. Blech.

      1. D1G – my name may still be on a plaque there because I am a lazy guy. When they told me I would work 12 hrs per day until I qualified and 8 hours per day after that, it was all the motive I needed to qualify as promptly as possible.

        1. Cool. Yes I remember the “incentives.” I qualified in four months (out of six alotted). Got some leisure after that and did a special school MTG (Maintenance Training Group I think) while waiting for a spot in ELT school.

          So you know D1G, therefore D2G which is I’m told the same thing, only they figured out how to minimize hideout and crud. California was very “clean” compared to Truxtun and Bainbridge.

  3. Rockwell has generated what is easily the best brief explanation of the radio-political issue I have yet seen. I wish I had written it!

  4. What are radiation protection standards protecting us from? The increased use of nuclear power, safe food that has been irradiated to destroy pathogens, and neutralizing both natural and synthetic contaminants for pollution control, environmental cleanup, and waste processing among other ‘threats’.

    They do this by creating unwarranted fear on one hand and raising costs on the other.

    1. How many people have died this year alone from contaminated cantaloupes? (Hint: More than Fukushima.) How many have died from contaminated meat? (Hint: More than Fukushima.) The cost of processing food with radiation would be far less than that of the inspection process alone. The food actually stays fresher longer saving even more money.

  5. I have an early 1940’s vintage military handbook explaining nuclear power to the average service man. In the section on dose limits it explains how the limit was established. Paraphrasing, not exact quote, I can’t locate the book at this time – “The total accumulated annual dose is restricted to one tenth of that amount that causes reddening of the skin. In this way you are not receiving any more damage to the body than a minor sunburn.” (Even today, this is expected and a normal occurrence in many radiotherapy procedures for cancer treatment!) It seems strange that 70 years later, today’s dose limit is just 1/10 of that amount. And I believe it has been that amount for more than 50 years! Sounds more like religion than science.

    1. Common sense says that extra precautions are most needed when we know least, and in a reasoned approach to any new technology we should start with a cautious limit which may be relaxed later, as instrumentation improves and our appreciation of it grows. The regulation of ionising radiation has resolutely gone in the opposite direction, driven by fear and mendacity.

      All things being equal, radiation limits would have been adjusted to more rational levels over time, but this is an area that has been influenced both by irrational public fear, and the actions of special interests. We have to keep in mind that there is money involved at several levels. From the incomes of professional antinuclear activists, through the industries involved with radiation protection, out to fossil-fuel interests that wish to keep nuclear power expensive, many are financially dependent on current standards.

  6. Chinese unveil ACPR 1000. As I understand it, this is a Gen III+ design that they will try to market internationally too. Their own I.P. Coupled with yesterday’s announced plan to build 1-2 prototype 100mwe SMR’s, which would also presumably have a big export market potential: Is it conceivable, that the Chinese could now spearhead an attempt to overthrow the erroneous LNT radiation theory in international nuclear regulatory bodies as a means to expand their export market? Unlike the USA and Europe, China does not seem to have pathological fossil fuel interests (nor their little green helpers, and sundry narcissists) with sufficient clout to muddy the waters.

  7. Load following…always a good topic. Rod is correct, most plants can be designed to load follow. It’s primiarly economics that they don’t. There is no reason when gov’t policy is to restrict the % of nuclear to the low double digits.

    France has high double digit nuclear generation, ergo their plants, or a need number of them, can load follow. They can even do so on direct digital control and response to drops or peaks in frequency.

    The AP1000 in fact is designed to load follow. It’s described on all their technical specs.

    If want to nuclearize generation mostly completely, toward the French 80% or even 100% we can do that. We need a large number of advanced smaller reactors, ones that can even be shutdown over night. Ones that can rapidly load change when huge sources of other generation trip offline or huge sources of load trip off line. It is not a technical problem.

    Economically. Even here times have changed. Back when the last plants came on line we needed to run the plants in baseload mode for economics. Now? Not so much. “Not running” is a very important ancillary surface generators can offer the ISO in determining rates. You think the so-called “merchant” plants get build, don’t run, and everyone is happy? No, they get *paid not to run*. this is critical in any system. The future will have contracts, as they have now for GTs, that make minimal payments to nuclear generators to follow load so they don’t go under if load is below par for a few days or weeks. It really is not an issue.

  8. All 104 LWR operating in the US are designed to load follow but it increases the thermal fatigue. It is more economical to use an old coal plant to load follow.

    New plants are also designed to load follow and will load follow in places that import fossil fuels because old coal plants are not more economical for load following.

    One difference between old nukes like ‘Rancho Seco B&W NPP vintage also included a 30% emergency run-back’ and the new ones is a 100% run-back feature. On a loss of offsite power, the new reactors (FERC requirements) will not trip on a LOOP and keep supplying house loads. This will make the grid more reliable since power plants can store power faster.

    “We’ve had three uncontrolled releases of radioactivity from serious malfunctions of nuclear power plants: Three Mile Island, Chernobyl, Fukushima.”

    Really! What uncontrolled release was there from TMI?

    I think not exposing workers and the public to fatal exposures is a good thing. When you get right down to it, I think it costs about the same to limit exposure to less than 5 Rem as it does to prevent acute fatal doses.

    It is a good thing that TMI met the standard. While Fukushima exceeded the standard by a marginal amount, it was not enough to hurt anyone.

    If we can meet standards why lower them.

    1. @ kit
      because the standards cannot be met in mining thorium so we cannot mine rare earth metals in the west. Sure you can build a plant to meet standards but the fight over Yuca is based on a false premise over the danger of radiation.

    2. @Kit P

      Unfortunately, the standard for new reactor plants is not 5 Rem. If it was, perhaps I would not be so adamant that we need to keep pushing the radiation protection community to recognize that the Linear No-Threshold dose response ASSUMPTION is a bad model that does not reflect the reality of how human bodies (not cells) respond to the damage caused by radiation.

      Instead of the standard that you and I were taught, which accepted doses of up to 5 rem per year as being perfectly safe for workers the real standard required by NRC regulation is ALARA as set in 10 CFR 50.34(a) which cites numerical examples from 10 CFR 50 Appendix I.

      Aside: Though I am not as young as Cal, I am old enough to have been interviewed by Admiral Rickover before being accepted into the Navy nuclear power program. End Aside.

      Here is a quote from 10 CFR 50.34(a)(1)
      “An application for a construction permit shall include a description of the preliminary design of equipment to be installed to maintain control over radioactive materials in gaseous and liquid effluents produced during normal reactor operations, including expected operational occurrences. In the case of an application filed on or after January 2, 1971, the application shall also identify the design objectives, and the means to be employed, for keeping levels of radioactive material in effluents to unrestricted areas as low as is reasonably achievable. The term “as low as is reasonably achievable” as used in this part means as low as is reasonably achievable taking into account the state of technology, and the economics of improvements in relation to benefits to the public health and safety and other societal and socioeconomic considerations, and in relation to the use of atomic energy in the public interest. The guides set out in appendix I to this part provide numerical guidance on design objectives for light-water-cooled nuclear power reactors to meet the requirements that radioactive material in effluents released to unrestricted areas be kept as low as is reasonably achievable. These numerical guides for design objectives and limiting conditions for operation are not to be construed as radiation protection standards.” (Emphasis added.)

      Here are some numbers from 10 CFR 50 Appendix I.

      Calculated annual total quantity of all radioactive material – 3 millirems to the total body or 10 millirems to any organ (emphasis added)

      Estimated annual air dose (noble gases) – 10 millirads for gamma radiation or 20 millirads for beta radiation

      Calculated annual total quantity of all radioactive iodine and radioactive particulates – 15 millirems to any organ

      In a world where the average background exposure is 300-600 millirem, those numbers are way, way down in the noise of normal variations. They are the numbers that allow antinuclear idiots like Caldicott to scare people by claiming releases in excess of standards. (I am not sure what the regulation writers were trying to say with the statement that Appendix I numbers “are not to be construed as radiation protection standards.” It does not really matter what they were trying to say because the numbers are accepted as de facto standards that must be achieved.)

      Unfortunately, the attitude that the radiation protection community has often taken during the past 40 years is a riff on your final statement. Instead of “If we can meet standards why lower them?” the driving question for them seems to have been “If those nuclear plants can meet standards so easily, why NOT lower them even more?” It is the ratcheting down from what were reasonable and affordable protection standards of the 1950s to the completely irrational protection standards of the 2000s that I am so deeply concerned about.

      It is the end result of the regulatory ratcheting that makes the equipment required for the nuclear way of boiling water so much more costly than the fossil fuel combustion way of boiling water. We have to keep our emissions to levels that are almost impossible to measure against normal background quantities. Fossil fuel plants require fluid and waste handling systems that are far less complete than ours. Their system purchases stop at an open hole; they dump their problems up the stack or into the ponds where scrubber waste goes or into the landfills where noncombustible ash goes.

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