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11 Comments

  1. Co-60 has a 5 year half life. With an outage lasting typically 30 days changes in concentration in the coolant is limited due to “waiting on entering the containment”. The main reason for waiting is due to Ar-41 with a two hour half life, which is effectively gone after about a day, and ion exchange has no effectiveness at removal. There are other isotopes that effect radiation exposure but these are the two biggies.

    The way for it to allow for a shorter time would have to be because it knocks the baseline coolant activity down so much by pulling the Co-60 out that the cumulative dose is is equivalent after 1 day (Argon decay) to the three days now. That is an impressive reduction for just changing out your resin!

    That could allow you to significantly increase the Co hardener use throughout the primary plant by a non trivial amount. Of course that decision goes back to the whole LNT debate… Seems like allowing ourselves to be wrong and explore different ideas can have a significantly beneficial impact.

    1. Cal,

      Are you only discussing shortening outage durations in your comment? There is a lower limit that could be reached regardless of radiation exposure limits due to cooldown times, head de-tensioning, physically moving fuel assemblies 1-by-1 into the SFP, and then the typical longest pole, needed maintenance.

      1. Joel,
        Not necessarily, the loading and unloading of the core is tedious process and occupies the majority of the primary critical path. There is other maintenance that can go on in the containment where 2 extra days would grant some more breathing room at the end. I have one commercial outage under my belt and saw it from the testing and maintenance closeout, not counting what I did in the Navy. It would allow the planning of more maintenance items based on the initial containment surveillance and less deferred maintenance. 2 days is a lot when it comes to an outage that is 6 8-hour shifts gained by the primary maintenance personnel. It would also change the major component replacements and perhaps allow more and larger work to be done in an outage while minimizing total down time. How about pushing past 90% capacity factor to 95% like Kit was talking about in a different post.

        EPRI continues to impress me with the research it sponsors that creates a meaningful contribution to the industry. In many ways, the industry is funding much of the research itself that would have normally been sponsored by the federal government.

        1. I might have to make a spreadsheet soon to estimate what the economic benefit would be of going from 90% to 95%, accounting for the fact that electrical demand is extremely seasonal and planned refueling outages are generally planned for low demand times of the year (so replacement power, if even needed, is generally considerably cheaper).

      2. So for technical detail as to commercial operations I am relatively under qualified to answer your question other than to answer from generalities.

        1. We can thank nuclear engineers who design fuel assemblies with high burn up and very few leakers for improved capacity factors. The good old days was a 9 month refueling cycle and now we are at 18 & 24 month cycles.

          Long outages are often the result of poor planning or some careless act that mucks things up. I have limited outage experience and they have nightmares. I went to help at one plant. I went to look at the schedule for the activity. I expected to see a three page printout with each task broken down into in minute increments. It only listed the task. From that I was able to tell my wife I would be home by Memorial Day. I was the only engineer at the plant on the 4th of July with a clipboard of authorizations because the engineers I was there to help had scheduled vacation.

          At another plant where I was staff, on the first day of outage a reactor engineer broke the refueling mast by driving in to cask pit wall. When you are moving the refueling bridge, you may want to check where the mast is. Just saying! That was just the start and yes we were still in the outage on the 4th of July. This year they were still in the outage in September. To be fair I think this group thinks it is doing well when they are only 30 days behind schedule.

          Radiation safety is serious on the refueling floor. However, I know of one event where the refueling bridge crushed the head of a worker killing him and other where an operator amputated his fingers.

          I was tasked by my boss with coming up with a plan that incorporated all previous lesson learned for initial fuel loads. Unfortunately, this required reactor engineers doing ‘work’. We lost two days leaning the amazing enough construction workers beak things. I got to spend 36 hours dressed out waiting but I was waiting with a very experienced engineer. This came in handy a few months later when an improperly vented demin caused a scram from the activation of Argon in the air.

          Then we lost two weeks when we dropped a source. I say we because the experienced engineer made it look easy for the utility wanted to take over. We used some of the time to implement my plan. We had spare parts, written work orders, and maintenance crew just waiting for a problem. When operators were changing shifts on the refueling bridge, the crew was looking for things about to fail and fix them before the refueling bridge broke with fuel on the hook. The rest of the fuel load went perfect.

  2. On a slightly different, but related subject…

    The cooling water clean up systems put into place at Fukushima Dai-ichi use zeolite, a natural mineral, to remove cesium and presumably other cations. Would synthetic ion exchange resins be more effective, and have a higher holding capacity? TEPCO could then later incinerate the plastic resins down to a small ash volume. Perhaps zeolite is less expensive, since so much of it will be required in the months and years ahead? Just something I have wondered about…

    1. Pete I am way out of date on best reactor water cleanup practices. The first problem in Japan is that they have inject seawater so typical ion exchange resins will deplete quickly. Second, this waste is going to be very radioactive and may have enough decay heat to worry about the removing the heat.

      There is also the issue of concentrating a critical mass of enriched U-235. If it was not mixed with fission products, incineration is a good way to concentrate and recover U-235. Not a bad idea but the issue is getting dose rates down. The way to minimize waste volume is to keep the fission products in the fuel rods. Japan is way past that.

  3. EPRI has done a lot of work in the area of cobalt reduction, at the behest of the member utilities. A tremendous amount of work was done in developing the NOREM material as a replacement for the use of Stellite alloys in various applications such as bearings and valve discs. The hardness of things like Stellite and NOREM is simply astounding. But the presence of cobalt in Stellite makes its use in nuclear applications problematic.

    1. This is your comment:

      Is norem really working well?

      It often happened cracking in weldment in our lab.

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