APR: your source for nuclear news and analysis since April 16, 2010

Sunday, September 18, 2011

Fukushima Daiichi: Reactor update

Two news reports on the reactors (as opposed to spent fuel pools or any other portions or locations) at Fukushima Daiichi...

First, TEPCO has greatly increased the amount of water being injected into No. 2 and No. 3 reactors through the core spray lines. This is an attempt to drive the measured temperatures down in order to establish a 'cold shutdown' condition.

TEPCO indicates that there was an increase in containment vessel pressure in No. 2 reactor plant shortly after the beginning of injection via the core spray line - thus it is certain that the water being injected through this line reached the core. It is important here to note that at this point, when either I or TEPCO use the term "core" this refers to the essentially deranged, or demolished, mass that contains the fuel elements' material and the control rods' material, in condition not fully known. (This is not news to long-time APR readers.)

After noting the success of the use of the core spray lines, TEPCO has decided to make a large increase in total water flow to these two reactors through the core spray lines (keeping the feed line amount the same) in order to attempt to determine what flow rate will give a cooldown rate to meet the desired 'cold shutdown' timetable. Even though the chances of recriticality are very remote, TEPCO has decided to inject borated water prior to each major increase (in steps) and monitor conditions closely.

The second news item concerns a test that TEPCO performed on No. 1 reactor's control rod position indication sensors. These sensors, one for each of this reactor's 97 control rods, are located below the reactor and are integral with the control rod drive mechanisms - mechanisms that position the control rods up and down in the core as required to adjust the core's power output. TEPCO believed that conducting some simple maintenance type tests on these units, which have a large number of magnetic switches inside to "mark off" the travel of the rods, might give a clue as to the condition of the bottom of the reactor pressure vessel.

Unfortunately, the results of the tests seem very inconclusive - or perhaps in better words, the results don't seem to give any sort of clear indication of the bottom of the pressure vessel because it seems as if the detectors and their interconnecting wiring may have been heavily damaged by heat, by radiation, and probably also by steam exposure for prolonged periods, all of which have affected the equipment such that any real idea of any specific damage location on the bottom of the RPV isn't detectable. In fact, only one of the 97 tested fully satisfactorily.

Below we see a part of the diagram TEPCO released showing some of the test results in what is unfortunately a very confusing graphic.

In the illustration above, we are looking down on the core. For control and indication purposes the core is divided into four sections or quadrants; note that there is a white line dividing these, and that each has its own color coded sensor system (again for the purpose of this illustration, we'll just refer to colors.) In terms of the small numbers in the blocks (each block represents one control rod drive mechanism position indicator) the lower the number, the better the test. As was reported by TEPCO, and apparently carried only widely by Kyodo News and then Fox News, we see that only one - the yellow block - passed fully.

If we assume that the general condition of all of the cable runs, the insulation and the containment penetrations is good then we might assume that RPV failure has occurred more in the area of the lower quadrants as seen here (note the black and the purple containment penetrations and wiring runs.) However, TEPCO states that it appears that there is enough indication of wiring damage that we cannot infer the condition of the pressure vessel from this test alone - the test results may be spurious. For example, the detectors might be OK but the interconnecting wiring shorted out. Thus, TEPCO feels that this test didn't really give it the kind of information it was looking for.

TEPCO might continue on with this test at No. 2 and No. 3 reactor plants; there is no sure word yet. What is sure is that this is the first deliberate test data TEPCO has taken to try to determine how bad the condition of the lower pressure vessel head might be at any of the plants.

We will keep up on this testing and relay results as they're available.

8:00 PM Eastern Sunday September 18, 2011


  1. UPDATE 1-Areva to shut down 2 French uranium plants

    Thu Sep 15, 2011 4:12pm GMT

    PARIS, Sept 15 (Reuters) - French nuclear group Areva on Thursday said it would temporarily shut down two uranium conversion plants in France during November and December.

    The temporary shutdown of the two plants, which employ around 570 staff, comes after a sharp fall in orders from Japanese nuclear power producers in the wake of the Fukushima nuclear disaster, said a spokeswoman at Areva.

    "This decision is justified by events that occurred in Japan and that are reducing Japanese power groups' delivery needs. Against this background we deemed it unreasonable to produce large amounts of converted uranium," the spokeswoman said.

  2. Rusty - if you want to start your own anti-nuclear blog, and then open it up so that I can go over to it and make smart-@$$ comments, please feel free to do so. I would love to see what information you can get out there to the public that they don't already have.

    I didn't publish both of your posts because you really do waste far too much space and time being snarky.

    OF COURSE the production of reactor fuel is going down, with Germany and Japan not ordering. Do you really think this is a revelation?

    Where is your report on the government of Japan going ahead with talks to export nuclear power to Vietnam? You must have missed that one. But that's all right - we see who you are.

    Please note that you're posting your way out comments on the most honest, complete blog there is on the events at Fukushima. No one gets a free pass here. You just reeeaaalllyy didn't like my post about Solyndra, and now you're mad as hell and aren't going to take it any more. Right?

    Did you go read Rod Adams' post on Atomic Insights yet? That ought to get you apoplectic.

  3. I have a question. I'm a complete non-expert, although broadly sympathetic to nuclear power. Another blog I read, Naked Capitalism, keeps posting articles claiming Reactor No. 1 is going through the "China Syndrome" and the fuel is actually no longer in the reactor vessel. (E.g., http://www.nakedcapitalism.com/2011/09/guest-post-will-tokyo-be-evacuated-due-to-fukushima-radiation.html). I think this is probably bullshit - wouldn't the cooling water temperature tell us if there was fuel in the reactor? - but I don't know enough to evaluate this myself. Is there any chance he's right?

  4. If they are increasing the water flowrates into Units 2 and 3, there must not be as much of a danger of overflowing the turbine building sumps, etc, as was the case earlier. The water cleanup and recycle system must be working well enough to accept this increase. Looking at Unit 3, the total flow is 12 cubic meters/hour, which is about 52 gpm. This actually isn't all that much when it comes to industrial sized pumps. (I still have to think in terms of gpm, psi, etc. to get a feeling for these values.)

  5. @Mark Lowell: The short answer is: They're probably NOT right over there at Naked Capitalism if they're using terms like "China Syndrome." That's just scare tactics. You see the results of the testing that TEPCO did - if the whole vessel bottom were gone, I'd expect that none of the tests would have been anything but total failures because all of the wiring would be open. I'd recommend highly that you go over to the Atomic Power Review YouTube Channel and check out some of the videos I've created to show the plant internals and to discuss details.

    The real sixty-four thousand dollar question, as it were, is just how bad is the damage to the lower vessel head - how much fuel if any did get out - and how much water is getting to how much of the damaged core. The fact that when core spray was started on No. 2 plant there was a pressure spike seems to indicate more direct contact with the core, meaning more rather than less of the core is still inside the vessel. This is probably the case for No. 1 and No. 3 plants as well.

  6. Thanks! I'll take a look at those videos.