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  1. rmattila

    What would be the best way to divide a depot tablet?

    The situation is as follows: there is an off label use for quinidine that would require a 10 mg dose. However, the only format available is a 200 mg plastic depot tablet that is very difficult to crush homogeneously. I am not aware of the chemical form quinidine is in at these tablets, and...
  2. rmattila

    Bioinformatics project to help find cure for ALS

    Hello, we (*) are trying to set up a combined neuroscience/information technology project for the following purpose: ALS is a fatal neurological disease that has no known cause or cure and kills its victims within a few years. Our view is that one reason why all drugs have failed in clinical...
  3. rmattila

    Mechanical Nuclear coolant pumps built on turbine to generator shaft?

    Also, in Fukushima the main turbines tripped and the shaft stopped right at the earthquake because the acceleration exceeded the turbine trip level.
  4. rmattila

    Fukushima Japan Earthquake: nuclear plants Fukushima part 2

    As regards the operating license of the reactor pressure vessel, I suppose the practice is about the same in all countries. Pressure vessels in VVER-440 PWR reactors are especially challenging with respect to neutron fluence due to very small diameter of the RPV and a welding seam in the core...
  5. rmattila

    Fukushima Japan Earthquake: nuclear plants Fukushima part 2

    My primary concern at Western plants and Defence-in-depth thinking is that the plant's internal electricity grid appears to be recognized simply as provider of power to the equipment, not as a means for fault propagation. There are several possible failure modes in the plants' busbars, including...
  6. rmattila

    Fukushima Japan Earthquake: nuclear plants Fukushima part 2

    I suppose the criticality issue arises from someone trying to explain the concept of criticality to a listener who has watched too much Ghostbusters, and hence the "if two rods touch each other" meme was born.. Qualitatively, there are three issues that might reduce the margin to criticality...
  7. rmattila

    Fukushima Japan Earthquake: nuclear plants Fukushima part 2

    Just to keep some international perspective, here's my post from two years ago:
  8. rmattila

    Fukushima Japan Earthquake: nuclear plants Fukushima part 2

    In the Fukushima design, the rupture disk is in series with the two closed valves that must first be opened in order for the pressure to work on the disk. If the valves are not opened in time, the containment will develop a leak and the pressure might never reach the disk burst pressure again...
  9. rmattila

    Fukushima Japan Earthquake: nuclear plants Fukushima part 2

    This argument is very difficult for me to follow, as the very idea behind the design in the 80's was to eliminate the need for unreliable decision-making in the case of a severe accident by enabling a completely passive initiation of venting. If your vent lines don't have filters, you probably...
  10. rmattila

    Fukushima Japan Earthquake: nuclear plants Fukushima part 2

    The filtered venting system is designed to conduct the hydrogen from the containment to the stack in a controlled manner. At least in the Finnish and Swedish system this happens completely passively by means of a rupture disk, unlike the Japanese/American hardened vents, which require active...
  11. rmattila

    Fukushima Japan Earthquake: nuclear plants Fukushima part 2

    http://pbadupws.nrc.gov/docs/ML1214/ML12143A336.pdf Some specifics of the Swedish and Swiss filtered vents as seen by the NRC. http://pbadupws.nrc.gov/docs/ML1217/ML12178A670.pdf Report from the fact-finding trip.
  12. rmattila

    Fukushima Japan Earthquake: nuclear plants Fukushima part 2

    See http://tvo.fi/uploads/julkaisut/tiedostot/ydinvoimalayks_ol1_OL2_ENG.pdf page 12 for a picture of the setup. The line connecting the scrubbers to the containment drywell (one of the two) has two manual valves that are kept open, and a rupture disk that will break automatically at certain...
  13. rmattila

    Fukushima Japan Earthquake: nuclear plants Fukushima part 2

    The large gravel bed dry filter is only installed in the poorly situated and now shutdown Barsebäck NPP. Other Nordic BWRs use a compact wet scrubber filtered venting with jet nozzles injecting in NaOH water. The wet scrubber takes 99.9 % of Cs and around 99 % of elemental iodine, but unlike the...
  14. rmattila

    Cold shutdown that doesn't require coolant circulation?

    That design gets pretty close: http://www.rosatom.ru/wps/wcm/connect/spb_aep/site/resources/f3b59380478326aaa785ef9e1277e356/AES-2006_2011_EN_site.pdf [Broken]
  15. rmattila

    Japan Earthquake: nuclear plants

    The NRC voting record on the venting issues: http://www.nrc.gov/reading-rm/doc-collections/commission/cvr/2012/2012-0157vtr.pdf
  16. rmattila

    Japan Earthquake: nuclear plants

    It appears the NRC has rejected the requirement for filtered vents in US Mark I/II plants: http://berkeley-nj.patch.com/articles/nrc-to-enhance-post-fukushima-vent-requirements-d1361586
  17. rmattila

    Why did Plymouth Pilgrim power plant shut down

    In some European BWRs, the strategy in load rejection is to perform a partial scram (about 10 rods are scrammed, another 10 screwed in within a couple of minutes) to reduce power to around 30 %, switch the turbine controller from pressure to RPM mode, and let the steam bypass valves take over...
  18. rmattila

    Cold shutdown that doesn't require coolant circulation?

    In a BWR, non-condensible gases end up in the condenser vacuum system, recombiners to recombine most O2 and H2 back to water, then to the off-gas system to be delayed and filtered, and eventually to the atmosphere through the stack. Hydrogen has a nasty habit of moving with steam in the...
  19. rmattila

    Fukushima Fukushima - Why did Unit 2 release so much more radioactivity than Units 1 and 3?

    In the attached picture there are half-times of different elements in the fuel matrix. For I, Xe, Cs and Te, the half-time at melting temperature is only 10 s, i.e. when the fuel reaches melting point, these substances are already out of the fuel matrix and in the containment.
  20. rmattila

    Fukushima Fukushima - Why did Unit 2 release so much more radioactivity than Units 1 and 3?

    Containment dome seal failure is - as far as I am aware - one probable bypass route, considering the rather high dose rates measured directly above it on the service floor.
  21. rmattila

    Cold shutdown that doesn't require coolant circulation?

    Burnup does indeed not have a big effect, but power density wrt total heat capacity in the core does. CANDU, RBMK and AGR are good in this respect but have other, less favourable characteristics in other fields.
  22. rmattila

    Cold shutdown that doesn't require coolant circulation?

    From the protection point of view, the heat exchangers are equivalent to main steam lines, which also contain clean water and can be broken in case of external hazards. In those situations, SBO need not be considered and the emergency feedwater may be credited. The SBO device is not the only way...
  23. rmattila

    Cold shutdown that doesn't require coolant circulation?

    I don't see how the existence of the outer containment is relevant for the feasibility of the steam-air heat exchangers, as they are in any case located outside the containment: [PLAIN]http://www.frontlineonnet.com/fl2824/images/20111202282403306.jpg [Broken] No water needs to be added...
  24. rmattila

    Cold shutdown that doesn't require coolant circulation?

    They're doing something like that at the Kudankulam VVER being built by Russia in India: http://www.frontlineonnet.com/fl2824/stories/20111202282403300.htm [Broken] http://www.frontlineonnet.com/fl2824/images/20111202282403305.jpg [Broken]
  25. rmattila

    Cold shutdown that doesn't require coolant circulation?

    The term "design basis" is internationally a bit vague, since in some countries it refers to the original US definition, whereas in some countries additional more extensive conditions ("design extension conditions") and even severe accidents are in fact within the design basis. For example, the...
  26. rmattila

    Why no jet pumps in PWRs?

    See http://www.tvo.fi/uploads/File/nuclear-power-plant-units.pdf page 20 for a picture of a wet(="canned") internal BWR recirculation pump.
  27. rmattila

    Why no jet pumps in PWRs?

    So it seems. I've been told that wet motors (which have been used in BWR internal pumps since 70's) would have so low efficiency that they would not be suitable in PWR applications where main coolant pumps are larger. But apparently that problem can be overcome.
  28. rmattila

    Why no jet pumps in PWRs?

    Attached is a sketch of what I was thinking about. The idea is not to replicate the exact BWR application, but to use the jet pump principle to reduce the pipe size (enabling isolation valves) and to make it possible to use two smaller pumps per loop instead of one huge.
  29. rmattila

    Why no jet pumps in PWRs?

    The coolant pump seal issue I have in mind concerns a station black-out, where the pumps have stopped. There are plant designs that can't tolerate a loss of seal injection water, because the resulting loss of inventory will prevent heat transfer to the secondary side, and all measures to get...
  30. rmattila

    Why no jet pumps in PWRs?

    I was thinking of putting the jet pumps in the PWR cold legs, not in the RPV. That way the leakage point would always be above top of active fuel. The solution to the cooling pump seal failure issue would come from the ability to put each recirculation pump behind isolation valves, which is...
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