Japan Earthquake

Japan Earthquake | Page 2390

@dean Is there any way to find out more info on the vents they use on the downcomer pipes to the torus? They call them two or three-stage Target Rock valves and said they have a tendency to stick open. In unit 2 Edano's info says containment was at much higher pressure than the suppression chamber making it sound like they didn't open?
by lillymunster 9/22/2011 3:31:45 PM

@ lilly, I believe they try to maintain an differential pressure between those two areas that is tied into the control also, assume it is automatic but may be manual. I will research it
by dean 9/22/2011 3:33:49 PM

@lillymunster Here's a notification from NRC RE: failure of Target Rock valve at Brown's Ferry: www.nrc.gov
by M.I.A. 9/22/2011 3:36:36 PM

@M.I.A. good find. This 1974 alert says the valve stuck open but because it was a nut that rattled loose I have to wonder of some sort of shock could cause something to come loose and stick shut?

During
blowdown of the reactor following main steam line isolation valve
closure, one of the pressure relief valves on the main steam header
failed to reseat until pressure had been reduced to about 20 psig. The
valve was subsequently removed and disassembled for inspection. It was
found that the keeper over the locking nut on the second stage piston
had worked loose and up to the stem over the securing wire. The
movement of the keeper prevented the second stage piston from
reseating.
by lillymunster 9/22/2011 3:41:23 PM

VALVE GEOMETRY and FUNCTION
The Target Rock vacuum relief valve is a reverse seated,
spring loaded valve that opens when the differential pressure
between the air outside the tank and inside the tank exceeds a
set pressure. The valve consists of a body that bolts to a
flanged opening on the top of a water storage tank. The disk
is located below the valve seat. The valve is held closed by a
spring that acts against the top of the valve stem. The vacuum
relief valve is shown in Figure 1, below. (lots of other info.) www.cfdconsulting.com
by M.I.A. 9/22/2011 3:50:52 PM

@lillymunster @Ian - I came across this side about Kyshtym_disaster / Mayak that looks worth regarding for study-infos (who and when) and its reference links

www.health.medicbd.com
www.health.medicbd.com

e.g.: external link on Mayak page:
"Inside the Zone" by Alexander Zaitchik. The most in-depth recent report on the history of the Mayak plant and its impact on local communities. (2007)
www.freezerbox.com
by Vivre 9/22/2011 3:54:17 PM

@lillymunster , there is another item that is of interest in the context of our venting discussion. The schema I posted on hardened vent lines shows a line from the dry well. If tepco could not relieve PCV pressure through the wet well, why did not they try open the path exiting the dry well?
by Peter 9/22/2011 3:55:04 PM

BACKGROUND INFORMATIONTarget Rock safety relief valves (SRVs) are currently installed in the main steam systems of 22 boiling-water reactors (BWRs). There have been several occurrences of improper operation of these SRVs both in spuriously opening and blowing down the reactor coolant and in opening at pressures significantly above technical specification requirements. There are two different designs of Target Rock SRVs. The earlier design is the three-stage SRV, which has had a history of spuriously opening and failing to reseat. This behavior was exhibited during several events which mostly occurred in the 1970s. The later design is the two-stage SRV, which is a modification of the three-stage SRV and was designed to eliminate the spurious opening and blowing down problem. Currently, there are 11 BWRs that use three-stage SRVs, and 11 BWRs that use two-stage SRVs.
www.nrc.gov
by M.I.A. 9/22/2011 4:01:29 PM

sorry. Title of previous post : Resolution of Generic Safety Issue B-55, "Improved Reliability of Target Rock Safety Relief Valves" (from Aug. 2000) www.nrc.gov
by M.I.A. 9/22/2011 4:02:51 PM

@Peter lots of questions. Unit 3 IIRC they sent someone to vent via the wetwell. There was a mention that passing the air and gasses through water lowers the releases. Maybe they thought a wet well release would throw less into the air outside? I also saw a mention that aerosolized radioactive particles can clog filtration systems quickly overloading them. Doesn't the emergency venting systems bypass the filters?
by lillymunster 9/22/2011 4:04:33 PM

@M.I.A. did it say anything more about when they opened at much higher pressures than they should have?
by lillymunster 9/22/2011 4:06:13 PM

@lillymunster , you remember this correctly. The effluent from the hardened vents is supposed to bypass the SGTS and leave the stack unfiltered. That is why tepco did not want to begin venting before the populace around the premises was evacuated. The water in the suppression pool is supposed to catch much of the radioactivity when the wet well is vented. However, why install a dry well vent, if you never intend to use it as a last resort?
by Peter 9/22/2011 4:11:54 PM

@Peter I would say the situation there qualifies as a last resort. Do we know what vents they tried to open at 1 and 2?
by lillymunster 9/22/2011 4:13:32 PM

@lillymunster , tepco only discusses their efforts of wet well venting.
by Peter 9/22/2011 4:14:41 PM

@Peter If they did wet well on 1 or 2 that could explain the gobs of highly radioactive junk in the filter box and stack base.
by lillymunster 9/22/2011 4:17:12 PM

just checking you have the venting explanationused by tepco in this release www.tepco.co.jp
by elainekirk 9/22/2011 4:22:14 PM

@lillymunster The problem with both the two-stage and three-stage valves (different causes, tho) : " For the two-stage SRVs, the primary cause of the upward setpoint drift problem was determined to be corrosion bonding of the pilot valve disk to its seat." Key words- "upward setpoint drift" of actuation pressure. These issues were supposedly resolved. "Additional pressure actuation switches counteract the effects of corrosion bonding by actuating the SRVs at the proper setpoints with external air power." If there's no power to initiate external air power?
by M.I.A. 9/22/2011 4:22:35 PM

3. Claim on the PCV ventilation has no filtration
In the program, it was mentioned several times that there were no filters in the primary containment vessel ventilation line. However, boiling water reactors that we operate use "wetwell vent", which has scrubbing effect to mitigate emission of radioactive materials at the comparative level to the filters. That is to say, in principle, our venting procedure uses the water in the suppression chamber as filteration and we have prepared and added the necessary equipment and procedures for accident management measures. Although a document that reads "wetwell vent" was shown in the program, NHK ignored this.
In the United States, the above-mentioned "wetwell" ventilation is adopted for boiling water reactors www.tepco.co.jp
by elainekirk 9/22/2011 4:24:20 PM

vent diagram from 6th april www.tepco.co.jp
by elainekirk 9/22/2011 4:27:36 PM

@M.I.A. WOW. So the solution was a power based mechanism to force them to open. If corrosion is a key problem Fuku would be the likely candidate considering age and maintenance of the plant.
by lillymunster 9/22/2011 4:30:14 PM

@lillymunster @lillymunster Sooo. If your not able to vent properly thru wetwell, you lose your main heat/pressure control system in a LOCA. #2 torus breached due to set point drift of pressure relief valve going so high that, when it finally opened, it shot thru and popped it like a balloon? During normal plant operation, the vacuum relief valve
remains in the closed position. When the tank is used as a
source of water for emergency cooling, pumps begin to draw
water from the tank. This results in a partial vacuum being
drawn in the tank. As the differential pressure between
outside air at ambient pressure and the inside of the tank
increases, a net force acts on the valve disk. The force causes
the spring to compress, which allows the valve to open. At
full flow, the valve is designed to pass a mass flow rate of air
that is sufficient to prevent buckling collapse of the tank. www.cfdconsulting.com
by M.I.A. 9/22/2011 4:46:39 PM

@M.I.A. seems so. Those valves look like another unsolved design flaw for the rest of the GE mark 1 units. Since the fix needs power and we know power can all be lost.
by lillymunster 9/22/2011 4:50:55 PM

@lillymunster Ooops, baby's awake- gotta go. BYE!
by M.I.A. 9/22/2011 4:53:02 PM

@M.I.A. thanks, your awesome! :-)
by lillymunster 9/22/2011 5:02:21 PM

good work @ MIA
by dean 9/22/2011 5:02:49 PM

hello all. Just to add to some recent papers being published on health effects of ionizing radiation. I wish I had time to put this together. But maybe someone here might find them useful or wants to store titles for later research. The role of miRNA in the direct and indirect effects of ionizing radiation. www.ncbi.nlm.nih.gov
by Cryptococcus 9/22/2011 5:15:33 PM

ah forgot to mention, there are two Supplement pds that go with this paper. Supporting data.
by Cryptococcus 9/22/2011 5:16:12 PM

older 2002 paper but important for plutonium effects on health. These effects are linked to the Mayak explosion of 1957. The Southern Urals radiation studies. A reappraisal of the current status. www.ncbi.nlm.nih.gov
by Cryptococcus 9/22/2011 5:18:02 PM

Cerebrovascular diseases in nuclear workers first employed at the Mayak PA in 1948–1972 August 2011 www.ncbi.nlm.nih.gov
by Cryptococcus 9/22/2011 5:19:07 PM

review of the Mayak explosion in 1957 www.freezerbox.com
by Cryptococcus 9/22/2011 5:19:42 PM

@Cryptococcus thanks! Adding them to the library page of the group website
by lillymunster 9/22/2011 5:23:03 PM

Thyroid cancer after Chernobyl: mechanisms of overestimation Claims that people came from other areas and were falsely registered as Chernobyl-related cases. www.ncbi.nlm.nih.gov Also, a response to this published too. Response to ‘‘thyroid cancer after Chernobyl: mechanisms
of overestimation’’ by Sergei V. Jargin
by Cryptococcus 9/22/2011 5:24:09 PM

@lillymunster , they vented units 1, 2 and 3, and yes I believe that is where the radioactivity at the stack bottom stems from.
by Peter 9/22/2011 5:24:57 PM

@lillymunster Dou itashi mashite (you're welcome). I hope it is useful. At least a list of papers helps people to catch and search.
by Cryptococcus 9/22/2011 5:25:07 PM

@Cryptococcus I have been trying to catch relevant papers that have technical, radiation or historical bits we need or will need at some point.
by lillymunster 9/22/2011 5:26:10 PM

@elainekirk , tepco is correct. The suppression pool is supposed to act like a water pipe, same as here in the US.
by Peter 9/22/2011 5:27:50 PM

@Peter Ty I wasnt disputing tepco's tale just thought their description of it would help with the vent deliberations taking place. I am feeling redundant I don't have any googling tasks :)
by elainekirk 9/22/2011 5:40:35 PM

www.ornl.gov for reading enjoyment.. it also contains some very good information around what we're talking about
by dean 9/22/2011 5:42:19 PM

@lillymunster - ot
Do you know how degrading it feels if one is mostly overlooked and then s.o. else post the exact same hint and gets a prompt regarding.
As this is not the first time - I'd rather like to be told directly not to 'disturb' your exclusive group further on instead of being ignored.
by Vivre 9/22/2011 5:55:59 PM

@Vivre I'm sorry you feel that way I don't think anyone intended it that way. If me or anyone else misses something it could just have been missed, overlooked etc.
by lillymunster 9/22/2011 5:57:21 PM

@elainekirk , totally okay. Who knows how well this type of filtering worked in actuality? We must not forget this was a unique situation. At TMI they had power and compressed air. All instrumentation was working. No comparison with the situation at Fukushima.
by Peter 9/22/2011 5:59:14 PM

@Peter I think they believe that one day computer programs will be able to forsee and neutralise all negative events but it isn't going to happen computers just bring another unknown into the equation methinks
by elainekirk 9/22/2011 6:02:00 PM

@Vivre , I check your links, :)
by Peter 9/22/2011 6:02:11 PM

@lillymunster
ok ~ I try to hang on
Nonetheless - the side I posted below is still worth regarding.
If you like you may clear our 3 comments hereafter.
by Vivre 9/22/2011 6:03:13 PM