Japan Earthquake: nuclear plants Fukushima part 2

[LabratSR]

Awesome Sotan! Thank you very much!

 

[LabratSR]

RFI for Innovative Approach for Fuel Debris Retrieval"As fuel removal from spent fuel pool (SFP) at Unit 4 has started on November 18, 2013, “Mid-to-Long Term Roadmap (RM) on decommissioning of Fukushima Daiichi Nuclear Power Station” has shifted into the Phase-2.

The goal of the Phase 2 is to start fuel debris retrieval from reactor core expected in 2020. Necessary onsite works and associated R&D programs should be accelerated. From TMI-2 experience, retrieval of fuel debris is envisaged to be conducted by full submersion approach, in order to minimize workers radiation dose."

EDIT: Adding where this stuff is from http://irid.or.jp/fd/

Overview
http://irid.or.jp/debris/RFI_AFDR.pdf (I had to "Save Target As" to get this one to work)Technical Aspect of RFI 1
http://irid.or.jp/debris/TA_RFI1.pdf

Technical Aspect of RFI 2
http://irid.or.jp/debris/TA_RFI2.pdf

 

[LabratSR]

Future Utilization of Fukushima Daiichi NPS Units 5 and 6

http://www.tepco.co.jp/en/press/corp-com/release/betu13_e/images/131218e0201.pdf

 

[Hiddencamper]

Hello everybody.
This is my first post on these forums.
But I have been following this thread for a while as I am interested in the discussion of Fukushima plant developments.
I am in no way a specialist in this field or in any physics field therefore I doubt I could contribute to these discussions. But I do happen to know Japanese at a fair level, though, and I thought… perhaps I could help with the Japanese translations, sometimes. Unless there's somebody better at this too, that is.

This is a test posting; please tell me if I am useful or I am in the way; no offense will be taken if it's the latter.

------------------------
This is an attempt to translate & summarize some of the things related to ADS from the TEPCO report of 20131213, link given in the posts above.

- ADS is mentioned first on page 32, in a chapter dedicated to the issue "The cause of the sudden/fast decrease of pressure in reactor #3 (and the possibility of it being due to some hole that appeared in the main installations of the reactor)".

The situation or level of knowledge before this study:
It was believed that the sudden decrease in reactor 3 pressure that occurred on March 13 around 19:00 hours was the result of operator action - that is, the opening of SRV (Safety Reliev Valves?).

The results of this study:
It was established that the decrease of reactor pressure occurred while the operators were making preparations to manually decrease the pressure. There is the possibility that the pressure decreased as specific conditions were met for the activation of ADS.

(jumping to page 33 - graph of reactor pressure vs time; on the time axis time increases from right to left)

(moving to page 34)

Investigation of the conditions needed for the activation of ADS

The sudden, quick decrease in pressure could be explained by the activation of ADS, but we used to believe that the conditions for the activation of ADS had not been met on reactor 3.

*one of the conditions for the activation of ADS is making sure that the low pressure water system is ready for operation.

The diagram on page 34 indicates that while 3 factors needed for ADS activation were indeed cleared, the output of pumps for the system of removing residual heat and the system for spraying the inside of the reactor was insufficient (these pumps couldn't be operated due to loss of electric power).

The conclusion is that, logically speaking, the ADS system was not supposed to operate.

We investigated the possibility of ADS ending up operating, in spite of the fact that the logical procedure for its operation did not appear as having being achieved.

(moving on to page 35)

We thought, what if the conditions for the operation of ADS were in fact met. What about this possibility.

Due to the rise in pressure in the S/C (suppression chamber?), even though the pump(s) in the residual heat removal system were not functioning, the fact that a certain (significant) value of pressure on the output of this pump could be read might indicate that the conditions for ADS operation were in fact met.

(the diagram indicates that) S/C pressure reaches 0.455 MPa (abs) -> the pressure is transmitted -> pressure gauge measures a value that exceeds the 0.344 MPa needed for ADS activation

(moving on to page 36)

The actually measured data as well as analysis data were considered in relation with the decrease in reactor pressure.

The graph on this page shows that various actually measured parameters (the SRVs and the water level) are consistent with the hypothesis that the ADS had in fact been activated around 08:56 hours.

(moving on to page 37)

Considering the possibility that the cooling by water might have been insufficient, they are modifying the proposed graphic depiction of reactor 3 damage as shown in these drawings. Left is what they used to believe - right is what they think now.

Alright, this is where I come in.

ADS (Automatic Depressurization System) is a part of each plant's ECCS (Emergency Core Cooling System) package. ADS does not directly cool the fuel in itself, but it is designed to automatically reduce reactor pressure to a level low enough that a low pressure ECCS system could inject water to the reactor. ADS works by sensing certain plant parameters, and, if those parameters are met, automatically lifting a select number of SRV (Safety Relief Valves) in their power operated relief mode to depressurize the reactor to the suppression pool.

The logic for an ADS initiation is roughly as follows:

Reactor water level < Level 1 (about 20 feet below normal, and a few feet above the fuel, this also starts the low pressure ECCS pumps)
AND
reactor water level < Level 3 (This is the low water level scram signal, about 2-3 feet below normal)
AND
any low pressure ECCS discharge piping has sufficient pressure for injection (signifies a low pressure ECCS pump is running)
AND
high drywell pressure (> 1.68 PSIG, this also auto starts all ECCS systems and puts the plant into LOCA mode)

Once all of the above are met, an alarm goes off in the control room for 105 seconds. If the operator does not manually inhibit the ADS system before the 105 seconds is up, ADS activates. ADS will blow down the reactor until the conditions are clear and the operator manually resets ADS.

If high drywell pressure is not present, but all the other conditions are present, the system will automatically activate after several (~6) minutes. High drywell pressure means a LOCA is in progress, so the ADS blowdown needs to happen as soon as possible. Without high drywell pressure, the 6 minute timer is long enough to give the operators time to restore cooling systems, and short enough that the fuel remains safe.

It looks like the torus/wetwell pressure was high enough to make the system think the low pressure ECCS pumps were running. The low pressure ECCS pumps take pressure from the suppression pool, so it makes sense that the logic was made up.

 

[Most Curious]

So, Hiddencamper, what is the effect on reactor water level from this blowdown if no new water is injected?

 

[Hiddencamper]

So, Hiddencamper, what is the effect on reactor water level from this blowdown if no new water is injected?

This is almost a trick question lol.

In terms of inventory, you end up with a very large reduction in inventory. I'll do a simulator run tomorrow and see about how much my plant loses, but I think its something on the order of 20000 gallons from a hot scram. This is why one of the permissive signals for automatic blowdown is that you have a low pressure ECCS lined up to inject water. However, in terms of core cooling, if you manually perform the blowdown at the right time, you can buy yourself an extra 20 minutes until core damage.

Right as your first few feet of fuel starts to get uncovered, you reach a point where the top of the fuel is going to overheat. If you initiate ADS manually at this point, the rapid flow of steam across the fuel is capable of providing adequate core cooling for an extra 20 minutes, so even though you uncovered fuel and are losing water inventory more rapidly you can delay the onset of core damage. This is useful if you know you can get a fire pump lined up or if you just need a little more time to get RCIC/HPCI reset or something. It also removes energy from the vessel and transfers it to the suppression pool, which can reduce the impacts to a core breach later on.

Another thing to remember, and the reason I say this is a trick question, is whenever you are blowing steam down you are going to have an increase in INDICATED water level, due to how the water level instruments work. This has tricked operators into thinking they have an overfill condition (this is what happened at Three Mile Island), and can also cause your high water level logic to trip your feed pumps and turbines, which can be very bad if you are in an failure to scram scenario and counting on feed pumps and turbines for injection and decay heat removal.

 

[Most Curious]

Ah, the detail I wanted.

I assumed substantial water would be lost but did not fully understand the rest of it. At what pressure is below that required to drive turbine for HPCI?

How many gallons of water does 1 foot of level represent in the core then above active fuel where I assume the "fill" of hardware is less?

 

[Hiddencamper]

Ah, the detail I wanted.

I assumed substantial water would be lost but did not fully understand the rest of it. At what pressure is below that required to drive turbine for HPCI?

How many gallons of water does 1 foot of level represent in the core then above active fuel where I assume the "fill" of hardware is less?

HPCI is designed to run down around the 150 PSIG range, but I'm pretty sure you can go a bit lower if you bypassed the interlocks. After a loss of condenser, HPCI equipped plants will run HPCI to drop pressure down low enough for decay heat removal pumps to start, instead of lifting SRVs, and the decay heat removal interlocks are in the 100-150 PSI range (depending on plant). RCIC is capable of running down to like 50 PSIG. Remember that this is pressure across the turbine, as wetwell pressure goes up (the steam exhaust point), your inlet steam pressure requirements will also increase.

As for water level...it kind of depends. I've been taught for my BWR that the 'rule of thumb' is 200 gallons per inch, but this could be off quite a bit depending on where you are. I'll say this much, when water is dropping, it always feels like its less than 200 gal/inch, but when you're trying to fill with non-ECCS systems, it feels like much more than 200 gal/inch lol. A typical BWR will have roughly 20 feet between normal water level and 2/3rds core height (minimum required for adequate cooling post LOCA)

 

[Sotan]

I thought it might interest others so here’s my translation of the last page of the TEPCO report located at:
http://www.tepco.co.jp/cc/press/betu13_j/images/131213j0101.pdf

(This report presents progresses regarding some of the 52 “unconfirmed/unclarified aspects” which have been identified in the past in relation to the nuclear accident. Page 6 of the report shows that TEPCO has solved about 10 of these aspects – and they are the ones given in this report; the solving of these 10 items has, though, led to 2 additional items to be investigated in the future, which brings the total to 54. Also, 10 aspects have been flagged as priority items for future investigations; and there are 34 remaining ones which have not been assigned a priority level yet.)

The last page of the report lists the 10 unconfirmed/unclarified aspects which are to be given priority:

- Investigation of the operation of SRV valves after the occurrence of the damage of reactor cores
- Circumstances of the release of radioactive material after March 20
- A more precise evaluation of the amount of water actually poured into the reactor(s) by use of fire trucks
- An evaluation of the effect of the HPCI system operation at reactor 3 on the course of the nuclear accident
- Behaviour of melt core falling towards the lower plenum
- Establishing the cause of high level radioactive contamination of the RCW piping at reactor 1
- Investigation of the rise in pressure that occurred in reactor 2, after the forced pressure reduction was carried out
- Establishing whether the rupture disk on reactor 2 operated or not
- Elucidation of the cause of RCIC system stopping at reactor 3
- Investigation of the temperature (related) stratification in the forced suppression pool at reactor 3.

(On page 6 it is stated that they will try to provide answers for this issues within 2 years.)

 

[Hiddencamper]

I did a simulator run. From normal water level post scram an ADS blowdown left me with the top fuel just starting to get uncovered. When I did the same thing starting from top of active fuel, I ended with the core uncovered. I then started a 5800 gpm ECCS pump. In the fuel zone it was very low to flood up, possibly because I drained the downcomer to help lower level and it needed to be refilled. After that, came up about 30" a minute until we got near the dryer skirt (close to normal range), then it was like 50"/ minute. This is a 1050 MWe bwr with a rather small core for its size. I wouldn't take it as a direct comparison to a Fukushima type plant, but qualitatively it seems like if you use ads you will uncover the fuel.

 

[SteveElbows]

Perhaps I should mention that another, much longer, document came out on the same date, I assume exploring the same topics in more technical detail. But as my attempts to machine-translate it have given very poor results, I haven't tried to work out if there is anything of note in it.

http://www.tepco.co.jp/cc/press/betu13_j/images/131213j0102.pdf

 

[Most Curious]

Hiddencamper, thank you for that effort. Helps me better understand the water level issues of an ADS event. No doubt the Japanese did not start with a normal level in the RPV initially so would have had even more uncovery of the fuel. With a lower flow rate to refill, (very likely) they were in deep doo doo no matter what they did!

I assume the steam would provide adequate cooling of the uncovered core but not for long? Seems "pulling the trigger" on ADS one needs to be confident of the ability to refill at high flow rate, which they did not have. I would think they may have had little choice once high pressure feed was no longer available but almost assured of fuel damage, at best, if they did blowdown to use low pressure feed. Heck of a choice to be faced with!

If radiation levels were already high when the HP injection pump failed, is it safe to assume fuel damage had ALREADY occurred? They were really up the creek with few, if any, options left it seems to me.

No doubt operational errors occurred, but even had everything been done exactly right, did they have ANY chance to prevent at least 2 if not 3 meltdowns with station blackout? TMI stopped just short of melt-out from the RPV - inside 4 hours - and they HAD power available!

 

[Hiddencamper]

Hiddencamper, thank you for that effort. Helps me better understand the water level issues of an ADS event. No doubt the Japanese did not start with a normal level in the RPV initially so would have had even more uncovery of the fuel. With a lower flow rate to refill, (very likely) they were in deep doo doo no matter what they did!

I assume the steam would provide adequate cooling of the uncovered core but not for long? Seems "pulling the trigger" on ADS one needs to be confident of the ability to refill at high flow rate, which they did not have. I would think they may have had little choice once high pressure feed was no longer available but almost assured of fuel damage, at best, if they did blowdown to use low pressure feed. Heck of a choice to be faced with!

If radiation levels were already high when the HP injection pump failed, is it safe to assume fuel damage had ALREADY occurred? They were really up the creek with few, if any, options left it seems to me.

No doubt operational errors occurred, but even had everything been done exactly right, did they have ANY chance to prevent at least 2 if not 3 meltdowns with station blackout? TMI stopped just short of melt-out from the RPV - inside 4 hours - and they HAD power available!

With regards to ADS, in the BWR Owners Group EOPs (Emergency Operating Procedures), down the EOP-1 Inventory control leg, you are supposed to save blowdown until you reach top of active fuel, even if you have a low pressure source available. Once you hit TAF, you blowdown, then try injecting using all available low pressure sources. As I said in an earlier post, I think this is the first time ADS has ever actuated in a GE BWR outside of testing.

As for saving the other units, I have an opinion that if they were better prepared, if they had SAGs (severe accident guidelines), prestaged portable equipment, and severe accident strategies, they probably could have saved unit 2 or 3. Unit 2 had over 70 hours of RCIC, and unit 3 had like 36 total. Unit 3 in particular was coming down in pressure on HPCI and had a portable pump aligned to take over, but they secured HPCI prior to starting injection, didn't understand their SRVs were not functional at the time, lost pressure control, and exceeded the portable pump shutoff head. (The indicating lights for SRVs come from AC power, but the actual SRV solenoids use DC power, so you can get the light but not have the valve lift. This is why its important to verify proper RPV pressure response, SRV tailpipe temperature, and SRV acoustic detection, to ensure your SRV did in fact operate)

 

[Sotan]

Perhaps I should mention that another, much longer, document came out on the same date, I assume exploring the same topics in more technical detail. But as my attempts to machine-translate it have given very poor results, I haven't tried to work out if there is anything of note in it.

http://www.tepco.co.jp/cc/press/betu13_j/images/131213j0102.pdf

Massive report, 327 pages... I am on the road now with limited time and internet access, but I intend to look through it eventually and will give at least a rough translation of contents. So that if anyone's interested in certain particular aspects I will try to find those chapters and respond.

In my translation the title sounds like this: "Estimation of the state of reactor 1 ~ 3 cores and containment vessels at Fukushima Daiichi Nuclear Plant and investigation of unsolved aspects. First progress report - 13 Dec 2013, Tepco".

It is a very detailed report which starts with the earthquake and the tsunami and their effects on the nuclear plant; then goes to analyze the accidents at reactors 1, 2 and 3, with detailed timelines of events and little conclusions chapters for each reactor; then there's an overall estimation of the state of each reactor core and containment vessel, from 1 to 3 (less than 1 page for each of them). Indeed, everything is discussed in more detail than in the other report published in the same day. And this brings us to page 54. The rest, up to page 327, are additional documents - something I haven't yet read at all, about the results of a MAAP (Modular Accident Analysis Program) analysis of the accident sequence; lots of graphs, each of them probably worth a separate discussion, and generally speaking lots of data which probably deserve more than what I am saying here.

It's an overwhelming document and I wouldn't know where to start (translating it all is close to impossible due to limited time). Perhaps there are some specific points you are interested in and would like to see what Tepco says about that; I could search for it and translate that portion. I'll be back home on Sunday. Even if there are no requests I will still post fragments that I find interesting (even though my poor knowledge of the field is not going to help much).

 

[Hiddencamper]

If this document gets translated, if anyone sees a translation of it online, please post it. This contains a lot of critical detail towards understanding and analyzing the sequence of events. My Japanese is barely good enough to understand what graphs I'm looking at lol.

 

[Sotan]

Good news, I think:
http://www.tepco.co.jp/en/press/corp-com/release/2013/1233101_5130.html

It is stated that

"Attachment:
-‘Report on the survey and study results of unconfirmed and unexplained events of the Fukushima nuclear power plant accident - First Progress Report' (Summary) (PDF 2.15MB)PDF

-‘Report on the survey and study results of unconfirmed and unexplained events of the Fukushima nuclear power plant accident - First Progress Report' (Full Edition) (PDF 14.3MB)PDF

*English translations of the full edition report is now being developed and it takes a while to complete them.
We will post the translations one by one when it is prepared.
(The documents written in Japanese below will be replaced by English translations.)
We apologize for this inconvenience caused."

 

[Sotan]

Looks like the shorter (summary) report has been translated in English:
http://www.tepco.co.jp/en/press/corp-com/release/betu13_e/images/131213e0101.pdf

 

[Hiddencamper]

Looks like the shorter (summary) report has been translated in English:
http://www.tepco.co.jp/en/press/corp-com/release/betu13_e/images/131213e0101.pdf

Read it. Still would be nice to know why the HPCI stopped functioning. It's possible they just didnt have enough decay heat to drive it at the time.

Another piece they talk about is the worker observations of water spraying. They claim it was from the spent fuel pool. GE's SFP (spent fuel pool) design has air vents directly above the pool. These vents provide suction to ensure any radionucleides that offgas from the pool get captured by the plant's HVAC/filtering system. It appears the earthquake caused sloshing in the pool, which allowed the water to enter these air ducts, and that the design of the system is to drain that water out to prevent duct damage.

My plant has overfilled these ducts before (due to poor operation of the system). And during the 2008 Earthquake in Japan, several BWRs had water slosh out of their spent fuel pools. So this seems plausible in my opinion.

 

[LabratSR]

Establishment of ‘Decommissioning Company' (tentative name)

http://www.tepco.co.jp/en/press/corp-com/release/2013/1233102_5130.html

 

[Sotan]

Read it. Still would be nice to know why the HPCI stopped functioning. It's possible they just didnt have enough decay heat to drive it at the time.

The main body of the full report has now been translated. Regarding the RCIC stop, I found these [STRIKE]two[/STRIKE] three paragraphs which indicate that they still don't have an answer to that:

Page 2: "On other hand, there are still unclear issues, e.g., the reason why the reactor core isolation cooling (RCIC) system of Unit-2 lost its functions still remains unknown, and some observed phenomena cannot be interpreted yet."

Page 25: "The assumptions made in the analysis could reproduce quite well the reactor pressure changes, but why the RCIC stopped is unknown. It is necessary, therefore, that the RCIC shutdown mechanism consistent with those assumptions in the analysis be investigated (Unit-2/Issue-2). "

Page 36: "The RCIC stopped automatically at 11:36 on March 12th and thereafter its status of shutdown was confirmed on-site but its rest art-up failed after all. It was found upon an on-site check that the latch for the trip mechanism of the RCIC turbine trip throttle valve had been detached and the valve had been closed, but the background to this and reasons remain unknown and are subjects for continued examination (Unit-3/Issue-1)."

 

[LabratSR]

Bits and pieces of the main, big report referenced above are being released in English.

http://www.tepco.co.jp/en/press/corp-com/release/2013/1233101_5130.html


What they call the main body is here

http://www.tepco.co.jp/en/press/corp-com/release/betu13_e/images/131213e0102.pdf

 

[zapperzero]

Bits and pieces of the main, big report referenced above are being released in English.

http://www.tepco.co.jp/en/press/corp-com/release/2013/1233101_5130.html

Started to read it. They are listing (on page 9,"event tree") the earthquake as a direct cause of failures. And further on:

Investigations in detail thereafter by
trench surveys and others in Yunodake Fault
revealed seismic activity marks at several loca
tions, resulting in the judgment that the
Yunodake Fault had been a fault which should
have been considered in seismic design.

 

[Sotan]

Not sure if this has much significance, but here’s a little info regarding a damaged fuel assembly from SFP at Unit 4 (the documents published by TEPCO are only in Japanese):- On Dec 18 TEPCO posted a report regarding a damaged (bent) fuel assembly that was sitting in the SFP at unit 4.
http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_131218_07-j.pdf
The assembly has apparently been damaged in a mishandling incident in April 1982 (which has been duly reported at the time).
This document shows how they plan to investigate the degree of damage of this assembly, sometimes around Dec 20-21, in view of its safe manipulation at the time of removal from the SFP.

- On Dec 27, a single page PDF report has been published at
http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_131227_04-j.pdf“Regarding the identification of cracks on the surface of a damaged fuel assembly from the spent fuel pool of Reactor 4”

They found cracks in the “channel box” (which, I learned from Japanese wikipedia, designates the metallic sheet/cover which wraps the fuel bundle at the exterior). It is believed that the cracks appeared at the time when the assembly was mishandled.

No changes in radiation values were observed in the pool water on the occasion of this check.

 

[SteveElbows]

A lot of the December 13th documents that still say 'to be translated' on the TEPCO page have actually been translated already, and are available in english by clicking the links. There are only a few exceptions.

 

[F X]

Any thoughts on this?

http://www.theecologist.org/News/ne...down_mystery_steam_rising_over_reactor_3.html

 

[Hiddencamper]

If you make your way back to the source material you see the steam is generated between 7 and 8 AM every few days.

It also appears that the sentence regarding the steam is after a sentance regarding waste transfers.

I think some anti nuclear organizations or fear / sensationalism groups used google translate on a plant daily status report and took it out of context.

 

[a.ua.]

Any thoughts on this?

http://www.theecologist.org/News/ne...down_mystery_steam_rising_over_reactor_3.html

http://ex-skf.blogspot.com/2013/12/for-record-fukushima-i-npp-reactor-3.html

 

[Rive]

Quietly, they moved...

The doomsters were tricked this time, but I'm not happy either.
I think this is the most dangerous op. till now.

 

[turi]

Any thoughts on this?

http://www.theecologist.org/News/ne...down_mystery_steam_rising_over_reactor_3.html

Tepco has posted a response to the steam over reactor 3 theories:
http://www.tepco.co.jp/en/press/corp-com/release/2014/1233338_5892.html
They refer further to pp 19 of
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d131031_04-j.pdf

 

[zapperzero]

I think this is the appropriate thread.
http://www.channelnewsasia.com/news/asiapacific/scientists-to-create/948474.html
How does this add anything of value? Also, I couldn't help but shudder when I read "very rapid fission process" in the article... I suppose they are going to use reflectors and/or an external neutron source?

 

[Hiddencamper]

What I read, and I can't find the link now, is they have a test reactor which will act as an external neutron source. They will put a BWR fuel cutout into a sealed capsule with no cooling flow and put it under a neutron flux to heat it past 2200 deg C to cause melting in a controlled fashion. Then they will shut down the reactor and pull the capsule out.

Should be low/no decay heat if they do it this way, so it would be a representative way to see how these things combine and behave when they melt.

 

[etudiant]

Did not the US run a somewhat more extensive experiment at INEL?
There was a Loss of Fluids test reactor built to assess these issues, although how far is not clear.
Presumably the Japanese believe that they can learn something more.

 

[Gary7]

From yesterday's (January 11th) Tokyo Shimbun. Thought it might be germane to the subject of whether or not the core material has solidified, and the necessity of keeping water poured into them.

"...In order to reduce the amount of contaminated water that needs to be treated, Tepco reduced the flow of water into Unit 2 by 0.5 tons every hour. They will further reduce the water in stages, eventually reducing the water by 1 ton per hour.
Unit 3 will also be reduced by 1 ton per hour, and together the amount of water used for cooling both units will be reduced by approximately 50 tons per day. They are not considering reducing the volume of water flowing into Unit 1, which in the past has had temperature increases after slight changes to the environment inside containment."

 

[a.ua.]

Monitoring air dose rates from a series of
aircraft surveys 30 months after the
Fukushima Daiichi NPS accident
http://www.nsr.go.jp/english/library/data/special-report_0114.pdf

 

[zapperzero]

plume's laid down to the northwest if I'm reading the map right
would be interesting to correlate with weather at the time of the accident, iirc most of the time the wind was blowing east or south east, out to sea? but then my memory is very bad.