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pressure loss

A loss-of-pressure-control accident (LOPA) is a mode of failure for a nuclear reactor that involves the pressure of the confined coolant falling below specification. Most commercial types of nuclear reactor use a pressure vessel to maintain pressure in the reactor plant. This is necessary in a pressurized water reactor to prevent boiling in the core, which could lead to a nuclear meltdown. This is also necessary in other types of reactor plants to prevent moderators from having uncontrolled properties.
Pressure is controlled in a pressurized water reactor to ensure that the core itself does not reach its boiling point in which the water will turn into steam and rapidly decrease the heat being transferred from the fuel to the moderator. By a combination of heaters and spray valves, pressure is controlled in the pressurizer vessel which is connected to the reactor plant. Because the pressurizer vessel and the reactor plant are connected, the pressure of the steam space pressurizes the entire reactor plant to ensure the pressure is above that which would allow boiling in the reactor core. The pressurizer vessel itself may be maintained much hotter than the rest of the reactor plant to ensure pressure control, because in the liquid throughout the reactor plant, pressure applied at any point has an effect on the entire system, whereas the heat transfer is limited by ambient and other losses.

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  1. V

    Mystery of Pressure Loss

    Had open vented system replaced with Combi boiler 3 months ago. Firebird Enviromax Oil condensing boiler. Had pressure dropping for last 6 weeks, needs topping up with water twice a day. Pressure dropping from 1.5 to 1. Here's the clues - any ideas? No sign of leak internally to house. Just had...
  2. D

    slow pressure loss vailliant turbo max plus

    Hopefully someone can offer best course of action! have slow pressure loss of approx 0.5 bar over 1 week on the title boiler above. Have british gas homecare and they have now visited 3 times without finding cause of problem. first two visits they just re-charged expansion vessel and...
    • domo
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    • Replies: 12
    • Forum: Plumbing Jobs | The Job-board
  3. S

    BG Upsell? Boiler pressure loss: Under concrete pipes leaking or Heat exchanger?

    Hi, I am new to the forum. Hopefully, I can get some advice regarding the Combi boiler / CH problems in my bungalow? The pressure keeps dropping every couple of days. I have BG out to try and fix (they've been out twice in the last week) They are suggesting it's either the heat exchanger or...
    • Sammyez
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    • Replies: 3
    • Forum: Plumbing Jobs | The Job-board
  4. L

    Worchester Greenstar 28i pressure loss help required!

    Hello all, I'm hoping for some help in diagnosing an issue with our WB Greenstar 28i JuniorMK4 (installed late 2011). Over the last year the boiler had needed topping up every now and again, however in the last couple of weeks the boiler has been losing it's 1.5 bar over a 24 hour period, each...
    • liamconnolly
    • Thread
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    • Replies: 1
    • Forum: Plumbing Jobs | The Job-board
  5. L

    Pressure Loss - Loose end please help!!!

    Hi Everyone, I moved into a new flat about 18 months ago. After a few months the boiler pressure started dropping to 0 daily which I just repressurized as needed. The boiler eventually stopped working all together (old) so had a new BAXI combi boiler put in. Since day one had the same...
    • lukesaw
    • Thread
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    • Replies: 17
    • Forum: Plumbing Jobs | The Job-board
  6. R

    Unvented hot water pressure loss

    Hello Got a flat I rent that's lost pressure to hot water. Hopefully it's a blocked strainer! It's in Slough if anyone is interested? Cheers Rct
  7. M

    Pressure Loss Ideal Logic 18

    Hi I am losing about 1 bar of pressure a day on my heating system. I have read loads of posts with suggestions about what the problem could be. There are no obvious leaks although unable to check hidden pipework but no obvious damp patches etc. I have tried to check whether the pressure...
  8. D

    pressure loss

    hi guys just a quick question just been round to my mates house and he said the boiler is working fine until he switches he's heating off then the pressure goes to zero. its discharging out of the PRV. my first thought was to fit an external expansion vessel on the return as I'm not gas safe...
  9. H

    Ideal logic+ combi 24 - Pressure loss - what to try next

    Hi, I have had an Ideal logic 24 in my flat for about 4 years. In the last month or 2 it has started needing the pressure topping up every 2 days. Its under warranty so Ideal came out and replaced the flow turbine, sump, heat exchanger and svalve but without any difference seen. We've not...
  10. M

    repeated pressure loss / leaking valve diaphragm

    Hi All. Firstly my apologies if this is a trade only forum. I'm not in the trade, just your average 'customer'. The 'Customers!' thread in here made me laugh. Promise I'm not one of them :) I have had a few different plumbers round who can't seem to fix the issue i have. I have a Remeha...
    • mordzy
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    • Replies: 9
    • Forum: Plumbing Jobs | The Job-board
  11. stings27

    Pressure loss

    I'm sure this has been covered a thousand times but here go's! I had a call off a relative about 6 Months ago with a pressure loss problem on a Duo-Tec. after having a good look round the bungalow I found a small weep on a fitting behind a fridge, repaired and re-filled the boiler and everything...
  12. J

    Potterton Boiler pressure loss

    Hi, My Potterton Powermax he is loosing pressure, i've changed a faulty pressure relief valve and its still loosing pressure but more slowly now, I cannot see any visable leaks. could it be leaking in to the hot water tank, is there any way to diagnose it? Thanks Jeff
  13. B

    Another Worcester pressure loss

    Now whilst I have looked at the past post regarding this, albeit after I went on the call out!, I have thought my issue was a leaking heat exchanger but i'd appreciate a bit of verification to this from those more experienced than myself - having only qualified a few months back. It's a...
  14. L

    Large water pressure loss

    Hello all. Am looking for some advice as to potential solutions to a worrying problem. Our boiler (Glow Worm Swiftflow ) is currently showing a loss of 0.5 bar pressure loss over a period of 12 hours. Having done some diy checks I fear the problem it is in the piping under ground floor level (...
  15. W

    Pressure loss in sealed central heating system

    I have a sealed central heating and hot water system running off of a Alpha CDR18 boiler. It has been experiencing significant pressure loss (from ~1.0 bar down to 0.2 bar) after the heating has been on and the water cooled back to room temperature. No water loss from the PRV (balloon put over...
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    • Replies: 6
    • Forum: Plumbing Jobs | The Job-board
  16. B

    Condensate output contains grit and pressure loss

    Checking the boiler before winter, I have found the condensate trap contains a lot of grit, rather like sand. I don't think that's normal, but what is it likely to be? It works normally, but keeps losing pressure, about 1 bar every 3-4 days, with no signs of escaping water. I keep topping it up...
  17. C

    Pressure Loss in Solar Thermal Systems

    One of my plumbing customers experiences a gradual small leak of the heat transfer liquid over a month or two. Eventually it stops working and they have to get it re-pressurised by their installer - its several years old now and they say the liquid is quite expensive. Is this usual and can...
  18. P

    Rapid pressure loss

    Hi all, I came home from work yesterday and the misses said there was no hot water. Checked the boiler (vailliant ecotec) and error code F22 showing (low pressure). So i filled it using the loop to 2.7 bar. Within 10 min it dropped to 2.5. Came back to it half an hour later and it said 1.5...
  19. A

    pressure loss on a morco feb24e boiler

    Please can anyone help, we have a static caravan with a morco feb24e boiler over the past few months the boiler keeps losing its pressure ive checked for any leaks in and under the caravan but didn't find any i did notice the prv was weeping slightly so i got it replaced i also had the expansion...
  20. D

    hammering and pressure loss - post boiler install

    Hello, just had a Worcester 30Si combi boiler installed and now one of the hot water taps developed a new problem. On the first twist - I get a bit of pressure, second twist - less pressure, third twist - loud disconcerting hammering, fourth turn - good pressure, no hammering. The problem...
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