🚀 go-pugleaf

jt3@ornl.gov (John F. Thomas) wrote:

>I'm confused, isn't the steam loop a closed loop.  Do the British nuke plant 
>operate like U.S. plants? - one pressurized water loop (which may have some 
>radioactivity) to take heat off the reactor which exchanges heat with a 
>water/steam second loop (which should have close to zero radioactivity) which 
>goes through the turbine.  The steam is condensed back to water and reused, 
>with the condensing heat exchanger swarming the Ocean or river (unless 
>cooling tower is used).  You imply that contaminated water was dumped in the 
>ocean?  Anyone who is informed care to explain this?  I wonder was the 
>regulations are?
>
>
>Big cut here
>
>>        An Englishman's perspective.
>
>John F. Thomas. Oak Ridge National Laboratory
>Thomasjf@ornl.gov

The system you describe is the same as in Sweden. All our reactors are 
placed at the coast so we have no cooling towers. The cooling water 
outlet is very close to zero concerning radioactivity. The activity is 
measured constantly. As the underpressure in the condensor is close to 
vacuum you have a higher pressure inside the titanium tubes where the 
seawater flows. If a leakage would occur no process water would 
come out due to the low pressure in the condenser. Instead sea water 
would come in and pollute the process water. That would cause a scram. 
The plant would autostop and no more steam would be produced. As the 
process water is deionized it is non-conductive. The conductivity of 
the sea water would start the scram process. I takes 4 seconds from 
alarm to autostop the reactor.

Inside the plant you have a lot of other systems with water that for 
different reasons might get contaminated. All this water systems go 
first to what is called the "waste handling facility". The water is 
monitored and collected in very big tanks according to activity 
level.If it is not contaminated or the activity lies below a certain 
permitted level it is let out together with the cooling water from the 
sea. If the activity is higher the water is treated in different 
ways (filtering, destilling, autodecay etc).

No privat persons are allowed to come nearer the outlet from the 
seaside than 300 m. So swimming near is not possible here. That has 
nothing to do with radioactivity. As a NPP is a security object and 
the distance is the "fence". Besides you could easily drown if you 
came too close to the enormous amount of water coming out at one spot.
At Barsebek (Swedens smallest NPP 2x615 MWe) it is 50,000 
litres/second.

Permitted limits in Sweden are:
Nearby population maximum 0,1 MSv/Year from the NPP
The normal outlet is around one single percent of that.
The ground in Sweden gives the avarage Swede 1 MSv
Your own body 0,2 MSv
All NPP:s give the avarage Swede 0,002 MSv

Hans Pedersen Dambo

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