Tuesday, January 22, 2013

Tritium and Nuclear Power Plants: "Blowdown" Worsens Contamination


Majia here: A friend - Sickputer - recently sent me this excerpt from the World Nuclear Society's discussion of how cooling works at nuclear power plants. 

I will include an initial discussion of how cooling works and then provide the excerpt I want to focus on, which concerns the "bleeding" known as "blowdown" necessary for plants like Palo Verde nuclear power plant in Arizona. 

The inevitable but never mentioned effect of blowdown is that more tritium and other radioisotopes contaminates the local environment.
  
FROM THE WORLD NUCLEAR ASSOCIATION Cooling power plants http://www.world-nuclear.org/info/cooling_power_plants_inf121.html

  • The amount of cooling required by any steam-cycle power plant (of a given size) is determined by its thermal efficiency.  It has essentially nothing to do with whether it is fuelled by coal, gas or uranium.   
  • However, currently operating nuclear plants often do have slightly lower thermal efficiency than coal counterparts of similar age, and coal plants discharge some waste heat with combustion gases, whereas nuclear plants rely on water. 
  • Nuclear power plants have greater flexibility in location than coal-fired plants due to fuel logistics, giving them more potential for their siting to be determined by cooling considerations. 
The most common types of nuclear power plants use water for cooling in two ways: 
- to convey heat from the reactor core to the steam turbines, and 
- to remove and dump surplus heat from this steam circuit.  (In any steam/ Rankine cycle plant such as present-day coal and nuclear plants there is a loss of about two thirds of the energy due to the intrinsic limitations of turning heat into mechanical energy.)  

The bigger the temperature difference between the internal heat source and the external environment where the surplus heat is dumped, the more efficient is the process in achieving mechanical work - in this case, turning a generator[1].  Hence the desirability of having a high temperature internally and a low temperature in the external environment.  This consideration gives rise to desirably siting power plants alongside very cold water.* 

[Majia here: Ok so nuclear power plants need water to cool down. Optimal conditions for nuclear power plants include access to unlimited, fresh, cold water. AZ where the plant is located is extraordinarily hot in the summer and there is no cold water. Now skip ahead to the discussion of how blowdown occurs in plants like the Palo Verde Nuclear Power Plant in Arizona because the plant uses recycled municipal waste and it operates in a very hot environment]

Recirculating or indirect wet cooling
Where a power plant does not have abundant water, it can discharge surplus heat to the air using recirculating water systems which mostly use the physics of evaporation..... 

Water evaporating from the cooling tower leads to an increasing concentration of impurities in the remaining coolant. Some bleed - known as "blowdown" - is needed to maintain water quality, especially if the water is recycled municipal wastewater to start with - as Palo Verde, Arizona*, and proposed for Jordan's Majdal plant.  Replacement water required is thus about 50% more than actual evaporation replacement, so this kind of system consumes (by evaporation) up to 70% of the water withdrawn.
Some 220 ML/day of treated sewage is pumped 70 km from Phoenix, Az to the 3-unit 3875 MWe plant. Evaporation is 76 ML/day per unit, and blowdown 4.7 ML/day at a salinity approx that of seawater, discharged to evaporation ponds. It has three mechanical-draft cooling towers for each unit. “
http://www.world-nuclear.org/info/cooling_power_plants_inf121.html

OK Why is this significant. Its significant because tritium and other radioisotopes, routinely produced by nuclear power plants, are being emitted into the atmosphere through evaporation and into the soil and water table through solid waste discharges. 

Tritium is a major contaminant from nuclear power plants. It is a radioactive isotope of hydrogen. It's almost impossible to contain and emits beta particles that research has found damage DNA. For background on the way radiation safety has been politicized see here

My friend Clyde Stagner studied tritium emissions and environmental contamination here in Maricopa County AZ. Please see my discussion of his book here
 

Clyde has analyzed tritium in Phoenix swimming pools:

May 13, 2012
Stagner is very concerned about the lack of monitoring of tritium emitted from Palo Verde Nuclear Plant. The only tritium monitoring in Phoenix is in drinking water. [CORRECTION to original post: Apparently the EPA doesn't ...

He also analyzed radioisotopes - like iodine-131 - from Palo Verde in Phoenix sludge:

Sep 12, 2012
Clyde Stagner's analyses of radiation contamination in the Phoenix area caused by the Palo Verde nuclear plant in Maricopa County, AZ. Capt. Stagner is author of Hidden Tritium and has had a long, distinguished career, ...
 
AND he has tried through tremendous letter writing campaigns to get the NRC to resume atmospheric tritium monitoring and to monitor tritium concentrations in bodies of water directly downwind from the plant.

Aug 14, 2012
Capt Stagner's data suggest that open water in the county, especially smaller bodies of water, such as lakes and swimming pools, may have become contaminated with tritium. Radiologically contaminated water poses ...

Jul 17, 2012
Clyde Stagner, Retired. He spent much of his professional life monitoring radiation readings for government agencies. I will post links to his book, Hidden Trituim and my previous discussions of his work at the bottom of this ...
Oct 20, 2012
Dear Mr. Stagner: The NRC has completed its follow up in response to the concerns you brought to our attention on July 6 and 7, 2012, regarding the Palo Verde Nuclear Generating Station and radiological monitoring in the ...
 
Majia's Blog: On EPA Censoring and Failure of Transparency in ...
Nov 27, 2011
Stagner has been investigating tritium contamination in Phoenix for some years. Tritium, as Capt. Stagner has pointed out in his written research (most specifically in the research reports "Tritium Hazard" and "Phoenix Women ...
 

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