Geology and hydrogeology ... …

Report No. SRL/FP/004.1 (10/05/2006)

measurements of impurities and toxins. But it is very scantily written being full of such expressions as “considered to be” and “understood to be”, which mean “not known” and “not understood”. Examples of the inadequacy of this appendix are appended hereto. Although RWE npower have recorded the data from the boreholes they have access to in the vicinity of Lakes H/I, they do not appear to have remarked on the extent of the problem they have caused.

# What might RWE npower do in relation to leaching from Lakes H/I?

They can try to measure the leach rate. A method that could be used is a standard one used in nuclear fusion experiments. The quantity they wish to know is the residence time

of water in the bunded lake if no water is

circumstances

is

then

the

leach

rate.

In

added or removed. The loss rate in these nuclear fusion experiments the comparable

quantity is the particle confinement time, τ. The rate of change of the total number of particles in any system, N, is given by the differential equation

# DN/dt = Sources – Sinks – N/τ,

Where the Sources term represents the rate at which particles are added to the system; the Sinks term represents the rate at which particles are removed from the system;

and N/τ represents the loss of confinement due to, in this case, leaching.

It is more convenient to rewrite this equation in terms of the Volume, V, of the water in the lake, and the driving term in terms of the volume excess ∆V =Ah where A is the surface

area of the lake and h is the height of the water level in the lake above the water table outside – both of which may vary with time. If the lake water level drops below the

groundwater level, ∆V becomes negative allowing for the possibility of flow of groundwater into the lake under such circumstances. Thus we get

dV/dt = [Inflow of water from Didcot] + [Rainfall over the lake] – [evaporation from the lake] – [outflow from the lake] – ∆V /τ

# All of the terms in the above equation can be measured or modelled for the prevailing

conditions, enabling the equation to be solved to find the confinement time, τ. τ should be

greater than a few decades if the bunding is to experiments, deducing the confinement time experiments and observations to be planned

be is to

effective. As quite difficult. optimise the

is found in nuclear fusion

It requires a

series of

measurement.

But any

competent physicist or engineer could deduce a set of suitable experiments to evaluate τ. Without an evaluation, it is always possible to assert that leaching may be occurring. With

a good measurement of τ one can establish, with reasonable certainty, whether the clay bunds work or not. Not to attempt such a measurement is unscientific. It should be made on Lakes H/I, before any further bunded Lakes are considered.

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© SAVE RADLEY LAKES 2006