Solute Travel Times

Question 1

What is one solution of storing nuclear waste as we can’t leave it indefiently in cooling pots

Answer 1

Bury it deep and impermeable so it can’t come back and contaminate is

Question 2

Why was sellafield chosen

Answer 2

A lot of waste was coming around the country to be processed here anyway and it has deep geology that is the least permeable in the uk anyway

Question 3

What is at depth beneath sellafield

Answer 3

Borrow dale Volcanic Group TUFF (slowly permeable)

Question 4

What is the government test for nuclear waste sites

Answer 4

If we put the waste underground and it leaked and comes back to surface within 10,000 years it’s not an acceptable site

Question 5

What are the chemical issues of burying nuclear waste

Answer 5

Radioactive decay - we should hang on as long as we can bc it gets more stable.
Chemical sorption - ions sorb tO soils qbe rock -> longer travel times do this is good.

Question 6

What element doesn’t sorb and so there is no retardation and it has fast travel time

Answer 6

Chloride 36

Question 7

How to work out pore-water velocity

Answer 7

Darcys equation -> average veoclirt over an REV face (area) but actually water is only through part of the face I.e the pores. Must divide Darcys law by porosity

Question 8

What is the key thing to look at when deciding to put a deposit in

Answer 8

How long Chloride 36 takes to get to the surface

Question 9

What did the government try to do

Answer 9

Build an underground laboratory but freenpeace saw the rock characterisation facilit would be a huge cavern underground and would be a backdoor to throw nuclear waste in

Question 10

Example of a borehole in sellafield

Answer 10

Borehole BH9A. Cost 1 million to investigate what was going on

Question 11

What is the packer test

Answer 11

Borehole year where you drill boreholes and you have inflatable packing units that you pump up to isolate different bits of the aquifer to do your test on

Question 12

What is the issue under sellafield

Answer 12

Aquifers are used for water supply so don’t want the sandstone and limestone contaminated

Question 13

In sellafield what would the element have to travel through to get to the surface

Answer 13

400m of TUFF, 300m of St Bees sandstone, 90m it Calder SST and 10m of glacial drift

Question 14

What is the distance that the elements would be allowed to travel

Answer 14

400m

Question 15

What was the nirex assessnent

Answer 15

Used medium hydraulic conductivity.
Worked out hydraulic gradient was 0.06 and porosity was 0.41.
To blunt radionuclei to top of tuff it will have decayed away.

400/ 0.00044 = 1,000,000 yrs

Question 16

What was the green peace assessment

Answer 16

Used highest Ks (precautionary principle)

Found it would only take 100 years before hitting the aquifer.

Question 17

What is the problem with using the highest Ks value

Answer 17

Assuming the small value you are reflecting on could reflect a whole aquifer is nonsense because if you have a fracture running through the block it has a huge effect on permeability on local scale but not overall. Unrealistic - pessimistic

Question 18

Problems with using the median Ks

Answer 18

Assumes measurements samples all preferential paths like fractures. If you use the middle value you have to really know the disruption of permeability but only measured a small area.

Question 19

What does the assessments ignore

Answer 19

Likely Ks patterns - when looking at profile of geology there’s all sort of layers with different permeability which affects how water moves. The contrast of permeability affects how water moves as it would refract and change direction.

Question 20

What is the most intensive borehole study in the Uk

Answer 20

Sellafield

Question 21

What does the sellafield study underestimates

Answer 21

The effects of long conductive features like Fleming hall fault which could shoot up thinga to the surface.
Velocity - overestimates travel time.

Question 22

What does the sellafield assessments need

Answer 22

Model Ks Patterns to dramatically alter the rates of water movement as we know.
Use only large scale Ks values.