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20 mohlfeld retreiving vs emergency_preparadness
1. Asse II Mine –
Retrieval of the Waste Taking into Account
the Best Possible Emergency Preparedness
Matthias Mohlfeld
Federal Office for Radiation
Protection (BfS), Germany
Washington, DC
September 7-9, 2016
2. Key Data
2
Asse II
salt
Asse II mine
Waste emplacement: 1967-78
Low and intermediate level waste
Brine inflow from the overburden rock since
1988
Intended option for decommissioning:
Retrieval
3. The Mine
3
A “research mine” that should never have
been used for the disposal of radioactive
waste.
4. The Asse II mine. The fault. The problem. The task.
Four Steps - One Problem.
4
5. Asse II – The Mine
5
The Asse II mine. The fault. The problem. The task.
6. Mining vs. Disposal
6
Purpose of mines Purpose of repositories
Maximal extraction of raw materials Safe enclosure of radioactive waste
12. Inflow of Brines since 1988
12
1988, 532 m
Since 1998 the collected brine rate is
about 12 m³/d
Brine is almost saturated
13. Asse II – The Task
13
The Asse II mine. The fault. The problem. The task.
14. Decommissioning According to
the Atomic Energy Act (AtG)
14
2009
§ 57b AtG
„The Asse II mine shall be decommissioned immediately.“
2009 -
2010
2013
Retrieval Relocation Backfilling
§ 57b AtG
„The Asse II mine shall be decommissioned immediately. […]
The Asse II mine shall be decommissioned after the retrieval of the radioactive waste.“
15. Tasks of the BfS
15
Decomissioning of the mine
Stabilisation and
emergency
preparedness
Operation of the mine under nuclear law and mining law
Tasks of the BfS
Shaft 5
Fact-finding
Interim storage facility
Retrieval machinery
Infrastructure
Retrieval of the waste
16. Stabilisation and
Emergency Preparedness -
16
Measures to stabilise the mine openings and to protect the
emplacement chambers:
• to continue safe operation
• to maintain the integrity as best as possible
• to achieve the best possible emergency preparedness in the event of
an increase in brine inflow
• to keep the basis for the retrieval of the waste
Prepatory measures for fast reaction in the event of an emergency:
• for fullfilling the waste chambers
• for flooding the mine with saturated brine
• for stabilizing the mine with compressed air
• for the shaft closures
19. Interim Storage Facility
19
Storage area with
buffer store
Salt processing
Collection of
waste water
Workshop and
decontamination
Store for additives
Supply building
Waste package
acceptance
Conditioning
Drying Measurement hall
Office and
social buildings
20. Demands and Contradictions
20
Retrieval? - Immediately!
Interim storage facility? - Nimby!
Disposal at Konrad Repository? - No!
Retrieval? - Mission impossible!
21. Asse Decommissioning Project –
Time Schedule
21
Planning / construction shaft 5
Retrieval
Fact finding step 1 - drilling
Emergency preparedness and remediation
Planning / construction of interim
storage facility incl. conditioning
“Lex-Asse”: Retrieval legally laid down as decommissioning option to be pursued.
Enables parallel action (to invest before the results of the fact finding are available)
Ladies and gentlemen,
I would like to tell you some things about a project in Germany
First problem. How should I call it:
Is it a repository? Well, at least once it was one, but it should not remain
or
Is it a pit? Yes, but then we should not forget that currently there is still radioactive waste in it
But maybe it is helpful if we begin with the history and some key data:
The Asse II mine is located somewhere near Hannover
It is an approximately 100-year-old potash and salt mine.
In early times the former operator used the Asse II mine as a "research mine" for the disposal of radioactive waste in salt formations.
In the period 1967-1978 the disposal of low- and intermediate-level radioactive waste took place.
Since 1988, we recognize an inflow of brine from the overburden rock.
And maybe the most interesting key data is the intended decommissioning option: The retrieval
Today I would like to explain to you a few backgrounds, how it came to this decision and what additional problems such a decision is connected with.
Let me start with the mining situation.
You can obviously see the high degradation density in the so-called southern flank
and you can also see the red highlighted storage chambers for low level radioactive waste on the 750m-level.
Another emplacement chamber with intermediate-level waste is located on the 511 m level.
You can´t see it here but nevertheless it is there.
By today's standards, it must be said that the Asse II is a research mine that never should have been used for the disposal of radioactive waste.
But you know, hindsight is easier than foresight and so we have to deal with what is there.
So how did it happen?
A little hint I can give you with these symbols:
There were 4 steps and (at least) 1 problem.
The first step was „Mining“
The purpose of mining is the maximum extraction of the raw materials
Here it was potash and rock salt.
When comparing this with the approach for the design of a planned repository, you can already see that there is a contradiction.
When designing a repository you focus on the maintaining of the barrier properties.
Independently on that we have to point out that the Asse is a ridge where salt mining was very usual.
However the two neighbouring pits (Shaft 1 and Shaft 3) are already flooded.
The second step describes the "Fault":
In the period 1967-1978, there was a trial-phase
for different storage techniques (lay in rows, put them in pillars or just dump the barrels in the chambers).
125,787 barrels with a volume of about 47,000 cubic meters and a total activity of about 2.4 x 10E15 (ten to the power of fifteen) Bq were stored.
First, this fact has not been identified as a fault.
This interpretation results actually only from the "third step"
the problem
(more specifically we have to name at least 2 problems):
First: We have very strong rock deformations in the mine
Second:
Since 1988 we recognize the entry of overburden solution
The collected amount of solution is since 1998 relatively constant at about 12 m³ / day and is almost saturated.
So we come to the fourth step, our task- the retrieval.
Maybe you´re asking yourself: Why do they do something like that?
I do not expect that I can convince any of you here today that the retrieval is the only right decision,
but perhaps you will understand how it came to the decision.
At the beginning of 2009, the Federal Office for Radiation Protection (BfS) took over the operatorship for the Asse II mine.
In Germany we have the Atomic Energy Act and in §57b you could read:
“The Asse II mine shall be decommissioned immediately.”
So the new operator started his job of planning what the best decommissioning option might look like.
Here you see the three main options which were compared:
- The retrieval - The relocation within the pit - And the complete backfilling with stabilizing concrete
According to this comparison of possible options for the closure of the Asse II mine,
the retrieving of the radioactive waste is, according to current knowledge,
the only option for a safe decommissioning.
Therefore in 2013 the law was supplemented by a small subordinate clause (with far-reaching consequences). "The Asse II mine shall be decommissioned after the retrieval of the radioactive waste."
So since 2013, we have a new legal order, how to proceed with the mine.
But unfortunately, the problems described in the "Step 3" are thus not fixed
(you may remember "strong deformations" and "existing brine inflow" of which nobody knows how it will continue to evolve).
So on the one hand we have to deal with the challenges arising from a retrieval of radioactive waste:
fact finding (what is in the chambers and how does it look like?),
Infrastructure (excavation of a new pit, the old one is not suitable for the tasks of the future),
Retrieval machinery (which technique is appropriate?),
Interim storage facility / plant for conditioning,
new Shaft (the old one is not designed for it))
But on the other hand we still have to take into account the aspects that result from the loss of stability of the pit and the planning of the so-called emergency preparedness.
In any case that might happen and which leads to the decision that the retrieval should stop
(for example, if the inflow of brine rises)
we must be able to represent that we have yet done anything to minimize the radiological consequences in the biosphere to a minimum
(although we cannot demonstrably meet the objectives).
Especially therefore the operator has developed actions for an emergency plan.
With this task, the following measures are currently already carried out:
Stabilization measures by backfilling remaining cavities with concrete
Precautionary measures necessary to be prepared for a possible event of an emergency to reduce the radiological consequences
A majority of these measures have already started or have been completed,
so that today the mine looks somehow like that with only a few open spaces.
By the way, this fact is also connected with fundamental logistical difficulties if you still have to act in the mine.
But let me come back again to the measures that are required only by the requirement of retrieval.
First, we have to sink a new shaft.
The tasks of this shaft are:
the safe transport of the waste,
an increase in the number of employees underground and
ensuring an adequate supply of fresh air.
currently suitable areas are being explored for that.
Furthermore, a necessary requirement to begin the retrieval is
a conditioning plant and
a sufficiently dimensioned interim storage facility
Maybe you can imagine that alone on this point we come to the next problem:
We have some demands and contradictions:
Where is the right or accepted place for the interim storage (nearby or possibly far away?)
and at least for the final disposing of the waste?
These questions are not answered yet and are actually a basic requirement in order to begin the retrieval.
But after all these problems,
the legislature has made us some free space.
We are allowed to parallelize the required work.
This permission is connected with the possibility to invest, before all the requirements are clarified.
So you can see, we are working on many subjects without really knowing how they will look like at the end
and this we can do although we know that there are some interfaces…
Maybe next time I can tell you something about the problems that result from that...
With these concluding remarks
I would like to thank you very much for your attention and if you have any questions, feel free to ask them.
