RD&D-Programme 2004 - SKB

• Trigger levels for action.
• Decision on action to be taken if trigger levels are exceeded.
Method and technology development take place continuously within the framework of planned
activities.
Temperature, microseismic events, groundwater pressure etc can be monitored during the
operating phase, along with resaturation and pressure build-up in the backfill. A safeguards
system must also be implemented.
The safety of the closed repository is not dependent on surveillance or monitoring, but some
institutional controls can be assumed to exist even after closure, for example safeguards
(see section 12.2).
12.2 Safeguards and physical protection
In order to have a well-functioning safeguards system, it is important to adopt a holistic view of
the entire fuel handling chain, which means that encapsulation, canister transport and deposition
of fuel must be regarded as a whole. After encapsulation of the spent nuclear fuel, verification
and measurement of the identity or contents of the canisters is more difficult (see Chapter 8
where safeguards for the encapsulation plant are presented). Good control of the flow of spent
nuclear fuel to and from the deep repository facility is therefore required during transport and
operation of the deep repository. This imposes demands on an inspection function.
Through international treaties such as the Nuclear Non-Proliferation Treaty, the Euratom Treaty
/12-6/ and other bilateral agreements, Sweden has undertaken to use nuclear materials for
peaceful purposes only as well as to keep records of all handling of nuclear materials, including
spent nuclear fuel. Sweden has also agreed to subject all material of this type to international
verification. These safeguards are administered by Euratom and the IAEA, and on a national
level by SKI. The purpose of the safeguards is that the inspection bodies should discover if
nuclear materials are diverted from the system.
The IAEA has also published a draft policy for safeguards for final disposal of spent nuclear
fuel /12-7/, where it is recommended that safeguards be maintained even after the final repository
has been backfilled and closed. The IAEA has concluded that a sealed repository needs to
be under safeguards control as long as similar control is exercised in other areas.
Work is being pursued internationally to define the requirements on the post-closure safeguards
system for a closed geological repository. There may be a need to develop new technology in
certain respects. This can be done via individual states’ support of the IAEA. The reason is that
encapsulated fuel, like deposited fuel, cannot be checked by measurement to determine the
fuel’s content of fissionable material. It is therefore necessary to have a number of mutually
independent components in the safeguards system that guarantee continuous knowledge of
conditions in the deep repository.
The canister comprises an accounting unit in the system. Each canister has a unique designation
which is recorded and its contents documented. Movement of canisters is documented in the
safeguards accounts. The canister’s unique designation is checked and documented when the
canister is lifted up out of the transport cask in the deep repository and deposited.
Measurement equipment which senses whether the canister or other equipment contains spent
fuel or not can be placed at the entrance to the deep repository. In this way it is possible to verify
that no spent fuel is diverted from the deep repository.
An important component in the system of safeguards control of a deep repository is being able
to verify that the facility has been built in accordance with the drawings presented, so that there
are no ways out of the facility that have not been indicated, or spaces in which other activities
take place than have been indicated. This means that the inspection bodies need to conduct
inspections before and during construction and during operation and closure.
RD&D-Programme 2004 141