Operational requirements for storage facilities

The operations carried out in a storage facility are limited to receipt, emplacement, integrity control (if required), retrieval, and preparation for dispatch of DSRS packages. The storage operations are essentially passive for the long period of time when packages are waiting pending retrieval until the repository facility is established.

All operations concerned with storage need to be carried out in accordance with the written authorized procedures.

9.3.1. receipt and emplacement

The storage areas are designated and operated as controlled areas to limit the spread of contamination and to minimize the exposure of workers to ionizing radiation. Adequate protective clothes/equipment need to be made available and worn/used as required.

The DSRS receipts should be planned in advance. The store operator examines the information to confirm that the source package is acceptable for storage, e.g. that it conforms to the storage WAC. If unacceptable, the details should be recorded and the documents returned to the consignor with an explanation, or request for further information. In the case of external contamination, the package has to be decontaminated and rechecked before acceptance for storage.

The design of the facility should usually permit package stacking, sorting, and visual inspection. On acceptance, the store operator needs to prepare the appropriate documentation to store the sources. At the store, a suitable location for the DSRS package needs to be identified and the location details recorded. The package should be placed in the designated location. Segregation of sources is desirable to facilitate retrieval for further reconditioning or any unplanned retrieval, which is deemed necessary by periodic inspections for possible degradation of source containers, or in the event that there are particular categories of sources to be emplaced eventually in particular disposal facilities. The records of the store inventory need to be updated, and periodic checking of the store contents against the records is required.

An example of segregated storage is shown in Fig. 60.

FIG. 60. Segregated storage of radioactive waste, including DSRSs.

9.3.2. Additional shielding

Additional shielding to that envisaged by the design in the store may be provided for the packages with high contact dose rates and where a large number of packages with low contact dose rate are placed in the store.

9.3.3. Integrity control

As the long term effectiveness of engineered or natural barriers against the release of radioactivity into the environment cannot be guaranteed for all future conditions, a monitoring programme for the storage area needs to be established. If technically feasible, monitoring is needed between the individual barriers (e.g. the package, the storage boundary and the facility boundary) so that migration of radioactivity is detected well before spreading

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outside the facility. In this case, measures need to be taken to minimize the spread contamination. Therefore, it is advisable to perform and record initial background measurements of the storage facility before it is commissioned.

The frequency of monitoring will depend on the number and types of DSRS packages.

The effectiveness of the ventilation system needs to be included in the surveillance programme. Radiation monitoring and personal dosimetry is mandatory.

9.3.4. retrieval and dispatch

Following receipt of the request to retrieve a package from storage, the store operator needs to obtain the details of the particular package from the store’s records and pass them to the appropriate party. If the details are in order, the package may be approved for retrieval from the storage facility. Once the store operator has authorized the release of the package, the package is retrieved from the store and taken to the dispatch area. Here, the package is subjected to radiological monitoring for contamination and radiation levels before it is released. The details of the package are transferred to the transport records, and the package is submitted for transport in accordance with the transport regulations [47]. The package storage records need to be amended to record the date of dispatch and the receiving party.

9.3.5. security systems

Security systems to prevent intrusion need to be an integral part of a storage facility. A typical security system includes features to delay access, detect unauthorized access and provide an alarm and response system. An example of the secure storage facility is given in Fig. 61. The operational personnel shall ensure its uninterrupted service under all foreseeable circumstances.

FIG. 61. A secure storage facility.

Access to the storage areas needs to be strictly controlled in order to prevent losses of stored materials, since this may not be detected until some considerable time after the removal has occurred. In the stores, security is usually achieved by locking the premises. Personnel with authorized access need to be kept to the minimum. Seals can be used for the detection of any unauthorized access. Other appropriate security measures (such as guards, barbed wire fencing, surveillance cameras, alarm systems, etc.) and regular stocktaking need to be considered in the context of the prevailing security situation. The effectiveness of the security system needs to be regularly audited and updated.