Technical complements: What are the transport safety measures?

All the equipment used for the transportation of the returned residues is designed in accordance with relevant regulations in order to prevent any risk of accident. However, possible accidental situations have been analysed, applying the safety in depth principle, to ensure the safety of the transport.

Events linked to the transport vessel

The ship is equipped with a modern radar and anti-collision system which drastically reduces the probability of a collision or grounding. A significant record of spent fuel transportation's (more than one hundred and fifty shipments) between Japan and Europe has been accumulated during more than 20 years of operation on the same class of ships without any incident. If a collision were somehow to occur, the consequences would be limited by the double-hull and anti-collision structure of the ship.

If, on top of that, the ship somehow became submerged, it could be located using the satellite tracking system. In addition, the vessel is fitted with sonar location beacons capable of locating a sunken vessel at depths in excess of 6,000 m.

Under international regulations, casks are subjected to an immersion test where they must withstand the pressure of at least 15 metres of water. In fact, it has been confirmed that the casks would maintain their integrity in several thousands of metres of water. Even in the extreme case of water penetration into the cask, the ultimate barrier to the dispersion of the radioactivity would be the glass itself.

Protection against the risks of internal fire is provided by the separation (by a steel wall) of the holds from the energy and propulsion equipment (engine room, fuel tank, shaft), and the installation of prevention and fire-fighting systems. The cargo itself is fireproof.

The risk of external fire from a collision is very low as described above.

The fire fighting systems (detection equipment, hold flooding system, sprinkler, halon, ...) provide the means to quickly detect and put out any fire on board the vessel. Moreover, the fire resistance of the cask is demonstrated by regulatory tests.

Events linked to handling

Drop
During handling of the transport cask, the crane used for loading the transport vessel has a maximum height below the 9 m level imposed by the regulatory test for a drop onto an unyielding surface.

Cask loading

The transport casks are loaded into the five available holds on two levels. This can be done using either shore based or floating cranes of about 150 tonnes capacity. The casks, mounted in frames, are then securely bolted to the ship's structure.

During voyages, routine checks are made of the hold cooling systems, radiation levels and cask securing arrangements are additionally checked in heavy weather conditions. The cargo space is segregated from the rest of the ship by radiation shielding which is extended forward from the bridge by concrete overlaid on the deck and beneath the hatch covers.

PNTL Manpower

PNTL's ships typically carry a crew which is approximately two to three times larger than that found on chemical tankers of a similar size. All navigating and engineering officers hold certificates of competence for a higher rank than the one they serve. For example, the Chief Officer must hold a Master's Certificate. All personnel are actively encouraged to enhance their skills and qualifications and to take relevant training courses.

All members of the ship's crew wear film badges to monitor individual radiation doses whenever casks of radioactive material are on board. The recommended maximum dose for transport workers involved in the movement of radioactive materials is 20 mSv/yr and the average dose to PNTL ship's crew over the last 10 years is 0.08 mSv/yr.