IRSN raises issues with design of Cigéo repository

The project to construct an underground radioactive waste repository in France has achieved "satisfactory technical maturity", the country's Institute for Radiological Protection and Nuclear Safety has said. However, it identified a number of issues that could potentially impact the design concept and timeline for the project.

The project to construct an underground radioactive waste repository in France has achieved "satisfactory technical maturity", the country's Institute for Radiological Protection and Nuclear Safety (IRSN) has said. However, it identified a number of issues that could potentially impact the design concept and timeline for the project.

Cigéo's underground operations will ultimately occupy 15 km2 (Image: Andra)

France plans to construct the Centre Industriel de Stockage Géologique (Cigéo) repository - an underground system of disposal tunnels - in a natural layer of clay near Bure, to the east of Paris in the Meuse/Haute Marne area. The facility is to be financed by radioactive waste generators - EDF, Areva and the French Alternative Energies and Atomic Energy Commission - and managed by waste management agency Andra. The application to regulators to construct Cigéo should be submitted by the end of 2018, with construction itself starting in 2020. The pilot phase of disposal could start in 2025.

Andra submitted a "safety options dossier" for the Cigéo project to the French regulator, the Autorité de Sûreté Nucléaire (ASN). This sets out the chosen objectives, concepts and principles for ensuring the safety of the facility. The dossier gives Andra the possibility of getting advice from ASN in preparation for the licence application on the safety principles and approach.

ASN requested its technical arm, the IRSN, examine the dossier and provide feedback. The IRSN said the main purpose of its examination of the file was to "assess the project's maturity status in order to judge the relevance of the options selected, from the point of view of safety and radiation protection".

The IRSN announced on 4 July that it had submitted a report to ASN on its conclusions. It said its examination of the dossier had involved numerous technical meetings and more than 600 questions to which Andra responded. It also organised meetings with stakeholders, in which Andra participated. All these exchanges, it said, resulted in the drafting of its opinion report.

IRSN said it considers the Cigéo project has "overall achieved satisfactory technical maturity at the stage of a safety options dossier and underlines the substantial design and research undertaken by Andra with a view to demonstrate the safety of the installation".

However, IRSN said it had identified four issues that may lead to a change in the design of the disposal facility.

It said the facility's architecture must be optimised to ensure that radiation cannot be released into the environment. IRSN also said there must be ways of monitoring risks during the facility's operation, as well as the possibility of intervening "to manage situations likely to lead to contamination of infrastructures".

Andra must consider the consequences of a fire in a cavity for storing packages of bituminous waste. This, IRSN said, is the "most sensitive" issue as the concept currently adopted by Andra "does not provide sufficient safety guarantees". Some 40,000 packages - about 18% of the packages to be stored in the Cigéo repository - are expected to contain such waste.

"The problem is that in the event of a fire [the packages of bituminous waste] rise in temperature and are likely to spread a heat wave and eventually spread the fire," IRSN director of waste Francois Besnus told Agence France-Presse.

IRSN recommends Andra and the waste generators consider the pre-treatment of such waste to eliminate its thermal reactivity or reconsider the disposal concept in order to eliminate the possibility of a fire spreading into the storage cavity. "In this respect, the work to be carried out by Andra on these issues could have an impact on the outline of the [application for authorisation to set up a nuclear installation] or the associated delays," IRSN said.

At the request of the ASN, the International Atomic Energy Agency (IAEA) conducted a peer review last November of Cigéo's "safety options dossier". The review was carried out against the relevant IAEA safety standards and proven international practice and experience.

The IAEA team said it considers Andra's methodology for evaluating operational safety is comprehensive and systematic. The review team encouraged ASN, Andra and IRSN to use the review of the dossier as a basis to make more precise the expectations for the licence application. It added, "This is especially important as the planned Cigéo facility is one-of-a-kind."

ASN is expected to soon issue its own opinion on Andra's safety options dossier for the Cigéo project. This will provide the framework for the creation of the application for authorisation.

Researched and written
by World Nuclear News