The Swedish nuclear regulatory authority SSM suppressed one of its senior engineer's doubts about the safety of the proposed scheme for storage of Swedish nuclear waste fuel, which he had set out in a memorandum in June 2016.
Earlier this year, SSM signalled a green light for the KBS-3 scheme to proceed to the next phase of the approval process. Whereas the organization claimed that its favorable finding was unanimous, a document leaked to Sweden's principal environmental organization shows that Björn Dverstorp, the engineer directly responsible for assessing the long-term safety of the scheme, had expressed serious concerns about the viability of the copper canisters in which the fuel waste is to be loaded and stored.
Dverstorp is not alone in his concerns. Issues relating to the choice of copper for the canisters have also been raised by a number of senior researchers at the Royal Technological University in Stockholm.
The criterion for approval is that the canisters may be presumed to remain intact for 100,000 years. Referring to the risks of creep strain, stress corrosion and hydrogen-induced embrittlement of the copper, Dverstorp warns that, at worst, the canisters might fail in the first 300 years after their interment. (Failure of the primary barrier at that stage could mean a 41-fold increase in radiation emissions from the repository.) He therefore urged his colleagues to demand that SKB, the nuclear industry-owned company charged to develop the scheme, do further testing and produce evidence that supported the canisters' integrity, before giving a go-ahead.
Dverstorp's concerns were apparently ignored when SSM gave its approval, and they are not reflected in the documents the agency subsequently submitted to the Environmental Court. What is more, SSM's statements to the Court and the general public suggest total agreement within the agency: "It is our policy to give everyone who has taken part in an evaluation an opportunity to express divergent opinions. But no one had any," stated the agency's communication director in an interview.
For his part, Björn Dverstorp does not know exactly when or on what grounds his views were rejected. He was not consulted.
No less worrying is an assurance SSM put forward when Dverstorp's dissent was made known: "SSM believes that SKB will be able to solve these problems [embrittlement and creep strain] at a later stage by one or another means."
Björn Dverstorp advised against making such assurances already in his memorandum of June 2016: "It is not reasonable for SSM to assume responsibility for [the supposition that] improvements in the canister design will resolve identified problems relating to premature canister failure due to creep, etc. That is something that SKB should have to demonstrate."
Sweden is a small country, and the nuclear community here is close-knit. All share a commitment to the technology, and many have sat side-by-side on the same school bench. That makes regulating difficult. Many who have read all of SSM's text production can point to 'telling' passages, where collegiality seems to have interfered with, or at least taken the edge off, regulatory duty.
The fact that the KBS-3 method has been under development for roughly 40 years can, for example, be interpreted differently. SSM takes it as reason to be cautious: "Considering that more than 40 years of work have been invested in the KBS-3 project, we have to make sure that we can explain exactly why we find that SKB's proposal might not meet the criteria [of approval]." (Sveriges Radio Ekot,11 October 2017)
By contrast, Björn Dverstorp puts the burden of proof on SKB: "Developing the canister is a complex and time-consuming task. SKB has been working on it for over thirty years, and so, it is hardly convincing when SKB 'makes guesses' about what further development of the canister design may be able to resolve." (Memorandum 13 June 2016)
The Environmental Court heard testimony, oral and written, from all concerned parties during five weeks in October and November. The panel of jurists will review the material in coming weeks and make a determination as to whether the project is mature enough to be presented to the government for a final decision. At the time of writing, their 'verdict' is expected on 23 January 2018.
Sources (all in Swedish):
Björn Dverstorp: Övergripande synpunkter på GLS-rapporten, Del 1 Om kravuppfyllelse (1:a remissutgåvan 13-3523, daterad 2016-05-27) [General comments on the GLS Report (GLS = Evaluation of long-term safety), Part 1 on fulfilment of approval criteria]. Unpublished memorandum, 13 June 2016.
Annika Digréus: Strålsäkerhetsmyndigheten: Risker med planerad slutförvarsmetod [SSM: Risks associated with planned method for final storage]. Sveriges Radio, Ekot: 11 oktober 2017
Kerstin Lundell: Dokumentet avslöjar: Så allvarliga är riskerna [The document reveals dangerous risks]. Sveriges Natur, 23 oktober 2017 (web article, updated 27 October).
Kerstin Lundell: Myndighet mörkade risker [Authority suppressed risks] Sveriges Natur, årg. 108, nr 5 (2017).