Jeffrey LewisMore on EPURE

Yesterday, I noted that the centerpiece of the UK-France agreement to cooperate on nuclear weapons stockpile stewardship was to be a new radiography facility at Valduc, called EPURE.

Today, a few more details are available.  It appears that the facility will be shared, but that French and British teams will work seperately.  Our friend, Bruno Tertrais, explained in an interview with Le Point — “Chacun reste maître chez soi.”

Quelles avancées concrètes permettra cette nouvelle installation de Valduc, baptisée EPURE ?

Il s’agit pour l’essentiel d’un centre de radiographie qui permettra d’étudier le comportement de matériaux soumis à des conditions extrêmes de température ou de pression, ce qui est le cas des armes nucléaires. Mais si l’outil technique de physique sera conçu et réalisé en commun, les activités seront complètement séparées. La machine est partagée, et les expériences seront faites par chacun dans son coin. C’est symboliquement important et politiquement très significatif, mais au plan de la dissuasion nucléaire et de ses outils, cela ne change rien du tout, ni pour les Français, ni pour les Britanniques. Chacun reste maître chez soi.

Jean-Dominique Merchet, a journalist with Marianne, has a detailed description of the proposed project, noting that AIRIX takes pictures on a single axis.  It is not clear whether EPURE will be a 2- or 3-axis facility.  (The D in DARHT, the US facility, stands for “dual” while the proposed UK Core Punch facility would have had three):

Avec les supercalculateurs Tera 10 et le laser mégajoule, le système Airix  est l’un des éléments du programme de simulation des essais, lancé par la France après la fermeture de Moruroa en 1996. Il s’agit d’observer ce qu’il se passe au moment de l’implosion, qui “allume” la réaction nucléaire au sein de l’arme. C’est un système de radiographie par rayons X, comparable à ceux utilisés en médecine, mais nettement plus puissant. Le but est de radiographier des matériaux, d’une densité pouvant atteindre 60, durant les quelques millièmes de secondes de l’implosion, alors qu’ils se déplacent à des vitesses comprises entre 2000 et 3000 mètres par secondes. La résolution du système actuel est de 0,5 mm. Il fonctionne à Moronvilliers (Marne) depuis 2000. Ces tests se font avec des matières inertes, proches de celles utilisées pour les armes.

Le système actuel ne permet que d’obtenir une seule image, alors que celui qui sera développé au Valduc, d’ici à 2022, permettra de radiographier l’implosion sur plusieurs axes. Un progrès notable, dont on ignore encore le coût.

[le snip]

Le partage d’installations scientifiques au Valduc ne signifie pas pour autant que les deux pays échangeront complètement les résultats de leurs expériences. “Il pourra y avoir des transports de matériels nucléaires britanniques en France” a précisé l’Elysée.

En matière de laser mégajoule, une coopération existe d’ailleurs avec les installations américaines de Livermore, sans pour autant que tout se fasse à livre ouvert avec les Etats-Unis.

The other interesting things to note here is that Merchet suggests the information barrier will be similar to CEA’s use of the US National Ignition Facility (NIF) which is something that is acknowledged, but seldom discussed in detail.

I don’t really know how this works for hydrodynamic research.  “Unless you say ‘On Mondays, Wednesdays and Fridays only French are allowed in the building, and on Tuesdays, Thursdays and Saturdays only Brits and we all take Sunday off to have a party,’ I don’t know how you don’t share information,” I told Geoff Brumfiel, who wrote a nice post on EPURE.

Nor, am I sure that I understand why the UK and France want to develop their own hydrodynamic test facility, when the UK has access to DARHT and France presumably could have access (as it does at NIF) if it wished.

Its all very strange.


  1. bob (History)

    Why would Core Punch need to be 3-axis? Two axis should be sufficient. Why have a totally asymentrical design? Possibly levitation, ports or lens layout for >1 point safe?

    • George William Herbert (History)

      Even 3 axis isn’t perfect for resolving the 3-D shape of the imploding pit assembly. The nature of flash X-ray photography doesn’t give perfect answers.

  2. Ataune (History)

    Another important question mark is regarding France’s, and to a lesser degree UK’s status regarding the NPT: Isn’t all of this considered new and improved research and cooperation among NWS on weapons and isn’t this running against, if not the letter at least the spirit, of the Non Proliferation Treaty?

  3. Geoff Brumfiel (History)

    Thanks for the link! So to add a bid of speculative stuff that didn’t belong in a news story: An informed source suggested that shots on DARHT are actually quite expensive, and of course, the facility is in demand by US weaponeers. For those reasons, the UK and France are building their own laser facilities, so (to me at least) it would make sense that they might want their own hydrodynamic test facility as well.

    I’m given to understand that it would be hard to share a DARHT-like facility without divulging sensitive data, but at the same time, I’m aware of a precedent for keeping classified data separate. AWE’s new Orion laser has been designed to route data to two completely separate networks: one classified, the other open. When I travelled there earlier this spring, they actually showed me how it worked–servers were kept in physically separate rooms (behind some heavy doors in the case of the secure machines). There were separate data analysis centres as well (more here:

    Could a similar system be planned for EPURE?

  4. John Ainslie (History)

    The new hydrodynamics facility for AWE, Hydrus, would initially have had two axis, with long term plans for a third. The project has been repeatedly delayed over the last decade. After receiving planning permission on 29 September, Hydrus is presumably cancelled.

    There is a history of the US “borrowing” the hydrodynamic facilities at AWE for their own projects. So the proceedures involved in carrying out these experiments overseas, without sharing data, may already be in place.

    The US would probably have been granted access to Hydrus, so will the American labs be allowed to use the new facility at Valduc ??

    The complex technology, with unknown cost, is in the supersize X-ray machines. The US developed the first models but they were improved by an Aldermaston scientist, Charlie Martin. His work was a rare British contribution to the US nuclear programme. AWE consider themselves as leading world experts in this field and they may take the main role in developing the machines for Valduc, based on the proposals for Hydrus.

  5. Peter Burt (History)

    Reading the announcements about the co-operation programme – especially the statement by UK Defence Secretary to Parliament – it seems that the programme is far broader in scope than just co-operation over a couple of research facilities. The long-term aim seems to be to integrate the warhead physics research infrastructure of the two nations much more closely in the long term.

    In the immediate future it appears that AWE’s role will be to develop x-ray technology for Valduc, as suggested by John, but this doesn’t mean that its new hydrodynamic facility, Project Hydrus, will be cancelled. AWE seem confident that Hydrus will continue. Both nations have considerable investment in new research infrastructure underway and the intention seems to be that as far as possible these will be optimised and modified for the mutual benefit of the future joint programme.

    Nuclear Information Service has put together a short briefing summarising all the info which has emerged so far on the joint programme – available at

    • Peter Burt (History)

      Copies of the original treaty documents are now also online at

    • George William Herbert (History)

      The integration of warhead physics programs could be what got some in the US up in arms, and is what I was afraid they were upset over.

      You can’t do that without showing the other guy what’s under your weapons design’s sheets, as it were. And much of the UK’s weapons designs are originally US designed components.

      France apparently had much less access to that type of info in the past.

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