Criticality cooldown: Transporting the fuel of the future (text version)

Through modelling and prediction, AFCP’s Nuclear Data project is enhancing international understanding of future fuels. Alfie O’Neill, Criticality Safety Consultant at the National Nuclear Laboratory, details how international collaboration has created cool results for future transport.

The video opens with the AFCP logo on a white background. At the bottom half of the screen is a dark green banner, with the words “Low Temperature Nuclear Data, Alfie O’Neill, NNL” on the left. On the right of the banner are white logos for the Department for Business, Energy and Industrial Strategy and the National Nuclear Laboratory. Alfie’s narration begins:

Across the Advanced Fuel Cycle Programme (AFCP) there’s lots of innovative work going on, with new fuel types and materials being considered.

One by one, the following icons and labels slide onto the screen to the right of AFCP’s logo: A grey cart full of blue minerals inside, labelled “Uranium Supply.” A grey fuel plant, labelled “Enrichment and Fuel Fabrication.” A grey and blue reactor with a symbol for hydrogen next to it, labelled “Reactors.” A grey recycle plant, labelled “Recycle.” A grey storage facility, labelled “Interim Storage.” And a green landscape showing underground storage beneath it, labelled “Final Disposal.”

Because the materials we handle have inherent risks associated with them, all of this work must be supported by a comprehensive safety case.

The video transitions to a new slide, showing a photograph of binders stacked side-by-side on a bookshelf. A yellow sticky note with the label “Safety Cases” is stuck to the bookshelf.

For fissile material, this includes criticality safety assessments.

The words “Criticality Safety” are scribbled across the side of one of the binders.

Criticality assessments, particularly for novel materials, are often based on computational modelling,

The photo of binders shrinks in size. Below it, a computer monitor showing a computational model appears.

which is used to determine how much fissile material we can have where.

To the right of the binders and computer monitor, the outline of a scale appears. One by one, a series of five illustrated, multicoloured barrels stack on top of the scale.

But the assessment also needs to consider any uncertainties in the code and underlying nuclear data, folding these into an appropriate safety margin.

The stacked barrels collapse, with two of them falling to the bottom of the screen. The scale horizontally shrinks in size to accommodate the three remaining barrels. To the right of the scale, a large white box full of three multicoloured question marks appears.

The greater the margin, the less material we can have in any one place or time.

From the top of the screen, another barrel falls onto the stack of three others. The background fades from white to dark orange, creating a gradient to white at the top of the screed not orange at the bottom to top of the screen.

For most systems, we know how well our codes work at room temperatures and above, so the uncertainties here are fairly small. But we don’t know how well our codes and data perform below room temperature.

Two of the stacked barrels off screen, leaving two behind. At the same time, the gradient orange background fades to bright blue and white.

This makes it hard to quantify an appropriate safety margin, meaning the safety case must be pessimistic and therefore more restrictive.

The binders and computer monitor move off screen to the left. The barrels and question marks shift right, falling onto the back of a cartoon transportation truck. The truck is bright green with the AFCP logo at the front.

This is particularly an issue for transport, where IAEA regulations require criticality safety is demonstrated to sub-zero temperatures.

The truck moves off screen to the right.

To help address this, NNL are working with Lawrence Livermore National Lab in the US

The animation begins a new scene, showing a photograph of the building sign for Lawrence Livermore National Laboratory in front of a solid white background.

on a new benchmark where critical assemblies will be cooled to -40°C.

The sign shrinks in size, situating itself at the bottom right corner of the scene. A photograph of lab equipment moves on screen from the left, showing a blue table surface with clear plastic containers sitting on top of it. On the left of the photograph is a cartoon image of a grey flagpole, with a small white flag resting at the bottom of it.

Nobody has done a criticality experiment at these temperatures before!  So far, NNL has contributed thermal modelling expertise,

The flag on the flagpole raises, revealing the NNL logo. Meanwhile, the lab photograph is replaced by a series of modelling images, showing a colourful graph.

as this was where we could add most value. Validation and critical experiments are a key UK skills gap,

The colourful graphs and Lawrence Livermore National Laboratory sign move off screen to the left, as a second flag – this one with AFCP’s logo – raises on the flagpole underneath the NNL flag. The flagpole then moves to the right of the screen as a green text box with the following words appears to its left: “Validation and critical experiments are a key UK skills gap.”

and the AFCP Low Temperature Nuclear Data funding is helping to address this. Particularly, we’re doing this by enabling technical mentoring

The flagpole moves off screen to the right as the green text box expands horizontally across the screen. Beneath it, several more text boxes appear. Another green box, directly below the original one, features the words: “The AFCP Low Temperature Nuclear Data Stream is funding…” Underneath the two green text boxes, five blue text boxes appear with the following text: “International Mentoring,” “ISCBEP Meeting,” “Internal training,” “UK/US Code Differences,” and “Contribution to development of LLNL low temperature benchmark (criticality aspects)”.

with subject matter experts from three different US National Labs.

In the first blue text box, labelled “International Mentoring,” the logos for Los Alamos National Laboratory, Sandia National Laboratory, and Idaho National Laboratory appear.

Funding attendance and contribution to the 2020 International Criticality Safety Benchmark Evaluation Project review meeting.

In the second blue box, labelled “ISBEP Meeting,” a screenshot of the title for the International Handbook of Evaluated Criticality Safety Benchmark Experiments appears.

We’re doing internal training within the NNL Nuclear Safety team to share the knowledge gained.

In the third blue box, labelled “Internal training,” an icon appears. It shows the outline of a person thinking, looking puzzled with a large gear over their head.

And working to understand the differences between the UK criticality safety code MONK and the US code MCNP, and the effect of using these with the US nuclear data library ENDA or the European JEFF data

In the fourth blue box, labelled “UK/US Code Differences,” a photo of a pink, green, and yellow computer-generated model appears. On its left is the word “JEFF” and on its right is the word “ENDF.”

in order to help us best contribute to the criticality aspects of the Lawrence Livermore experiments.

In the fifth and final blue box, labelled “Contribution to development of LLNL low temperature benchmark (criticality aspects),” the previously used photograph of a lab setup appears. It shows a blue tabletop and clear plastic containers sitting on top of it.

All of this gives us a much better understanding of nuclear data and its effects on criticality safety.

The various blue box images, icons, and logos swipe offscreen, once again revealing the blue boxes and their original title text. The five blue boxes and two green boxes shrink vertically, revealing a new yellow text box below them. In this yellow text box are the words: “Much better understanding of low temperature nuclear data and its effect on criticality safety. UK being able to contribute to and influence to international validation programmes.”

It’s also raising the UK’s profile in the international criticality validation community, setting us up to be better able to influence international programmes in the future.

The animation ends by transitioning to its original scene, which again shows the AFCP logo on a white background. At the bottom of the screen is a dark green banner, with the words “Low Temperature Nuclear Data, Alfie O’Neill, NNL” on the left. On the right of the banner are white logos for the Department for Business, Energy and Industrial Strategy and the National Nuclear Laboratory.

Thank you for listening. If anybody would like further details, my email address is on the screen.