Features editor
What should we do with nuclear waste? It’s a question which has dogged the nuclear industry for decades, and it isn’t going away any time soon. The only practical answer is to bury it, somewhere where it’ll be secure and protected for as long as is necessary for its radioactivity to decline to safe levels. This week, the UK’s Nuclear Decommissioning Authority published its generic safety case for a depository to hold the UK’s wastes.
There are several slippery terms in that paragraph, and it’s worth going through them. The first is ‘bury’. We’re not just talking about digging a hole in the ground here. We’re talking about excavating a series of caverns, up to a kilometre below the ground, in carefully-surveyed rock that meets a number of stringent criteria; lining the caverns; filling them with waste which is either encased in cement (for intermediate-level materials) or set in molten and solidified glass and canned in steel and copper cases (for high-level waste and spent fuel), then sealing it up and leaving it while the radioactivity declines. The UK will have a total of some 50,000 tonnes of these categories of waste by the time the current fleet of nuclear reactors is decommissioned. Some of the legacy waste dates back to the 1940s.
The next tricky concept is ‘as long as necessary’. How long? A hundred thousand years. Just to put that into context, Stonehenge is about 5000 years old, and let’s face it, it’s not in good shape. Coincidentally, that’s also estimated to be the earliest date that humans started to write. The last ice age was at its peak 20,000 years ago. So a thousand centuries takes in the entire history of civilisation and reaches even further back. Designing something that’s going to remain intact — and, even more importantly, safe — for that distance in the future must surely be one of the most daunting engineering challenges possible.
Bruce McKirdy, the managing director of the NDA’s Radioactive Waste Management Directorate, is the man in charge of the project, and he doesn’t seem phased by it. However, launching the generic safety study, he was scrupulous in pointing out that word ‘generic’. The reason it’s there is that the UK doesn’t have a site for its depository. The only site selection process that’s ever worked is a voluntary one, he explained, and the process of communities volunteering a site is still ongoing.
It has to be a big ask for any community to volunteer to house such a facility. It’s happened in Sweden, however, where a site in Forsmark was selected in 2009 and is now undergoing tests of its geology.
McKirdy is adamant that volunteerism is the only approach that can be considered, and if a suitable site doesn’t come forward, the process will continue until one does. ‘This isn’t the kind of thing that you could force on a community, and we can make the current waste storage facilities secure for as long as it takes,’ he told The Engineer. The reason for publishing the safety study now is that waste is currently being packaged and it needs to be placed in a form that would be suitable for a repository in a range of geological conditions, depending on the site that’s finally selected.
Clearly, a despository full of toxic, radioactive material is not the sort of legacy that any society would want to leave. But McKirdy believes that in the absence of any technology that can render waste less hazardous, it’s the only responsible course. For engineers, it’s a task which will have to be tackled.
Arguably the waste in temporary storage is more of a risk than it would be in secure storage, but what a legacy for our descendants!
I have never understood why radioactive waste cannot be placed in part of the ocean floor where the mantle is being dragged down and into the earth. I suppose feasability studies, the unknown variables and money have all something to do with it. Any answers?
It seems to me that a strategy based on bury it and forget it is not likely to be a wise cholce. First, remember that the higher level waste still has a lot of untapped energy that a not too distant future generation will learn how to use, so will want to be able to safely access it. Second, in the case of Yucca Mountain, a lot of science and engineering went in to developing a solution, but toward the end the science and engineering people were tasked (I can only assume by lawyers) with determining the probalilities of certain problems occuring and thereby showing acceptable risk, rather than assuming the worst and then figuring out how to deal with them.
Better would be an approach that provides a safe, secure, maintainable storage, something like the water pools now in use, but maybe somewhat better secured.
Clearly distributed storage is better than all in one place – or the not-in-my-backyard scenario will overwhelm. Storage at individual power facilites does not seem all that bad (and has a fairly good record so far), and the ability to recover individual containers and move or maintain them has been demonstrated over and over. Just improve security and specifically recognize theats from persons who do not care if they live through an attack on such a facility.
Why is only “burial” considered when nuclear waste disposal is contemplated.
Why not store in an intermediate area until the reactor is shut down ,then when the reactor has bean decommissioned, place all the accumulated waste in the reactor shell and seal the whole thing until the half life is reached. This would keep the whole unit under observation and any interference would be obvious l
Lots of facts and figures here to help in the debate for Wind turbines over future Nuclear Energy!
How much of the waste is actually radioactive and how much of it is ‘along for the ride’.
Before becoming a Welding Engineer I was a Metallurgist and did a post grad fellowship in Hydrometallurgy for metal winning and refining. Essentially using chemical properties and reactions to separate out the materials we want from the materials we don’t want.
Radioactive waste contains radioactive isotopes that are formed by nuclear fission of the nuclei of an atoms into 2 or smaller nuclei that capture electrons from their environment to form smaller atoms, one or more of which may be unstable radioactive isotope. Radioactive decay will progress naturally until eventually all the products form stable non radioactive atoms
Radioactive waste is a combination of things ranging from a spent fuel rod to the building materials forming a nuclear reactor and the building housing it and the barium meal patients eat in hospitals!
We take the spent fuel rods from a reactor and we use hydrometallurgy to reprocess them to extract the required radioactive isotopes comprising the remaining nuclear fuel and the new fuel formed. If why do that, why can’t we use a combination of mineral processing and extraction metallurgy to process nuclear waste to extract the radioactive material only.
Once the radioactive isotopes deemed as waste are isolated they can be disposed of as high grade waste – possibly by projection into the sun as additional fuel , OR, as radioactive isotopes are formed by neutron bombardment CAN they also be disposed of by placing them back into a reactor and using the neutron bombardment occurring in the reactor to split their nuclei to form 2 or more smaller atoms and continuing the bombardment until non-radioactive isotopes are formed.
I don’t know the costs that will be involved in re-processing this 50,000 tonnes of nuclear waste and then storing it but I do know the horrendous cost of manufacturing the waste disposal containers. Has anyone evaluated the costs of such re-processing as an alternative to waste storage?
Was it at Yucca Mountain last year that the USA government decided not to complete the tunneling out of the mountain to provide a “safe” storage after using up more than $20m dollars? If not Yucca then there is a mountain with a big hole in it with nothing to fill it.
One hundred thousand years is a long time and I am mindful of the ongoing continental shift process and ice ages. This time frame will allow huge alterations to geological structures that at present seem quite safe. Current deep holes could end up very near the surface or breached by the oceans. Perhaps in this time our descendants will have solved this issue and perhaps found a use for the material in inter-stella space travel to ease the population. There is no easy answer.
To try and put this into perspective, an estimated timescale is :-
– the planet Earth is 4.5 Billion years old
– multicellular life started 1 Billion years ago
– the genus Homo appeared 2.5 Million years ago
– Modern man (Homo sapiens) appeared 200,000 years ago
and let’s not forget that entirely natural radioacivite material exists on our planet.
Check out: thorea.org This is the website for the Thorium Energy Amplifier Association. We are committed to the development of clean nuclear energy for a low-carbon future.
The “right” in USA contends nuclear power is “safe, clean, and in-expensive”.
It clearly is none of the above. Yes, more incentive for renewable expansion.
I believe that everything is useful, may be we have not yet discovered the usefulness of the radioactive waste. If elaborated, a solution / discovery may be given. Please give the detailed report of how the waste was generated, what is the content of waste, what are the radiations etc.
Storage of high-level waste will always be a cause for concern. If we can reprocess it down to low-level waste, the all the waste could be kept in secure storage in near surface stores where they can be accessed as required in the future, either for resealing or reuse.
Nowhere on Earth is suitable for a ‘store and forget’ solution. (The dark side of the Moon however, might be a possible candidate. It’s the one place we could probably just leave it sitting on the surface.)
We should have fusion reactors viable in less a hundred years – so it makes much more sense to keep all the waste on the sites where it is generated – which will in any case require 100 years of monitoring – so that it can be burned in fusion furnaces in due course.
Many of the suggestions described above for dealing with nuclear waste have been considered by engineers over the past 30 years but all have concluded that deep geological burial is the best solution. The CORWM consultation on this subject was one of the longest investigations every commissioned by the UK Government and it also concluded that burial was best. The engineering of a geological disposal facility is well understood – we just need to get on with it now. The faster we make a decision to build the facility the more money we will save by not building above ground, ‘temporary’ stores. Volunteer communities around Sellafield have already come forward so we need to move forward and engage with these communities so that they can begin to see the potential benefit of being the host for this important facility.
Over a 100,000 year period it might well be the ‘unknown unknowns’ that are the real problem.
Does anyone really have a defined and proven methodology for predicting reliably what will and will not happen over such a timescale, and if not, then risk assessment can’t adequately be performed?
Future generations will have to resolve any problems if they occur – mortgaging the future, hardly sustainable.