Written by Will Davis on location at the ANS 2015 Winter Meeting
This morning’s session entitled “Updates on Nuclear Waste Repository Projects” provided two very interesting and different views on the entire topic of storage of waste; it’s valuable to compare the experiences (which are just two of a number discussed at this important technical session.)
WIPP – Recovering from the Unexpected
Tim Runyon of the US DOE Carlsbad Field Office led off with a presentation covering the incidents at the Waste Isolation Pilot Plant or WIPP in 2014 and the recovery of the site from these. WIPP is used primarily for the storage of waste material gleaned from the cleanup of many “legacy sites” which were operated in support of the weapons program, and operated successfully and for the most part outside of the news cycle until Feburary 2014.
In that month, there was, first, a salt haul truck fire which caused damage far more serious than just the loss of the 29-year-old vehicle itself, as the soot spread throughout the site and affected cables and equipment. Just nine days later, a drum of waste overheated (due to having been filled with an incompatible mixture of materials that should simply not have been mixed) and burst in Panel 7, Room 7, spreading contamination through the underground areas and causing the evacuation of these areas for some time. Some radionuclides did leak to the atmosphere even though the automatic ventilation system, upon detecting the release, shifted immediately into a filtered mode. An Accident Investigation Board identified over 200 action items or areas of concern after the event.
Runyon was clearly focused not on the events of the past but the recovery and eventual reopening of the WIPP site to new shipments. He noted that the facility is designed so that the salt formation will eventually over time “creep” and encapsulate the waste drums stored therein. This is a natural action of all salt mines, and it occurs irrevocably. WIPP was essentially unoccupied for nine months, so that much supporting of the overhead (called “bolting”) had to be accomplished after re-entry just to ensure the facility was again safe. (This process normally occurs almost as a daily maintenance task under normal operations, he related.) This activity is itself over 85% complete.
Decontaminating, or perhaps remediating the shafts built in a salt formation, Runyon says, incorporates an interesting twist. Since the material is salt, and the majority contaminants are Americium and Plutonium which are primarily alpha emitters (alpha having a very short range), the walls and floor are simply sprayed with water. The water and salt form a brine that essentially encapsulates the materials when it dries. The floor is then covered with an impermeable yellow cloth first, and then a heavy load of four to six inches of salt. This fixes the contamination in place, and has no radiation effect at the surface of the new salt layer. If the salt layer were to wear down to the point where the yellow were visible, it would be a sign to redistribute the salt — but the contamination would still be fixed to the surface of the floor, unable to spread.
Runyon described to an interested crowd the many other aspects of the recovery, too numerous to list here. The site has made great progress toward re-opening to receive further defense related legacy waste — waste which Runyon says would have had nowhere to go had WIPP not been built so that the whole legacy cleanup would have been impossible.
Bernard Faucher of ANDRA was up next to describe the planned CIGEO waste storage facility in France. This facility is remotely like WIPP in that it is underground, but the similarity stops there.
Faucher related that some years ago an attempt was made in France to build a similar facility, but the tremendous pushback that occurred from the public (who were not consulted initially at all) stopped the whole project. From that point on, long-term waste storage had to be a public/political project as well as a technical one, and CIGEO certainly is — or will be — that.
The site itself will be built in an underground clay seam, whose median depth is 525 meters and which runs about 148 meters thick. This clay deposit is not by any means in a totally unpopulated area, so that much stakeholder involvement has had to take place (and will continue to.) In fact, the decision was made to access the facility by a shallow sloping ramped tunnel instead of a vertical shaft; this way the surface handling facility is actually in a different town from the one that sits directly over the actual CIGEO storage chambers themselves. This spreads any political pressure between two different areas or communities.
Perhaps most interesting about the facility is its physical construction related to the actual waste storage, which unlike WIPP will incorporate a designed in ability to remove waste once stored. This again is a socio-political concession, made to allow nearby people to feel better about the facility in the sense that “if anything did go wrong we could theoretically go back and get the material out,” said Faucher. “But the intention is to never get it out.” Faucher added that “this reversibility helps us; it was required to incorporate that feature in order to build it, really.”
Construction in the clay deposit has similarities to salt in sense that the clay creeps. To ensure that the waste cans (very large, really) can be removed the shafts are not allowed to creep in but must be permanent. To this end the French are using a large boring machine that actually applies the casing of the tunnel behind it as it drills. When the desired run is finished the boring machine is removed back through the same casing that it just laid.
One commenter in the audience noted the very different scheme of “permanent disposal,” in the sense that in the USA the idea is that the salt (in WIPP) is intended to creep in and encapsulate the waste, while in the other French case the clay will never actually encapsulate it – thus throwing into question the actual permanence of the French site in the first place. Faucher reiterated that the permanent storage intention of CIGEO is to never get the waste out, even though theoretically you could (and the equipment to do that is designed and tested already.)
Many other interesting things too numerous to reproduce here were brought up about these two facilities, as well as others, and once again a fine ANS Winter Meeting technical presentation led all in attendance to a greater understanding of the developments in the nuclear energy and technology sphere.
Will Davis is Communications Director and board member for the N/S Savannah Association, Inc. He is a consultant to the Global America Business Institute, a contributing author for Fuel Cycle Week, and writes his own popular blog Atomic Power Review. Davis is also a consultant and writer for the American Nuclear Society, and serves on the ANS Communications Committee. He is a former US Navy reactor operator, qualified on S8G and S5W plants.