Nuclear and Chemical Wastes at the Hanford Reservation:
A conversation with Dirk Dunning
From the Environmental Review Newsletter Volume Three Number Five, May 1996
The Hanford nuclear weapons production facility occupies 560 square miles along the Columbia
River in south-central Washington state. It was established in an isolated area near the Columbia River
which provided the water necessary to cool the reactors. For forty-five years the facility ran several nuclear
reactors simultaneously, but instead of producing electricity they produced plutonium for our nuclear
weapons. Now closed, the site is the subject of a massive cleanup campaign by the Department of Energy
to find all the contaminated areas on the surface and beneath the site and to figure out how to retrieve or
contain the nuclear and chemical wastes and keep them from entering the Columbia River.
We spoke with Dirk Dunning - Hanford Program Coordinator for the State of Oregon Department of Energy - about the history of the Hanford nuclear reservation and some of the dangers posed by the massive nuclear and chemical contamination of the site.
Dirk Dunning has a B.S. in chemical engineering from Oregon State University, and many years of engineering experience in fields as diverse as submarine nuclear power plants, industrial waste water treatment, toxic and hazardous materials, and fire and building codes.
ER: Mr. Dunning, what is Oregon's stake in the cleanup of the Hanford nuclear reservation?
DD: Our first stake is being downwind and downwater from a high level waste repository site at Hanford; we have a million people downriver. The second stake is a disaster preparedness issue; there are many facilities and activities at the Hanford site which are quite dangerous. Several of those facilities have the potential to have accidents large enough to have impacts in Oregon. So we work with the people on the Hanford site in the state of Washington to insure that we are prepared should something go wrong. And we do the best we can to insure that something does not go wrong.
We have a stake in transportation of radioactive and toxic materials moving to and from Hanford through Oregon. If they use the road route it goes up over Cabbage Hill and then on through Ladd Canyon and the conditions on those roads can change rapidly. Even if a truck sets out in fairly decent weather, at the wrong time of year the weather can shift quickly and the road becomes icy and windy. This is just outside the Pendelton area in eastern Oregon. Farther east the road runs into Ladd Canyon which has sharp turns and severe cross winds. Both areas have severe road grades and there can be problems with runaway trucks. If they use the railroad, the railroad runs through a canyon overlooking the Umatilla River, and if there was an incident there, it could be very difficult to respond to it.
Another safety issue is more protracted: What happens to the Hanford site over time? A large amount of the wastes that have been disposed of or buried or leaked at the Hanford site through its fifty years has gone to the ground water already. There is an even larger amount of waste hanging in the soil which may in the future move into the groundwater and then towards and into the Columbia River. This is a problem today where some of the material along the river at the N reactor, at the K reactor, at the H and D reactors and a couple of other locations is already moving into the Columbia River. At the N reactor, strontium 90 is entering the river at levels well above the drinking water limits. At the D and H reactors, hexavalent chrome is entering the river in an area of spawning beds for some of the native salmon at levels toxic to salmon fry.
We also have an immensely large underground plume of tritium moving across the site and into the river at the old Hanford town site, at levels well above the drinking water standard. In all those cases the levels in the main Columbia River are not significantly elevated, and are below the drinking water standards. But that does not take into account the effects as waste enters the river, particularly for the salmon and many other organisms that live on the edges of the river.
ER: The contamination is below drinking water standards. Is that because of dilution after it enters the river?
DD: Yes. But dilution is not immediate. As the pollutants enter the river they slowly mix into the river and
as they move downstream they mix ever more. But as they immediately enter the river, they enter in fairly large concentrations and so in some sections of the river, the concentration of tritium is significantly above the drinking water standard; a very short distance away, it is not. But the salmon redds are right on the bottom of the river and so the mixing zone does not really help them a whole lot.
The plumes entering the Columbia River are not having a tremendous impact today - other than the chrome which is of great concern. However, within about a hundred years, carbon tetrachloride from the center of the site will be entering the river at high levels, possibly high enough to cause a major impact on the river.
ER: That is not radioactive.
DD: No. It is just toxic; it is a known carcinogen. Even though Hanford is the best understood of any site in the U.S. in terms of its groundwater, it is not understood well enough to get accurate predictions for over a hundred years from now. But we do know the waste materials are moving through the soils and many of them will reach the river because their half lives as radioactive materials are so long, or because they are not degrading as toxic materials; carbon tetrachloride is a good example of that.
ER: When did the Government start making nuclear weapons materials at Hanford?
DD: Construction began in late 1942 and the first reactor was operational in 1943. The Hanford operations were created to provide the plutonium and uranium for nuclear weapons production. The first reactor was the B reactor, it was a prototype of a total of eight reactors that came later. The ninth reactor built at the Hanford site for production of weapons material, plutonium, was the N reactor and it was the first one that did not discharge its coolant water directly to the Columbia River. It came on line in 1979.
The original eight reactors were built by building a large pile of graphite blocks that were criss-crossed with fuel pipes, control rod pipes and safety control rod pipes. They brought in water from the Columbia River, filtered it, added a trace of sodium dichromate to it for corrosion prevention, and fed that directly into the operating reactor around the uranium rods. When the water came out of the back side of the reactors, it was discharged into several multiple million gallon basins. The water had two to eight hours of retention time in those basins where it had a chance to cool thermally, and to become a little bit less radioactive. As the water came out of the reactor it was intensely radioactive. And by the time they discharged it to the river, it was still radioactive enough that fish could not live in it.
ER: It would kill fish outright?
DD: Yes. From radiation exposure. The temperature of the water coming out of the reactors was at or near boiling and when they were running the reactor as hard as they could, the waste water was upwards of 185 degrees F. They would take their reactor feed water from the near shore of the river and discharge out near the middle, where the heat increase in the river did not affect downstream reactor operations so they could keep as many reactors as they could running. The radioactive load to the river was quite large.
The discharged radioactivity was mostly from activation products where the river water itself was made radioactive by going through the reactor. However, during the years of operation at Hanford, there were 1963 fuel elements that failed in the reactors to one degree or another. Some of those were complete failures, and when that occurred during the first years there was not a lot they could do about it. But they developed means that if they detected a tremendous rise in radiation levels in the discharge water they would turn off the discharge from the basin into the river and divert the waste water into trenches. So the trenches became a large soil filter where the radioactive material was delayed in getting to the river. Many of those trenches today are still a big problem because radioactive materials in them are slowly seeping into the river. The area called N springs at the N reactor is an example of that, where strontium 90 levels are extremely high entering the river.
The reactors along the Columbia River converted some of the uranium 238 in the fuel to plutonium
239. They discharged the fuel periodically from the reactors into holding basins behind the reactors where they would allow it to cool for 90 to 120 days. During that time the short-lived fission products decayed away and the decay heat dropped greatly. More importantly, by the time you have reached 90 to 100 days, iodine 131, which has about a nine day half-life has gone through ten half-lives of decay and is pretty much all gone. So after that decay occurred they would take the fuel from the basins and transport it to facilities in the center of the site where they would chemically dissolve the fuel. This released some of the fission products to the atmosphere, particularly some radioactive noble gases and radioactive iodine and ruthenium. They separated the uranium and plutonium from the radioactive fission products and fuel cladding. They recycled the uranium and converted it back to metal to produce new fuel. The plutonium was sent on as a plutonium nitrate solution to the plutonium finishing plant. At the plutonium finishing plant they converted the plutonium nitrate solution first to plutonium fluoride and then to plutonium metal. And the so-called button they produced was shipped to Rocky Flats for the final finish weapons production. During the early years they didn't separate the uranium and it ended up going to the tanks as waste. Later on they found they needed that uranium and they recovered it.
ER: How long were the first eight reactors discharging their coolant water into the Columbia River?
DD: They were discharging through all of the sixties for the most part. The last of the first eight reactors ceased operation in 1971, that was K east reactor, the last of the single pass reactors. The original B reactor ended its operations in 1968.
ER: Were these new generations of reactors new and improved models?
DD: Actually not. The B reactor was a completely unproven design. The very first reactor built was the pile in Chicago, and I have heard people say that it was the A reactor. I have also heard that the A reactor was intended to be built upstream of B reactor, near the Vernita bridge. But, the B reactor was the first at Hanford. As it was designed by DuPont and Enrico Fermi and the other physicists, it was intended almost as a proof of concept and just to be able to produce enough plutonium to produce a weapon. When they designed the reactor, the DuPont engineers had the data from the physicists about what would be required, and being the good engineers they were, the first thing they did was add about ten percent to the design. They figured that if the physicists said it was big enough to have so many fuel rods, they had better allow for more than that. As it turns out there were some physics things that did happen during the operation of the reactor that were different than anticipated and so not too long after they started up the reactor for the first time, it shut down on its own. One of the fission products acted as a nuclear poison; it was taking up some of the neutrons that run the reaction and so the reactor was not large enough to run but because the engineers had allowed for this, they were able to put fuel into the remaining fuel channels and the reactor did run. The reactors that came after B; the C, D, F H and K reactors, were each bigger reactors but the design was almost identical to the original B reactor. There were some modifications but for the most part they were just made bigger and more powerful. The whole philosophy during the production years was focused on how to produce the maximum quantity of plutonium. You can see by looking at where the fuel elements were that failed in the reactor cores that from an engineering perspective they were pushing the cores as hard as they could and there was allowance for a certain amount of failure. So it was an engineering driven operation, not a safety driven operation.
ER: The operators pushed the reactors to the failing point and lost containment of the nuclear fuel?
DD: Yes. In a reactor the most powerful region is the center of the core and it gets less powerful as you go out from there. The fuel rods would go in horizontally and the water flows from the front face through the reactor to the back face. Its inlet temperature was whatever the river temperature was and its outlet temperature was boiling at the back face of the reactor. The fuel failures occurred in an area just behind the center of the reactor. That indicates the temperature there was hot enough that some of the water boiled to steam and there was two phase flow. In the two phase flow the heat transport from the fuel to the water is not as good as it is with liquid water, and there is greater probability that the fuel will overheat and fail; which is what you can see in the records of the reactors. It is not direct evidence where somebody said what they did, but it becomes very apparent when you look at how the reactors operated and failed.
ER: How could they get away with dumping radiation into the Columbia River?
DD: The whole operation was run very much in secret. The people at one plant did not talk to people at another plant except minimally. When the facilities in the middle of the site - PUREX, REDOX, and other processing facilities - produced waste, they would talk to the people in the tank farms who had responsibility for taking that waste only enough to tell them how much they were producing. There were not a lot of discussions of what the impacts were, at least not at the lower levels.
Throughout the history of the site the tanks were something that was going to be taken care of later. There was always a rush for plutonium production and the waste was something we would handle another time. The waste tanks were only designed to last twenty to thirty years, and during the initial design phases, the engineers were very forthright that they expected they would produce plutonium through the war years and that following the war, the reactors would be shut down and then they could figure out what to do with the waste. But after the war ended the Cold War started in earnest and there was no opportunity to slow down in production or to do anything about the waste. And being a closed operation and behind classification, there was never input enough from the outside for people to recognize how large this problem was. Cost was always an issue, very much in the forefront of everyone's mind. So they would do things as inexpensively as they could and in many cases that resulted in the problems we have today.
ER: How would you prioritize the problems at the site?
DD: The risks at Hanford come in several different kinds and over different time frames. There are those things which are absolutely urgent risks today, and those things that will be in all probability very large risks in the future if we do things wrong. One of the issues that has come to the forefront in the minds of the people at the Department of Energy is that there are a number of risks at the site that are quite urgent. The most notable of these has to do with the tanks on the site. As they processed the fuel they used a variety of different organic chemicals, in addition to the nitric and other powerful acids. [Organics are chemicals with a carbon backbone. ed.] Over the years they very seldom had as much tank space as they would have liked, so they wound up concentrating waste in the tanks when they ran out of space. In some cases that meant the tanks overheated and vented material to the air. In that case they would go through long campaigns of removing the most intensely radioactive materials, cesium 137, strontium 90. They had other needs for medical and other reasons to recover other isotopes, so they mined the waste periodically.
As they ran the tanks, many of the fission products were precipitated out as solids in the tanks. They operated some tanks in a cascade with waste going first into one tank, then overflowing into a second, then overflowing into a third. The overflow from the third tank was sent to cribs, trenches, reverse wells or other drain equipment, into the soil. In the cases of those operations as well as many cases where they were discharging directly into the soil they attempted to determine how much ion exchange capacity the soil had. They then utilized each disposal location just to the point that it did not release to the ground water. So there are very large quantities of radioactive material in the soil.
With all of this movement of material around through the tanks, it created a situation where every tank in the tank farm is unique; they all have their own chemical makeup; they are all different from one another. It also creates a problem where many of the wastes are not compatible with each other. In a number of the tanks the chelants used to hold on to some materials are reacting with aluminum oxide and caustic to slowly degrade and convert into hydrogen and nitrous oxide gas. The gas is being trapped down low in the tank under a layer of solids that have formed a mat. Slowly over time as the gas builds up, the sludge on the bottom of the tank becomes so buoyant that it lifts the waste above it; the tank waste in effect turns over and releases a large burp of gas. You end up then with ten to fifteen
thousand cubic feet of hydrogen gas along with about an equal volume of nitrous oxide gas. These two gases are even better at burning together than hydrogen and air, and with a very minor spark you could have explosions in the tanks. There has been a lot of discussion about how big that explosion might be and whether or not it would be enough to rupture the tops on the tanks. The people on the Hanford site believe that it would not. However in any event it would cause enough of a release that it would probably dislodge the ventilating equipment on the tanks and cause a release to the air, even if it did not fail the tank. In addition, the pressures generated in an explosion would probably be large enough to cause the failure of the tank itself so that the tank waste then would be allowed to seep into the soil. That is one of the problems in the most urgent category.
The other kinds of risk on the site are somewhat different. They have to do with a large quantity of radioactive spent fuel that is stored in a couple basins on the site. Towards the end of the operations at Hanford, there was pressure from many quarters to shut down the chemical reprocessing. There were also economic pressures to continue running the N Reactor which was producing power as well as producing plutonium. So we ended up in a strange situation where the money was removed from the PUREX facility and it was forced to shut down while the N Reactor continued to produce spent fuel. DOE intended to continue operating PUREX; it was just a question of when they were going to restart. They did not clean out the plant. They just turned it off. And so, for the past many years, PUREX sat intact with all of its solutions in place, ready to run, and yet it was not able to.
ER: What does PUREX stand for?
DD: Plutonium URanium EXtraction facility, and REDOX is the REDuction OXidation facility.
The problem this created then, was that as the N reactor ran, it was producing spent fuel which had no place to go. And so they accumulated it in two of the basins on the site which were not being used, those are near the K reactors. The fuel that came out of all the reactors at the Hanford site was metallic uranium, and by its design it was never intended to be kept around. It was intended to be processed shortly after it was produced.
They would push the fuel out of the fuel channels and allow it to drop vertically from the back of the reactor into a pool and the fuel then was put into storage. If it was processed in the first six months to a year or so, it did not cause a lot of problems, other than some releases of radioactive materials into the basin water; and they had purification facilities to control that. But in the case of the fuels from the N Reactor in the K basin, most of it has been there for over ten years and so this fuel has been slowly corroding in the water. Today these two basins have slightly different problems: in the K East basin where the fuel was stored exposed directly to the water in open containers, the fuel has corroded badly enough that along with the sand that has blown into the building and the corrosion of all of the iron structures in the pool, there is now about seven inches of radioactive uranium, iron oxide and sand sludge on the bottom of the basin.
In the K West basin they lined the basin with epoxy and they put the fuel into closed containers. Unfortunately in closed containers as the uranium reacts with water it produces not only uranium oxide but uranium hydride which is quite flammable. In the case of the fuel in both basins there is a concern that it may be pyrophoric; that is, it may burn when exposed to air. British Nuclear Fuels reported about some similar fuel they had, of about similar age, that reacted with the air when they removed it from pool storage. In some cases within twenty to thirty minutes it was glowing at red heat and ignited.
ER: The fuels react so strongly with air they burn?
DD: That's right. Decay heat from radiation and also chemical reactions from exposing it to the air was enough in some cases.
In addition, the basins were never designed for the kind of earthquakes we now know can occur there. The original design of the B reactor was carried forward into the later reactors. The reactor building was built first along with the base of the reactor; then the basins were built abutting the reactor building.
That left a large construction seam between the two, where a part of the basin is actually a part of the reactor building. The reactor buildings and the basins were not directly joined. There is a masonite seal between them but the two structures are just sitting up against one another. In a large earthquake, because these structures have such different masses and shapes, there is a good chance they could walk away from each other. If they did that, obviously it opens a hole where the basins can drain. To respond to that DOE has put in place some metal gates in a portion of the pool to prevent that from happening. But even then, the basin itself was not designed for large earthquakes. So it is important that the fuel be removed.
The tanks and K Basins fuel are probably the two largest risks on the site today. The next largest has to do with earthquakes in general. There is a lot of plutonium in the plutonium finishing plant and a lot of radioactive materials in many of the buildings which were not designed for large earthquakes. As a consequence, if we are unfortunate enough to have a quake of sufficient size, any one of those facilities or a couple of them might have releases which can have some impacts on site. For those kinds of impacts, we don't expect it to go off site or if it does, not to go very far. However, we continually prepare for the worst. For the workers on site this is a bigger issue because they would be directly affected by an earthquake. Those are the near-term risks. There are also other risks associated with handling of material and transport and those types of things. But for disaster hazards, those are the largest.
For many of the wastes the far future is the bigger concern. Where if you look at the long-lived radioactive materials, the ones with half-lives in excess of one hundred years - many with half-lives in excess of a million years, several of them are of great concern. One is iodine 129 because it is mobile and moves with the water. Another is technicium 99 which has a similar problem. Some of the radioactive wastes are cationic and tend to bind to the soils. Even then, they will move slowly through the soils. These include isotopes of plutonium, americium, uranium and some of the other actinides. The risks come from many places on the Hanford site, including the tank waste which has leaked. In excess of half a million gallons of high level wastes leaked to the soil in one tank failure at tank A 105.
ER: That's in addition to the trenches and intentional discharges?
DD: Right. Then you have the trenches, the reverse drains, the cribs and a number of other facilities, each one is built somewhat differently but they have the same general purpose. But those were all direct intentional discharges of less concentrated radioactive waste. Then in addition, there were a lot of burial grounds. Particularly in the early years, if they ended up with material that was highly contaminated, the response was to bury it. Some of that waste is buried in locations that are unknown.
ER: But on the reservation?
DD: On the reservation. In other cases in the early years there were not the same kinds of limits as there are today on how you handle plutonium contaminated wastes. And so the transuranic or plutonium wastes were buried in burial grounds under conditions that are not acceptable today. That waste may or may not ever be removed from the site. And if it is not, it will slowly move away from where it is now. Because plutonium has a 24,000 year half life, that poses a risk for a very long time.
ER: The argument is how slowly will it move away from the site?
DD: That is precisely the argument. The argument by many of the engineers on the site is that this material is immobile and will not move. However, in many cases in the past we have seen that belief turn out to be wrong. In particular, at the plutonium finishing plant there were a couple of disposal facilities where they expected the plutonium would not move and it has moved considerable distances from where they thought it would be. At one facility they processed plutonium and discharged contaminated solvent into the soil column at a place called the Z9 crib. They discharged on the order of a thousand tons of carbon tetrachloride. Carbon tetrachloride is a dense non-aqueous liquid, a known cancer causing agent, and it is believed that a large quantity of it is underneath the groundwater below the plutonium finishing plant. That
creates a problem because it will continue to leach into the ground water as the ground water moves by.
Another large quantity of carbon tetrachloride is hanging in the air space of the soil. So there are processes in place today where they pull air out of the ground and run it through activated carbon, and pump groundwater and treat it to remove carbon tetrachloride. Mostly this is intended to remove the vapors from the vapor space and to hold the contaminated material where it is, under the groundwater. The carbon tetrachloride carried a small amount of plutonium with it so that plutonium was discharged along with the carbon tetrachloride into the Z9 crib. During the 1970s they recognized they had a problem in the Z9 crib and they went back and mined the crib and they removed over ninety kilograms of plutonium from the soil. [Ninety Kg is about 200 pounds. ed.] At the same time they also drilled a couple wells through the crib to find out where and how deep the plutonium was. They found there were some leakage paths down through the soil they had not anticipated and plutonium was found quite deep under the crib. So there are a lot of problems there.
In effect all of the disposal units associated with the plutonium finishing plant have plutonium in them and this is one of the problems on the site that almost everybody expects DOE won't be able to solve. Those areas will have to be off limits effectively forever.
ER: How does one prioritize a problem that gets more serious thousands of years from now?
DD: It becomes difficult. There is a longer time you can work on it. It is not as urgent as tanks that may explode or fuel that may burn. There is a document - in internal review at US DOE - called the Hanford Remedial Action Environmental Impact Statement. In that document are maps showing what DOE and its contractors expect will be the fates of many of these materials over the next 10,000 years. This particular EIS is limited: it does not include the tank wastes and many of the associated disposal facilities, it does not include the reactors themselves and some of their disposal facilities, but it does include the other waste sites surrounding all of those. It shows large areas of the Hanford site, particularly to the north of the center of the site running up towards the Columbia River, where there is a large section of land that the cancer risk over the next 10,000 years becomes quite large. Over a large triangle of land it exceeds one percent; and that ends up going all the way to the Columbia River. They used several different scenarios: One where people live there; one where people work there; one where they are growing crops; and one where it is just for recreational use six days a year. And in each of those scenarios - with the exception of recreation - the cancer risks are about the same. Recreational is quite a bit less but the risk is still large.
The second thing to know about the one percent increase in cancer risk is when the EPA or even the U.S. DOE estimate the cancer risks, one percent is an upper limit where if you exceed that you are no longer in a range where you can use a linear model. So it is hard to project what the risk is above one percent. So in some cases they will say greater than one percent and that means anywhere from one percent up to certainty.
ER: One percent means given an exposure to that radiation over time the number of people who would be expected to get cancer would be an additional one per hundred?
DD: Yes. That's correct. So the risks potentially from that are quite large. The advantage we have is that over the next hundred or so years we have to prevent much of that from happening. But we can also make decisions that do not prevent it. There are costs today and there are also costs in the future. It is relatively easy to measure the cost today; it is hard to measure the cost in the future.
ER: This recapitulates the problems they were faced forty years ago where they were making decisions that created problems for us now.
DD: It does. And some of the people on the Hanford site do not believe in some of the aspects of the cleanup. In particular there are a number of people on the site who have argued that the tank wastes should be stabilized in place by adding sand and concrete and then putting a large barrier over the top and then just making the whole place a restricted area indefinitely and allow radioactive decay to take care of it.
Copyright 1996 Environmental Review