The major risk avenue for release of radionuclides may not be at Yucca Mountain through geologic mechanisms, but during transportation and placement of nuclear spent fuel at the site. Fortunately, the disaster scenarios envisioned by NWPO consultants appear to be overstated. Nevertheless, there are a number of legitimate concerns that have been raised regarding the transportation of nuclear spent fuel:
1) Cask design, durability and testing methods.
2) Transportation routes to be utilized.
3) Perceived risks along transportation routes.
4) Acceptable exposure levels of bystanders during transport.
5) Emergency response to worst case disaster scenarios.
Originally, the plan was to transport spent fuel rods in shipping casks capable of holding one to three assemblies, both on truck beds and on railcars. If a design option called Multi Purpose Canisters (or similar alternatives) is chosen, almost all shipments would be by rail in large casks weighing from 75 to 125 tons in and carrying up to 24 spent fuel assemblies.
CASK DESIGN AND VALIDATION
From the outside, nuclear shipping casks appear to be simple shiny stainless steel cylinders. In reality, the casks are sophisticated devices meant to provide both radiation shielding and isolation from the environment, even in severe accident conditions. Spent fuel has been shipped safely in casks for decades and a number of designs have evolved. Present spent fuel transport in the United States is mostly an attempt to shift current waste among various storage pools, however these shipments have also provided a record of safe nuclear waste transportation.
A typical state-of-the-art nuclear waste shipping container has a number of layers which function synergistically as structural, shielding, heat transfer and moderating elements. An example is shown in Figure 16, a GA-4 transportation cask showing layers which function in the following manner:
DEPLETED URANIUM - A good shield for gamma rays.
POLYETHYLENE - The hydrogen and carbon of the plastic are good at absorbing neutrons.
STAINLESS STEEL SHELL- For structural rigidity, crash resistance and added radiation shielding.
Among the purposes of this layered approach is to reduce the exposure of anyone approaching the casks to low levels, prevent leakage of radioactive material to the environment, provide structural support and to act as armor against physical and chemical assault.
The present effort is to move to 75 to 125 ton Multi-Purpose Canister (MPC) canisters capable of being used in on-site, transportation and storage modes depending on the overpack associated with a base container (see Figure 18 for MPC design concept) . There are a number of advantages inherent in the large MPC cask design:
1) Existing on-site storage casks are not licensed for transportation or disposal. This would require them to return to pools for unloading and reloading into transportation casks. Large MPCs would minimize handling at all stages.
2) Present technology is not standardized, creating both compatibility and safety concerns.
3) Large rail delivered casks would diminish total shipments perhaps by a factor of five or more over present designs.
4) This concept would allow for possible at-reactor storage by 1998, allowing shutdown reactors to proceed with the decommissioning of spent fuels..
5) Total system cost may be $500 million less than current concepts using Monitored Retrievable Storage.
Despite the promise of the MPC concept, there are a number of unresolved technical issues that
have not yet been adequately addressed. These include:
1) Burnup credit, a technical issue regarding how much internal shielding is required to avoid criticality.
2) Canister retrievability. The MPC concept is designed around permanent closure of the units., but Yucca Mountain is to remain open for one hundred years and retrieveability technology is improving.
3) Criticality issues arise with a submersed repository and leaching of moderators from breached canisters. Since the likelihood of this scenario is small, this may be a moot issue.
The challenge in choosing transportation routes for nuclear spent fuel has been to minimize radiation and accident risks without breaking the budget for infrastructure. Taking advantage of existing roads and rail lines minimizes the cost but assures the waste will be shipped through population centers. Building dedicated routes, however, could be so expensive it would make the project impossible. This is especially a problem in regard to building a railroad spur to service both Yucca Mountain and the Nevada Test Site, a project projected to cost multiple billions. Within Nevada, a number of routes have been studied over the years, but now appear to be narrowing to a few as shown by figures 18 and 19. The preferred transportation method now appears to be by rail because large Multi Purpose Canister could be used. The large casks would lower the number of shipments and other problems.
Polls conducted by Mountain West in 1987 showed that one of the issues the public feared most about the proposed nuclear waste repository was the risk of transportation accidents involving spent fuel being shipped to the Yucca Mountain site. The scenario the state focused media attention on was the danger at the "Spaghetti Bowl". The very center of Las Vegas sports a traffic nightmare, an interchange complex that threads highways I-15 and I-95 together very near Fremont Street and the downtown casinos. Because the interchange was designed in days when Las Vegas was never expected to be a booming metropolis, the spaghetti bowl is often a traffic nightmare. The state suggested the risks of a nuclear waste shipping container being overturned in the middle the Spaghetti Bowl during rush hour traffic were non-negligible, possibly spilling radiation over the entire city.-
Studies have considered the Las Vegas route because it takes advantage of already existing roadways, but the downtown Las Vegas overpass is just one route among many and not very likely due to political considerations. Shipment of nuclear waste through Las Vegas is unlikely because the Governor of the State of Nevada has the right to reject any such route by the Code of Federal Regulations:
49 CFR Ch.I section 177.825 Routing and Training requirements for Class 7 (radioactive) Materials . . . .
(b) . . . a carrier or any person operating a motor vehicle containing a highway route controlled quantity of Class 7 (radioactive) materials . . . shall operate the vehicle only over controlled routes. An Interstate System bypass or Interstate System beltway around a city, when available, shall be used in place of a preferred route through a city, unless a State routing agency has designated an alternate route.
(1) A preferred route is either or both an Interstate Highway System for which an alternative route is not designated by a State routing agency as provided in this section in accordance with the following conditions:
(i) The State routing agency shall select routes to minimize radiologic risk under "Guidelines for Selecting Preferred Highway Routes for Highway Route Controlled Quantity Shipments of Radioactive Material", or an equivalent routing analysis which adequately considers overall risk to the public. . . . .
(ii) State routing agencies may designate preferred routes as an alternative to, or in addition to, one or more Interstate System highways, including an Interstate System bypass or an Interstate System Beltway.
While nuclear waste shipments could theoretically travel through the spaghetti bowl, neither the Governor nor NWPO will ever sanction this route, making the issue moot. Consequently, the words "spaghetti bowl" in relation to Yucca Mountain are something of a political football.
One of the prime reasons the perceived risks of transportation safety and routes has been debated so strongly by the state is because of the New Mexico court ruling that awarded a couple $337,815 for the loss of property value due to the perceived fears of neighbors. On November 14, 1988, the City of Santa Fe condemned 43.431 acres of a 673.77 acre parcel owned by John and Lemonia Komis. The property was condemned to permit the construction of a bypass around the City to be used for transportation of hazardous nuclear waste from Los Alamos to the Waste Isolation Pilot Project (WIPP) in Carlsbad, New Mexico. At the time of the taking the highest and best use of the parcel was speculative investment for subdivision into rural homesites or for recreational purposes.
A jury made the following awards to the Komises:
1. $489,582 for the 43.431 acres condemned.
2. $60,794 for severance damages to the buffer zone.
3. $337,815 for severance damages for perceived loss due to public perception.
The New Mexico Supreme Court held that property owners are entitled to compensation for the loss in value to land which is caused by public fear, whether or not that fear is reasonable. [City of Santa Fe, 845 P.2d at 756-757].
Consequently, discussions of the transportation safety issue must now include not only a rigorous analysis of the cask hardware and crash testing, but perhaps more importantly an analysis of the public's perceived risks. Unfortunately, this means that if welding the fins from a '57 Cadillac to the canisters improved the risk perception of the casks, though not diminishing the real risk, such a design might be well preferred.
The fact that Nevada sees the transportation perceived risk issue as the Achilles heal of the repository is evidenced by the efforts of Bob Loux and NWPO transportation consultant Bob Halstead to spread fear of nuclear waste transportation nationwide:
STATE SENDS ANTI-NUKE PITCH ON ROAD
. . . With words like "Every American is a Nevadan when it comes to the disposal of radioactive waste" and transporting it "would unleash a Pandora's box of health and safety risks," Loux and his staff set out to reinforce the fears that the nuclear power industry is trying to erase.
Loux's cross-country, anti-dump crusade began in Omaha Neb., on a Monday in April.
It ended 11 days later when he and four staff members returned to Reno on a commercial jet. They had spent $25,689 and contacted 72 media outlets in Cleveland, St Louis, Chicago, Nashville, Washington D.C., Kansas City and Omaha.
The money for the trip came from a special fund the Legislature appropriated to the Nuclear Projects Commission for informational efforts of this type, Loux said.
[Rogers, Keith; Las Vegas Review Journal, August 1, 1993, p1B]
A mitigating factor in transportation risks is that most of the spent fuel now in storage pools has already been decaying radioactively for more than ten years. Since radioactive decay is exponential, we are actually faced with much less of a radiation exposure problem than what the casks were originally designed for. Estimates publicized by DOE handouts suggested casual radiation exposure to bystanders would be minimal:
Evaluations show that the additional exposure to people situated 30 meters (100 feet) from the route of a vehicle carrying spent fuel or high-level radioactive waste moving 24 kilometers per hour (15 mph) is one-thousandth to one millionth of a millirem per shipment. [Transportation: Overview of the Issues, February, 1993]
These figures reflect exposures utilizing older style casks with limited capacity. The situation changes for Multi Purpose Canisters which while potentially carrying 125 tons of waste, are unlikely to increase bystander exposure because of their shipment by rail. The large MPC units also have some self-shielding qualities because of their bulk, so surface emissions would not be substantially changed even for the greater mass carried. There has been some argument that pregnant women stuck in traffic at the I-15 spaghetti bowl in mid Las Vegas next to a waste canister might recieve unacceptable doses, but this seems to be a rather contrived scenario given present designs and routing.
Bob Halstead, $125,000 per year NWPO transportation consultant, is not a transportation engineer but something of a science historian by training. While not a technician, he has attempted to earn his keep by traveling and photographing nearly every inch of the possible truck and rail routes through Nevada, producing a complete slideshow of potential problems along the highway and rail routes leading to Yucca Mountain. Halstead originally worked in Wisconsin as part of a state nuclear advisory board and has been an active opponent of nuclear energy since the early eighties, in part perhaps because of a belief that a daughter has a disease condition caused by atmospheric testing.
We mention this history not necessarily to criticize Halstead's tenacious study of the issues regarding nuclear waste transportation in Nevada, because he has proven to be a diligent worker. However, when it comes to designing emergency response measures to possible accidents along a nuclear waste shipping route, we are left with the uneasy feeling that political appointees may not be able to produce convincing technical arguments. Indeed, that is why the studies at UNLV's Transportation Research Center have utilized Civil Engineers with PhDs as consultants, at much smaller wages by the way.
NWPO transportation risk assessment tends to depend on the analysis of Marvin Resnikoff, who projected in a report for the state that a nuclear waste transportation accident could cause thousands of deaths and cost $9.5 million. According to Resnikoff, drastic measures would be required in the 1.5 square mile contaminated area. Bulldozers would have to scrape up all the earth in the area and then be dismantled and buried. Workers and residents would have to undergo medical tests for years after the accident. Estimates from national labs tend to suggest an accident which released 1 percent of the contents of a canister in the presence of a petroleum tanker explosion would cause perhaps 22 cancer deaths over 50 years within a fifty mile radius. Such a disaster, already improbable, could be nearly eliminated by rules governing the proximity of fuels and other canisters in multi-car trains.
Yet, even given the improbability of major disasters resulting from the shipment of spent nuclear fuel, it is likely that the occasion might arise when workers would have to handle a derailment type accident in which there was little or no breach of containment but a sizeable mess. One problem with the Multi Purpose Canister is that finding cranes to lift 125 ton steel casks is not that easy, especially in rough terrain. Safety crews themselves would also need to be trained to deal with worst case disasters and respond to each derailing as if it were such a case. Among the equipment crews reporting to such an accident might need are:
*Sensitive monitoring devices to determine whether radiation is leaking from a breached cask.
*Radiation shielding clothing that covers the bottom of the feet and the top of the head.
*Built into the protective gear electronic equipment that allows safety personnel to communicate with each other and officials at a base station.
*Decontamination equipment to wash radioactive dust and particles from safety workers clothes and equipment.
*Lead shielding on trucks and other equipment that carry public safety workers.
*A lead shielded mobile command post containing a computerized link with a national data bank that provides details on how to combat a spill.
*Giant vacuums to suck up contaminated materials.
*Radiation absorbent substances that encapsulate contaminated materials.
Thus, even if the most extreme disaster scenarios are discounted, nuclear waste transportation safety response is likely to be expensive. It may well cost over $1 million to equip each five man response team, and such teams might be spaced every fifty to two hundred miles along the route.