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Q: What are the NRC acceptable standards regarding building the project in a seismically active area? A: The NRC requires an evaluation of the seismic activity in the area where a site is proposed. In addition to the historical earthquake record, the NRC typically requires that the potential for faults geologically active within 100 km (about 60 miles) from the proposed siting area be considered in the evaluation. The facility must be designed to withstand the resulting earthquakes if the faults slip. Q: Will the facility be directly on a fault line? A: Yes. Two minor fault lines lie beneath the site. One, which we label "E," is estimated to be at least 160,000 years old. The other, "D," is estimated to be about 24,000 years old. Both of these small faults are considered in the site seismic evaluation. However, larger faults farther from the proposed facility are dominant earthquake sources in the analysis to determine the seismic design basis for the facilities and storage system.
Q: Are there other faults that could affect the site? A: There are three faults off the site but nearby that might be the source of earthquakes. They are the Stansbury Fault, which is about 6 3/4 miles east of the site, an assumed Cedar Mountain Fault, which is about 8 miles west of the site, and a third fault, which we call the Eastern Fault, is about one-half mile east of the site. Even though the Eastern Fault is much smaller in physical size than the nearby Stansbury Fault, it is closer to the site and, therefore, also is considered in the seismic design. Q: What tests are conducted when determining if a place is safe to build on? A: PFS conducted three types of tests to determine if the site was seismically active. The first was a reflection test using a vibrator that creates shock waves that reflect off the various layers of soil and rock below the surface. The reflection survey is used to identify where faults are located and how long ago they last slipped. The reflected waves are recorded using sensors called Geophones. The phones are placed in three-to-six-foot increments in four lines thousands of feet long.
The second activity involved digging test pits and trenches. Based upon the results of the reflection tests, PFS dug two trenches, each approximately 200 feet long and about 20 feet deep. The trench under the facility through the center of the site, going east-west, looked for recent fault activity but found none. The second trench, also running east-west, was near Hickman Knolls. At this location, the deposits above bedrock are many millions of years old. Hydraulic shoring was used to maintain the trench opening so that someone could safely go into the trench and study the layers (stratigraphy). The layers were then mapped and age dated to reconstruct the history of faulting near the site.
The third activity was core drilling. This was conducted with a large machine that drilled through various layers to take soil samples. The borings were drilled to approximately 50 feet below the surface. Trenches provide a continuous view of near surface conditions. Borings provide information at depths below the reach of trenches.
Q: What would happen to shipments on the proposed rail line if an earthquake were to occur during shipment? A: Earthquake activity in Skull Valley will not affect the safety of shipments on the proposed railroad line. In the unlikely event that a quake caused a rail car to derail, its cargo would be well protected by the shipping cask that is designed to withstand all conceivable accidents. These casks are licensed by the Nuclear Regulatory Commission and meet rigorous standards. They must be able to withstand being dropped on an unyielding surface from 30 feet; submersed under water at a depth of 50 feet, subjected to a fire at a temperature of 1475 F for 30 minutes, dropped from a distance of 1 meter onto a 6" diameter pin, and be subjected to a crush test by dropping an 1100 pound unyielding mass from 30 feet onto the test cask. Q: What will you do if there is an earthquake? A: First of all, the facility is designed and constructed to withstand all earthquakes generated from the area. In the highly unlikely event of an earthquake, we would not expect any significant damage to the storage system or the canister transfer building. The NRC regulations also require an emergency preparedness plan. In this plan we must consider credible "worst-case scenarios" and be able to react to them quickly. Employees will be trained to respond to many different specific emergencies. Q: What will happen to the casks if there is a sizeable earthquake? Will they come open? A: Our analysis indicates that in a nearby earthquake, the casks may rock back and forth a bit, tilting as much as four inches at the top. Some may even rotate on the bottom rims, the same way a can might, if spun on its rim. The casks will not tip over during an earthquake. Even though this situation cannot occur, the casks have been designed to withstand this event also. Q: Do the findings of your seismic study mean that this site is not suitable for your project? A: No. Our original investigations and the more recent augmented program all confirm that the proposed site is suitable for use as a storage facility. Q: Why don't you just move your site away from the faults? A: The detailed studies performed as part of the siting process all show that the proposed site is suitable for use as a storage facility. Faulting in the earth's crust is a normal phenomenon everywhere in the United States. Seismic studies are required no matter where you are in the United States. Q: Will there be on-going seismic monitoring during the project? A: The University of Utah maintains a statewide seismographic network to monitor earthquake activity. A separate monitoring system specifically for this project is not necessary because the analysis performed now determines the design basis for the facility. This basis is reviewed by the NRC and becomes part of the license. A Safety Evaluation Report (SER) is issued by the NRC certifying that the proposed design and site are suitable for use as a storage facility. Q: What is a Deterministic Seismic Analysis? A: A deterministic analysis is one method for assessing the seismic design basis for the proposed site. To do this, a great deal of research is performed to identify all significant faults within about a 60-mile radius from the site. From this research, a controlling active fault and its magnitude are determined. The analysis then calculates the vibratory ground motion (acceleration) to which the site would be subjected if the fault were to slip and cause an earthquake. The results are then used in the design of the various systems needed for safe storage of the spent fuel. The analysis does not include any consideration for how likely the design earthquake is. It only assesses the potential effects at the site from the largest earthquake sources. Q: What is a Probabilistic Seismic Hazard Analysis? A: A Probabilistic Seismic Hazard Analysis is a newer method that is now commonly used to assess the seismic design basis for a facility. It assesses the combined effects at the site from all the potential earthquake sources, taking into consideration the likelihood of earthquakes from each source. The results again calculate the vibratory ground motion (acceleration) to which the site could be subjected. Q: Why did you change the method of analyzing the seismic information? A: We didn't change the method of analyzing our seismic information. We have added additional techniques that have now become accepted by the NRC since our original application was submitted. This probabilistic analysis is a more realistic approach for determining the relative seismic hazard of a particular site. Q: Has the Utah Geological Survey reviewed your analysis? A: We provided all of our data and analysis to the State of Utah, as well as other intervenors in the licensing process, at the same time we sent it to the NRC. The State of Utah requested a copy of the raw data from our recent work and it was provided following completion of the data acquisition phase of the project. We assume the state of Utah will have these data processed and reviewed by the Utah Geological Survey and potentially other experts. This and other issues will be argued before the Atomic Safety and Licensing Board in 2002. Q: Who performed the fieldwork and analysis for PFS? A: PFS has contracted all of the technical and licensing activities to Stone & Webster Engineering Corporation. Stone & Webster assembled a team of independent specialists through the use of outside subcontractors. Bay Geophysical Associates, Inc. was contracted to perform the seismic reflection surveys under the supervision of Stone & Webster. Geomatrix Consultants, Inc. was contracted to perform the field investigative studies and assess the results, again under the supervision of Stone & Webster. Geomatrix is a firm that specializes in site geologic and seismological characterization studies in the nuclear industry as well as other industry sectors. Q: Have scientists from the State Geological Survey been out to the site to collect their own data? If not, why not? A: No. It is not the responsibility of the state to gather the seismic data for this facility. Q: Why should anyone rely on data collected by people on your payroll? A: In a NRC licensing process, the applicant is responsible for performing the research necessary to respond to questions from NRC staff and to contentions filed by intervenors. All of the data and analyses are then reviewed independently by the NRC, as well as any experts engaged by the intervenors. Q: What if the shaking during an earthquake at the site was bad enough to, in effect, cause the pellets to grind each other into dust? Then if a cask broke open, the spent fuel could easily become airborne. A: The forces applied to the fuel during an earthquake are much smaller than the forces that could occur during other postulated events. Maintaining fuel integrity is the most important design condition to meet to receive a license from the NRC. The storage systems to be used at the facility must be designed to handle all possible events at the site, including an earthquake, without degrading the fuel integrity. Q: How would these particular faults cause damage? By lifting sections of the earth, or dropping them? Or what? A: The controlling fault for the site, the Eastern Fault, is about 1/2 mile east of the site. In the unlikely event that this fault slipped and caused an earthquake, the most likely observable feature would be disturbed soil with some measurable offset over a zone many feet in width. The faults under the site have a very small probability of slippage and even if they did, the observable feature again would be disturbed soil but to a much smaller degree than other faults in the region. In comparison, the Wasatch Fault running though Salt Lake City is very large and has a much higher probability of occurrence, several times more frequent than the Stansbury Fault. Q: In case an earthquake did cause significant damage at the site, what safeguards will be built in to protect the people of Tooele, Grantsville, and other neighboring communities? A: Our analysis shows that any potential damage at the site would be minimal and would not involve the storage system or canister transfer building. Therefore, all recovery work would be contained within the boundaries of the site and would involve the non-nuclear portions of the facility. The PFS facility would pose no risk to people in Tooele, Grantsville, or other neighbors off the site. Q: Do your calculations take into consideration how the concrete casks may deteriorate over time? In other words, would the impact of a major earthquake in year 20 (or 40) of the facility operation be any more likely to damage the casks and fuel than an earthquake in the first few years of the facility operation? A: The design of the storage system utilizes a steel canister to contain the fuel. The concrete overpack (or cask) provides shielding and passively holds the canister inside. The design life of the storage system is 40 years or longer, which equals or exceeds the maximum design life of the facility. The design life of the storage system is the minimum duration for which the system is engineered to perform its intended function. Therefore, the storage system is safe and fully functional at the end of 40 years. Q: What if all the casks (up to 4,000) were to tip over due to an earthquake; is it true you would have only 48 hours to pick them up? What would happen if they were not picked up in 48 hours? A: The casks are designed so that they will not tip over, even in an earthquake far greater than one could reasonably expect to occur at the site. The NRC requires a very rigorous analysis to confirm that a large margin of safety exists for cask tipover. The NRC also requires that the casks be designed to withstand a tipover, for an additional level of safety, even though a tipover is highly unlikely.
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