Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States (2006) / Chapter Skim
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2 Transportation Package Safety
2 Transportation Package Safety
Pages 55-108
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From page 55... ...
The slogan "safety is built into the package" is commonly used by package manufacturers and vendors to describe the ability of these packages to maintain their containment effectiveness under most conceivable accident conditions. This chapter provides a summary of investigations carried out in the United States and several other countries to examine the performance of transportation packages.
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From page 56... ...
2.1 TRANSPORTATION PACKAGE DESIGNS AND REGULATIONS Packages for the transport of spent fuel and high-level waste are designed to meet three basic requirements both during normal conditions of transport4 and during a range of hypothetical accident conditions established in 10 CFR Part 71:5 1. Prevent an unsafe configuration (i.e., accidental criticality6)
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From page 57... ...
The package closure system consists of one or two steel lids that are attached to the open end of the package body with steel bolts. Elastomer or FIGURE 2.1 Generic truck and rail spent fuel packages.
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From page 58... ...
and can weigh 150 metric tons (165 short tons) or more when loaded.
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U.S. regulations for the packaging and transport of radioactive materials are provided in 10 CFR Part 71 (see footnote 5)
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free-drop tests on rail packages were carried out at this facility in late September 2004 in conjunction with the 14th International Symposium on Packaging and Transportation of Radioactive Materials (PATRAM 2004)
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From page 61... ...
. However, other presenters pointed out that the spent fuel transport experience in the United States is limited, and that the planned large future shipping campaigns to a federal repository could expose transportation packages to a wider range of loading conditions and longer-term use than have been experienced to date.
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From page 62... ...
SIDEBAR 2.1 U.S. Regulations for Type B Transport Packages Type B packages for transporting spent fuel and high-level waste are designed to withstand severe accident conditions without a loss of containment or an increase in external radiation to levels that would endanger emergency responders or the general public.
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From page 63... ...
drop onto unyielding drop onto steel bar fully engulfing fire 2 MPa (290 psi) surface for 30 minutes for 1 hour Illustration of the hypothetical accident conditions in 10 CFR Part 71.
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From page 64... ...
. An article such as a spent fuel transportation package that is dropped onto such an unyielding surface will be subjected to higher impact forces and will con sequently experience greater deformation than if the same article is dropped onto a surface that is itself deformed by the impact (i.e., a yielding surface)
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From page 65... ...
examined the expected responses of spent fuel transportation packages to thermomechanical conditions de
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From page 66... ...
This is of particular value when the structure is very expensive, the article needs to be tested to a point at which it has no further utility, and/or the loads that must be applied exceed the capacities of readily available testing apparatuses. Typically models of at least one-quarter scale are used in engineering tests of spent fuel transport packages, although models as small as one-eighth scale have been used for initial scoping tests.
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From page 67... ...
In cases where some features of the test article cannot be modeled accurately at reduced scale (e.g., the valve assemblies used on spent fuel transport packages) , it may be possible to combine a simplified re duced-scale model to determine decelerations and then separately test the full scale component when subjected to the appropriately scaled decelerations.
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From page 68... ...
carried out two 9-meter regulatory drop tests in September 2004 at its recently completed testing facility near Berlin. One of the tests was conducted on the180 metric ton (198 short ton)
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From page 69... ...
This approach has come to be known as damage tolerance methodology. There are built-in margins of safety for the design of spent fuel transportation packages.
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From page 70... ...
mechanical and thermal loading could result in package (1987) conditions derived from historical releases in excess of accident records regulatory limits Modeling the performance of two No package penetration at Spent fuel generic truck packages and two any orientation or impact shipment risk generic rail packages for impacts at speed against yielding or reexamination various orientations against unyielding surfaces; study: Sprung unyielding and yielding surfaces at package seals may leak et al.
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From page 71... ...
The accident scenarios marked with an asterisk were determined to produce consequences that would approach or exceed regulatory limits. SOURCE: Fischer et al.
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From page 72... ...
The release of significant quantities of radioactive materials from a loaded spent fuel transport package into the environment during a severe accident would occur only if the package and one or more fuel rods were breached (small amounts of radioactive contamination from the external surfaces of the fuel rods [crud] could be released from the package if the package seals were compromised, even if the fuel rods maintained their integrity)
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From page 73... ...
Once air pressure between the package interi or and outside environment was equalized, further material releases would occur by much slower diffusion processes. The process for the release of radioactive materials from transportation pack ages containing high-level waste is similar to that for spent fuel with three notable exceptions.
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From page 74... ...
. The radiological effects considered included releases of radioactive materials from the package as well as increased radiation doses resulting from damage to the package shielding.
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From page 75... ...
. 2.2.3 Historical Accident Reconstructions Additional investigations have been undertaken to reconstruct the thermomechanical conditions from a number of historical accidents that, had they involved spent fuel or high-level waste transportation packages, could have provided a severe test of package performance.
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From page 76... ...
and Ginn, 2004) from the Sandia National Laboratories examined the thermomechanical conditions for 12 historical accidents, some of which had been identified by the State of Nevada as potentially being severe enough to compromise the containment effectiveness of spent fuel transportation packages (Table 2.3)
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From page 77... ...
exploded caused package failure after a truck accident July Miamisburg, A train carrying yellow Fire would not have 1986 Ohio phosphorus and molten exceeded the 30-minute sulfur derailed and regulatory thermal test caught fire April Amsterdam, Several cars and a truck Impact would have been 1987 New York plunged off an interstate less severe than the highway bridge, falling 9-meter drop test onto an about 24 meters (80 feet) unyielding surface into a rain-swollen creek December Memphis, A tanker truck carrying Package would have 1988 Tennessee about 9500 gallons of experienced only propane caught fire and superficial damage exploded February Helena, A runaway train collided Fire would not have 1989 Montana with a locomotive at exceeded the 30-minute 15 to 25 miles per hour, regulatory thermal test causing two large explosions from hazardous cargo February Akron, Ohio One railcar carrying Fire would not have 1989 butane ruptured, exceeded the 30-minute releasing its contents in regulatory thermal test the form of a fireball May San Bernardino, A train derailed at high Impact would not have 1989 California speed (100 miles per caused package breach or hour)
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From page 78... ...
(2000) to be necessary to cause package seal failure October Oakland, The upper level of a Collapse of viaduct onto a 1989 California viaduct collapsed onto truck package would not the lower deck have been severe enough to cause seal failure, but package shield could be somewhat compromised December Cajon, A runaway freight train No significant damage to 1994 California struck the rear of another package would have train at a speed of about occurred 45 miles per hour February Cajon Junction, The derailment of a Fire conditions would not 1996 California freight train caused a fire have exceeded those shown that burned for several by Sprung et al.
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From page 79... ...
19The Holtec Hi-Star MPC package was modeled. This rail package is designed to hold five-year-old pressurized water reactor spent fuel assemblies with maximum burn-ups of 45,000 megawatt-days per metric ton.
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From page 80... ...
from the fire source and that the fire burned for seven hours, a shorter time than the original analysis. According to the draft paper, the analysis shows that the maximum temperatures on the seals of the TN68 and NAC-LWT packages would have exceeded their rated service temperatures, making it possible for the release of radioactive materials to occur.
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From page 81... ...
and completely destroyed several tanker cars. The analysis showed that fire conditions in the tunnel exceeded those required in the regulatory thermal test, which suggested that there could have been releases of radioactive materials had a spent fuel transportation package been involved in the derailment and fire.
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From page 82... ...
Part of the tunnel ceiling has collapsed onto one of the tank cars. SOURCE: Photos taken by a member of the West Yorkshire Fire Brigade or Manchester Fire Brigade (used with permission of www.todchat.com)
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From page 83... ...
9-meter free-drop test onto an unyielding surface Crash of a truck carrying a 20 metric Superficial package Huerta (1977) ton (22 short ton)
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From page 84... ...
sponsored a full-scale testing program at Sandia National Laboratories to obtain a better understanding of the behavior of transport packages in severe accident environments (Jefferson and Yoshimura, 1977)
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Impacts of tractor-trailer rigs carrying spent fuel transport packages into a concrete barrier at nominal speeds27 of 100 kilometers (62 miles) per hour and 130 kilometers (about 80 miles)
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) crash of a spent fuel package mounted on a truck trailer into a massive barrier carried out at Sandia National Laboratories in 1977.
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involved a crash of a locomotive traveling at 130 kilometers per hour (81 miles per hour) into a tractor-trailer holding a spent fuel transport package at a simulated grade crossing (Figure 2.6)
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From page 88... ...
Analyses of this kind are particularly important for comparing the relative severity of full-scale crash tests and regulatory free-drop tests. The tests described in this chapter were designed to generate large forces on transport packages by accelerating them to a known speed and then impacting them against rigid barriers.
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From page 89... ...
. Curve showing the variation in package acceleration as a function of time after impact in the Sandia National Laboratories grade-crossing test.
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From page 90... ...
) crash of a locomotive into a package mounted on a truck trailer carried out at Sandia National Laboratories in 1977.
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From page 91... ...
The peak strain readings were below the yield strain for the package material. Railcar Impact Tests The third full-scale Sandia test involved the high-speed crash of a railcar-mounted spent nuclear fuel package into the same concrete barrier used in the truck crash tests (Huerta, 1981)
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) crash of a spent fuel package mounted in a railcar into a massive barrier carried out at Sandia National Laboratories in 1977.
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The impact performance of transportation packages was investigated over a period of four years through a carefully planned progression of analytical studies, scale-model testing, drop testing, and a full-scale crash test. A discussion of these tests is provided in Blythe et al.
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From page 94... ...
Most spent fuel transport in the United Kingdom is carried out using rail, so the analysis focused on the identification of potential hazards along current and future rail routes used to transport packages to Sellafield. CEGB recog 33These are given by the A values described in Sidebar 2.1.
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The package was subjected to a 9-meter (30-foot) drop onto an unyielding surface.
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From page 96... ...
, which was the speed limit for trains carrying spent fuel packages at the time these tests were carried out.34 A third scenario was added because it was frequently mentioned as a cause of public concern: a derailed package-flatrol struck by a train traveling at a closing speed of greater than 20 meters per second (45 miles per hour)
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From page 97... ...
on the same package. In other words, this visually spectacular crash was actually a much less severe mechanical test of package containment than the 9-meter free-drop test used in the IAEA standards and USNRC regulations (see Sidebar 2.1)
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From page 98... ...
2.3.4 Package Performance Study In 1999, the USNRC initiated a five-year project, referred to as the Package Performance Study, which had the following three objectives (USNRC, 2003c, p.4)
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From page 99... ...
identified several common concerns: Some commenters asserted that the regulatory testing requirements in 10 CFR Part 71 were unconvincing as a demonstration of a transport package's performance under severe accident conditions. They wanted more realistic full-scale testing to demonstrate package performance.
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From page 100... ...
· A test of a truck package with its impact limiters to the same regulatory limits, except that the 2-megapascal pressure test might be eliminated if the truck and rail packages are tested in combination. · A full-scale crash demonstration of a rail package with impact limiters and its railcar with a simulated bridge abutment at about 75 miles per hour (120 kilometers per hour)
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From page 101... ...
Finding a way to resolve this issue continues to be a challenge to regulators in the United States and may eventually become a challenge for DOE and the private sector in their commercial spent fuel transportation programs. The packages used to transport spent fuel and high-level waste are designed to contain their radioactive contents under normal transport conditions and to withstand accident conditions without an increase in external radiation to levels that would endanger emergency responders or the general public.
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From page 102... ...
. The safety of transporting spent fuel and high-level waste depends to a great extent on the "inherent" safety of transportation packages to contain their contents even under severe accident conditions.
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From page 103... ...
However, there would be no reason to change the testing requirements or package designs if effective operational controls could be implemented. The committee received several comments at its meetings on the testing of transportation packages under extreme loading conditions, especially 38The historical accident record provides perhaps the best available information to identify bounding accident scenarios.
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From page 104... ...
Many commenters asserted that the regulatory testing requirements in 10 CFR Part 71 are unconvincing as a demonstration of a transport package's performance under severe accident conditions. They wanted realistic full-scale testing to be conducted to demonstrate package performance.
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From page 105... ...
When pressed for specifics, the committee understood that what was generally meant was that full-scale testing should be carried out to destruction, presumably to establish the ultimate strength of transportation packages. The State of Nevada specifically recommended that the USNRC undertake an evaluation of the costs and benefits of destructive testing of a randomly selected production model cask (Hall, 2003, p.
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From page 106... ...
FINDING: Transportation packages play a crucial role in the safety of spent fuel and high-level waste shipments by providing a robust barrier to the release of radiation and radioactive material under both normal transport and accident conditions. International Atomic Energy Agency package performance standards and associated Nuclear Regulatory Commission regulations are adequate to ensure package containment effectiveness over a wide range of transport conditions, including most credible accident conditions.
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From page 107... ...
Full-scale testing is a very effective tool both for guiding and validating analytical engineering models of package performance and for demonstrating the compliance of package designs with performance requirements. However, deliberate full-scale testing of packages to destruction through the application of forces that substantially exceed credible accident conditions would be marginally informative and is not
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From page 108... ...
RECOMMENDATION: Full-scale package testing should continue to be used as part of integrated analytical, computer simulation, scale-model, and testing programs to validate package performance. Deliberate full-scale testing of packages to destruction should not be required as part of this integrated analysis or for compliance demonstrations.
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