Radiation Shielding for Storage and Transportation Cask Using Depleted Uranium Oxide in Cementitious Matrices Leslie R. Dole Juan J. Ferrada Catherine H. Mattus
U.S./Russian Depleted Uranium Workshop: Review of ISTC Projects
Oak Ridge National Laboratory Oak Ridge, Tennessee May 17–21, 2004
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY BACKGROUND
•Combinations of gamma adsorbing DU and neutron absorbing hydrated binders are shown to effectively reduce the size and weight of storage, transport, and disposal casks
•DUCRETE will become one of the materials of choice for advanced spent nuclear fuel (SNF) casks 9Requires the demonstration of low-cost fabrication processes 9Requires the demonstration of long-term durability under expected service conditions
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Comparison of Equivalent
Wall Thickness (in.) Shield Thickness 30 Neutrons Gamma 25
20
15
10
5
0 DUCRETE Uranium Metal Lead Metal Stainless Steel Concrete
Dr. J. Sterbentz, INEEL J. W. Sterbentz, Shielding Evaluation of a Depleted Uranium Heavy Aggregate Concrete for Spent Fuel Storage Casks, INEL-94/0092 (Idaho Falls, Idaho: Idaho National Engineering and Environmental Laboratory, October 1994). OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY DUCRETE Casks are Considerably Smaller and lighter than Casks Constructed of Ordinary Concrete The DUCRETE cask is 35 tons lighter and 100 cm smaller in diameter than casks made from Cask Lid Air Outlet ordinary concrete.
Multipurpose Sealed Basket (Shell Wall) SNF Fuel Assemblies Concrete Cask Liner
Concrete
Comparison of conventional and DUCRETE Air Inlet Duct spent-fuel dry storage casks/silos
Air Entrance OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY For the USA, Estimated Cumulative Number of SNF Assemblies for PWR and BWR Light-Water Reactors Through 2020, Low-Case
300,000 250,000 200,000 150,000
Assemblies 100,000 Cummulative Cummulative
Number of Fuel Fuel of Number 50,000 PWR 0 PWR 2002 2004 2006
BWR 2008 2010 2012 2014 2016 2018 Total Year 2020
U.S. Department of Energy, Integrated Data Base Report —1994: U.S. Spent Nuclear Fuel and Radioactive Waste Inventories, Projections and Characteristics, DOE/RW-0006, Rev 11 (Washington, D.C.: September 1995), p. 36. OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY DUO2 Use in Storage/Transport Casks for USA Commercial SNF at 55.7 tonnes per Cask
Potential Use of DUO2 in SNF Storage for 24 PWR and 61 BWR Assemblies per Storage Cask
500,000
400,000
300,000 , tonne 2 200,000
DUO 100,000
0 BWR
BWR 2002 2004 2006 2008 2010
PWR 2012 2014 2016 2018 Total tonnes Year 2020
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Russian Dry Storage of SNF
• No site selected, but has a potential candidate site near Chelyabinsk • Russia has proposed development of an international repository and to Import 30000 tons of spent fuel
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Dry Storage and Transport Casks have been Developed for Russian SNF A Metal Concrete Cask for Storing and Transporting the Spent Fuel of RBMK Reactors A. Zubkov, V. N. Fromzel’, V. Yu. Vasil’ev, B. K. Danilin, V. A. Nikitin, and L. V. Fromzel’ A cask was developed for storing and transporting the spent fuel of a nuclear power station with RBMK reactors. Nuclear and radiation safety has been appraised and an analysis of the thermal state and the strength of the cask under normal and emergency conditions has been made. It is shown that the cask complies with the requirements of international and Russian regulations. OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Russian RBMK Spent Fuel Cask with Heavy Concrete
Heavy concrete with steel shot and barium sulfate
GNB CONSTOR test cask for RBMK SNF OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY RMBK SNF Shipments in Russia
A train carrying a load of SNF from a Ukrainian nuclear power plant arrived to Zheleznogorsk, Krasnoyarsk. OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY DUAGG Briquettes are Stabilized DU Aggregates with Basalt Sintering Agent
To get high strengths Briquettes are pressed, solidified by liquid-phase sintering, crushed, and gap- graded for use in high- strength DUCRETE at 5000 to 6000 psi, (35–42 MPa)
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Current Accelerated DUAGG Exposure Studies Using ASTM C289-94 Standard Test Method At a consistent surface-to-liquid ratio of 1:10, the sintered DUAGG samples are exposed to (1) distilled water (2) 1N sodium hydroxide standard solution (3) saturated water extract of high-alkali cement
Simulating expected service conditions, there are three exposure temperatures and six times: 25, 66, and 150ºC at intervals of 30, 60, 90,180, 360, and 730 days
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY View of DUAGG Before Testing
C
B
C A
Detail of the surface (secondary electrons) Particle A contains Al Particle B contains Ti and some Mg Area C contains DUO particles surrounded by dark basalt OAK RIDGE NATIONAL LABORATORY 2 U. S. DEPARTMENT OF ENERGY DUAGG 6 Months in DI Water
50 µm
Backscattered electrons A A Secondary electrons
A
10 µm
50 µm
150°C — secondary electrons Particles A contain Ti and some Mg
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY DUAGG 6 months in Cement Pore Water
50 µm
67°C—Backscattered electrons
67°C — secondary electrons
20 µm 50 µm
67°C — secondary electrons
Covered by CaCO3 and needle-like crystals containing Ca, Si, and some Al OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Uranium Leached from DUAGG
0.160
0.140
0.120
0.100 20°C 0.080 66°C 150°C
% leached 0.060
0.040
0.020
0.000
m m m m m m m m m m m m 2 6 3 2 3 - 3 13 - 1 - 2 r- r- 6 1 l. l. l.- e H o o o l.- 1 te ter- 3 m er- OH - 1 O OH - 6 m s o t a OH - t s t s t water- 1wa wa wat Na NaOH - Na N n n n t s wa e e e n DI DI DI DI Na m m m e DI e e e c c cement sol.-c 3 m cem
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Comparison of Release Rates for Uranium with Data from the Literature
•DUAGG tests: 0.25 mg/(m2•day) after 1 month at 66°C in DI water ~0.40 mg/(m2•day) after 13 months in cement pore solution
2 •UO2 (Thomas & Till) : 5 mg/(m •day) after 8 days at 70°C in DI water
G. F. THOMAS and G. Till, “The Dissolution of Unirradiated UO2 Fuel Pellets under Simulated Disposal Conditions,” Nucl. Chem. Waste Manage. 5, 141–147 (1984)
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY DUCRETE Aggregate is Leach Resistant
Leach Rate Test Results for DU 6 Subjected to USEPA TCLP Test 5 DU Material Concentration in Conc rete Leachate (ppm) 4 Magnetite DUCRETE 3 DUCRETE 0.42 Steel DUAGG 4 2 Lead Uranium UO2 170
Half Value Thickness (cm) 1 U O 420 0 3 8 0 5 10 15 20 UO3 6900 Material Density (g/cm3) UF4 7370
DUCRETE half value thickness comparison
USEPA= U.S. Environmental Protection Agency OAK RIDGE NATIONAL LABORATORY TCLP= Toxicity Characteristic Leach Test U. S. DEPARTMENT OF ENERGY Conclusions
• After 13 months of exposure, the release rate of uranium in a cement pore solution is low and
shows that DUAGG is superior to pure UO2
• A protective layer of recrystallization products from the basalt phase of DUAGG cover the surface, slowing the release of uranium
• In the cement pore solution, after 6 months of exposure, no deleterious products from the alkali- aggregate reaction were seen
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Summary
• Results show that DUAGG can be expected to be stable under the casks’ service conditions
• We are continuing laboratory experiments to characterize DUAGG/DUCRETE materials and their behavior in SNF cask applications
• We are pursuing a collaboration with Holtec International, Inc., and Russians to design and demonstrate the next generation of SNF storage and transport casks
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Additional Technical features of DUCRETE
• Thin cask walls and higher thermal conductivity increase thermal transport resulting in greater capacities for fuel bundles • Increased fracture toughness contributes significant physical protection against missiles and explosive blasts
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY DUCRETE Enables Increased Thermal Loading Capacity of Casks
• Reduce wall thickness • Increase thermal conductivity • Both • Increase internal diameter and wall area by r2
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Theoretical Thermal Conductivities of Composites
Concrete Volume percent of component W/(m•K)
Cement Steel Lime- Barium UO2 Paste stone Sulfate powder Normal .25 .10 .65 2.9 Concrete Heavy .25 .10 .65 3.4 Concrete DUCRETE .25 .12 .63 7.0
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Fracture Toughness with Microreinforcement
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY ISTC Micro-Reinforcement Project Micro-reinforcement of Concrete in SNF Cask Shielding Performers: Lead Institution: Russian Federal Nuclear Center – All Russia Science and Research Institute of Experimental Physics (RFNC-VNIIEF), Project Manager: S. Ermichev, V. Shapovalov. Other participating institutes: VNIIKhT–Seredenko; RAS ICP–Gromov; VNIINM–Orlov, Sergeev; the RAS IHT–Mineev
Description: The addition of micro-reinforcement to concrete structures increases their fracture toughness and therefore the ability of the concrete to absorb energy (e.g., rocket from a terrorist attack or airplane crash). This enhances the durability and reliability of an SNF cask under high-impulse stresses and provides for more effective physical protection of the cask contents. It is proposed that the tensile strength of concrete be increased by adding metal and/or polymeric fibers
Benefits: The use of micro-reinforcement may eliminate, the need for rebar in construction of concrete structures specifically concrete SNF storage casks.
Cost: $800K over 3 years
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Proposed ISTC “Micro-Reinforcement” Tasks Increase the fracture toughness of SNF casks through development of micro-reinforcement technology: 1. Prepare and test laboratory specimens to establish an experimental base
2. Production of DUAGG and DUO2 steel cermets containing micro- reinforcement
3. Model-scale studies to evaluate efficiency of concrete fracture toughness and ability to absorb energy
4. Final testing and evaluation of micro-reinforcement concrete properties
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Microreinforcement
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Energy Absorption by Concrete
Combination of concrete, steel, and plastic (e.g., Kevlar®) fibers
Concrete alone
Normalized Stress Concrete and steel rebar
Elongation
Metal and fiber reinforcement of concrete greatly increases fracture toughness (i.e., area under the curve) (Ref. www.civil.columbia.edu/meyer/fiberreein.html)
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 03-085 Baseline DUAGG Preparation Facility
• Uses DUAGG process as we found it, circa Year 1999 • Assumes US labor and construction requirements • Uses unmodified commercial equipment • Facility size to meet only 30% of USA cask market • Does not use later processing innovations
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY DUO2 Sintering Binding Silo Material Material
Special Container With DUO2
Homogenizing Crushing System Special Container Briquette Dump Silo Briquetter Final Product Classifier Mixer
Crusher
Sintering Furnace Sintered Material Silo
Size A Size B Size C Final Product Out OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY DUAGG Process Space Requirements 170’
120’
DUAGG Process Plant 70’
70’ 20’ Maintenance 30’ Building Utilities 60’ 100’ 265’
40’ 20’ Office 30’ Expansion Lot 110’
Parking
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Summary of Estimated DUAGG Costs
Transportation Transportation and Baseline: zero-cost disposal credit + and disposal DUO2 DUO2 delivered as credit briquettes Labor cost Labor cost ($/h) Labor cost ($/h) ($/h)
80 40 80 40 80 40
Capital $11.6 $11.6 $11.6M $11.6M $8.9M $8.9M M M Operating $5.2M $3.8M $6.4M $4.7M $4.2M $2.4M (year) $104K $76K $129K $94.9K $82K $48K Unit (cask) ($1.67 ($1.34 ($2.27 ($1.67 ($1.32 ($0.84 /kg) /kg) /kg) /kg) /kg) /kg)
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Percentage Contributions to the Operating Costs for the Baseline Case
Cost of UO2 0% Capital Recovery 36%
Chemicals Labor 1% 62% Electricity 1%
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Baseline Cask Fabrication Based on Most Complicated Version of GNB’s CONSTOR Cask
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Assumptions for the Cask Fabrication Plant from a Private Firm Stand-Point The baseline case assumes a penetration of 30% in the spent fuel cask industry that translates in the manufacturing of 50 casks per year. The manufacturing plant receives DUAGG, cement, and steel pre-fabricated parts to make the casks. It takes three days (1 shift) to make a cask The plant will work 5 days a week The plant will work 150 days a year (30 week per year or 1200 hr per year) OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Reinforcement Bars in Inner Cyl.
FABRICATION SEQUENCE Sliding Outer Cyl Into Inner Cyl.
Inner Inner Cylinder Cylinder Cleaning Inner Cylinder Surface Preparation
Upside Down Filling cask with DUO2 and cement
Welding Bottom Outer Welding Head Cover to Cylinder To Inner Cyl. Outer Cylinder Surface Preparation Cask
Upside position Cover and store OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY FABRICATION STAGES
UO2 DUCRETE preparation
Cleaning and Machining Add Slide Inner Cleaning and Fill Inner Cylinder Reinfor- Into Finished Machining, cement Outer Cask Cask Cleaning and welding Outer To Inner Upside Clean Storage head to Outer Cylinder Cylinder Cylinder Down Paint
HEPA Waste Utilities Room Manag- ment Administration
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Summary of Estimated Cask Fabrication Costs Baseline: zero-cost
DUO2
Labor cost ($/h)
80 40
Capital $18.5M $18.5M
Operating $18.3M $12.6M (year)
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Summary of Total Cask Fabrication Costs
Baseline: zero-cost
DUO2
Labor cost ($/h)
80 40
Capital $30.1M $30.1M
Operating $24.7M $19M (year)
Unit (cask) $494K $380K
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Conclusions
• After 13 months of exposure, the release rate of uranium in a cement pore solution is low and
shows that DUAGG is superior to pure UO2
• A protective layer of recrystallization products from the basalt phase of DUAGG cover the surface, slowing the release of uranium
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Conclusions (continued)
• Using DU dioxide aggregates in concrete for shielding is technically feasible using off-the-self processing and production technologies
• Using DUAGG/DUCRETE in casks used to store and dispose of SNF can reuse the nation’s inventory of DU
• Using standard ASTM testing protocols for extended times and constant temperature show that the chemical and physical stability of DUAGG is adequate to ensure very long service lives for the composite casks
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY Conclusions (continued)
• A current incomplete cost analysis shows that the estimated simple manufacturing costs of DUCRETE storage casks, ~$400-500K, are well within the current cask market cost, considering the very conservative assumptions used in this baseline case. (The simple manufacturing cost does not include licensing, marketing, transportation, or other significant costs, which bring the final costs of current, similar casks to $1.0M to 1.2M in the United States.)
• These results show that DUCRETE casks can be made at a cost that could be competitive in today’s market.
OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY