Cermet Spent Nuclear Fuel Casks and Waste Packages

Charles W. Forsberg and Leslie R. Dole

Paper NN-8.8 Room Constitution A (Sheraton) Scientific Basis for Nuclear Waste Management XXX Materials Research Society Fall Meeting Boston, Massachusetts 11:00 AM; November 29, 2006

Oak Ridge National Laboratory* P.O. Box 2008, Oak Ridge, TN., 37831 United States of America E-mail: [email protected]

GNS Storage and Transport Cask (Current Technology)

OOAKAK R RIDGEIDGE *Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. OAK RIDGE NATIONAL LABORATORY Department of Energy. The United States Government retains and the publisher, by accepting the article for NATIONALATIONAL L ABORATORYABORATORY U. S. DEPARTMENTN OF ENERGYL publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. File: DU Viewgraphs: MSR 06 Cermet 1 The United States and Russia have been Examining Cermet Spent Nuclear Fuel (SNF) Casks Storage, Transportation, and Waste Disposal • Multiyear program • Several factors have created an interest in cermet casks − New fabrication methods − More emphasis on physical protection − The availability of depleted uranium dioxide (DUO2) − An understanding of how waste package (WP) composition can improve repository performance • Paper summarizes results • References in the paper to the detailed reports GNS Storage and Transport Cask OAK RIDGE NATIONAL LABORATORY (Current Technology) U. S. DEPARTMENT OF ENERGY 2 Cermets Combine the Best Properties of Ceramics and Metals Ceramics: Shielding, Hardness, etc.; Metals: Strength, Ductility, etc. Cermets Are Used for Cermet-Body Cross Section Demanding Applications Clean Steel Ceramics

-Armor (Al2O3, Brake Shoes SiC) - Neutron Shielding

(DUO2, Gd2O3) - Gamma Shielding

(DUO2) Metal Matrix Main Battle - Strength Tank Armor Cask Body - Thermal Conductivity Cutting Tools

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 04-070 3 Outline: Cermet Casks

• System applications • Shielding performance • Assault protection • Repository performance

− Optimized geochemical environment − Neptunium and technetium sorption − Nuclear criticality • Depleted uranium (DU) disposal • Co-disposal of SNF and DU • Fabrication • Conclusion

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 4 System Applications

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 5 Cermet Casks have Multiple Applications Overpack for Transportation, Aging, and Disposal (TAD) Canister; Shielded TAD; Component of WP

Dry Store Transport Repository Disposal (At Reactor)

Cask Removable Repository Overpack Overpack (2 cm C-22) Transport Overpack Cask Surface Facility Minimal Facility No SNF Shuffle (Surface Store SNF for Heat Management)

Underground Overpack Functions (Intact Package) Storage: Heat Removal No Remote Operations Transport: Accident Protection Redundant/Alternative Barrier Disposal: 10,000 year lifetime

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 03-1476 Shielding Performance

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 7 DUO2-Steel Cermets are High- Performance SNF Casks

• Maximize number of SNF assemblies based on − Maximum allowed cask weight − Maximum allowed cask diameter • Cermet construction − Steel matrix • Strength • High-thermal conductivity

− DUO2 ceramic • Shielding • Repository compatible − No concrete − No RCRA metals (lead) − No organics − Cost constraints (no tungsten) − No reactive metals (uranium metal)

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY ORNL DWG 2001-221 8 Assault Protection

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 9 Cermet Casks can have Extraordinary Resistance to Assault

• Cermets are a traditional form of tank armor − Ceramic breaks up shaped charge or penetrator − Metal absorbs the energy • SNF Casks are heavy relative to military tanks − Main battle tank: 70 tons and large − SNF rail cask: 100 tons and much smaller German Rail Gun for Testing Casks: 1 Ton Projectile at 300 m/s OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 10 Repository Performance

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 11 Cermet WPs (Fe and DUO2) may Offer Superior SNF Waste Isolation

• Cermet WP composition (metals and ceramics) chosen to limit radionuclide migration • Multiple mechanisms for better performance − Control of geochemical environment − Neptunium and technetium sorption − Nuclear criticality control

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 12 Uranium Oxide and Metallic Iron Deposits have Slow Water Flow, Gas Diffusion, and Oxidation

Natural UO2 Ore Deposits Roman Nail Deposits

Boltwoodite

6+ K(U ) ()SiO (OH).4HO S 2 O223 2 2 2 S

A Uranophane

M 280 6+ . T Ca ( O )6HSi O O I 2 2 2 7 2 N U

U 240 R Oxidizing

E Intact P Groundwater Nails L 6+

A . (Iron) 3 200 UOSchoepite3 2H2O R E (cm /kg) N I Soddyite M

6+ Hydrated 160 UO3 ()U O SiO.2HO F 242 2 Iron Oxide O

Uraninite U O E 38

M 120 4+ 6+ U (OU1-XU) X 2+X L UO

O 2 V 80 Cermet WPs Slow Radionuclide Migration EVOLUTION OF URANIUM OXIDE UNDER OXIDIZING GROUNDWATER CONDITIONS by Similar Mechanisms

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 13 Uranium Oxides Slow Release of Neptunium and Technetium

• Experimental data indicates uranium oxides slow radionuclide migration − Neptunium − Technetium (less data) • EPRI analysis indicates major impact on Yucca Mountain (YM) performance • Added DU should provide further benefits EPRI YM Assessment

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 14 DU Cermet Casks Reduce Long-Term Criticality Issues in the Repository

Cf-251 902 y SCML = 5 g • Most fissile isotopes decay to longer- lived uranium isotopes before large- Cm-247 Cm-243 15.6x10 y scale WP failure SCML = 900 g 29 y Bk-247 6 SCML = 90 g 1400 y

EC 99.8% Long-term repository criticality issues 0.2% • 235 233 Am-243 Pu-239 are U and U 7370 y Pu-243 24.1x10 y 3 SCML = 25,000 4.96g h 235 6 SCML = 450 g − U: T1/2 = 700 · 10 years 233 5 Np-239 − U: T1/2 = 1.6 · 10 years 2.35 d U-235 CM = No U-239 700x10 y 6 23.5 m SCML = 700 g • DU in cermet WP isotopically dilutes Pa-231 32.5x103 y CM = Yes SNF uranium fissile isotopes (>3 tons Th-231 25.5 h DU per ton of SNF) • Average WP enrichment: <<1% Actinide Decay Chain

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 15 Depleted Uranium Disposal

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 16 WPs Provide a DU Disposal Pathway

• World inventory ~106 tons DU • Hazardous − Alpha: ~100s nCi/g − Toxic heavy metal • Repository use − Cermet WP • Engineered barrier • Beneficial use − Safe disposal Paducah Gaseous Diffusion Plant Cylinder Storage of DU (14-ton Containers)

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 17 Co-Disposal of SNF and DU

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 18 Cermet WPs Enable Co-Disposal and Co-Recovery of DU and SNF The Future is Uncertain; if the Future Adopts a Closed Fuel Cycle, the WP has the SNF and DU

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 19 Fabrication

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 20 Cermet Fabrication • Cermets are extraordinary materials; but − Difficult to fabricate − Almost impossible to weld • Cermet SNF cask viability depends upon economic fabrication methods • Three viable fabrication methods examined − Forged cermet cylinder (FCC) process − Cermet extrusion section (CES) process − Casting • CES process is the currently preferred option − Lowest front-end capital equipment cost − Fewer uncertainties − Allows for variable-composition cermet

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 21 Cermet Extrusion Section Process

Steel/DUO2 Particulate Fill Extrude Section Add Particulate Die Fill to Can Hydraulic Compress Can Layer Ram Add Next Powder Press Layer (Hot)

Compact Fill Machine Extrusions

Seal Preform, Cermet Heat, and Degas Extrusion Assemble Cask Steel Can (Braze or Weld) Inner Cask Wall Powder Mix Outer Cask Wall

Not to Scale Heat and Degas OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 06-010 22 Conclusions

• International consortium has examined cermet cask options • Cermet casts are technically viable − Preliminary economic analysis is favorable • Cermet cask system can integrate − SNF physical protection − SNF storage − SNF transport − Integrated SNF and DU disposal • Significant R&D remains

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 23 Abstract Cermet Spent Nuclear Fuel Casks and Waste Packages Scientific Basis for Nuclear Waste Management XXX; Materials Research Society Fall Meeting Boston, Massachusetts; November 30, 2006

Charles W. Forsberg and Leslie R. Dole Oak Ridge National Laboratory; P.O. Box 2008, Oak Ridge, TN., 37831 E-mail: [email protected]

Multipurpose transport, aging, and disposal casks are needed for the management of spent nuclear fuel (SNF). Self-shielded cermet casks can outperform current SNF casks because of the superior properties of cermets, which consist of encapsulated hard ceramic particulates dispersed in a continuous ductile metal matrix to produce a strong high-integrity, high-thermal- conductivity cask.

A multiyear, multinational development and testing program has been developing cermet SNF casks made of steel, depleted uranium dioxide, and other materials. Because cermets are the traditional material of construction for armor, cermet casks can provide superior protection against assault. For disposal, cermet waste packages (WPs) with appropriate metals and ceramics can buffer the local geochemical environment to (1) slow degradation of SNF, (2) reduce water flow though the degraded WP, (3) sorb neptunium and other radionuclides that determine the ultimate radiation dose to the public from the repository, and (4) contribute to long-term nuclear criticality control. Finally, new cermet cask fabrication methods have been partly developed to manufacture the casks with the appropriate properties. The results of this work are summarized with references to the detailed reports. OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 24 Biography: Charles Forsberg

Dr. Charles Forsberg is a Corporate Fellow at Oak Ridge National Laboratory, a Fellow of the American Nuclear Society, and recipient of the 2005 Robert E. Wilson Award from the American Institute of Chemical Engineers for outstanding chemical engineering contributions to nuclear energy, including his work in waste management and hydrogen production. He received the American Nuclear Society special award for innovative nuclear reactor design and the Oak Ridge National Laboratory Engineer of the Year Award. Dr. Charles Forsberg earned his bachelor's degree in chemical engineering from the University of Minnesota and his doctorate in Nuclear Engineering from MIT. After working for Bechtel Corporation, he joined the staff of Oak Ridge National Laboratory, where he is the Senior Reactor Technical Advisor. Dr. Forsberg has been awarded 10 patents and has published over 200 papers in advanced energy systems, waste management, and hydrogen futures. OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 25 Forged Cermet Cylinder Process United States Patent: 6,811,745: November 2, 2004

Steel/DUO2 Add Steel/DUO2 Particulate Fill Particulate Fill Consolidate Particulates to Cermet to Annular Steel Shells Preform Forge or Roll Idle Roller Drive Weld and Roller Seal Preform Vacuum Anvil Axial and Degas Degas Rollers Powder Mix

Future Cask Cermet Lid Mating Preform Surface

Heat Machine Cask Lid Preform Mating Surfaces Weld Bottom onto Package (Steel-to-Steel Weld)

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 02-090R3 26 Casks can be Constructed of a DUO2- Steel Cermet: 3-8 kg DU/kg SNF Manufacturing Demonstrated for Small Objects: Cermets were Used as Fuels in Some Reactors

Cermet Applications

Shielding Optional Layer: Cermet Steel Jacket SNF Assembly Slot Edge Void Structural Cermet (22.64 cm x 22.64 cm Space Support x 458.5 cm) Stainless Steel or Cermet Corrosion Resistance: C-22 (2 cm)

Inside St eel (1 cm) length 458.5 cm Basket Structure Depleted Neutron Absorber: Uranium Cermet with Dioxide Added Neutron Absorber Steel (Continuous Thermal Shunt: Phase) Aluminum (0.5 cm) Inside diameter 142.4 cm

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY ORNL DWG 2001-10327 Cermets Maximize Cask SNF Capacity Because of Superior Shielding Cask Weight and Size Constrained; Strong Economic Incentives to Maximize Number of Fuel Assemblies per Cask

Steel Jacket Gamma Shielding Better Than Steel - Steel: 7.86 g/cm3 Cermet 3 - DUO2: 10.9 g/cm Steel Neutron Shielding

- High-density oxygen (DUO2) moderator Depleted - Other neutron absorbers can be added Uranium Dioxide Good Physical Properties - High thermal conductivity - No organics (no fire; acceptable to repository)

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY ORNL DWG 2001-10928 SNF in Cermet Cask Oxidized Slowly by Oxygen in Groundwater Idealized Thermodynamic Calculation: Oxygen Only from Groundwater

350 0 Cermet and Fill WP 1 300 Cermet and Fill WP, Cermet WP YM WP 2

250 3 Start of SNF UO 2 Oxidation (Idealized) 4 200 aining ( ) ( aining

m 5

e Cermet WP R

150 ) ( pH

2 6 O 7 ol U ol 100 m k 8 50 YM WP 9

010 0 100 200 300 400 500 Oxygen (kmol)

0 0.51.0 1.5 2.0 2.5 Time (millions of years) OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY 03-099 29 Some Uranium Ore Deposits have Remained Intact for >106 Years: Similar Mechanisms for Cermet WPs

DUO2 is the Only Sacrificial Compound to Preserve SNF UO2 Under All Conditions

Barrier Crust Formation Slow Uranium Dissolution Chemically Reducing Conditions Natural UO 2+x Waste Ore Body Package Spent Nuclear Fuel Assemblies Criticality Control by Isotopic Dilution Radionuclide Adsorption on Uranium Oxides

OAK RIDGE NATIONAL LABORATORY U. S. DEPARTMENT OF ENERGY ORNL DWG 2000-40030