Sandia’s Salt Design Concept for High Level Waste and Defense Spent Nuclear Fuel

Ed Matteo, Ernie Hardin, and Teklu Hadgu

Sandia National Laboratories

Middelburg, The Netherlands

September 5-7, 2017

Sandia National Laboratories is a multi-mission laboratory managed and operated by

National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary

of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear

Security Administration under contract DE-NA0003525. SAND2017-9337 C.

Disclaimer

This research was performed as part of the Defense Waste Repository (DWR) project. Based on revised DOE priorities in mid-2017, the development of a DWR has been discontinued; current work unique to the development of a DWR is being closed out and documentation will be completed by the end of fiscal year (FY) 2017. Implementation of any recommendations made in this report for further research regarding a DWR would require resumption of the DWR project at some future time.

Key Acronyms

HLW = High Level Waste

DSNF = Defense Spent Nuclear Fuel (or DOE-Managed Spent Nuclear Fuel)

CSNF = Commercial Spent Nuclear Fuel

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Main Objectives: Operational and post-closure safety

Disposal Concept ≡ waste form + geologic setting + concept of operations

Waste form:

Mostly High Level Waste (HLW) glass, low heat output, Stainless Steel pour canisters

Defense Spent Nuclear Fuel (DSNF) of various types, pre-canistered

Geologic setting: Salt

Concept of operations: ?

Preliminary Disposal Concepts for Salt Repository:Identify Candidate Concepts for Evaluation

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Low-thermal (up to 1 kW per 3- or 5-m canister)

Long-lived radionuclides (~106-year assessment)

Large numbers of canisters (data from Carter et al. 2012)

3,542 DSNF (99.4% < 1 kW in 2030)

23,032 HLW (Savannah River Site(SRS, Hanford & Idaho; all < 1 kW)

Small canisters (mostly 18- and 24-inch diameters)

Neglecting Naval SNF which is most similar to Commercial Spent Nuclear Fuel (CSNF)

(Assume Idaho calcine is package in standardized canisters.)

Canister Handling Weights

DSNF 2267 kg to 4536 kg + overpack ~15 MT

Shielded transport wt. >34 MT

HLW 2500 kg to 4200 kg (no overpack)

Shielded transport weight > 32 MT

Material: stainless steel (welded, no heat treatment)

Preliminary Disposal Concepts for a Salt Repository:Defense Waste Characteristics

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Plastic formation

Creep behavior impacts concept of operations

Excavations will close due to creep

Just-in time drift construction

Self-healing

Geochemical environment Brine pore water

Virtually impermeable media (diffusion dominated)

Repository Access

For bedded salt, shaft access only

For domal salt, shaft or ramp access

Preliminary Disposal Concepts for a Salt Repository:Salt Geologic Setting

Bedded or Domal Salt Constructability

• Opening stability

• Salt backfill

Superior Heat Dissipation

Nominal and Disturbed Performance

• Releases dominated by human intrusion

Natural Barrier

• Insignificant groundwater abundance and mobility (nominal)

• Brine saturation (esp. human intrusion)

Engineered Barriers

• Backfill and seals

• Robust containment during operations

• Emplacement borehole behavior (e.g., backfill reconsolidation)

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Preliminary Disposal Concepts for a Salt Repository:Design Considerations

Preliminary Disposal Concept for a Salt Repository

Direct Disposal of Pour Canisters

• HLW glass stability in operational environment

Robust Overpack for Other Waste Forms

• Carbon steel overpack (e.g., DSNF)

Just-in-Time Drift Construction

• Minimize handling of crushed salt

In-Drift Emplacement (axial or transverse)

• Relatively small, lightweight canisters (e.g., 6 MT HLW)

• Immediate backfilling with crushed salt

Constructability Challenges

• Remote operation in unshielded environments

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The Inventory is ~80% by volume is glass

Projected volumes in the year 2048 ( m3)

Commercial and DOE-Managed

HLW and SNF

DOE-Managed

HLW and SNFDOE-Managed HLW

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data from SNL 2014

Waste Packages

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HLW Glass

Diameter = 61cm (direct disposal)

Length = 3m or 4.57m

Defense Spent Nuclear Fuel

Diameter = 61cm (80cm including Steel overpack)

Length = 3.1m or 4.6m

(not used for Naval SNF)

From DOE 2008 -- Yucca Mountain repository SAR (Figure 1.5.1-8 and Figure 1.5.1-18)

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Distribution of Thermal Output per Canister (by # of canisters)

From Matteo et al. 2016

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Distribution of Thermal Output per Canister (by % of each waste type)

From Matteo et al. 2016

Decay Heat for Different Waste Types

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From Wilson 2016

Temperature Histories at Waste Package Surface (10 years surface storage)

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From Matteo et al. 2016

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From Matteo et al. 2016

Temperature Histories at Waste Package Surface (50 years surface storage)

Salt Preliminary Design Concept by the Numbers

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Preliminary Design Parameters Selected on the Basis of Design Criteria Thermal Analysis, 1/2

Waste Package Emplacement Concept is simple and cost effective Just-time- construction

Run-of-mine (ROM) salt from advancing drift used for backfill on adjacent drift post-emplacement

Minimizes ROM handling operation

Provides shielding for DSNF packages

The tranverse emplacement of packages keeps the repository footprint compact

DSNF overpack is robust, direct disposal of HLW reduces handling burden

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Preliminary Design Parameters Selected on the Basis of Design Criteria Thermal Analysis, 2/2

Drift details Drift length = 500m

~50 DSNF packages per drift (~3000 total)

~50-150 HLW packages per drift (~25,000 total)

14m pillars could be increased to 30m, if necessary

Waste Package Spacing

DSNF - ~8m (center to center)

HLW - ~3 to7.7m (center to center)

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From Hardin et al. 2015

An Approximate Illustration of the Preliminary Design in Salt including notable differences

References

DOE (U.S. Department of Energy) 2008. Yucca Mountain Repository License Application Safety Analysis Report. DOE/RW-0573, Revision 1. U.S. Department of Energy, Washington, DC. (http://www.nrc.gov/waste/hlw-disposal/yucca-lic-app/yucca-lic-app-safety-report.html#1 )

Filbert, W., E. Biurrun, W. Bollingerfehr, B. Haverkamp and R. Graf 2010a. “Optimization of Spent Fuel Direct Disposal Technology for a Geological Repository in Rock Salt in Germany– 10504.” Proceedings of Waste Management 2010. March 7-11, Phoenix, AZ.

Hardin, E., L. Price, E. Kalinina, T. Hadgu, A. Ilgen, C. Bryan, J. Scaglione, K. Banerjee, J. Clarity, R. Jubin, V. Sobes, R. Howard, J. Carter, T. Severynse and F. Perry 2015. Summary of Investigations on Technical Feasibility of Direct Disposal of Dual-Purpose Canisters. FCRD- UFD-2015-000129 Rev. 0. U.S. Department of Energy, Office of Used Nuclear Fuel Disposition.

Matteo, E. N., E. L. Hardin, T. Hadgu, H. Park, C. Jové-Cólon, and M. Rigali 2016. Status of Progress Made Toward Preliminary Design Concepts for the Inventory in Select Media for DOE-Managed HLW/SNF. FCRD-UFD-2016-000081, U.S. Department of Energy, Office of Used Nuclear Fuel Disposition.

SNL (Sandia National Laboratories) 2014. Evaluation of Options for Permanent Geologic Disposal of Used Nuclear Fuel and High-Level Radioactive Waste Inventory in Support of a Comprehensive National Nuclear Fuel Cycle Strategy. FCRD-UFD-2013-000371. SAND2014-0187P; SAND2014-0189P. Revision 1. Albuquerque, New Mexico: Sandia National Laboratories.

Wilson, J. 2016. Decay Heat of Selected DOE Defense Waste Materials, FCRD-UFD-2016- 000636, SRNL-RP-2016-00249.

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