State of Practice Approaches in Geomorphology, Geochronology and Probabilistic Analyses for Addressing Fault Capability at Nuclear Facilities

Presentation to Department of Energy Natural Phenomena Hazards Meeting

October 21-22, 2014 Overview

• Case history on application of state of practice site characterization investigations for assessing the suitability of two sites for a proposed second nuclear power plant (NPP) at Krško, • Site Characterization investigations to evaluate capability of faults within 5 km of planned NPP sites (2) • PFDHA conducted to assist utility in making informed decision on suitabilityClick to edit of proposedMaster title NPP style sites with respect to the probability of surface fault displacement

2 Overview

• Site characterization investigations follow IAEA SSG- 9 guidance include • Tectonic geomorphic analyses related to landscape evolution • Geochronology based on multiple methods for constraints on faulting • High resolution seismic (refraction & reflection) surveys to identify extent of faulting in site vicinity • Probabilistic evaluationClick to edit of Master fault displacementtitle style hazard to support • Utility in assessing nuclear safety • Regulatory decision-making following IAEA SSG-9 • Focus of investigations on Fault that is mapped in close proximity to proposed eastern NPP site 3

BACKGROUND

• Krško, Slovenia is located in southeastern Slovenia in an area defined by a triple junction between the Alps, Dinarides, and the Pannonian Basin • Region is within the transition zone between the Folds and the southeastern extension of the Mid-Hungarian Shear Zone • Region of moderate seismicity • Paleoseismic investigations conducted prior to 2012 demonstrated the Libna Fault to be: • Capable basedClick on ageto edit Master title style • within 1-2 km of the existing proposed sites for Krško NPP 2

4 Background (Cont’d.)

• Utility and expert reviewer questioned the interpretation of the Libna Fault’s capability by previous investigators based on: • Questionable optical stimulated luminescense (OSL) ages (possible at saturation limits – i.e. the maximum age capacity) • Inferred projections of the Libna and other faults • Judgments madeClick based to edit onMaster limited, title styleand potentially unreliable data

5 Tectonic Framework of Adriatic Microplate transition zone at northern extent of Mid Hungarian Shear Zone

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6

Libna Flt Sites

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Approximate Lineament Map surrounding the Krško Basin

7 Trench Excavated Across Libna Fault

Trench excavated in high-density, karst landscape -- brings into question the mode of recent displacement

Trench wall faces south

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From GeoZS 2013

8 Trench map of notable Karstic dissolution features

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9 1m DEM 5m DEM LiDAR DEM

Deep-seated landslide provides local analog for ‘exaggeration’ of the Libna Feature – site located ~12 km from Libna Trench

Extensive karst is common to region (note the sinkholes)

Note difference between 1m LiDAR DEM and conventional Click to edit Master title5m style resolution DEM

10 Lineament map Based on DEM derivatives

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11 Libna Hill Morphology

Signatures of: • Faulting? • Landsliding? • Karst?

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12 3D oblique images

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13 Enhanced LiDAR DEM showing location of trench relative to karst and landsliding

Apparent continuity in SE corner is a fluvial Click to edit Master title style scarp – proven with additional Indicating trenching location of trench Fluvial scarp

14 High Resolution Seismic Survey

• Seismic survey designed to explore extension of the Libna fault in the Krško basin • Used high resolution refraction & reflection approach designed for identifying near surface features • Develop hybrid, diving wave refraction tomography for additional near-surface characterization • Faults were identified but no faulting observed in the

upper MioceneClick marls to edit Master title style • Marl underlie young valley fill (10-120m) • Dip direction of faults identified in HRS survey tend to have dip direction opposite that of the Libna fault • Suggests a lack of fault continuity

15 Plan View Showing Possible Faults

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16 Krsko Basin Sediments

OSL sediment “depositional” ages

• CRN elevation (322 m) ~1.8 Ma

• Libna Trench (140 ka) (315- 320 m) elevation

• OSL elevations Click to edit Master title style (150-215) m

17 Conceptual capacity of OSL in the Krsko Basin

OSL date CRN date

All other age datesClick to edit Master title style

18 Quaternary Aggradation and Incision Scenarios

To accept the Libna Trench OSL age, there are two scenarios necessary: • Catastrophic aggradation of Sava River: greater than 100m/ 1,000 years Long term = 0.09m ka-1 • Catastrophic incision of Sava River: greater than 100m/1,000 years *There is no evidence for any catastrohic events that occurred in the region that could have led to either of these scenarios • Moderate incisionClick ofto editSava Master River title style (0.09m/1,000 years) this is consistent with incision rates of the southern Alps • Suggests provides a more representative age than the Libna Trench OSL age.

19 Findings of Geomorphic, Geophysical and Geochronology Investigations Investigations

• Libna Hill and surrounding area is dominated by karst and landsliding • Apparent offset of the Globoko Fm. May be greatly exaggerated by karst and landsliding • CRN analyses suggests age of Globoko Fm. Is approximately same as published interpretations • Use of OSL may be limited to dating sediments around 200Ka in the regionClick to (notedit Master unusual title style for OSL limitations) • Libna fault, if displacement of Globoko is tectonic has an age of less than 1.7 Ma • Libna fault may be discontinuous within the Miocene bedrock with a maximum length of 1.5 to 4.5 km 20 PFDHA

• Methodology: Petersen et al. (2011) • Extension of “earthquake” approach developed by Youngs et al. (2003) for the Yucca Mountain Project • Treats on-fault and off-fault displacement • Uses Petersen et al. fault displacement data base • Accounts for uncertainty related to fault mapped location accuracy & faultClick complexityto edit Master title style

21 Key PFDHA Inputs

• Probability of activity • Fault length • Fault location • Slip rate • Maximum magnitude • Hazard calculation cell size Click to edit Master title style • Fault location uncertainty (mapping accuracy and fault complexity)

22 Fault Model

46.05

Orlica N

Mocnik 2 Libna Gabrnica

Orlica S

Stara Vas 45.95 Latitude (Deg N) Sromljica Mocnik 1 Click toGorica edit Master title style

45.85 15.4 15.5 15.5 15.6 15.6 15.7 15.7 15.8 15.8 Longitude (Deg E)

23 Krško PFDHA Results

1.E-05

Total Hazard

1.E-06

1.E-07

1.E-08

East Site 1.E-09 Click to edit Master title style West Site MeanAnnual Frequency of Exceedance

1.E-10 0.001 0.01 0.1 1 10 Displacement (m)

24 Fault Source Contribution-East Site

1.E-05 East Site Orlica South 1.E-06 Stara Vas B 1.E-07

Libna A & B 1.E-08

1.E-09

1.E-10 0.001 0.01 0.1 1 10

MeanAnnual Frequency of Exceedance Displacement (m) Click to edit Master title style Total hazard Artice_Extended_East Artice_Extended_West Artice_Long Artice_Short Gabrnica_A Gabrnica_B Gorica_A Gorica_B Hrastnik Libna_A Libna_B Libna_C Mocnik_1 Mocnik_2a Mocnik_2b Orlica_North Orlica_South Sromljica_A Sromljica_B Stara_Vas_A Stara_Vas_B

Source: RIZZO (2013a, Figure 14) 25 PFDHA Findings

• Petersen et al. methodology is appropriate for PFDHA application in the geologic setting of Krško • The probability of exceeding surface displacement values of about 5 cm or greater at the Krško East and West Sites is very low: about 10-8 or less • Libna fault does not pose a suitability issue for either sites Click to edit Master title style • This finding also applies to the existing Krško 1 NPP Site

26 Conclusions

• Tectonic geomorphic and landscape evolution methods should be applied, that rely on multiple age dating methods and high resolution topography. Combined, these methods allow for a broader understanding of the processes that shape the landscape, including faulting, karstic dissolution, landsliding and fluvial erosion. • PFDHA has hadClick limited to edit Masterapplication title style in assessing suitability of existing and proposed NPP sites; however, its application has been beneficial to aiding decision makers in assessing site suitability.

27 Contact Information

• K. Cline – [email protected] • M. Logan Cline – [email protected] • Richard Quittmeyer – Click to edit Master title style [email protected]

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