1

Lessons Learned in Modeling, Monitoring and Remediation of Radionuclide Movement thru the Environment – Ground Water

Background: Significant quantities of water containing high levels of radionuclides (e.g., Cesium-134 and Cs-137, Strontium-90, Americium-241, Carbon-14) and atmospheric deposition of radionuclides (e.g., Iodine-131 and Cesium-134 and Cs-137) were released to the environment during the Fukushima Daiichi nuclear accident. An ongoing issue is the large leakage of contaminated water into the reactor and turbine buildings, and offsite. The Japanese safety objective is to preclude any further contaminated water from reaching the ocean environment. Current technical issues: Based upon NRC staff interactions with the U.S. resource teams in Tokyo and at the NRC emergency response center, a critical issue was assessing the fate and transport of radionuclides, not normally monitored at nuclear power plants, which were released to the environment thru various pathways associated with the ongoing leaks at the Fukushima Daiichi nuclear power plants. Information and monitoring data on the source term, soil contamination and ground-water transport are critical in evaluating risk, and in deciding on remediation strategies and methods. Modeling and monitoring of these abnormal radionuclide releases are needed to confirm the effectiveness of various remediation activities implemented to reduce dose to humans and non-human biota both onsite and offsite. Proposed steps forward: Share information and field data from the ongoing Fukushima Daiichi monitoring activities to answer the following questions: • How did the radioactive “source term” evolve as the accident progressed? • What radionuclides have been released, and in what time-varying concentrations were

those releases to the atmosphere and to ground water as the accident progressed? • How do these radionuclides move through the environment? • How are these radionuclides impacting the biota in the area? • How is the “source term” influencing the selection of remediation strategies and methods? • How effective are these remediation activities? • What short-term and long-term monitoring programs are being developed and implemented

to assess the effectiveness of the selected remediation methods?

Discuss modeling of the ground-water flow and radionuclide transport as input to decision-making in formulating and executing a ground-water remediation program. Questions to be considered are: • How is environmental risk determined, and how are uncertainties in the conceptual model,

including the source terms, addressed? • How is monitoring data used to confirm the ground-water flow and transport models? • How is the monitoring program integrated with the modeling needs and results? • How are short- and long-term dose estimated using the ground-water and atmospheric-

depositional monitoring and modeling analyses?

Contact: Tom Nicholson, Thomas.Nicholson@nrc.gov 301-251-7498

2

Lessons Learned in Modeling, Monitoring and Remediation of Radionuclide Movement through the Environment - Bioaccumulation

Background: Significant quantities of water containing high levels of radionuclides (e.g., Strontium-90) and atmospheric deposition of radionucldies (e.g., Iodine-139 and Cesium-137) were released to the environment during the Fukushima Daiichi nuclear accident. An ongoing issue is the leakage of contaminated water to the reactor and turbine buildings, and the objective to preclude contaminated water to enter the ocean environment. Current technical issues: Because three reactor cores suffered damage, and the safety systems designed to contain radioactive contamination were leaking, the probability of release to the environment of radionuclides usually contained within plant systems is high. This event provides a unique opportunity to study the bioaccumulation of these abnormal releases to aquatic biota previously not monitored in the ocean or through ground-water pathways to aquatic biota. This study would provide a unique opportunity for monitoring and modeling pathways where there is a paucity of data. In recent years, scientists have not evaluated the bioaccumulation of radionuclides into the marine food chain. In addition, there is little data on marine bioaccumulation of radioactive Cr, Mn, Fe, Y, Zr, Nb, Mo, Tc, Ru, Ag, Te, Ba, La, Ce, W, Np, Am, and Pu. These radioactive elements may now exist in measurable quantities in the marine environment adjacent to the plant, providing a unique opportunity for intensive scientific study. Proposed steps forward: Share information and field data from the ongoing Fukushima Daiichi monitoring activities to answer the following questions: • What are the radionuclide concentrations in marine sediment, water, and biota? • What are the transport mechanisms within the marine environment? • What are the pathway transport constants for the radionuclides in the marine systems?

• Do these transport constants validate the values assumed in our present dose models? • How fast will the marine system return to normal background? • Does the contaminated marine vicinity require remedial action?

Contact: Dr. Steven Schaffer, Steven.Schaffer@nrc.gov 301-251-7473

OverviewOverview•• Cooperative agreement between NRC and twelve Cooperative agreement between NRC and twelve

foreign countries.foreign countries.

Investigations of Zirconium Fires during Investigations of Zirconium Fires during Spent Fuel Pool LOCAsSpent Fuel Pool LOCAs

•• Sandia National Lab is performing the experiment.Sandia National Lab is performing the experiment.

•• Two test phases to be completed over a 3Two test phases to be completed over a 3--4 year 4 year period.period.

• Validate severe accident codes for whole pool LOCA analyses.

• Phased experimental approach.

– Study physical phenomena separately

1

Study physical phenomena separately

• Provide input parameters to accident codes.

– Examine nature of Zircaloy fires in prototypic assemblies

• Validate codes predictive capability.

• Develop mitigation strategies.

Spent Fuel Pool

SFP Experiment ObjectivesSFP Experiment Objectives

• Provide full scale thermal hydraulic and zirconium ignition data for severe accident code validation under air flow conditions:– Gas flow conditions

• Spent fuel pool complete loss of coolant accident (LOCA)• Complete loss of water during refueling• Dry cask storage performance• Air ingress during late stages of core melt-down

– Prototypic components• Eliminate scaling arguments

2

Eliminate scaling arguments• Represents fuel design intricacies

– Code validation• Closely coupled into experimental design• Pre-test (Blind) and post test code data is compared to

experimental results to ensure code adequacy

SFP Zirc-Fire Research OverviewPhase 1 Testing Phase 2 Testing

•Top nozzle

PWR full length assembly

•Insulation•Top nozzle

•Guide Tubes

•Spacer

•Annulus

• Storage cell

•Assembly

Single heated and insulated

•Bottom nozzle

assembly Two storage cell used, i.e.

Cell 1 and Cell 2 Study the axial heat and

burn propagation

Five (5) assemblies in a 1 × 4 center heatedPeripheral unheated neighborsStudy the axial and radial heat

propagation as well as ballooning

3

SFP Test ProgramSFP Test ProgramMilestone/Event Purpose Configuration Material

• Separate Hydraulics – Determine form loss and laminar Single

Full Length SSEffects friction coefficients

Full Length (P)

SS

• Ballooning rod design

Test pressurized rod performance, preliminary data on ballooning as function of initial internal

pressureSingle rod Zr-2

• Pre-IgnitionThermal hydraulics – Determine temperature

profiles and induced convective flow

Single Full Length

(P)Zr-2

• IgnitionAxial Ignition – Temp profiles, induced flow,

axial O2 profile, nature of fireSingle (P) Zr-2

1 × 4• Pre-ignition

Thermal radiation coupling and induced convective cooling in a 1 × 4 arrangement

1 × 4Full Length

(P)Zr-2/Zr-4

• Ignition with ballooning

Radial fire propagation and effect of fuel rod ballooning

1 × 4Full Length

(P)Zr-2/Zr-4

CompletedFuture

P: Prototypic SS: Stainless Steel

Legend

4

Phase I TestsPhase I Tests1. Insertion of a

prototypic spent fuel rack into a fuel

1 2

rack into a fuel assemblies

2. Final assembly test configuration

3. Ignition (fire) of the zirconium cladding fire

5

3 4

4. Inspection of damage.

1

Spent Fuel Pool Scoping Study(SFPSS)

• Technical Objectives:– Estimating the effect on SFP accident consequences of a reduced

amount of spent nuclear fuel being stored in the SFP based on realistic analysis using readily available and technically defensible deterministic methods and assumptions as well as probabilistic insights.

– Capturing the relevant technical considerations and findings in a form that is conducive to informing deliberation on the issue of SFP accident consequences and whether to expedite movement of spent fuel to dry storage while not addressing any specific regulatory user need.

– Expediting attainment of preliminary insights by (1) relying exclusively on available information and methods, (2) focusing on a single SFP/operating cycle, and (3) using past experience to narrow the scope to a particular scenario of interest.

1

SFPSS Technical Approach 

• Short-term scoping study to be completed by June 2012• Two conditions to be considered:

– Representative of the current situation for the selected site (i.e. high-density racking and a relatively full SFP)

– Representative of expedited movement of older fuel to a dry cask storage facility (i.e. low-density racking)

• Elements of the study include– A single site/single operating cycle– Site characterization (seismic response, etc.) based on readily

available information to define initial and boundary conditions– MELCOR accident progression analysis– MACCS2 offsite consequence analysis– Probabilistic considerations– Emergency planning assessment

2

9/29/2011

1

CEUS Seismic Source Characterization

• Current Central and Eastern United States (CEUS) SSC models are more than 20 years old.

• RG 1.208 allows the use of current models (EPRI-SOG and LLNL) as a starting point subject to the incorporation of any new information available.

• Individual updates to these hazard models address time, cost, and consistency issues.

• The CEUS SSC project will provide an up-to-date generic assessment of seismic source characterization for the CEUS.

• Updated assessment of seismic source characterization will include:– Full assessment and incorporation of uncertainties– Incorporation of the range of diverse technical interpretations from the informed scientific

community– Consideration of an up-to-date database– Proper documentation– Peer review

• This project will be completed in Fall 2011. 1

September 30, 2011

Soil‐Structure Interaction (SSI)

• NRC ESSI Simulator– It is a simulation system for conducting direct, time-

domain, finite element Earthquake Soil Structure Interaction (ESSI) simulations.

– Builds on an existing open-source modeling tool called OpenSEES

– Addresses multidirectional, inclined, and incoherent elements of seismic loading

– Pilot case studies will support the development of the technical basis for the update of Regulatory Guide 1.208.

– This platform is under development via a contract to LBNL.

– Will remain as an open-source platform that can be further enhanced by the NRC, industry and academia

2September 30, 2011

9/29/2011

2

Seismic Fragility Characterization for Components & Structures

• Assessment and updating of median SSC fragilities through physical testing, numerical modeling, and review of SSC performance in past earthquakes

• Assessment of ageing and common environmental factors on SSC fragilities

• Dependence on component failures • Applicability of generic fragility data• Recent and ongoing research efforts include:

– Study of correlations on in-structure response and component failures

– NRC-JNES cooperative effort on large scaling testing and analysis of SSCs

– Confirmatory review of fragility functions and data 3

September 30, 2011

12/13/2011

1

Integrated Used Fuel Management

• Performance of Neutron Absorber Materials– Understand degradation mechanisms

– Focus on what individual plants credit in calculations

• Extended Dry Storage• Extended Dry Storage– Identify knowledge gaps

– Bolster technical bases from 120 up to 300 year of storage

1September 30, 2011

1

Long Term Operations

• Covered in dedicated addenda to the MOUs withEPRI– EPRI

– DOE• Expanded proactive material degradation assessment

– Broader range of primary and secondary systems– Cables and electrical components, and– Concrete structures– Beyond 60 years of operation

• Audits of Aging Management ProgramsAudits of Aging Management Programs– Assess what if any revisions are needed for subsequent license

renewal• Domestic and international collaboration, e.g., IFRAM• Need better integration with programs which NRC is not a

direct participant

September 30, 2011 1

1

Integrated Used Fuel ManagementBurnup Credit

Technical Objectives:– Extension of the technical basis for allowing fission products in

Burnup Credit for PWR spent nuclear fuel for transportation and storage casks (Revising NMSS ISG 8 Rev.2)

– Develop a technical basis for NRR(NRO) on the use of burnupcredit in criticality evaluation of spent fuel pools (Part 50)

Status:Two draft NUREG/CR reports under review at NRC- An approach for validating actinide and fission product burnupcredit criticality safety analyses – isotopic composition predictions- An approach for validating actinide and fission product burnupcredit criticality safety analyses – criticality (keff) predictions

1

Integrated Used Fuel ManagementBurnup Credit – Status 

• NMSS has developed draft revised Interim Staff Guidance 8 and technical basis

• Finalize after 2 NUREG/CR reports are completed• Plan to issue draft ISG 8 Rev. 3 and technical basis for

public comments (late 2011)• Prepare finals and public comments’ response for ACRS

reviewSub committee meeting in Feb. 2012 (tentative)Full committee meeting in Mar. 2012 (tentative)

2

9/29/2011

1

Primary Materials/NDE ActivitiesWeld Residual Stress (WRS) & Extremely Low Probability of 

Rupture (xLPR)

• WRS Analysis Model Validation & Advancement– WRS shown as the primary driver for PWSCC growth– WRS vary with fabrication procedures and weld repairs– Short Term: validate WRS models and assess near‐term adequacy of industry's flaw evaluations and mitigations

– Long Term: input to xLPR with valid WRS profiles to assess Leak‐Before ‐Break in piping systems susceptible to PWSCC

• xLPR Modular Probabilistic Code Development– Probability of failure of reactor coolant system components

– Primary piping systems susceptible to PWSCC approved for Leak‐Before‐Break remain in compliance with 10CFR50 Appendix A GDC‐4 to allow dynamic effects from double‐ended guillotine breaks to be excluded from design basis

September 30, 2011 1

Primary Materials/NDE Activities Weld Residual Stress Program

September 30, 2011 2

9/29/2011

2

September 30, 2011 3

Inspection Requirements• Industry programs‐MRP‐139• Rulemaking – ASME CC N‐770

PWSCC Mitigation• Mechanical stress improvement• Weld overlays• Weld in/on‐lays

Operating Experience• Circ cracking is limited• Inspection basis effective

Primary Materials/NDE ActivitiesNear Term Efforts & xLPR Modular Probabilistic Code

September 30, 2011 4

Probab

ility Density (%)

Failure Frequency (Year ‐1)

Version 1.0 Pilot Study: Mar 2011Version 2.0 Leak‐Before‐Break: Dec 2013Version 3.0 Other RCS Components: Dec 2016*

Change in risk

Primary Materials/NDE ActivitiesNear Term Efforts & xLPR Modular Probabilistic Code

* Dependent on availability of resources.

9/29/2011

3

Primary Materials/NDE Activities Non‐Destructive Evaluation (NDE)

• NDE In‐Service Inspection Programs– Evaluate effectiveness & reliability of NDE based ISI for detecting 

fabrication defects & degradation (DMW/CASS Piping/HDPE)

• Visual Testing (VT) NDE Examination– Utilities expressed interest in greater use of VT– VT significantly relied upon for vessel examinations– Assess capabilities and limitations of remote visual (ASME VT‐1) to 

detect cracking in RPV internal components– Round‐robin to evaluate application and assess new technologies– Phase 1 Round Robin testing at EPRI NDE Center completed 08/10

September 30, 2011 5

Images of three 12‐µm wide cracks using diffuse axial lighting on three different surfaces

9/29/2011

1

State‐of‐the‐Art Reactor Consequence Analyses (SOARCA)

• Goal: develop a body of knowledge on the realistic outcomes of severe reactor accidents– Incorporate plant improvements not reflected in

earlier assessments– Evaluate benefits of recent improvements –

10 CFR 50.54 (hh)– Incorporate state-of-the-art modeling

(MELCOR/MACCS)– Enable NRC to communicate severe accident

aspects of nuclear safety to diverse stakeholders– Update the quantification of offsite consequences

found in earlier publications

SOARCA  Process

• Select “important” accident scenarios (CDF ≥10-6, 10-7 for bypass)

• Model progression of accident• Model mitigative measures• If core is damaged and

containment does not prevent release,– Model dispersion of

radioactive material– Model emergency

planning/evacuation– Model health consequences

Peach Bottom

Surry

9/29/2011

2

SOARCA Project Status

Peach Bottom and Surry NUREG/CR reports, Main Report NUREG, and Communications Brochure completed

October -December 2011

Issue Main Report for public comments and hold public meetings

January –February 2012

Public briefings for Commission and ACRS

March – April 2012

Complete SECY paper with results and recommendations

June 30, 2012

1

Analysis of Cancer Risk in Populations near Nuclear Facilities – Phase 1

Background

• Staff identified need for contemporary cancer epidemiology information for responding to recurrent stakeholder concerns– The sentinel 1990 National Cancer Institute (NCI) report “Cancer in

Populations Living Near Nuclear Facilities”– Demographic changes in the last 20 years– Limited cancer incidence information– Does not include facilities operated after 1982– Staff desire to reduce the county size study unit to something smaller

• Selected NAS after reviewing their capabilities and the commercial organizations through the sources sought notice

1

Objectives

• Provide an up-to-date review of cancer incidence and mortality risk for populations living near past, present, and proposed NRC-licensed nuclear facilities

• The study is to be performed in two phases to start in summer 2010

• Provide opportunities for stakeholder input during the study process

• NAS will establish a committee to develop a stand alone document recommending a study design and approach

2

2

3

National Academies Meetings and Schedule

• Public information gathering meetings held in DC, Chicago, Atlanta, Irvine CA

• Final meeting in DC on Oct. 20, 2011• Phase 1 report due in late December,

2011• Two month public review period• NRC decision on Phase 2

PRAB PRA Scope and Quality

Resolution of Key Technical Issues

1. Support System Initiating Events (SSIE) methodology • Currently incorporating SSIE methodology, including SSIE fault trees, developed via the

RES/EPRI MOU for service water systems, closed cooling water systems, and instrument & control air systems in each SPAR model.

• Open items − Intake structures and raw water quality − Common cause failures − Others (e.g., CCF, HRA, importance measures)

2. Loss of Off-site Power (LOOP) methodology

• Incorporating portions of the Loss of Off-site Power (LOOP) methodology developed via the RES/EPRI MOU in each SPAR Model.

• This work should be finalized

3. Proposed a standard PRA modeling approach for low pressure emergency core cooling injection following containment failure for Boiling Water Reactors. • Industry feedback desirable

Level 3 PRA Project

1. Submitted Commission paper on options for Level 3 PRA (SECY-11-0089) in July 2011

2. SRM issued on September 21, 2011 • Commission approved modified version of Option 3 • Staff to conduct full-scope comprehensive site Level 3 PRA over 4 years • Staff to engage industry stakeholders in selecting pilot site and explore collaboration with

EPRI

3. Current Activities • Assembling project team • Developing project and staffing plans • Initiating contract actions • Interacting with EPRI to pursue cooperation under the MOU

Contact Person: Kevin Coyne (NRC/RES/DRA) Kevin.Coyne@nrc.gov (301)-251-7586

Risk Assessment Risk assessment methods:

Fire Protection (methods and data)

• RES and EPRI are working together very effectively under the “Fire Risk (Rev. 3) Addendum” to the NRC/EPRI MOU.

• The current Agreement is effective through September 30, 2016.

• Under Item E. “Testing” there is one new NRC International initiative that we would like to make EPRI aware of. Through the OECD, NRC is proposing an International Testing program to better understand High Energy Arc Faults (HEAF). The current proposal is the NRC will provide funds to perform the testing and member countries will provide the used electrical equipment that will be used in the testing. The NRC would like to open the membership up to the US Licensee through EPRI similar to how the DC circuit testing was performed. The DC test program was greatly enhanced by EPRI’s ability to locate and supply 125V Station Batteries for the testing. The NRC believes there may be similar enhancements to the HEAF program if EPRI participates.

Contact: Mark Henry Salley (NRC/RES/DRA) MarkHenry.Salley@nrc.gov (301)-251-7613

9/29/2011

1

• Approvals to use HDPE piping in Class 3 safety‐related apps• Essential service water systems at Catawba and Callaway• ASME N‐755 under development for generic use of HDPE• Plans to expand N‐755 beyond service water systems• Confirm design requirements proposed in ASME CC N‐755• NRC has not endorsed CC N‐755• Identified three areas of concern:

– Long‐term piping integrity (mechanics)– Fusion process qualification (joining)– Volumetric inspection (NDE)

September 30, 2011 1

High‐Density Polyethylene Piping (HDPE)

9/29/2011

1

Digital Instrumentation & Control 

• DI&C MOU collaboration scope:– Digital OE, failure modes and analysis– Digital PRA and risk assessment– Digital Human Factors research– EMI/RFI issues

• Share digital I&C event and failure analysis data • Peer review research reports• EPRI input on digital PRA research, and support at ACRS. • Industry input on research topics • Next Steps: EMI/RFI Update & improve engagement for HF 

research

September 30, 2011 1

Human Factors Research – Sean Peters, Branch Chief, RES/DRA/HFRB

1. Areas for research with respect to human performance in DI&C • The effects of new DI&C technologies on operator performance • Human factors engineering in the design process of DI&C • Human factors considerations in DI&C system degradation/failures • Means to minimize the impacts of human error in the use, maintenance, and upgrades of

DI&C systems • Assessment of human reliability with respect to DI&C systems

2. HF research for DI&C in the US NRC

Past • NRC issued Interim Staff Guidance on DI&C (computerized procedures and minimal

control room HSI inventory) • “Human factors aspects of degraded DI&C systems,” report published as BNL report and

will be published in NUREG/CR. On-going

Technical basis and guidance reports will be produced from these projects: • Impacts of automation on operations personnel • HSI complexity • Computerized procedures in control rooms

Near future

Planned research activities in HF for DI&C: • “Impact of degraded DI&C on human performance” • OpE review of DI&C related events and failures to understand contributing factors and

pitfalls in system design, human operation (procedures and training), and human-system-integration

• Developing a plan for human factors research in DI&C through collaboration of HF, HRA/PRA, and DI&C efforts.

3. Research on control room staffing • Advanced technologies may lead to reduced size of control room crew. • RES is studying the safety impact and critical human performance considerations of a

reduced crew size. • FY-2011: RES performed OpE review about the impact of crew size on performance

associated with the introduction of new technologies. • FY12: RES will develop a technical basis report on critical staffing characteristics and

human factors considerations for control room staffing. • FY 12-13: RES will work with user offices to update NUREG-1791 (review guidance for

exemption of 10.54(m) staffing requirements.