Nuclear Power Reactors An Example of Improvements in ... - Gehin...¢  Reliability of Nuclear Power Plants

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  • Nuclear Power Reactors – An Example of Improvements in

    Reliability and Potential for Improvement

    Dr. Jess Gehin

    Director, Consortium for Advanced Simulation of Light Water Reactors

    Oak Ridge National Laboratory

    5th Accelerator Reliability Workshop (ARW 2015) Knoxville, Tennessee

    April 26 to May 1, 2015

  • 2 2 2 2

    Outline

    • Nuclear Energy in the United States

    • Availability and Reliability in Nuclear Plants

    • Historical Experience on Key Performance Indicators

    • Reliability of Nuclear Fuel

    • CASL Research to Improve Operations

    • Conclusions

  • 3 3 3 3

    There are 100 Commercial Nuclear Power Reactors in the

    U.S.

  • 4 4 4 4

    Five Nuclear Reactors are Currently Under Construction

    in the US TVA Watts Bar Unit 2

    V.C. Summer Units 2 & 3

  • 5 5 5 5

    Several More Reactors have been Previously Proposed

    Most of the Plants Delayed Because of Low 2008 Economic Downturn and Low Natural Gas Prices

    Source: U.S. NRC

  • 6 6 6 6

    New Reactor Designs Being Developed/Certified by NRC

    • Westinghouse AP1000® - Design Certified

    • General Electric ESBWR - Design Certified (2014)

    • NuScale Small Modular Reactor - Certification application to be submitted in 2016

    • mPower Small Modular Reactor – Certification application suspended

    • AREVA EPR – Design certification suspended

    • Mitsubishi USAPWR – Design certification delayed

    • Korea APR-1400 – Schedule TBD

    Most Schedules Delayed Because Scale Back in Planned Construction

  • 7 7 7 7

    Availability and Reliability of Commercial Reactors

    • Utilities require high availability and capacity factors for nuclear power plants – Availability Factor – fraction of the of time a reactor is able to produce

    electricity

    – Capacity Factor – ratio of the actual energy output to the potential output

    • Desire for high capacity factors is driven by: – Large capital costs for nuclear plants

    – Large cost of replacement power when the plant is shutdown

    – Very low production costs compared to other sources

    • Factors that affect Availability/Capacity – Planned refueling outages

    – Unplanned shutdowns due to mechanical failures or offsite issues

    – Major outages for maintenance, upgrades, component replacements

  • 8 8 8 8

    Nuclear Energy Has a High Capacity Factor Compared to

    Other Energy Sources

    Source: NEI, updated 4/14

  • 9 9 9 9

    Capacity Factors Have Increased Significantly

    2014 Capacity Factor 91%

    Source: NEI, updated 4/14

  • 10 10 10 10

    The US Nuclear Fleet as a Whole is Performing Well

    Source: NEI, updated 4/14

  • 11 11 11 11

    Improvements in Capacity Factors Largely Driven by Optimization of Refueling

    Outages

    Outages are planned for spring/fall – time of low demand

    Source: NEI, updated 4/14

  • 12 12 12 12

    Significant Power has Been Added Through Uprates

    Plant power uprates range from 1 – 20%

    Source: NEI, updated 4/14

  • 13 13 13 13

    Reliability of Nuclear Power Plants

    • Reliability – A measure of plants expected generation when expected to be available.

    • Scheduled Outage - The shutdown of a generating unit, transmission line, or other facility for inspection, maintenance, or refueling, which is scheduled well in advance (even if the schedule changes)

    • Forced Outage - The shutdown of a generating unit, transmission line, or other facility for emergency reasons, or a condition in which the equipment is unavailable as a result of an unanticipated breakdown. – An outage is considered "forced" if it could not reasonably be delayed beyond 48 hours from

    identification of the problem, if there had been a strong commercial desire to do so. In particular, the following problems may result in forced outages

    – Any failure of mechanical, fuel handling, or electrical equipment or controls within the generator's ownership or direct responsibility (i.e., from the point the generator is responsible for the fuel through to the electrical connection point)

    – A failure of a mine or fuel transport system dedicated to that power station with a resulting fuel shortage that cannot be economically managed

    – Inadvertent or operator error

    – Limitations caused by fuel quality

  • 14 14 14 14

    Several Performance Indicators are used

    • U.S. NRC (primarily safety focused, but informs on reliability): – Automatic Reactor Scrams While Critical (IE)

    – Significant Events (IE)

    – Safety System Actuations (MS)

    – Safety System Failures (MS)

    – Forced Outage Rate (MS)

    – Equipment Forced Outage Rate/1000 Critical Hours (MS)

    – Collective Radiation Exposure (OR)

    • World Association of Nuclear Operators– performance & safety – Capability factor

    – Unplanned capability factor loss

    – Fuel reliability

    – Thermal performance

    – Chemistry performance

    – Collective radiation exposure

    – Volume of solid radioactive waste

    – Forced Loss Rate

    – Unplanned automatic scrams

    – Industry safety accident rate

    – Safety system performance

  • 15 15 15 15

    Unplanned Automatic Scrams (Worldwide)

    Source: WANO 2013

  • 16 16 16 16

    Unplanned Capability Loss Factor (Worldwide)

    Source: WANO 2013

  • 17 17 17 17

    Forced Loss (of capacity) Rate (Worldwide)

    Source: WANO 2013

  • 18 18 18 18

    Forced outage rate of U.S. nuclear reactors from FY 2000

    to FY 2013 4.24%

    3%

    1.7%

    3.04%

    1.88%

    2.34%

    1.47% 1.41%

    1.34%

    2.21%

    1.74% 1.8%

    2.77%

    2.98%

    0.0%

    0.5%

    1.0%

    1.5%

    2.0%

    2.5%

    3.0%

    3.5%

    4.0%

    4.5%

    2000* 2001* 2002* 2003* 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

    F o rc

    e d

    o u

    ta g

    e r

    a te

    Source: US NRC

    Force Outage Rate: Fraction of total generation time that plant is not available

    to operate

  • 19 19 19 19

    The U.S. Industry has a Focus in Improving Nuclear Fuel

    Reliability

    • Improving the economics by reducing the requirements to replace failed fuel

    • Increase fuel utilization and lifetime

    • Reduced unplanned outages to replace fuel avoiding operation and replacement power costs

    Fuel Failure – cladding breach and release of fission products into coolant water

  • 20 20 20 20

    Anatomy of a Nuclear Reactor Example: Westinghouse 4-Loop Pressurized Water Reactor (PWR)

    Reactor Vessel and Internals

    17x17 fuel assembly

    Core • 11.1’ diameter x 12’ high • 193 fuel assemblies • 107.7 tons of UO2 (~3-5% U235) Fuel Assemblies • 17x17 pin lattice (14.3 mm pitch) • 204 pins per assembly

    Fuel Pins • ~300-400 pellets stacked within 12’ high x 0.61

    mm thick Zr-4 cladding tube Fuel Pellets • 9.29 mm diameter x ~10.0 mm high

    Operating Conditions • 2200°C – max fuel centerline • 350°C – max clad surface) • 300°C, 15 MPa – coolant water • Radiation environment • 6 year residence time

    ~50,000 fuel pins and over 16M fuel pellets in the core of a PWR

  • 21 21 21 21

    Details of a Nuclear Fuel Assembly

    US Plants require ~1.5M fuel rods/year (500M pellets)

  • 22 22 22 22

    Reported Fuel Failures

  • 23 23 23 23

    Causes of Fuel Failures (2000 – 2008)

  • 24 24 24 24

    Approaches for Improving Fuel Reliability

    • Improve fabrication quality to reduce fuel pellet and cladding defects

    • Reactor operations that improve fuel performance – Slower power ramp rates to reduce strain

    – Additional of chemicals to coolant reduce corrosion

    • Improvements in fuel designs – Add lower nozzle strainers to filter out debris

    – Improved grid designs to minimize flow induced vibration

    – Improved core designs to minimize power peaking to reduce corrosion

    • Research and development – Improved modeling and simulation to predict failures

    – Improved materials that are more tolerant of conditions

    – Experimental investigations of performance in laboratories

  • 25 25 25

    CASL was the first DOE Innovation Hub

    Core partners

    Oak Ridge National Laboratory

    Electric Power Research Institute

    Idaho National Laboratory

    Los Alamos National Laboratory

    Massachusetts Institute of Technology

    North Carolina State University

    Sandia National Laboratories

    Tennessee Valley Authority