1 / 13

Debris Effects in Long-Term Post-LOCA PWR Cooling

Debris Effects in Long-Term Post-LOCA PWR Cooling. Graham WALLIS American Nuclear Society Northeastern Meeting October 23 2013 . Short-Term Cooling. 1960 “No need for ECCS” 1971 Public Hearing Creati o n of NRC LOFT RELAP TRAC 10CFR 50.46 Appendix K PCT<2200F

sherry
Télécharger la présentation

Debris Effects in Long-Term Post-LOCA PWR Cooling

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Debris Effects in Long-Term Post-LOCA PWR Cooling Graham WALLIS American Nuclear Society Northeastern Meeting October 23 2013

  2. Short-Term Cooling • 1960 “No need for ECCS” • 1971 Public Hearing • Creation of NRC • LOFT RELAP TRAC • 10CFR 50.46 Appendix K PCT<2200F • Realistic/uncertainty 95/95 confidence

  3. Long-Term Cooling • As important as short-term cooling • Water sources: • Inside containment • Outside containment • Recirculation • Fukushima • External water source. Hundreds of storage tanks

  4. GSI-191 • 1992 Barsebäck BWR event • 1996 GSI-191 “Assessment of Debris Accumulation on PWR Sump Performance” • Utilities required to demonstrate effective long-term cooling • No predictive codes • Prototypical tests

  5. Sump Strainers • NRC allowed strainers to be 50% blocked • Some were “the size of a garbage can”. 10s of square feet of surface. • ACRS presentation “30-50 pickup loads of debris from a large break LOCA”. • Utilities have installed strainers with 1000s of square feet of surface

  6. Functional Requirements • Protect downstream devices, particularly the core • Work for all LOCAs • Head Loss not to exceed allowable pump NPSH

  7. Protecting the Core • Spacers and grids. Complex shapes with small spaces may trap particles and fibers. • Tests desirable before designing strainers. • Tests are still underway after installing strainers.

  8. LOCA Debris • Fiberglass. Wide range of lengths. • Particles. Paints, coatings, insulation (CalSil), latent debris. • Chemicals. Hot acidic jet. Long residence in sump at high pH. AlOOH.

  9. Comparison with Short-term Cooling • Because of the variety of debris constituents the development of a knowledge base and predictive techniques differs from the short-term case in which the medium was water alone. • Relating head loss and bypass tests to reality is tenuous and risky. • Numerous surprises and anomalous results from tests.

  10. Effects on Head Loss and Bypass • Fiberglass and CalSil prepared in blenders. • Specifying amounts is inadequate. Size matters. More may be better. • Size spectra. Micron-sized particles.

  11. Some Effects • Flow history • Arrival sequence • Sump, Pumps • Surrogates

  12. Tests • Should be realistic. Uncertain what may be “conservative”. • Prototypical tests • Use of single module (fuel assembly) tests to predict multi-module (core) performance

  13. Alternative approaches • Change injection location • Backflushing • Bypass or control rod flow paths • Other, such as removing all fiberglass and CalSil • Risk-inform using PRA?

More Related