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PWR Owners Group Post-Accident Chemical Effects Work. NEI Chemistry Meeting, January 26, 2012. Chemical Effects. Issue: Chemical interactions between materials in the containment sump and cooling water additives may affect performance of the sump strainers.

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PWR Owners GroupPost-Accident Chemical Effects Work

NEI Chemistry Meeting, January 26, 2012

chemical effects
Chemical Effects
  • Issue:
    • Chemical interactions between materials in the containment sump and cooling water additives may affect performance of the sump strainers.
    • The key effect is generation of precipitates that may increase head-loss across the fiber beds.
  • PWR Owners Group Approach to Resolution:
    • Testing has been conducted to;
      • Identify key interactions, and,
      • Elucidate the factors that control these interactions, and,
    • Develop generically applicable tools to evaluate post-accident chemical effects at plants.
    • PWR Owners Group work does not preclude plants from performing their own plant-specific post-accident chemistry effects work
icet program
ICET Program

ICET Program: Integrated Chemical Effects Test

  • Program conducted by NRC, EPRI and PWR Owners Group
  • Purpose: Assess if chemical products would form
  • Approach: Integrated testing using typical plant materials at bounding material loadings and sump chemistries (3 buffers used at bounding pH values)
    • Five distinct sets of conditions tested
      • Buffer agents; sodium hydroxide, trisodium phosphate, sodium tetraborate (for ice condenser containments)
      • Material included; aluminum, copper, concrete, calcium silicate, fiberglass, zinc (galvanized material)
  • ICET Program demonstrated
    • Chemical products would form over time
    • Dominant chemical products included
      • Aluminum
      • Sodium, and,
      • Calcium
    • Also demonstrated potential for passivation over time
pwrog program wcap 16530 np a
PWROG Program – WCAP-16530-NP-A
  • Performed to augment ICET Program Results
    • Included materials not included in ICET program; mineral wool, min-k
  • Objective was to support replacement sump screen testing by developing:
    • Testing and developmentment of a generic Chemical Model
      • Predict bounding quantity and types of precipitates
      • Use plant conditions as a function of time (i.e. pH, coolant volume, mass of debris sources)
    • Recipes and a Particulate Generator to produce three “worst case” (maximize head loss) particulates:
      • Aluminum Oxyhydroxide
      • Sodium Aluminum Silicate
      • Calcium Phosphate
  • Reviewed and approved by NRC with limits and conditions
  • Used by:
    • Licensees to perform screen testing
    • PWR Owners Group to perform fuel debris head loss testing
refinement of chemical model inputs wcap 16785 np
Refinement of Chemical Model Inputs – WCAP-16785-NP
  • Program evaluated plant-specific inputs for incorporation in the WCAP-16530-NP chemical model spreadsheet
  • Program results:
    • Confirmed that;
      • Silicate inhibits corrosion of aluminum
      • Phosphate inhibits corrosion of aluminum
    • Sodium aluminum silicate should continue to be treated as insoluble in current buffer agents
    • Calcium phosphate should continue to be treated as insoluble in trisodium phosphate buffered solutions
    • Demonstrated;
      • For plants using trisodium phosphate buffer, a reduced aluminum release rate was supported by data
      • Solubility limits of aluminum oxyhydroxide as a function of temperature
  • Not submitted for NRC Safety Evaluation
  • Available for participating licensees to use
alternate buffer evaluation wcap 16596 np
Alternate Buffer EvaluationWCAP-16596-NP
  • Objective:
    • Evaluate candidate buffering agents as potential alternatives to trisodium phosphate (TSP) or sodium hydroxide (NaOH)
  • For high-calcium plants
    • Changing from TSP to sodium tetraborate (NaTB) buffer would reduce the total precipitate formation by more than 40 percent
    • No new types of precipitates would form at a target pH of 8.0 or less, irrespective of the calcium loading
  • Note submitted for NRC Safety Evaluation
  • Available for participating licensees to use
    • Approach used by at least one PWR
proposed work increase fiber limit for fuel
Proposed Work – Increase Fiber Limit for Fuel
  • Proposed Objective:
    • Provide data to support the use of lower flow rates in fuel assembly post-LOCA debris testing when chemical surrogates are added
    • Show that chemical product production does not occur until after hot leg switch-over
    • If chemical surrogate addition cannot be delayed until the time of hot leg switch-over in for some plants justify the use of;
      • Less chemical surrogate, and,
      • A surrogate that causes less pressure drop
  • To be reviewed for approval by PWR Owners Group first week of February, 2012
  • Will be available for participating licensees to use
proposed work effect of water chemistry on head loss
Proposed Work - Effect of Water Chemistry on Head Loss
  • Proposed Objective:
    • Evaluate impact of water chemistry on the maximum head loss values in fuel assembly (FA) testing
  • Basis:
    • New data that indicates differences in water type could cause non-prototypic test results resulting in overly conservative fiber limits.
  • Goal is to increase fiber limits to at least;
    • 20 g fiber/FA for plants with an available driving head of 14 psid
    • 50 g/FA for plants with an available driving head of 18 psid
    • 35 g fiber/FA for plants that can maintain sump temperatures greater than or equal to 130°F and have an available driving head of 12 psid.
  • To be reviewed for approval by PWR Owners Group first week of February, 2012
  • Will be available for participating licensees to use
summary
Summary
  • PWR Owners Group has undertaken post-accident chemical effects work to address GSI-191
  • The work is applicable to and may be used by all PWRs
  • The PWR Owners Group work does not preclude individual plants from pursuing a different post-accident chemical effects strategy