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Spent Fuel Pool Evaporative Losses

Spent Fuel Pool Evaporative Losses

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Spent Fuel Pool Evaporative Losses

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  1. Spent Fuel Pool Evaporative Losses Richard Conatser Calvert Cliffs Constellation Energy Group June 2004

  2. Objectives • Review Calvert Cliffs experiences • Discuss pool evaporative loss equation • Discuss parameters and variables • Plant system interrelationships • Accountability methods • Review uncertainties in methods

  3. Overview of Topics • Introduction • Analysis for H-3 in main vent • Methods for estimating evap losses • ASHRAE Equation for evap losses • System interrelationships, ventilation • H-3 Correlation: SFP to Main Vent • Conclusions

  4. Introduction • Evaporative losses from SFP are large • The SFP [H-3] is relatively high • Evaporative loss can be estimated • Evaporative losses exhaust via M/V • H-3 surveillance is done on M/V • Compare M/V H-3 to SFP evap losses

  5. Sampling: H-3 in M/V • Sample M/V continuously • 40 cc/minute sample flow • Desiccant cartridge collects H-3 • Silica gel is distilled each month • Graph shows results

  6. SFP Evaporation: Method 1 • Evap can’t be measured directly • Water is added to pool with hose • Volume added is not measured • Pool level recorded 2/day • Assume pool level increase = evapaL • Then calc evapaL

  7. Method 1 Uncertainties • Any losses (not evap), add error • RFP flood-up/open transfer tube • Fuel Assy removal (500 gal/can) • Fuel pool temp changes • SFP leakage (1 liter/day) • Chemistry sampling (20 gal/wk)

  8. SFP Evaporation: Method 2 • Calculate from standard equations • ASHRAE Handbook • Rough estimate of evaporation • Vapor pressure of SFP water (Pw) • Vapor pressure at dew point (Pa) • Heat of vaporization of water (Hv) • Then calc evapaF

  9. ASHRAE Evap Equation • W=(A+BV)(Pw-Pa)/Hv • W = evap rate, lbm/hr per ft2 • V = air velocity above pool, mph • Pw = Vapor pressure of SFP water • Pa = Saturation vapor pres at dew point • Hv = Heat of vaporization of water • A, B = Constants, (for wind speed)

  10. SFP Evaporation: Method 3 • 468 gpd is 0.33 inches SFP per day! • Reviewed typical SFP data • Excluded RFO fuel transfers • Excluded high temperature changes • Excluded transcription errors • The real evaporation rate appeared

  11. SFP H-3 • Have been trending (PC) since 1998 • Records prior to that are in vault • SFP H-3 related to RCS H-3 • Next slide shows trend

  12. Comparison: Preliminary Results

  13. Final Results

  14. Update with 2003 Data • 12 Ci H-3 from site (2 units) in 2003 • 9.54 Ci discharged from U-1 M/V • U-1 M/V average = 0.795 Ci/month • Expected SFP = From 0.6 to 0.7 Ci/month • Excellent agreement

  15. Conclusions • Selection of evaporation rate is critical • Validate the evaporation calculations! • Use the ASHRAE equation (it’s easier…) • Tweak evap rate for seasonal variations • Compare M/V H-3 to SFP evap yearly • Comparison on monthly basis not difficult

  16. Questions?