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Spent Fuel Pool Evaporative Losses

Spent Fuel Pool Evaporative Losses. Richard Conatser Calvert Cliffs Constellation Energy Group June 2004. Objectives. Review Calvert Cliffs experiences Discuss pool evaporative loss equation Discuss parameters and variables Plant system interrelationships Accountability methods

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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?

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