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

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

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

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

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

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

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

10 SFP Evaporation: Method 2 u Calculate from standard equations u ASHRAE Handbook u Rough estimate of evaporation u Vapor pressure of SFP water (P w ) u Vapor pressure at dew point (P a ) u Heat of vaporization of water (H v ) u Then calc evap aF

11 ASHRAE Evap Equation u W=(A+BV)(P w -P a )/H v u W = evap rate, lbm/hr per ft 2 u V = air velocity above pool, mph u P w = Vapor pressure of SFP water u P a = Saturation vapor pres at dew point u H v = Heat of vaporization of water u A, B = Constants, (for wind speed)

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

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

21 Comparison: Preliminary Results

22 Final Results

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

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

26 Questions?