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Polishing, Dearation and Makeup
of Deinoized Process Water for APS

Presentation by R. Dortwegt on June 27, 2000

Purpose of Systems
Makeup System
Process Water (PW) Polishing system
Dearation System
Dearator Pressure Summary
Issues Well Understood
Issues To Be Considered

Purpose of Systems

  • Maintain quality of non-conductive water >4-5 Mohm-cm
  • Maintain dissolved oxygen (DO) content <10 ppb
  • Maintain parent metal integrity of APS technical components near that of original
  • Maintain a supply of makeup water
  • Deliver makeup water to the Process Water (PW) System upon demand
  • Provide for ultrafine filtration of primary water

Block Diagram of Process Water System
Block Diagram of Treatment System

Makeup System

  • Source used is domestic laboratory water (from Lake Michigan)
  • Reverse osmosis (RO) system (rental agreement) installed in July, 1999
  • Production rate is approximately 2500 gal/day
  • Normal demand is between 50-1000 gal/day
  • 5000 gallon storage tank
  • RO system starts when tank level is low
  • Pretreatment process includes:
    • Softening
    • Activated carbon filtration
    • Cation polishing
  • RO membrane produces nominal 100.000 ohm water
  • Resin polishing provided to bring makeup to 18 M-ohm
  • Resins also used to maintain quality of storage tank (>2 M-ohm) due to ingress of DO
  • Pump delivers makeup water from tank when PW system pressure reaches low setpoint
  • Makeup water is treated in polishing or dearation loops before introduction to PW system

Process Water (PW) Polishing system

  • Total flow of 150 gpm
  • Two paralled streams of 75 gpm limited by contact time required for DO scavenging
  • Each stream provided with
    • 30 cu. ft oxygen scavenger resin tank
    • 30 cu. ft mixed bed resin tank
  • One stream (only) has additional 30 cu. ft mixed bed resin tank (in series)
  • Total 90 cu. ft mixed bed resin on line, but net effect is same as 60 cu. ft.
  • Original APS resins still in use
    • Reprocessed in 1999 after storage for 2 years
    • Analysis indicated less than perfect condition but still useable
    • Added 30 cu. ft. new resin
  • Filtration (2 micron absolute)
  • UV treatment for microbes (seems to be enough)
  • PW bulk is running around 10 Mohm-cm compared to 5-7 Mohm-cm originally
  • Regeneration processing done offsite in Delaware by licensed recovery operator
  • Diagram
  • UV treatment for microbes (seems to be enough)

P-W Polishing System

Dearation System

  • Design flow 450 gpm
    • 3 pumps at 225 each (upgraded from 2 pumps at 150 each)
    • can run 3 pumps at 185 gpm each (total 560 gpm)
  • Dearator vessel 4 ft diameter x ~30 ft tall
    • Spray nozzle at top of vessel
    • Tower packing material in vessel midsection (140 cu. ft or around 12 ft. vertically)
    • Liquid gathered in bottom of vessel below packing
    • Operating pressure ~22-24 absolute
    • Diagram
  • Operating principle (droplet diagram)
    • Filtration:        2 micron absolute (90% of 0.5 microns removed)
    • Prefilter:         0.5 micron absolute
  • Vacuum system:
    • ~250 cfm (net) liquid ring vacuum pumps - water sealed - 2 x 50% units
    • "Roots" type blower provided to augment flowrate below 100 torr
    • Ejectors mandatroy when blower not in operation (prevents cavitation in pump)
    • Diagram
  • Performance:
    • Steady state DO in dearator effluent of 3-5 ppb (>60 originally)
    • Recovery from 50 ppb upset in ~12 hours

Dearator Operation
Vapor Space
Dearator Vacuum System

Dearator Pressure Summary

  65 ppb
in effluent
15 ppb
in effluent
<5 ppb (in effluent)
Partial pressure of water (75F)
in vapor space (torr)
22.2 22.2  
Partial pressure of oxygen
in vapor space (torr)
1.3 0.3  
Partial pressure of nitrogen
in vapor space (torr)
9.5 2.2  
Total pressure
in vapor space (torr)
33 24.7  
Observed 30-35 23-24 21-23

Original System
Dearator System

Issues Well Understood

  • Oxygen is a bad actor and we need to keep it below 10 ppb
  • Corrosion rate maximized at 200-300 ppb
  • Supported by:
    • EPRI document
    • Experience of generator manufacturers
    • APS experience
  • Avoid "dead legs" in piping to prevent "reservoirs" of DO
  • Keep water circulating
  • Do not open water piping for work unless really needed

Issues To Be Considered

  • Water quality upset on 5-27-00
  • Impact of pH
  • Relationship between pH and resistivity (limits)
  • Experience of Siemens Corp
  • Impact of higher resistivity in APS water than in past
  • Ph of APS water = ??
  • Pourbaix diagrams
  • Should we reduce resistivity so that pH can be a little higher?
  • Should we add NaOH?

High Quality Water and pH
Average Corrosion Rate of Copper
Shaft Seal-Oil & Primary Water Supply Systems
Copper hollow conductors
Water chemistry of cooling systems made from copper-based materials in the loops of power-generating units