Primary Water Chemistry Flashcards
What resin is used in the in “normal” use (in service) mixed bed demineralizer
Lithium Hydroxide (Li7OH) mixed bed resin
{Removes undesirable ions from the RCS}
What is the decontamination factor (DF) for resing approaching exhaustion
Approching a DF = 1 (typically around 3-4)
How is differntial pressure used to determine the condition of a demineralizer resin bed
An increase in dP can be an indication of resin fouling and may indicate resin depletion
Why is enriched Lithium-7 (Li7) used as a pH control additive
Lithium-6 (Li6) will generate tritium
Why does hydrazine have an upper temperature limit of effectiveness
At temperatures greater than 200 oF Hydrazine breaks down
Why are the CVCS ion exhcangers bypassed when hydrazine is present in the RCS
Decomposition products of hydrazine will exhause resin and cause release of chlorides into the RCS
Why is the concentration of Lithium allowed to lower over core life
Lithium is varied to maintain pH wihtin a band of 6.9 to 7.2 as boron concentration lowers
What is the pH control agent that is added to the RCS
Lithium Hydroxide (Li7OH)
List five different gases that are normally present in the RCS
- Oxygen (O2)
- Nitrogen (N2)
- Argon (Ar)
- Helium (He)
- Xenon (Xe)
- Krypton (Kr)
State two reason for the upper limit of the at power oxygen control agent
- Excess H2 is a waste
- Greater H2 concentrations cause problems degassing (i.e., limited number of GDTs)
- Excess H2 can be an explosive concern
Name three locations in the RCS system or subsystems where RCS gases could be removed
- CVCS HUTs
- BA Evaporator gas stripper
- VCT during RCS degas
- Pressurizer due to high temperatures (increased pressurizer spray)
What is the primary source of oxygen in the RCS at power
Radiolytic decomposition of water
What resin is used in the Cation demineralizer
H+ resin
{Removes Cs137 and control RCS Li}
How is excess Lithium removed from the RCS
Cation demineralizers
What is the decontamination factor (DF) for completely exhausted resin
DF = 1
What resin is used in the Deborating demineralizer
OH- resin
{Removes up to 50 ppm of boron per bed}
What is chanelling in a demineralizer
Excessive flow rates (high velocities) can create flow channels in the bed
What resin is used in the standby mixed bed demineralizer
HOH resin
{Cleans up CRUD burst and removes Lithium}
State two methods by which a demineralizer purifies water
- Mechanical Filtration
- Ion Exchange
What oxygen control agent is used in the RCS while at power
H2 blanket is established in the VCT
State the effect of differntial pressure on demineralizer performance
As dP increases, due to solids forming a layer on the resin bed, reduced flow reduces the effectiveness of the demineralizer
What is the TRM temperature value at which oxygen concentraton limits are in effect
RCS > 250 oF
When in core life is a deborating demineralizer used and why
Deborating bed is used at the end of core life to remove boron due to the large amounts of primary water that would be required to dilute the RCS
What effects does channeling in a demineralizer have on performance of the demineralizer
RCS flow may either not pass through any resin or the contact time may become reduced to the point as to make the oin exchange very ineffective.
Low dP can be a sign of channeling
What is the decontamination factor (DF) for newly regenerated resin
Approximately 25 (or the highest DF)
Where is the oxygen control agent added to the RCS while at power
To the VCT
What is the oxygen control agent used in Mode 5 (< 200 oF)
Hydrazine (N2H4) is added to the CVCS
State the four reasons for maintaining primary chemistry control.
- Maintain material integrity
- Minimize Corrosion
- Reduce radioactivity
- Assist in reactor control
State two reasons for using the cation demineralizers
- Remove radioactive impurities (Cs137)
- Control RCS Litihium (Li)
