Primary Water Chemistry

Question 1

What resin is used in the in “normal” use (in service) mixed bed demineralizer

Answer 1

Lithium Hydroxide (Li⁷OH) mixed bed resin

{Removes undesirable ions from the RCS}

Question 2

What is the decontamination factor (DF) for resing approaching exhaustion

Answer 2

Approching a DF = 1 (typically around 3-4)

Question 3

How is differntial pressure used to determine the condition of a demineralizer resin bed

Answer 3

An increase in dP can be an indication of resin fouling and may indicate resin depletion

Question 4

Why is enriched Lithium-7 (Li⁷) used as a pH control additive

Answer 4

Lithium-6 (Li⁶) will generate tritium

Question 5

Why does hydrazine have an upper temperature limit of effectiveness

Answer 5

At temperatures greater than 200 ^oF Hydrazine breaks down

Question 6

Why are the CVCS ion exhcangers bypassed when hydrazine is present in the RCS

Answer 6

Decomposition products of hydrazine will exhause resin and cause release of chlorides into the RCS

Question 7

Why is the concentration of Lithium allowed to lower over core life

Answer 7

Lithium is varied to maintain pH wihtin a band of 6.9 to 7.2 as boron concentration lowers

Question 8

What is the pH control agent that is added to the RCS

Answer 8

Lithium Hydroxide (Li⁷OH)

Question 9

List five different gases that are normally present in the RCS

Answer 9

1. Oxygen (O²)
2. Nitrogen (N²)
3. Argon (Ar)
4. Helium (He)
5. Xenon (Xe)
6. Krypton (Kr)

Question 10

State two reason for the upper limit of the at power oxygen control agent

Answer 10

1. Excess H₂ is a waste
2. Greater H₂ concentrations cause problems degassing (i.e., limited number of GDTs)
3. Excess H₂ can be an explosive concern

Question 11

Name three locations in the RCS system or subsystems where RCS gases could be removed

Answer 11

1. CVCS HUTs
2. BA Evaporator gas stripper
3. VCT during RCS degas
4. Pressurizer due to high temperatures (increased pressurizer spray)

Question 12

What is the primary source of oxygen in the RCS at power

Answer 12

Radiolytic decomposition of water

Question 13

What resin is used in the Cation demineralizer

Answer 13

H⁺ resin

{Removes Cs¹³⁷ and control RCS Li}

Question 14

How is excess Lithium removed from the RCS

Answer 14

Cation demineralizers

Question 15

What is the decontamination factor (DF) for completely exhausted resin

Answer 15

DF = 1

Question 16

What resin is used in the Deborating demineralizer

Answer 16

OH^- resin

{Removes up to 50 ppm of boron per bed}

Question 17

What is chanelling in a demineralizer

Answer 17

Excessive flow rates (high velocities) can create flow channels in the bed

Question 18

What resin is used in the standby mixed bed demineralizer

Answer 18

HOH resin

{Cleans up CRUD burst and removes Lithium}

Question 19

State two methods by which a demineralizer purifies water

Answer 19

1. Mechanical Filtration
2. Ion Exchange

Question 20

What oxygen control agent is used in the RCS while at power

Answer 20

H2 blanket is established in the VCT

Question 21

State the effect of differntial pressure on demineralizer performance

Answer 21

As dP increases, due to solids forming a layer on the resin bed, reduced flow reduces the effectiveness of the demineralizer

Question 22

What is the TRM temperature value at which oxygen concentraton limits are in effect

Answer 22

RCS > 250 ^oF

Question 23

When in core life is a deborating demineralizer used and why

Answer 23

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

Question 24

What effects does channeling in a demineralizer have on performance of the demineralizer

Answer 24

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

Question 25

What is the decontamination factor (DF) for newly regenerated resin

Answer 25

Approximately 25 (or the highest DF)

Question 26

Where is the oxygen control agent added to the RCS while at power

Answer 26

To the VCT

Question 27

What is the oxygen control agent used in Mode 5 (< 200 ^oF)

Answer 27

Hydrazine (N₂H₄) is added to the CVCS

Question 28

State the four reasons for maintaining primary chemistry control.

Answer 28

• Maintain material integrity
• Minimize Corrosion
• Reduce radioactivity
• Assist in reactor control

Question 29

State two reasons for using the cation demineralizers

Answer 29

1. Remove radioactive impurities (Cs¹³⁷)
2. Control RCS Litihium (Li)