Secondary Water Chemistry

Question 1

Briefly explain why cation conductivity is a better indicator of condenser tube leakage than a standard conductivity measurement

Answer 1

Cation conductivity is taken after cations have been removed from the sample. This provides a very sensitive detection range due to the lower “background” conductivity.

Question 2

What benefit is gained in terms of RCS Hot Leg Temperature when power is reduced due to high S/G contamination

Answer 2

Intergranular & stress corrosion cracking is very temperature dependent. Therefore, “less damage” occurs at lower RCS Hot Leg tempeartures.

Question 3

What benefit is gained in terms of S/G Heat Flux when power is reduced due to high S/G contamination

Answer 3

Lower S/G Heat Flux reduces sludge formation and results in less hideout/damage

Question 4

What Chemistry parameters are used to set the limiting conditions for S/G operation as set forth by 12-THP-6020-CHM-201

Answer 4

• S/G Sodium
• S/G Chloride
• S/G Sulfate

Question 5

Tube cracking at the S/G U bend caused by chlorides and/or stress

Answer 5

S/G tube stress corrosion cracking

Question 6

What two functions does hydrazine provide in reducing secondary plant corrosion

Answer 6

1. Scavenges oxygen
2. Elevates pH

Question 7

Corrosion caused by the presence of oxygen or oxygen generating contaminants

Answer 7

General S/G tube degradation

Question 8

What benefit is gained in terms of concentration rate when power is reduced due to high S/G contamination

Answer 8

If contamination is from a condenser tube leak, a reduction in power will reduce buildup in crevice areas and allow the leak to be identified more easily due to reduced flow rates.

If the concentration rate is high then extra measures may be required to prevent or minimize damage to the SGs.

Question 9

Mechanical damage from impingement of S/G tubes from suspended corrosion products or reactive chemicals

Answer 9

S/G tube errosion-corrosion

Question 10

Circumferential tube cracking as a result of cyclic flow or temperature stress

Answer 10

S/G tube fatigue

Question 11

Corrosion of S/G tube grain boundaries at tube sheet crevice or dry out areas

Answer 11

S/G tube intergranuluar attack

Question 12

What locations are sampled for cation conductivity on the High Range Conductivity recorders located in the control room

Answer 12

• Total Hotwell
• Total Feedwater
• S/G blowdown
• Feedwater Cation
• Hotwell Cation
• Maekup plant effluent

Question 13

Localized corrosion caused by acidic attack in low flow areas

Answer 13

S/G tube wastage

Question 14

Plastic deformation occuring at the tube support plates due to corrosion buildup

Answer 14

S/G tube denting

Question 15

Localized attack at sludge sites that may penetrate the S/G tube

Answer 15

S/G tube pitting

Question 16

What is the final maximum power permitted (long term) when conditions require entry into any of the three action levels for high S/G contamination

Answer 16

• Action Level 1: 100%
• Action Level 2: 30%-50%
• Action Level 3: <5%

Question 17

Local wear from impact or sliding of tubes against support plate or other tubes due to flow induced vibration

Answer 17

S/G tube fretting