Secondary chem.

Question 1

Match the definition to the corasponding type of corrosion.

1. Localized corrosion caused by acidic attack in low flow areas.
2. Local wear from impact or sliding of tubes against support plate or other tubes due to flow induced vibration.
3. Tube cracking at the S/G U bend caused by chlorides and/or stress.
4. Circumferential tube cracking as a result of cyclic flow or temperature stress.
5. Localixed attack at sludge sites that may penetrate the S/G tube.
6. Corrosion caused by the presence of oxygen or oxygen generating contaminants.
7. Plastic deformation occurring at the tube support plates due to corrosion buildup.
8. Corrosion of S/G tub grain boundaries at tube sheet crevice or dry out areas.
9. Mechanical damage from impingement of S/G tubes from suspended corrosion products or reactive chemicals.

A. General.

B. Denting.

C. Wastage.

D. Pitting.

E. Stress corrosion cracking.

F. Interganular Attack.

G. Erosion-Corrosion.

H. Fatigue.

I. Fretting.

Answer 1

1. C.
2. I.
3. E.
4. H.
5. D.
6. A
7. B.
8. F.
9. G.

Question 2

State the two functions provided by Hydrazine in reducing secondary plant corrosion.

Answer 2

1. elevates pH.
2. Scavenges oxygen

Question 3

Explain why cation cartridge conductivity is a better indicatior of condenser tube leakage than a standard conductivity measurement.

Answer 3

First rember cation conductivity is a conductivity measurement after the cations have ben removed. This provides a very sensitive detection range due to lower background conductivity. as an impurity like NaCl passes through the cation, the Na+ is exchanged for H+ which combines with the Cl- to form HCI which has a strong conductivity signature.

Question 4

State the specific locations sampled for cation conductivity on the High Range Conductivity Recorders located in the Control Room.

Answer 4

• Total Hotwell
• Total Feedwater
• S/G Blowdown
• Feedwater Cation
• Hotwell Cation
• Makeup Plant Effluent.

Question 5

What are the benefits of reducing power for high S/G contamination levels?

Answer 5

• Concentration rate- it will reduce buildup in crecice areas and will allow the leak to be identified more easily.
• Reduce RCS T-Hot- Intergranular and stress are very temperature dependent.
• S/G Heat Flux - Reduce heat flux will reduce hard sludge formation.