Secondary Chemistry

Question 1

Define Denting

Answer 1

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

Question 2

Define Fretting

Answer 2

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

Question 3

Define Erosion- Corrosion

Answer 3

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

Question 4

Define Fatigue

Answer 4

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

Question 5

State 2 functions provided by Hydrazine in reducing secondary plant corrosion

Answer 5

Scavenges oxygen and elevates pH

Question 6

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

Answer 6

First remember cation conductivity is a conductivity measurement after the cations have been removed. This provides a very sensitive detection range due to the lower “background” conductivity As an impurity such as NaCl passes thru the cation column the Na+ is exchanged for a H+, the H+ combines with the remaining Cl- forming HCl which has a strong conductivity signature

Question 7

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

Answer 7

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

Question 8

Define General S/G degradation

Answer 8

Corrosion caused by the presence of oxygen or oxygen generating contaminants

Question 9

Define Stress Corrosion Cracking

Answer 9

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

Question 10

Define Wastage

Answer 10

Localized corrosion caused by acidic attack in low flow areas

Question 11

Define Pitting

Answer 11

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

Question 12

Define Intergranular Attack

Answer 12

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

Question 13

State the benefit gained from concentration rate when a power reduction is made in response to high S/G contamination:

Answer 13

If from makeup, will reduce buildup in crevice areas.

If from tube leak in condenser, will reduce buildup in crevice areas, but concentration in condensate will increase due to lower flow, and will allow leak to be identified more easily.

Question 14

State the benefit gained from RCS Hot Leg Temp when a power reduction is made in response to high S/G contamination:

Answer 14

Analysis has shown that “less damage” occurs at lower RCS Hot Leg temperatures than at elevated temperatures

Question 15

State the benefit gained from S/G Heat Fluxwhen a power reduction is made in response to high S/G contamination:

Answer 15

As with RCS Hot Leg temps above, the lower the heat flux the less hideout/damage to the S/Gs