Digital Feedwater

Question 1

Describe how DFWCS feeds in RTO (5 points).

Answer 1

• RTO signal is generated by the UV relays (1&2 or 3&4)
• Controller will feed based on Tavg (564F) instead of level
• Will stop feeding at 51.9% NR
• Master controller is tracking
• MFPs receive speed signals from their own DFWCS

Question 2

Describe the inputs to digital feed in single element control (<14%).

Answer 2

• SG level error drives the master controller demand
• TLI (RRS) and SBCS master demand signal are used as an anticipatory input for better transient response

Question 3

What conditions will automatically shift the DFWCS master controller from 3E to 1E?

Answer 3

• 8% deviation; in FW flow
• 50% deviation is steam flow
• 13.5% and lowering reactor power

Question 4

Describe the ATUN lockout.

Answer 4

Deviation in either FW temperature or Control channel power will cause the controller to throw out the failed transmitter and use a canned value.
- ALARM = 4% temperature difference
- CANNED = 8% temperature difference…inserts 425F canned value

• ALARM = 4% reactor power difference
• CANNED = 8% reactor power difference…inserts 5% if below 16.5% inserts 60% if above 16.5%