STP currently performs a Power Coastdown at the end of each cycle.  I have been tasked with exploring performing a Temperature Coast (on Tavg) to the lower Safety Analysis limit, followed by a Power Coast.

We reach Valves Wide Open on the turbine in about 4 days (2F drop in Tavg). After that, the efficiency of the secondary side drops.

For those who perform a temperature coast, I would like to know:

1. What type of temperature coast do you use (Tavg, Treference, others)? Why?
2. What instrument recalibrations are usually necessary?
3. When do you reach valves wide open on the turbine?
4. How does the secondary side efficiency drop with steam pressure?
5. What operational issues/lessons learned would you care to pass along?

Thanks in advance.

Duane Gore

Supervisor, Reactor Engineering

STPNOC

(361) 972-8909