BWR Feedwater Check Valve Integrity
BWR Feedwater Check Valve Integrity
(OP)
Some BWR's seem to have problems with check, or non-return valves in their feedwater circuits. These valves either stick open or leak water when they should be closed.
What methods are used to ensure satisfactory operation of these valves?. What sort of leak rates are acceptable? Should these valves be damped so that any tendency towards water hammer is avoided?
What methods are used to ensure satisfactory operation of these valves?. What sort of leak rates are acceptable? Should these valves be damped so that any tendency towards water hammer is avoided?





RE: BWR Feedwater Check Valve Integrity
I can give you some information regarding US requirements, if you want.
Patricia Lougheed
RE: BWR Feedwater Check Valve Integrity
I recently took on a new job with a Nuclear Inspectorate (Switzerland). The plant with which I'm involved is GE BWR-6 built in 1984. There are moves to modify the (inclined) check valves so as to reduce leakage and reduce risk of stiction. Thks Pete
RE: BWR Feedwater Check Valve Integrity
The requirement to test CIVs is found in 10 CFR Part 50, Appendix J "Primary Reactor Containment Leakage Testing", which specifies that the total leakage from all lines penetrating containment be less than or equal to 0.6La, where La is specified in the Technical Specifications Bases as the acceptable amount of leakage to the environment, post accident for 24 hours at peak containment pressure. (Actual number for La varies considerably by plant - from 0.5% at 56.5 psig to 2% at 45.7 psig to 0.65% at 9 psig)
Appendix J requires that valves be tested with air at the containment pressure. Feedwater checks tend to be very large (24") valves that don't do well under air testing. Some US plants have installed keep fill systems so that they don't have to do the testing. Others have found that very exact machining and tolerances help keep the valves in spec.
I don't have any current information about leakage rates for individual valves - you might try posting this in the valve forum and see whether there's anyone who knows. Also, I've never seen or heard about dampening systems being installed to prevent water hammer. That's not been a concern on US BWRs as far as I know.
Hope this is helpful.
Patricia Lougheed
RE: BWR Feedwater Check Valve Integrity
Pete
RE: BWR Feedwater Check Valve Integrity
Pete
RE: BWR Feedwater Check Valve Integrity
Patricia Lougheed
RE: BWR Feedwater Check Valve Integrity