ML20080R732
| ML20080R732 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 02/22/1984 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| 5211-84-2032, NUDOCS 8402280391 | |
| Download: ML20080R732 (3) | |
Text
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GPU Nuclear Corporation NggIgf Post Office Box 480 Route 441 South Middletown, Pennsylvania 17057 0191 717 944 7621 TELEX 84 2386 Writer's Direct Dial Number:
February 22,1984 5211-84-2032 Office of Nuclear Reactor Regulations Attn: John F. Stolz, Chief Operating Reactors Branch No. 4 U. S. Nuclear Regulatory Commission Washington, D.C. 20555
Dear Sir:
Three Mile Island Nuclear Station, Unit I (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 EFW Flow Instrumentation In response to your letter of January 18, 1984 on EFU Flow instrumentation oscillations at low flow condition, enclosed please find results of a recent test performed under test procedure (TP 233/4) dated January 12, 1984.
Sincerely, H. D. Iu i;.1 VP - TMI-1 HDH:mle cc:
R. Conte J. Van Vliet O
9 PDR O
GPU Nuclear Corporation is a subsidiary of the General Public Utilitlec Corporation i
y J
Item:
1.
With regard to the Emergency Feedwater (EFW) flow indicators:
a.
What is the full scale flowrate on the meter faces?
b.
What is the magnitude of the oscillations at 50 gpm, 100 gpm, 200 gpm, and each 100 gpm increment thereafter up to full flow?
c.
The preliminary evaluation concluded that cavitation on the outlet of the feedwater flow control valve during low flow conditions caused the oscillations.
What are the conclusions of the final evaluation.
Response
a.
Control room indication full scale is 800 gpm.
b.
At 50 gpm Zero flow indication - 50 gpm is below cut off point of signal conditioning electronics.
At 100 gpm Establishing an oscillation free flow indication at anything below 120 gpm is not possible in our testing because of cavitation of the EFV-30 valves due to low flow against negligible backpressure.
The magnitude of oscillation is variable.
Also the signal conditioning electronics (square root extractor) low signal cut-off is 75 anm.
at 120 gpm Meter movement is noticeable.
However, with 25 gpm meter face graduations the oscillations are not readable.
Recorder traces indicate the peak-to-peak oscillation is 12 gpm.
At 200 gp'm As above for 120 gpm, except traces shows 15 gpm peak-to-peak At 300 gpm As above for 120 gpm,except traces shows 20 gpm peak-to-peak At 400 gpm As above for 120 gpm, except tracer shows 20 gpm peak-to-peak At 500 gpm As above for 120 gpm, except traces shows 25 gpm peak-to-peak At 600 gpm As above for 120 gpm, except traces shows 25 gpm peak-to-peak c.
GPUN has reviewed the most recent test data and concluded that the oscillations at low flows (less than 120 gpm) in the EFW instrumentation are mainly due to cavitation in the vicinity of the EFV-30 valves.
This effect has been substantiated analytically based on data from an earlier EFW System Test (600/3).
The drop out of the square root extractor at about 75 gpm also contributes to indicated oscillations.
F Item:
2.
With regard to operator use of the indicators, do any abnormal transient procedures for TMI-l (emergency operating procedures) direct the operators to EFW flow indication? If so, which procedures, under what circumstances, and over what range of L
indicated flow?
' Response:
Abnormal Transient Procedure 1210-10 " Abnormal Transients Rules, Guides and Graphs" directs operators to EFW flow indication in two instances.
1.
Section 1.5, Emergency Feedwater Throttling Criteria, directs operators, upon incore TC's not decreasing, to increase EFW flow to at least 450 gpm (225 gpm per SG) until 0TSG 1evel setpoint is reached. This rule is to b2 followed whenever EFW is initiated.
2.
Section 2.3, Emergency Feedwater Actuation Response (Step D),
directs operators to verify EFW flow by flow indication if OTSG 1evel is below it's setpoint.
This guideline is for verification that an EFW flow path to the OTSG's is available.
Operators are first directed to verify EF-P-1, 2A, 2B, start, and to verify discharge pressure greater than 1010 psig.
If flow indication is greater than 120 gpm, this is sufficient to verify flow. As OTSG 1evel approaches the setpoint the control valves are throttled to low flow conditions and flow is verified by OTSG 1evel (per step E).
At flows below 225 gpm EFW flow indication is not relied upon for flow control. The important aspect at low flow is the verification of adequate OTSG heat removal.
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