ML20040A558
| ML20040A558 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 01/15/1982 |
| From: | Jackson E VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0619, RTR-NUREG-619 FVY-82-3, NUDOCS 8201210242 | |
| Download: ML20040A558 (5) | |
Text
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VERMONT Y AN KEE NUCLEAR POWER CORPORATION SEVENTY SEVEN GROVE STREET 3
l RUTLAND, VEIO10NT OG701 FVY 82-3 REPLY TO:
ENGINEERING OFFICE 1671 WORCESTER ROAD FRAMINGH AM, M ASS ACHUSETTS 017o1 i
TELEPHONE 817 872-8100 l
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January 15, 1982 i
j D
O United States Nuclear Regulatory Commission gr, Q
1 I
Washington, D.C. 20555 f
W5'j(T) i g
Attention:
Office of Nuclear Reactor Regulation l
D.C. Eisenhut, Director 12 0199 5 5 DQ Division of Licensing 7
IK e
er s
References:
a)
License No. DPR-28 (Docket No. 50-271) j b)
Letter, USNRC to VYNPC, dated 7/29/81
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c)
Letter, VYNPC to USNRC, FVY 81-141, dated 9/25/81
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d)
Letter, VYNPC to USNRC, FVY 81-142, dated 9/'!5/81 e)
General Electric Company Report NEDE 21821-02, 8/79 4
l Paragraph 3.4.3 i
i
Dear Sir:
i
Subject:
Vermont Yankee Position on NUREG 0619 Items Regarding j
Feedwater System Changes and Results of Blend / Radius l
Bore Inspections from 1981 Refueling Outage i
Reference (c) responded to portions of the subject NUREG, providing a i
partial response to Reference (b).
Vermont Yankee's position on the remainder f
of that NUREG is presented in Part I below.
Part II contains supplementary information to that submitted by Reference (c), which was obtained during the 1981 Refueling Outage and subsequent start-up.
I.
NUREG-0619 System Items 1.
RWCU Reroute Vermont Yankee does not believe that rerouting Reactor Water Cleanup Flow to both feedwater lines of fers any improvement because data from our 1976 inspection shows that more cracks and deeper cracks were present in the feedwater nozzles to which RWCU Flow was routed than in the ones with no RWCU flow (see below).
In light of this information, we question the benefit of im-plementing the recommendations; and even if marginal benefit I
would be demonstrated, we feel that it would be more than offset b
U.S. Nuclear Regulatory Commission January 15, 1982 Page 2 VERMONT YANKEE NUCLEAR POWER CORPORATION by ALARA considerations. We continue to believe that the ke/ to preventing nozzle cracking is the elimination of bypass flow.
Installation of an on-line bypass leak detection system, which was completed during the 1981 refueling outage, will provide the ability to detect this deleterious leakage and subsequently to plan for corrective action.
This is a more positive step toward preventing significant nozzle cracking than rerouting RWCU lines.
RESULTS OF 1976 DYE PENETRANT INSPECTION Nozzles Total Indications Base Metal Grindants 45 18 0
135 25 0
- 225 22 7
- 315 65 0
- RWCU is routed to these nozzles 2.
Low Flow Feedwater Control The Vermont Yankee design includes a low flow feedwater control system which has been demonstrated to meet or exceed the low flow criteria specified by General Electric.
During the startup following the 1981 Refueling Outage, all relevant feedwater control parameters were monitored throughout the entire startuo period which included a variety of low power test conditions.
A detailed description of the Vermont Yankee design, tests, and procedures is contained in Appendix I.
As a result of our testing and analysis, we conclude that criteria a,
b, c and f of Reference (e) are fully satisfied at Vermont Yankee. The functional requirements of criteria d and e are also met in that necessary redundancy is available through alternate flow control systems; testing, component reliability, and bumpless transfer, have been operationally demonstrated; and changes to the station operating procedures have been initiated to provide the necessary instructions regarding use of the low flow and main feedwater control system.
Since all criteria have been met, no additional changes to the Vermont Yankee design are considered necessary.
3.
CRD Return Line Reroute Vermont Yankee implemented the reroute option to a feedwater line (via the RWCU return) in 1979.
The CRD return nozzle blend radius, bore region, and vessel wall beneath the nozzle were dye-penetrant tested and all cracks removed at this time.
System
U.S. Nuclear Regulatory Commission January 15, 1982 VERMONT YANKEE NUCLEAR POWER CORPORATION Page 3 performance testing in accordance with the guidelines of OPE 3-377, had been completed earlier in 1977.
All subsequent system operations have been with the rerouted line valved open.
Since system performance remains essentially identical to the original design, we conclude that no additional testing is necessary.
4.
CRD - RWCU Tee Inspection We will commit to an inspection of the CRD to RWCU joint, as discussed in the NUREG, by UT methods for three consecutive refuel outages including the recently completed 1981 refueling (refer to Section II for results).
Upon completion of these inspections, we will reassess the inspection frequency based upon the inspection results.
5.
CRD Pressure Control Station As noted previously, the CRD system at Vermont Yankee has per-formed satisfactorily with a flowing return to a feedwater line since 1979.
System performance and individual control rod temperatures are monitored by station operators.
To date, we have not identified a problem with the existing cooling water header pressure control station.
We have found that the infrequent pressure adj ustments made to the system during plant startup are very minor in nature and not unlike those made during routine shifting of CRD pumps or changing system strainers. Further, our communication with the one facility that has installed a cooling water pressure control station revealed that they also make similar and possibly more frequent pressure adj ustments during startup.
Therefore, we conclude that an additional cooling water pressure control station is unnecessary and are unable to commit to this modification.
6.
Operating Procedures With regard to station operating procedures, we have found that existing procedures adequately provide guidance to the operator relative to utilizing the CRD system to maintain reactor vessel water level. New procedures are being developed in accordance with the BUR Owner's Group Guidelines and consistent with an NRC approved schedule. These procedures, specifically the Guideline on Level Control, will contain additional guidance for achieving maximum CRD flow to the reactor vessel.
II.
REFUELING OUTAGE - 1981 - RESULTS 1.
In-Vessel Liquid Penetrant Inspection of Feedwater Nozzle Blend Radius / Bore
U.S. Nuclear Regulatory Commission January 15, 1982 VERMONT YANKEE NUCLEAR POWER CORPORATION Page 4 All four nozzles were inspected in accessible areas of blend radius and about 5 inches into the bore - No relevant indications were present. This is the third in-vessel PT inspection performed since interference fit spargers were installed in 1976, with identical results.
2.
Leak Detection System Vermont Yankee installed a fee:aater nozzle annulus leak detection system of the type described in NUTFCH Topical Report ADV-13-002N, Rev. O, during the 1981 outage.
Initial data, recorded during startup, at various feedwater flow rates and temperatures, show very consistent temperatures at all four nozzles.
Thermocouple Readings at 100% Power A
B C
D Top 498 496 492 493 Bottom 457-475 433-447 434-454 444-456 The correlation with analytically predicted temperature distribu-tion in a non-leaking interference fit sparger is excellent.
The preliminary evaluation indicates that bypass leakage is not present at any nozzle.
Data will continue to be recorded bi-weekly during steady-state cperation, and more often during startup-shutdown. This data reinforces the arguments made previously in Appendix A to Reference (c).
Based on data ob-tained at the 1981 outage and the information supplied in Reference (c), it is Vermont Yankee's position that replacement of the interference fit spargers with another design cannet be justified at this time.
3.
CRD-RWCU Tee Inspection An inspection of the three CRD to RWCU welds confirmed there were no UT indications.
We trust that the information contained above adequately justifies our position with regard to systems requirements of NUREG 0619.
If you have any questions, please feel free to contact us.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION SW E.W.
ackson Manager of Operations EWJ/dm
APPENDIX I The original Vermont Yankee design included one 10% capacity and two 55% capacity feedwater control valves in a configuration which does meet criterion b of Reference (e).
In response to plant operator and General Electric Company recommendations, the original low flow (10%
capacity) valve and controller were replaced with a drag type valve having improved flow characteristics and a single element water level control system possessing both manual and automatic features.
Station operating procedures were written to permit the flexibility of using the low flow valve or either 55% capacitysvalve in concert with another downstream motor operated globe valve to control vessel level during plant startup. Although the automatic option was available, station operators have typically, and quite successfully, controlled vessel level manually during startup operations.
During the startup following the 1981 refueling outage, a new technique consistent with criterion 'c of Reference (e) was introduced in our station operating procedures.
Prior to withdrawing control rods, the low flow controller was placed in automatic level control and a continuous discharge of approximately 80 gpm was established from the reactor vessel to the main condenser via the reactor water cleanup system (RWCU).
Since Vermont Yankee does not utilize flow measuring instruments capable of accurately detecting feedwater flow in the range of criterion f of Reference (e), performance was judged by observation of RWCU drain rate, flow controller position, vessel level, and feedwater nozzle temperatures.
System operation was examined throughout the entire startup period from cold shutdown to 10% power operation, including during the performance of several routine but dynamic surveillance tests.
The maximum variation of control valve travel was only 10% and occurred during the startup of a high pressure feedwater pump. At this time, vessel level rose three inches, then returned promptly to the original setpoint.
Throughout the startup, the low flow controller maintained a constant ver,el level and responded promptly to changes in RWCU drain rate, HPCI anc CIC full flow surveillance testing, repeated manual main steam relief valve actuations, and transfer to the 55% control valve.
Continuous monitoring of sixteen feedwater nozzle temperature indicators, four on each nozzle, confirmed that there was no measurable thermal cycling of the nozzle bore regions.
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