ML20058K473
| ML20058K473 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 06/28/1973 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9102080403 | |
| Download: ML20058K473 (7) | |
Text
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NSIB NORTHERN STATE 5 POWER COMPANY i
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June 28,1973 usAEc f,
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,s-S, JUL2 1973* r3 g>RE ElVL ss c
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g WJdL SECTION 6
5 ov 2 jf/3 k2 Mr. J F O' Leary, Director O
Directorate of Licensing 6
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,.e,bgy United States Atomic Energy Comiss Cn c m,en Washington, D C 20545 Cf M "cr s/
ol swen
Dear Mr. O' Leary:
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MONTICELLO NUCIIAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Main Steam Isolation Valve Leakage and Closure Time This report is submitted in accordance with paragraph 6.7.C.5 of Appendix A, Technical Specifications, of the Provisional Operating License for the Monticello Nuclear Generating Plant. Paragraph 6.7.C.5 requires a report of main steam isolation valve (MSIV) leakage and closure times to be made 90 days after completion of MSIV leakage tests. This particular submittal j
will also contain information necessary to complete our earlier " Report 1
of Main Steam Isolation Valve Performance" dated December 28, 1972.
Table I is a sumary of regularly scheduled MSIV surveillance testing at i
Monticello since the date of initial comercial service.
Tests of automatic closure, time to close, partial exercising and local leak rate testing are tabulated listing number of valve tests conducted and number of discrepancies experienced. Table II is a detailed listing of the results of the MSIV local leak rate tests conducted during the 1973 spring outage.
Leakages before and after maintenance are tabulated along with a sumary of maintenance performed.
Table III is a detailed listing of results of regularly scheduled MSIV ti2ning tests at Monticello since the date of initial comercial service. Future reports will contain only results of closure tests conducted since the date of the previous report.
Main Steam Isolation Valve Leakage Measurements Four of the eight MSIV's tested failed to meet the 11.5 scfh leakage limit established by the Monticello Technical Specifications.
These valves were disassembled and inspected for pilot and main valve disc and seat damage.
No physical damage was found.
Stellite was deposited on the main seat of 4
I 9102000403 730628 CF ADOCK 0500 263
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NORTHERN OTATES POWE R COMF'ANY MS' / 2-86A to cover base metal that had been < tposed during repairs in Ja:
ty, 1972. All four valve discs were machined and main seats and pilot seats were lapped smooth. During the lapping process indications of slight main seat warpage were observed.
Following these repairs all valves demon-strated satisfactory leak tightness.
Two of the valves requiring repair also required maintenance in January,1972.
Operating experience to date seems to indicate that some valve repairs may be necessary at every annual outage to meet the somewhat conservative Technical Specification Icakage limits. We believe tha t the experience gained in MSIV maintenance techniques over the past two years has begun to show results, however, and that steady improvements in MSIV Icak tightness will result.
Summarv of MSIV Leakage Experience From Other Facilities Frograms being conducted at other boiling water reactor facilities to reduce MSIV leakage have been closely followed.
Paragraph 4.7.A of the Bases for the Monticello Technical Specifications requires a report of this evaluation to be made to the Commission.
Methods proposed to date generally involve one of the following schemes:
a.
Water sealing system i
b.
Gas sealing system c.
Bleed off between MSIV's to standby gas treatment system d.
Installation of third MSIV in each steam line No currently operating BWR is known to have installed a sealing system to minimize MSIV Icakage.
Several plants in the construction stage have agreed to design and install such a system, but utility or AEC acceptance of a specific design apparently has not yet taken place.
We will continue to follow developments in this area but believe that it will be several years before sufficient information is available on a vari-ety of MSIV sealing systems to complete a comprehensive evaluation of their 1
performance. When such an evaluation is possible, plant modifications will be considered, if necessary, to meet the objectives of 10CFR100.
MSIV Closure Time Tests 1
Two regularly scheduled MSIV closure timing tests were conducted since the December 28, 1972 report. All valve closure times were within the 3 to 5 second limit.
During the 1973 spring outage new air operators were installed on all eight MSIV's.
These operators utilize poppet type valves which are not as susceptible to binding as the spool type valves used on the original 6
-m._
NORTHERN CTATES POWER COMPANY l
operators. This modification is described in detail in our letter of June i
27, 1973 to D J Skovholt, Assistant Director for Operating Reactors, concern-ing MSIV reliability.
l As indicated in Table I, one exercise test discrepancy has been experienced with the new air operators. This failure resulted in MSIV over travel during the first routine MSIV exercise closure at the conclusion of the 1973 spring outage.
Replacement of the AC test solenoid on the affected operator was required. Additional operating data is being collected on the reliability of the new MSIV operators and a substantial improvement in MSIV performance is expected after the initial break in period.
Yours very truly, h.
L 0 Mayer, PE Director of Nuclear Support Services LOM/DMM/br cc: B H Grier G Charnoff Minnesota Pollution Control Agency Attn. K Dzugan l
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.m TABLE I Main Steam Isolation Valve Surveillance Testing Requirements and Sunraary of Results (7/1/71 - 6/23/73)
No. of Valve Tests No. of Test Performed Discrepancies Surveillance Test Frequency Test of simulated automatic Each operating 8*
0*
closure Cycle (TS 4.7.D.1.a)
Trip test and measurement Quarterly 72 3
8*
0*
of closure times (TS 4.7.D.1.c (2))
Partial closure and Weekly 552 1
40*
1*
reopening MSIV exercise (TS 4.7.D.2)
MSIV Local Irak Rate Test Each operating 16 8
(TS 4. 7. A. 2. e) cycle
- Indicates testing done following installation of new MSIV air operators.
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. _.. _.. _ _.. _ -. ~. _ _.. _... _.... _.. _ _ _ _ _ _,.
TABLE II Results of Main Steam Isolation Valve Leakage Tests Conducted During 1973 Spring Outage Leak Rate (SCHI)
Valve Identification
@ 25 psig Summary of Maintenance Performed to Improve Leak Tightness As Found As Left 2-80A 130 1.63*
Truing' cut made on main disc.
Pilot seat and main seat lapped.
2-86A 8.3 Truing cut made on main disc.
Stellite deposited on main disc.
Pilot seat and main seat lapped.
2-80B 0
0 None 2-86B 6.6 0
Truing cut made on main disc.
Pilot seat and main seat lapped.
2-800 3.3 0
. Truing cut made on main disc.
Pilot seat and main seat lapped.
2-86C 4.99 4.99 None 2-80D 6.65 6.65 None 2-86D 1.66 1.66 None i
- Indicates that combined inboard / outboard leak rate for valves 2-80A and 2-86A was determined.
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l TABLE 111
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Results of Main Steam Isolation Valve Quarterly Timing Tests (7/1/71 - 6/23/73) l l
l I
Valve Identification 2-80A 2-86A 2-80B 2-86B 2-80C 2-86C 2-80D 2-86D 8/26/71 3.8 3.0 3.2 3.2 3.8
.0 3.6 3.5 f
f.2) f0.h 4.3 3.9 3.5 3.9 11/13/71 4.2 3.4 1/22/72 3.9 4.0 4.1 4.0 4.0 4.2 3.9 4.0 l
5/12/72 3.7 4.8 4.5 3.2 4.0 3.2 4.3 3.5 6/3/72 4.0 4.7 4.0 3.6 4.0 4.2 3.9 3.7 l
7/16/72 3.8 4.9 4.4 3.4 4.3 4.4 4.0 4.3 i
l 10/15/72 3.4 5.0 4.7 3.8 3.8 5.0 4.3 4.1 i
12/14/72 4.0 5.0 4.2 3.6 3.9 4.8 3.9 3.7 I
3/3/73 3.6 4.2 4.6 4.2 4.0 4.0 3.9 3.3 l
5/12/73 4.2 4.6 4.2 4.2 4.6 4.9 4.0 4.5 i
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AEC DIf 'EUTION FOR PART 50 DOCKET MATP S g
(TDiPORARY FORM)
CONTROL NO: 5135 FILE:
FROM:
DATE OF DOC DATE REC'D LTR MD 0 RPT OTHER Northern States Power Company Minneapolis, Minnesota 55401 L. O. Mayer 6-28-73 7-2-73 x
7t):
SENT LOCAL PDR X
J. F. O' Leary 39 CLASS UNCLASS PROP IhTO INPUT NO CiS REC'D DOCKET NO:
40 50-263 x
DESCRIPTION:
ENCLOSURES:
Ltr furnishing info re Report of Main Steam
[g g]
Isolation Valve Performace dtd 12 -2 8 -7 2.'...
w/ attached Tables I, II & III......
PLANT NAME: Monticello FOR ACTICN /I:.TC2iATICN 7-3-73 LB BUTLER (L)
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