ML20235C521
| ML20235C521 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/18/1987 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 87-520, IEB-85-003, IEB-85-3, NUDOCS 8709240477 | |
| Download: ML20235C521 (7) | |
Text
. _ _ _ - _ _. _ - _ _ _.
VINGINIA }$LECTHIC AND l'OWER COMPANY llIC11MOND,VIHOINIA 2 0 2G1 W L. STEWART -
vice r===m==r September 18, 1987 Nt rt. san ormaATIONM U. S. Nuclear Regulatory Commission Serial No.87-520 Attention: Document Control Desk NAPS /JHL Washington, D. C. 20555 Docket Nos. 50-338 50-339 License Nos. NPF-4 NPF-7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT NOS. 1 AND 2 RESPONSE TO THE REQUEST mR ADDITIONAL INW RMATION CONCERNING NORTH ANNA'S RESPONSES TO IEB 85-03 Enclosed is the response to your August 18, 1987 request for additional information concerning North Anna's responses to.IEB 85-03,
" Motor Operated Valve Common Mode Failures During Plant Transient Due To Improper Switch Settings."
If you have any further questions, please contact us.
Very trul yours, L
W. L. Stewart Enclosure cc:
U. S. Nuclear Regulatory Commission 101 Marrietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. J. L. Caldwell NRC Senior Resident Inspector North Anna Power Station 8709240477 070918 h
POR ADOCK 05000338 6
P PDR
_=
i ENCLOSURE RESPONSE TO THE REQUEST FOR ADDITIONAL INFORMATION1 CONCERNING NORTH ANNA'S RESPONSES TO IEB 85-03 NRC COMMENT 1.
Has water hammer due to valve closure been considered in the determination of pressure differentials? If not, please explain.
RESPONSE
'The effects of water hammer due to valve closure are negligible and therefore have not been considered in the determination of pressure differentials.
Water. hammer, which is caused by the sudden decrease in velocity of a flowing fluid, is a relevant design consideration when the fluid flow is stopped instantaneously.
The motor operators for the valves identified have a sufficiently long travel time to closure and the corresponding decrease in fluid velocity..is gradual enough such that a shock wave does not develop.
Consequently, the MOVs will not be subjected to the pressure increases associated with water harner conditions.
NRC COMMENT 2.
Please explain why the following MOVs are not included in Attachment 2 of the response of 10-17-86, or revise Attachment 2' to include them.
As required by Action Item "a" of the bulletin, assume inadvertent equipment operations.
(a) FW-100A(-200A) and FW-100C(-200C) are shown normally open in discharge lines of the AFW pumps, near the lower left corner of UFSAR Figure 10.4-7, Revision 2,
6/84.
Note that similarly located FW-100B(-200B) and FW-100D(-200D) are listed.
(b) 1275A(2275A),
1275B(2275B),
1275C(2275C),
1381(2381) and 1373(2373) in miniflow ifnes leading from the charging pumps to the seal water heat exchanger are shown normally open, on UFSAR figures 9.3-41 and 9.3-44.
Similarly located valves are listed for five other Westinghouse three-loep facilities.
(c) 1287A(2287A),
1287B(2287B),
1287C(2287C),
1869A(2869A), and 1869B(2869B) in safety injection lines of the charging pumps to the hot legs are shown on UFSAR figures 9.3-41 and 9.3-44.
I
RESPONSE
(a) Auxiliary Feedwater (AFW) System motor operated valves (MOV)
FW-100A and C and FW-200A and C were not included on Attachment 2 of our October 17, 1986 response to IEB 85-03 since these valves are not used in normal operation to control AFW flow to the A and C steam generators, respectively. Further, since these AFW lines are isolated by locked closed manual valves downstream of the subject MOVs inadvertent operation of these MOVs will have no effect upon the AFW system flow to the steam generators.
In addition, no single active failure of a component within the AFW system would require the use of MOV-100A (200A) or MOV-100C (200C) to maintain the unit within its design basis.
Should a r
single pump or valve within an independent header f ail to operate,
~ ~ - -
the minimum number of steam generators required for design basis accidents would still be available.
(b) MOV-1275A, B and C (2275A, B and C) and MOV-1373 (2373) will be added to the North Anna IEB 85-03 valve program.
Due to the orientation of the valves and the size of the valve actuators, the maximum differential pressures of MOV-1275A, B and C (2275A, B and C) are provided for both the open to closed and closed to open positions. A revised Attachment II from our October 17, 1986 response to IEB 85-03 is attached.
During a conference call between Mr.
R.
Kiessel and representatives of the Virginia Electric and Power Company on September 9, 1987, Mr. Kiessel stated that MOV-1381 (2381) is deleted from the request for additional information. The reason this MOV is outside the scope of IEB 85-03, as agreed upon, is that MOV-1381 (2381) is an outside containment isolation valve in the reactor coolant pump seal water return line. These valves are not in the high head safety injection flow path to the reactor coolant system. The operation of these valves will not affect the operation of the charging pump recirculation flow path.
(c) MOV 1287A, B and C (2287A, B and C) were not included in the list of valves required by IEB 85-03 since these normally open valves are not in the initial high head safety injection flow path to the RCS cold legs. In addition, inadvertent operation during the initial injection mode would not isolate flow to or divert flow from the reactor coolant system.
MOV-1869A and B (2869A and B) were not included in the list of valves required by this bulletin since these valves are not in the initial high head safety injection flow path to the RCS cold legs.
These valves are opened approximately 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> after a loss of coolant accident to establish hot leg recirculation.
In addition, if these valves inadvertently opened during the initial cold leg injection mode, safety injection would not be isolated or diverted from the reactor coolant system.
NRC COKMENT
-3, Please expand the proposed program for action items b, c and d of the bulletin to include the following details as a minimum:
(a) commitment to a training program for setting switches, maintaining valve operators, using signature testing equipment and interpreting signature?,
(b) commitment to justify continued operation of a valve determined to be inoperable, and (c) description of a method possibly needed to extrapolate valve stem thrust measured at less than maximum differential pressure.
RESPONSE
(a) North Anna does have a training program for the maintenance of MOVs. This training program, for electricians, includes training on limit switch settings, torque switch settings, mechanical operating characteristics, lubrication and maintenance of valve actuators, use of diagnostic dquipment and adjustments indicated by the use of the MOVATS test equipment.
In addition, job istformance measures are performed on gear driven limit and torque switches for MOVs and the repair, replacement and adjustment of gear driven limit switches for MOVs. Continuing training for electricians is determined on an annual basis by performing a needs assessment.
In addition, six station engineers have attended a MOVATS class on signature interpretation.
Should additional personnel be required for the maintenance of MOVs, they would obtain the required training to perform a specific job function.
(b) equipment that is governed by the Technical Specifications must remain operable or the Technical Specification action statement must be entered.
A justification for continued operation (JC0) j cannot supersede the requirements of a Technical Specification action statement.
l For equipment that is not governed by the Technical Specifications, Station Administrative Procedure 16.1,
" Station i
Deviation Reports" provides a determination of whether c JC0 is j
needed in the event there is a safety impact on the plant because a piece of equipment is determined to be inoperable.
This determination for the need for a JC0 also applies for IEB 85-03 valves.
l (c) A descrip*1cn of the extrapolation method for valve stem thrust measured at less than maximum differential pressure has been obtained from MOVATS Incorporated (attached). To date, no partial pressure testing has been performed or is expected to be performed on any IEB 85-03 valves.
L________
Page 1 of 3 CMfUIATTC 02&TMNCE IWES
Reference:
1.
Business Statistics, 3rd Edition, 1983, by Wayne Daniel and James C. Terrell, (Chapter 9).
Assumptions:
1.
The thrust required to open and close a gate or globe valve is a linear function of differential pressure across the valve.
2.
For every differential pressure (x), therb is a subpopulation of thrust values (f) for identical valves. 'Ihe thrust values are normally distributed about same mean value.
3.
3he standard deviation of thrust values is the sane for all subpopulations and is unknown.
4.
The mean values lie on some straight line.
(i.e., There is a linear relationship between differential pressure and the average thrust values.)
Procedure:
1.
Perform a regression (least squares) analysis of the measured DP thrust (thrust above running load) vs differential pressure for at least 4 identical valves. 3he (0,0) point can be used along with this measured data. The result is an equation of the form:
y = a + bx where y = thrust required x = differential pressure 2.
Calculate the estimated thrust (yl) required for valve operation at some differential pressure, (x1).
y1 = a + bx1 3.
Calculate the confidence band for the calculated (yl) value as follows:
i
~
confidence
+tSjx 1 + 1/n +
(xg - 32) 2
=
y l
band at x1 Exi (Exi) 2
)
(
where: E = average of reasured differential pressure values (and zeru)
/
4 l
Page 2 of 3 n = number of DP tests plus 1 (for 0,0) t = value of " Students T" distribution factor (depends on n and confidence, Table E of Reference 1, attached)
Sy/x =
E (yi - y)2 n-2 y1 = measurcd thrust at each DP value, xi y = calculated thrust at each DP value
o Page 3 of 3 90fo CCYN11%
l n
,4 TABLE E i
- ~
- 08" Percentiles of the
~ '
0" 0 "'
t distribution 1
3.078 6.3138 12.706 31.821 63 657 P(t 5 to) 2 1.886 2.9200 4.30'27 8 965 9 9248 3
1.638 2.3534 3.1825 4 541 5 8409 4
1.533 2.1318 2.7764 3.747 4 6041 5
1 476 2 0150 2.5706 3.365 4 0321 6
1.440 1.9432 2.4469 3.143 3.7074 7
1.415 1.8946 2.3646 2.998 3 4995 8
1.397 1.8595 2.3060 2.896 3 3554 9
1 383 1.8331 2.2622 2 821
'3 2498 10 1 372 1.8125 2.2281 2.764 3.16S3 11 1.363 1.7959 2.2010 2.718 3 1058 12 1.356 1.7823 2.1788 2.691 3.0545 13 1.350 1.7709 2.1604 2.650 3 0123 14 1 345 1.7613 2.1'.48 2.624 2.9768 15 1.341 1.7530 2.1315 2.602 2 9467 16 1 337 1.7459 2.1199 2.583 2.9208 17 1.333
?.7396 2 1098 2.567 2 8982 18 1.330 1.7341 2.1009 2 552 2 8784 19 1.328 1.7291 2.0930 2.539 2 8609 20 1 325 1.7247 2.0860 2.528 2 8453 21 1.323 1.7207 2 0796 2 518 2 8314 22 1.321 1.7171 2.0739 2.508 2 8188 23 1.319 1.7139 2.0687 2.500 2 8073 24 1 318 1.7109 2.0639 2.492 2 7969 25 1.316 1.7081 2.0595 2.485 2.7874 26 1.315 1.7056 2.0555 2 479 2.7787 27 1.314 1.7033 2.0518 2.473 2.7707 28 1.313 1.7011 2 0484 2 467 2.7633 29 1 111 1 6991 2 0452 2.462 2.7564 30 1310 1 6973 2.0423 2 457 2 7500 35 1 3062 1 6896 2 0301 2 439 27239 40 1.30.11 1 6839 20211 2 423 2 7045 45 1.3007 1.6794 2 0141 2 412 2 6896 50 1.2987 1 6759 2.0086 2.403 2 6778 60 1.2959 1 6707 2.0003 2.390 2 6603 70 1.2938 1.6669 1.9945 2.381 2 6480 80 1.2922 1 6641 1 9901 2.374 2 6388 90 1.2910 1.6f,20 1.9867 2.368 2.6316 100 1.2901 1.6602 9,.9840 2.364 2.6260 120 1.2887 1.65,77 1.9799 2.358 2.6175 n
)
140 1.2p76:
1.6558 1.9771 2 353 2.6114 160 1.28'69'
'6545 1.9749 2.350 2 6070 180 1.2863 6534 1.9733 2.347 2.6035 200 1.2858 1.6525 1.9719 2.345 2 6006 to 1.282 1 645 1.96 2.326 2.576 l
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