ML20195E442
| ML20195E442 | |
| Person / Time | |
|---|---|
| Site: | Mcguire |
| Issue date: | 10/31/1988 |
| From: | Tucker H DUKE POWER CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8811080063 | |
| Download: ML20195E442 (5) | |
Text
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11 1
Duke Ibwr Company lin R Tm PO Bax33198 iice President Clwrlotte; N C 28242 Nuclear Produai<m (701}373 453I DUKEPOWER October 31, 1988 U.S. Nuclear Regulatory Oxmission Document (bntrol Desk Hashington, DC 20555
Subject:
R:Chtire Nuclear Statim, Diit 2 Docket No. 50-370 Gentlemen:
By letter datal August 9,1988, Duke Power identified deficiencies in the design and preoperational testing of the hyttrcgen skinmer (VX) system.
Required VX syst e flow rates were revised based on curren : regulatory guidelines.
On August 16, 1988, ficw measurments were cm pleted that dmonstrated the operability of the Qiit 2 VX systm. As noted in the August 9,1988 letter, a modification was needed to cross connect the cuction piping of the VX system in order to improve the flow balance capability of the syste i
(See Figure 1).
j During the preparation of this modification, it was recognized that suction darpers were needed to prevent reverse flow through an idle fan.
Such a situation could occur following a design basis accident if both trains receive a start signal, isolation dagers open and fans start en toth trains.
If power is subsequently lost on one of the trains, the fan wculd stop but the l
l notor cperated dager would fail in the open position. As a result, air would backflow through the idle fan and oren deper.
With the current piping l
configuration, the open dager was initially not considered significant due to l
the high flow resistance of the pipirg.
l l
Following flow balance testing of the Unit i VX systm during the current refueling outage, the decision was made to perform additional flow balance testing with tM idle fan isolation dmper in the open position. h test was j
ccnductal by reasuring the flows in the fcur ccrpartrents farthest away frcn tM operating fan (See Figure 2).
hoe ccupartrents wra sclected on the assurption that they would see the greatest inpact frts the open isolation i
i danper.
Total fan flow and reverse flow through the oren isolation deper were also measured.
msults of this test are shown in Table 1.
msults on Unit 1 indicated that tM tailed open idia fan isolation deper did not reduce any of the flows in the measured cccparttrnts belcw the acceptance c;riteria.
Een the Uhit 1 test data was ccmpared to the previcus Unit 2 results, it was not possible to conclude that the corresponding Unit 2 ccrpartment flows would be acceptable with the idle fan suction dager open. Wrefore, at 1045 a.m.
l on October 26, 1988, both trains of the Unit 2 VX cystem were declared inoperable.
Sulaxpently, power was rmaved frcm the B train fan and isolation danper at 11:10 a.m. on Octeter 26, 1988. This action zustortx1 Train A to operable status and placed Unit 2 in a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> actico staterent.
0 0011000063 881031 1
I PDR ADOCK 05000370 gg i
P PNU.,
l Document (bntrol Desk October 31, 1988 Page 2
%e previously identified modification to the VX systm would overcme this single failure vulnerability by the use of passive check danpers (See Figure
- 1).
%e nodification was ready for installation on Unit 1 but the design calculaticms had not been empleted for Unit 2.
Werefore, a ta porary modification was identified on Octcber 26, 1988 which would overcme the identified single failure.
mis nodification would provide an alternate sAce of pwor to close the idle fan suction danper by emss connecting the respective powr supplies through nortully deenergized cables and red-tagged open breakern.
Q1 October 28, 1988, Duke provided a copy of the 50.59 evaluation and other documentation to the lac Ibsident Inspectors.
During a conference call with raC on that same day, Duke Ibwer rcquested and was granted discretionary enforement of 'Ibchnical Specification 3.6.5.6 until such tirn as the thit 2 VX systm is modifial as shown in Figure 1.
%is perranent nodification will be installed at the next refueling outage, ncw scheduled for July 1989, or during an outage of sufficient duration following ecopletion of the design.
Later that evening, the tenporary nodification to provide backup powr to each Unit 2 VX suction isolation danper iras ccepleted, appropriate revisions wru approved for station mergency precedures and the training package was released for reviw by on-shift operators. With these neasures in place, the thit 2 VX system was restored to a nonml aligreent and rmaved from the Technical Specification Action Iog at 2355 on Octcber 28, 1988.
Very truly yours, Ital B. 'Ibcker RIE/416/mf xc Dr. M.L. Prnst
/cting Pegional 7dministrator, Ibgion II U.S. Ibclear Irgulatory Ormission 101 lbrietta Street, N.W. Suite 2900 Atlanta, Crorgia 30323 Darl S. ! bod P.K. Van Iborn U.S. IbcInar Itgulatory Omnission
?SC Ibsident Incpector Offico of tbclear Ibactor Ibgulatico It(bire !bclear Station Washington, DC 20555
TAM.E 1 UNIT 1 HYDROGEN SKIMMER FAH TRAIN SEPARATION TEST MSY-1A MSF-15 Required 10/18 10/25 10/18 10/25 Compartment Flow
(*)
_(_ l}
(*)
(**)
80-1A 121 214 189 916 8G-15 121 671 360 162 SG-10 121 521 258 162 40-1D 121 300 143 771 PER 121 85 241 ACC-1A 4
46 37 ACC-il 4
36 20 ACC-1C 24 65 86 42 ACC-1D 24 43 36 70 Inc. Rs.
15 138 107 Rx. Hd.
172 44 86
- 3. Tan Rs.
29 71 68 47 71 51 57 W. Fan Rs.
_29 _
143 146 Reverse Flow Total ran Tiow 3_307 3387 3212 3327 and are given The above flows were measured per TT/1/A/9100/292 in SCFM.
aas-found" flow data, performed with suction isolat.'n for the operating fan open; idle fan suction isolation caused.
(*)
(") - train separation flow test, performed with BOTH suction isolation valves open.
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P. W. Roberson HP Engineer, Performance f11endvx.dw4.vxflo2.ut.102508
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