ML20207H998
| ML20207H998 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 12/23/1986 |
| From: | Rice P GEORGIA POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-86 GN-1250, NUDOCS 8701080248 | |
| Download: ML20207H998 (4) | |
Text
c,wn e-com PJ;t Oftce Box 282 C #7:o?;; L ~ n 404 724 E M 1. E <
GG 0EC 29 Pl?. : 37 Georgia Power P. D. Rice
/to Presdei
- wa e meet December 23, 1986 United States Nuclear Regulatory Commission Region II, Suite 2900 File:
X7BG03-M133 101 Marietta Street, Northwest Log:
GN-1250 Atlanta, Georgia 30323
Reference:
Vogtle Electric Generating Plant-Units 1 & 2; 50-424, 50-425; B0P/ESFAS Channel Voltage Attention:
Mr. J. Nelson Grace On November 26, 1986, Mr.
R.
E.
Folker, Vogtle Project Quality Assurance Engineer, informed Mr. E. F. Christnot of the USNRC Region II of a potentially reportable condition associated with an undetected channel voltage loss within the balance-of-plant / engineered safety features actuation system (B0P/ESFAS).
Georgia Power Company has completed its evaluation and determined that a reportable condition as defined by the reporting criteria of Part 10CFR50.55(e) and Part 10CFR21 does exist.
Based upon NRC guidance in NUREG-0302, Revision 1, and other NRC correspondence, Georgia Power Company is reporting this condition pursuant to the reporting requirements of Part 10CFR50.55(e). A summary of our evaluation is attached.
This response contains no proprietary information and may be placed in the USNRC Public Document Room.
Yours truly,
/
P. D. Rice CWH/PDR/wkl xc:
U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555 H. G. Baker D. R. Altman L. T. Gucwa J. P. O'Reilly J. A. Bailey C. W. Hayes G. F. Head G. Bockhold G. A. McCarley R. E. Conway J. F. D'Amico R. W. McManus R. H. Pinson W. D. Drinkard Sr. Resident (NRC)
- 8. M. Guthrie C. C. Garrett (OPC)
J. E. Joiner (TSLA)
R. A. Thomas D. Feig (GANE)
NORMS 8701080248 861223 PDR ADOCK 05000424 g
y o
EVALUATION OF A P0TENTIALLY REPORTABLE CONDITION B0P/ESFAS. CHANNEL V0LTAGE Initial Report: On November 26, 1986, Mr. R. E. Folker, Vogtle Project Quality Assurance Engineer, informed. Mr.
E.
F. Christnot of the USNRC Region II of a potentially reportable condition associated with an undetected channel voltage loss within the balance-of-plant / engineered safety features actuation system (B0P/ESFAS).
This undetected loss, if conincident with the manual (maintenance / surveillance test) bypass of the remaining channel, could result in the undetected loss of both system actuation trains for either the control room or the fuel handling building HVAC isolation.
This condition was initially identified as a result of the design review conducted to verify conformance of VEGP design with the FSAR.
~ Background Information: The B0P/ESFAS is comprised of two basic systems; control room ventilation isolation (CRI),
and fuel handling building ventilation isolation (FHBI).
The -CRI is actuated to limit doses in the control room to those specified in 10CFR50, APP. A GDC #19 (for radioactivity) and R.G.1.78 (for chlorine).
Isolation is actuated upon detection of either high gaseous ' radioactivity or high chlorine concentration in the air supply to the main control room.
CRI ' is - initiated by the safety injection signal (SIS) in case of a LOCA, or by radiation monitors for other design basis events, i.e.,
rupture of the waste gas decay tank.
Radiation and chlorine sensors are two-channel-oriented, 'and orovide digital actuation signals to the CRI portion of the BOP /ESFAS when preset radiation or chlorine levels are exceeded.
The FHBI is actuated upon detection of high gaseous radioactivity within the fuel handling building (FHB),
or on low FHB interior-to-exterior differential pressure (d/P).
FHBI is actuated to limit offsite dose release to a small fraction of the guidelines of 10CFR100.
Similar to the CRI, the radiation and d/P sensors are two-channel-oriented, and provide digital l
actuation signals to the FHBI portion of the B0P/ESFAS when preset radiation-or d/P levels are exceeded.
The existing VEGP CRI/FHBI design, as modified to address NRC concerns in draft safety evaluation report (SER) open item 57, provides for the manual (maintenance or surveillance test) bypass of a single automatic initiation channel sensor, while maintaining the capability for initiation of both HVAC i
isolation trains from the remaining channel sensor.
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The VEGP design for CRI and FHBI provides for voltage monitoring at the train I
(or equipment actuation) level, but not downstream of the maintenance / isolation L
fuses at the channel (or sensor digital input) level of the actuation system.
Accordingly, fault clearing action by the maintenance / isolation fuses would result in an undetected loss of channel sensor digital input voltage.
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If a manual bypass were to be initiated, on one sensor channel, coincident l
with' an undetected voltage loss to the remaining sensor channel, the result would be the inoperability of both sensor channels and, in turn, the loss of actuation signals to both trains of equipment associated with the l
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bypassed / inoperable channels.
This condition does not meet the requirements of GDC #21 for protection system reliability and testability and, therefore, could accordingly have plant safety implications.
Enineerinc Evaluation: This evaluation was conducted separately for the i
CRI w hi,I due to the differences in their safety design basis, i.e., control habitat :iity versus prevention of infiltration of contaminated air.
1.
Impact of undetected CRI channel voltage failure:
A.
During normal plant operational modes with no CRI radiation or chlorine channels manually bypassed, actuation capability would exist for both trains of CRI from the remaining operable (radiation or chlorine) channels and no safety impact would exist as a result of the described condition.
8.
During operational modes with one radiation or one chlorine channel manually bypassed for maintenance or surveillance testing, the effect on control room habitability and plant safety is analyzed as follows:
(a) Loss of both radiation channels would prevent CRI initiation and could lead to doses in excess of those specified in GDC
- 19 for the control room.
(b) Loss of both chlorine channels would prevent CRI ini1iiation and could result in chlorine levels in the control room to be in excess of those specified in R. G.1.78.
2.
Impact of undetected FHBI channel voltage failure:
A.
During normal plant operational modes with no FHBI radiation or d/P channels manually bypassed, actuation capability would exist for both trains of FHBI from the remaining operable channels and no safety impact would exist as a result of the described condition.
B.
During operational modes with either one radiation or one d/P channel manually bypassed, the effect on plant safety is analyzed as follows:
(a) Loss of automatic FHBI from radiation detectors:
i The VEGP accident analysis performed by Westinghouse to evaluate offsite dose release as a result of a fuel handling accident with an inoperable FHB filtration system concluded that releases as a result of this condition amount to a small fraction of 10CFR100 guidelines.
It is, therefore, concluded that this condition would not adversely impact plant safety.
(b) Loss of automatic FHBI from d/P sensors:
1 Since no credit was taken for the FHB d/P sensor channels in the VEGP accident analysis, it is concluded that this condition would not adversely impact plant safety.
j Evaluation of Quality Assurance Program Breakdown: A broadness review for i
f
~
implementation of the testability provisions of GDC #21 was performed, and it was concluded that the described condition is limited to the one-out-of-two channel coincidence logic for the CRI and FHBI systems which comprise the BOP /ESFAS.
Due to the uniqueness of this design detail, and its limited application, a quality assurance review concluded that the identified condition is an isolated' case and as such does not represent a breakdown in the Bechtel quality assurance program.
==
Conclusion:==
Based on the above evaluation, the described concern could have created an ur, analyzed condition by preventing control room ventilation initiation.
Therefore, Georgia Power Company has concluded that a reportable condition as defined by the reporting criteria of Part 10CFR50.55(e) and 10CFR21 does exist, since the plant safety could have been adversiy impacted had this condition gone uncorrected.
Based on guidance in NUREG-0302, Revision 1,
concerning duplicate reporting of an event, Geor Power Company is reporting this event per the criteria of Part 10CFR50.55(gia e).
Corrective Action:
Corrective action has been taken to replace the existing CRI/FHBI maintenance / isolation fuses with copper bus bars.
This will allow 7
for existing control room annunciation, which detects (vital ac power) channel voltage loss (due to distribution panel power loss or branch circuit breaker overcurrent trip), to be extended to provide voltage loss detection for the CRI/FHBI channels.
l The modified design retains the overcurrent protection for CRI/FHBI circuitry, l
as a function of the existing dedicated (one per channel)' distribution panel breakers, while the replacement bus bars, which are installed in existing l
CRI/FHBI fuseblocks, retain the original individual channel maintenance / isolation design intent.
1 For Unit 1 Change Control Package (CCP) B10312E has been issued for implementation of the fuse replacement prior to fuel load.
For Unit 2,
replacement of these same fuses within panel 21620Q5ESF will be covered by FECO number J-49-B, which is being tracked by PCW action item #281281.
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