ML17305A440
| ML17305A440 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 11/30/1989 |
| From: | James M. Levine ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 2-SR-88-009, 2-SR-88-9, NUDOCS 8912130296 | |
| Download: ML17305A440 (8) | |
Text
ACCE1ERATED DISAIIBUTION DEMONSTRON SYSI'EM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION N'3R:8912130296 DOC.DATE: 89/11/30 NOTARIZED: NO DOCKET FACIL:STN-30'-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi 05000529 AUTH.NAME AUTHOR AFFILIATION LEVINE,J.M.
Ar'izona Public Service Co. (formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control 'Desk)
SUBJECT:
Suppl RO 2-SR-88-009 re radiation monitoring unit inoperable for greater than 72 h.
DISTRIBUTION CODE:
IE22D COPIES RECEIVED:LTR
/ ENCL I
SIZE:
TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.
NOTES:Standardized plant.
D 05000529 8
.RECIPIENT ID CODE/NAME PDS L'A CHAN,T INTERNAL: ACRS MICHELSON ACRS WYLIE AEOD/DSP/TPAB DEDRO NRR/DET/EMEB9H3 NRR/DLPQ/LHFB11 NRR/DOEA/OEAB11 NRR/DST/SELB 8D NRR/DST/SPLB8D1 NUDOCS-A'BSTRACT, RES/DSIR/EIB EXTERNAL EGGG WILLIAMSi S LPDR NSIC MAYS,G.
NUDOCS FULL TXT NOTES:
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1 RECIPIENT ID CODE/NAME PD5 PD DAVIS,M.
ACRS MOELLER AEOD/DOA AEOD/ROAB/DSP NRR/DET/ECMB 9H NRR/DET/ESGB 8D, NRR/DLPQ/LPEB10 NRR/DREP/PRPB11 NRR/DST/SICB 7E NRR DST SRXB SE EG FICE 02 RG FILE 01 L ST LOBBY WARD NRC PDR NSIC MURPHY,G.A COPIES LTTR ENCL 1
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II C~
JAMES M. LEVINE VICE PRESIDENT NUCLEAR PRODUCTION Arizona Public Service Company PALO VERDE NUCLEAR GENERATING STATION P.O. BOX 52034
~
PHOENIX. ARIZONA85072-2034 192-00558-JML/TDS/SBJ November 30, 1989 U. S. Nuclear Regulatory Commission NRC Document Control Desk Washington, D.C.
20555
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)
Unit 2 Docket No.
STN 50-529 (License No. NPF-51)
Supplement to Special Report 2-SR-88-009 File:
89-020-404 Attached please find Supplement Number 1 to Special Report 2-SR-88-009 prepared and submitted pursuant to Technical Specifications 3.3.3.8 and 6.9,.2.
This report is submitted to provide updated information from the original report.
'f you have any questions, please contact T.
D. Shriver, Compliance
- Manager, at (602) 393-2521.
Very truly yours, JHL/TDS/SBJ/kj Attachment cc:
W.
F.
Conway J.
B. Hartin T. J. Polich M. J.
Davis A. C.
Gehr (all w/a) 8912130296 891130 PDR ADQCK 05000529 S
PNU
0 0
PALO VERDE NUCLEAR GENERATING STATION Radiation Monitoring Unit Inoperable for Greater Than 72 Hours License No.
NPF-51 Docket No.
STN 50-529 Supplement No.
1 to Special Report 2-SR-88-009 This Special-Report is submitted in accordance with Technical Specifications 3.3.3.8 ACTION 42(b) and 6.9.2 for an event in which the Condenser Vacuum Pump/Gland Seal Exhaust High Range Effluent Monitor (RU-142) and Plant Vent High Range Effluent Monitor (RU-144) were inoperable for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
The 72-hour limit for operability was exceeded at approximately 0700 HST and 0630 HST respectively on December 9,
1988.
At approximately 0630 MST on December 6,
1988, with Palo Verde Unit 2 in Mode 1
(POWER OPERATION) at approximately 100 percent power, the Condenser Vacuum Pump/Gland Seal Exhaust low and high range monitors (RU-141 and RU-142) were declared inoperable to perform corrective maintenance on. the low range monitor.
At approximately 0700 MST on December 6,
1988 the Plant Vent Honitor (RU-143 and RU-144) were also declared inoperable to perform corrective maintenance on the low range monitor.
Both 'low range monitors were exhibiting intermittent spiking; however, this condition did not cause the monitors to be inoperable.
In each case the monitors work as a pair with RU-1'41 and RU-143 as the low
,range monitors and RU-142 and RU-144 as the high range monitors.
Normal configuration consists of the low range monitors operating with the high range monitors in standby.
When the low range monitors reach a predetermined
- setpoint, the high range monitors start and the low range monitor goes to standby.
The high range monitors are provided for tracking radioactive effluents during postulated accident scenarios.
The high range monitors must be declared inoperable when the low range monitors are inoperable.
Pursuant to Technical Specification 3.3.3.8 ACTION 37, the Preplanned Alternate Sampling Program (PASP) was initiated at approximately 0712 MST and 0645 respectively on December 6,
1988.
The PASP continued until the radiation monitors were returned to service.
RU-143 and RU-144 were returned to service at 1117 HST on March 22, 1989.
RU-141 and RU-142 were returned to service at 0935 HST on June 23, 1989.
The term "spiking" as used in this report is defined as an apparent rise in current level which is causing the radiation level to appear to increase although no actual rise in radiation exists.
ANPP has been experiencing these spikes since licensing of the units.
In each previous case, actions. were taken to troubleshoot and correct the problems as they occurred.
Additionally, overall recommendations were made, and plant changes instituted on the basis of the spiking being caused by a grounding problem.
When incorporated into the units, these plant changes have not fully resolved the spiking problem.
On December 6,
- 1988, a decision was made to leave RU-141 and RU-143 inoperable for an extensive testing program to determine the root cause of the spiking.
The testing program was initiated on December 20, 1988.
0
Special Report 2-SR-88-009-01 Page 2
The'low range monitors use beta scintillation detectors to monitor the process and generate an electrical pulse that -is proportional to the particular type of radiation being monitored, i.e. particulate,
- gas, or iodine.
The detector's outer housing is metal and is connected to plant ground by its mounting arrangements.
The detector's preamplifier is referenced to an independent Radiation Monitoring System (RMS) instrument ground bus rather than plant ground.
Due to the potential differences between the detector preamplifiers'ignal ground and the detector's grounded outer housing, parasitic capacitance coupling exists between the preamplifier's signal ground and the detector's grounded outer housing.
Noise on the plant ground is able to couple into the detector's preamplifier through these parasitic capacitance paths.
These stray capacitances provide a feedback path from output to input of the preamplifier.
Thus occasionally noise couples into the preamplifier and forces the preamplifier into oscillation due to the capactitive feedback path.
This can result in the detector generating spurious output pulses of sufficient magnitude that the amp/discriminator circuit in the microcomputer treats them as valid signals resulting in the generation of spurious high readings.
These spurious output pulses will be prevented by eliminating the capacitive feedback path.
This will be accompli, shed by isolating the detectors'ousing from plant ground and connecting it to the preamplifiers'ignal ground.
This eliminates the capacitance feedback path.
This modification has been implemented in Unit 2 on the single detector of.
RU-141 and the three detectors of RU-143 by temporary modification (T-MOD) 82-89-SQ-004 (RU-141) and T-MOD 82-89-SQ-005 (RU-143);
The radiation detectors have not experienced any spiking since completion of the temporary modification.
A plant change request has been initiated to make this a permanent design change.
This modification will be incorporated on Units 1, 2,
and 3 radiation monitors RU-141, RU-143, and RU-145.
Only these radiation monitors are being modified because beta scintillation detectors are significantly more sensitive than the detectors used in other radiation monitors.
This modification is scheduled to be complete by April 1, 1990.
0 J,