ML20079B927
| ML20079B927 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 06/11/1991 |
| From: | Creel G BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-88-17, TAC-69730, TAC-69731, NUDOCS 9106180194 | |
| Download: ML20079B927 (6) | |
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A B ALTIMORE GAS AND ELECTRIC CHARLES CENTER e P.O. BOX 1475
- BALTIMORE, MARYLAND 21203-1475 GEORGE C CREEL v.cc p come,o NvC L E A R (,d R G
- t aco reso 4 4 ne June 11,1991 U. S. Nuclear Regulatory Commission Washi gton, DC 20555 ATTENTION:
Document Control Desk S U I3J E Q Calvert Cliffs Muclear Power Plant Unit Nos.1 & 2: Docket Nos. 50-317 & 50-318 Generic Letter 88-17," Loss of Decay Heat Removal
l (TAC Nos. 69730 and 69731) l Gentlemen:
In our June 30,1989 response to Generic Letter 881'7, we described our modification plan for Reactor Coolant System (RCS) level monitoring instrumentation. We also described our actions to assess the effectiveness of Shutdowu Cooling (SDC) System instrumentation, and committed to provide an additional response following SDC system testing.
These tests have been completed. The purpose of this letter is to provide you with information on our planned modifications to improve SDC system instrumentation. This information is contained in Enclosure (1). The enclosure also describes our revised plans regarding narrow. range RCS level monitoring. An ultrasonic level transmitter, in lieu of a continuous level probe, will be installed on a RCS hot-leg. All modifications will be completed by the end of the upcoming refueling outages for Unit 1 (spring 1992) and Unit 2 (spring 1993) [ Refueling Outage Nos.10 and 9, respectively).
Should you have any further questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, l
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Docurnent Control Desk June 11,1991 Pagc 2 cc:
D. A. Brune, Esquire J. E. Silberg, Esqts R. A. Capra. NRC D. G. hicDonald, Jr., N RC T. T. hiartin. NRC L E. Nicholson, NRC R. I hfclean. DNR J. II. Walter, PSC
Document Control Desk June 11,1991 Page 3 bec:
J. A.Tiernan/A.J.Slusark ht. J. hf jernicki W. R. Corcoran C. II. Cruse /P. E. Katz R. C. DcYoung R. ht. Douglass/R. F. Ash R. P. licibel/P. N. Pritchet.
C. P. Johnson C. C. Lawrence, Ill/A. R. Thornton R. B. Pond, Ji./S. R. Buxbau..:. Jr.
L D. Russell /R. E. Dentonh. R. Lemons W. A.Thornton/E I. Bauercis G. L Adams A. D. Anuje J. E. Baum P. G. Chabot J. J. Connolly G. L Deter G. J. Falibata L D. Graber D. V. Graf R. C. Johnson (2)
W. J. Lippold B. S. hiontgomery R. E. Nagel R. C. L Olson P. A.Pieringer R. II. Waskey, Jr.
L O. Wenger L S. Larragoite G. Tesfaye B. C. Rudell bf. G. Polak R. L Szoch hf. S. Kostelnik P. K. Doran D. Weaver, h1PR Associates Dr. B. Ilannah, IIAI I ile 60 05.02 l
June 11,1991 ENCLOSUltE (1)
CALVEllT CLIFFS NUCLEAll POWER l'LANT FOLLOW UP_I_t1SI'ONSE TO GENEltlC L1-lTEll 8817 in our June 30,1989 response to Generic Letter 88-17, we described planned modiGeations to our Reactor Coolant System (RCS) level monitoring instrumentation [ Reference (a)].
We also described our actions to assess the effectiveness of Shutdown: Cooling (SDC) system instrumentation, and committed to provide an additional response following bDC system testing. The following de,cribes planned modifications to improve SDC system instrumentation. and revised plans for the narrow-range RCS level instrument.
SI)C INSTRUMENTATION:
Shutdown Cooling system tests were performed during the recent Unit 2 refueling outage. The test objectives were to:
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Evaluate Low Pressure Safety Injection (LPSI) pump performance at reduced RCS inventory, and Determine the best parameters for monitoring SDC system performance.
Test instrumentition was used to monitor LPSI pump flow, suction and discharge pressure, motor current, vibration. and suction piping acoustics. Each pump was tested at various RCS levels from the top of the hot-leg down to 15 inches from the bottom of the hot-leg. At each level, Dow was incrementally increased from 500 gpm to 4000 gpm.
The test veriGed that our existing procedure controls for RCS level and SDC system now are adequate to avoid system conditions leading to loss of SDC due to vortexing. However, some evidence of air entrainment was experienced at the Technical SpeciGeation required flow rate of 3000 gpm at mid loop. Therefoce, following approval of our License Amendment request regarding SDC minimum flow requirements (Reference b), sufficient margin will be available to prevent air ingestion. This is consistent with Generic Letter 88-17, Section 3.5.2 of Enclosure 2.
Based on evaluation of the test data, the following approaches will be employed to monitor SDC t
l system performance and detect the onset of vortexing during reduced reactor coolant level conditions:
1.
RCS level and SDC system now will be monitored. Alarms for both the allowed limits of level and flow will be ins:alled; 2.
LPSI pump suction pressure wil! be monitt red, trended, and alarmed; and 3.
Existing Control Room LPSI pump motor current indication will be available to the operator.
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4 Juric 11,1991 JCNCLOSURE (1)
CAlWERT CLIFFS NUCLEAR POWER PIANT FOI. LOW UP RESPONSE TO GENERIC 1,lilTER 8817 i
ne following modifications will be made during the upe; ming refueling outages for Units 1 and 2:
1.
a.
New RCS wide-and narrow-range levei histruments and alarms will be added (discussed below).
b.
Alarm capability will be added to the existing Control Room SDC Dow indication.
2.
Control Room LPS! pump suction preseure indication and trend capability will be added. Currently, only LPSI pump suction pressure alarms exist in the Control Room.
RCS 1.EVEL INSTRUMENTATION:
Ir. our June 30, 1989 letter, we described the planned narrow-and wide-range RCS level instrumentrtion modifications. In lieu of a narrow-range continuous level probe, we will install an ultrasonic level transmitter. For convenience, the following deanbes both the narrow and wide-range RCS level modifications:
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A wide-range levelinstrument will be installed on the same hot-leg tap as our refueling level indicator. The instrument will consist of a stilling well with heated and unheated continuous Resistance Temperature Detector (RTD) probes (see Figure 1). The measurement range will be from the bottom of the hot-leg to the Reactor Vessel Gange. The detector will be referenced to Reactor Vessel IIcad pressure. A gauge glass will be installed in parallel with the stilling well to provide local indication.
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A narrow-range ultrasonic level measurement system will be installed on the bottom of a RCS hot-leg. The range of level indication will be from the top of the hot-leg to approximately rour inches above the bottom of the hot-leg. This diverse and independenti method of monitoring RCS level, as well as the improved accu:acy obtained at this criticr.1 level where vortexing can occur, more than compensate for the limited range ofindication.
Both level detectors will have operator adjustable alarms and at least one will have trend capability.
REFERENCES:
(a)
Letter from Mr. G. C. Creel (BG&E) to Document Control Desk (NRC), Response to Generic Letter 88-17, " Loss of Decay IIcat Removal," dated June 30,1989 (b)
Letter from Mr. G. C. Creel (BG&E) to Document Control Desk (NRC), Request for Amendment to Operating Licenses, dated November 5,1990 1 Consbrent mth the guidance provided in NRC Generic Letter 88-17 for instiument independence.
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RCS Mid-Loop Level Instrumentation Pre!!minary Concept Schematic E5
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3-Inch LevelStandpipe with Continuous Level Probe
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