ML17265A416
| ML17265A416 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 09/16/1998 |
| From: | Mecredy R ROCHESTER GAS & ELECTRIC CORP. |
| To: | Vissing G NRC (Affiliation Not Assigned), NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TAC-MA0389, TAC-MA389, NUDOCS 9809240042 | |
| Download: ML17265A416 (5) | |
Text
REGULAT KY INFORMATION DISTRIBUTIO YSTEM (RIDS)
/%
ACCESSION NBR:9809240042 DOC.DATE: '98/09/16 NOTARIZED: NO FACIL:50~244 Robert Emmet Ginna Nuclear Plant, Unit 1, Rochester AUTH,.NAME,,
AUTHOR AFFILIATION MECREDY,R.C.
Rochester Gas
& Electric Corp.
RECIP.NAME RECIPIENT AFFILIATION VISSING,G.S.
DOCKET ¹ G
05000244
SUBJECT:
Discusses leak detection sys in support of LBB application of portions of RHR sys at RE Ginna Nuclear Power Plant.
Description of successful leak detection event that occurred on 980819,provided.
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ytNry ROCHESTER GAS ANO ELECTRIC CORPORATION 89EASTAVENVE, ROCHESTER, NY. 146490001 AREA CODE 716-546-2700 ROBERT C. MECREDY Vice President Nvcteor Operations September 16, 1998 U. S. Nuclear Regulatory Commission Document Control Desk Attn:
Guy S. Vissing Project Directorate 1-1 Washington, D.C. 20555
Subject:
Discussion of Leak Detection System in Support of Leak-Before-Break (LBB)
Application of Portions of Residual Heat Removal (RHR) System (TAC No.
MA0389)
R. E. Ginna Nuclear Power Plant Docket No. 50-244
Dear Mr. Vissing:
Qn September 3, 1998 at 10:30 AM, RG8cE and NRC personnel held a telephone conference to discuss NRC concerns on the RGEcE response to the request for additional information (RAI) regarding RG8cE's LBB application ofportions ofRHR system.
The NRC had independently generated critical flaw sizes for the hot leg portion ofthe piping using more conservative 3-R resistance curves and methodology documented in NUREG/CR-6235.
Applying the margins specified in NUREG-1061, Vol. 3, the minimum leakage detection requirement becomes approximately 0.25 gpm. RGBs response to the RAI asserted that this is within the capability ofGinna's leak detection system.
NRC personnel were looking for a level ofconfidence ofthis capability with specific examples ofactual events.
Dr. Fred Mis, from the RG&E Radiation Protection/Chemistry Dept. described a successful leak detection event that occured on August 19, 1998. This event involved R-11, Containment AirParticulate Monitor, which is the most sensitive instrument currently available at Ginna to detect reactor coolant system (RCS) leakage into containment.
R-11 is a Victoreen Beta Scintillator Detector covered with a thin window oftitanium. It consists ofa moving filter and a detector.
Victoreen generated the initial calibration and response curves for R-11 in 1986, when it was installed. The calibration technique involved four radioactive sources, C-14, Tc-99, Cl-36 and Sr/Y-90. These sources were chosen because they allowed verification ofthe linearity ofthe detector for four different energy ranges ofbetas (0.05 MeV, 0.10 MeV, 0.27 MeV, and 0.9MeV respectively).
In 1997, RGkE performed a periodic,,
calibration ofR-11 using Procedure CPI-MON-Rl 1, and the results were consistant with historical values.
9809240042 9809ih PDR ADQCK 05000244 P
QPDR
On August 19, 1998 at 2:30 AM, operations personnel noted a trend upward on R-11 response'(see ). Background readings for R-11 had varied from 90 cpm to 120 cpm, but by 5:30 AM,the count rate has increased and stabilized at 150 to 200 cpm. Analysis ofa containment air sample showed radioisotopes ofthe types Na-24, Mo-99, and I-133, with a total concentration of2.0E-11 uCi/cc. The operators later pinpointed the leak at a vent connection on the Letdown piping with 2" nominal diameter.
The leak was estimated to be from 0.05 - 0.10 gpm. In the past, there have been other instances where R-11 detector has indicated higher count rates and triggered a search using walkdowns or noting liquid inventory changes ofRCS make-up system.
NRC asked why RG&E has more success with our Containment AirParticulate Monitor than other plants. RG&E cited the following possible reasons:
- a. Ginna containment is relatively small, having a volume ofapproximately 970,000 cu ft.
- b. Effective recirculation ofair inside containment.
- c. R-11 is a second generation, improved design detector which was installed in 1986.
Historical background readings for R-11 were attributed to electronics and ambient containment gases. It should be noted that RCS radioactivity consistent with no fuel cladding leakage (clean fuel) was able to trigger an increase ofR-11 count rate to a point where operators were alerted.
Very truly yours, Robert C.
Mecredy'ttachment xc:
Mr. Guy S. Vissing (Mail Stop 14B2)
Project Directorate I-l Division ofReactor Projects MI Once ofNuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King ofPrussia, PA 19406 U.S. NRC Ginna Senior Resident Inspector
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