ML13309A298
| ML13309A298 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/14/1992 |
| From: | Rosenblum R SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9208180173 | |
| Download: ML13309A298 (12) | |
Text
Southern California Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 R. M. ROSENBLUM August 14, 1992 TELEPHONE MANAGER OF (714) 454-4505 NUCLEAR REGULATORY AFFAIRS U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
SUBJECT:
Docket No. 50-206 Neutron Noise Monitoring Criteria for the Reactor Vessel Thermal Shield Monitoring Program San Onofre Nuclear Generating Station, Unit 1 This letter provides the remaining items resulting from the NRC staff's review of the neutron noise monitoring criteria for the San Onofre Nuclear Generating Station Unit 1 (SONGS 1) reactor vessel thermal shield supports.
This information is submitted in response to requests by the NRC staff during telephone conversations on May 22, 1992 and June 9, 1992. This submittal completes our actions with regard to the thermal shield monitoring program for SONGS 1.
Provided as Enclosure 1 is a revised curve of Power Spectral Density (PSD) vs.
Frequency for detector 7B in the neutron monitoring system, based on data taken on September 25, 1991.
The NRC reviewer had identified a concern with an earlier version of this curve. It was subsequently determined that the earlier curve had been plotted using incorrect acceptance criteria. is a current set of neutron noise signal data curves for all eight detectors in the neutron noise monitoring system. Also included in this letter is a chronology of the NRC staff's review of the neutron noise monitoring criteria methodology for SONGS 1.
BACKGROUND We submitted our proposed acceptance criteria for the SONGS 1 reactor vessel thermal shield monitoring program by letter dated September 20, 1991.
The submittal included resolution of the applicable open items identified by the NRC in their December 19, 1990 safety evaluation of the thermal shield support design. The criteria contained in the September 1991 submittal is our current basis for Cycle 11 operation of SONGS 1. Following their review of the criteria, the NRC staff requested that consideration be given to reducing the criteria by 25%.
9208180173 920814 PDR ADOCK 05000206 P
Document Control Desk
-2 CRITERIA CURVES To facilitate discussion of this issue, we provided the NRC reviewer with a set of PSD vs. Frequency curves for all eight detectors based on data taken on September 25, 1991. During a telephone discussion on April 9, 1992, the NRC reviewer identified an area of concern on the curve for detector 7B where a dip occurred near the 10 Hz region. It was later determined, and indicated to the NRC reviewer in a telephone discussion on May 22, 1992, that the dip was attributable to a data transposing error. The error involved inadvertent substitution of a data file from detector 8B in the detector 7B data set, causing an erroneous curve for detector 7B. We have verified that all other curves were plotted correctly. The curve for detector 7B has been replotted using the correct data, and is included as Enclosure 1. The revised plot shows no unusual increase in the neutron noise levels measured by detector 78.
During the May 22, 1992 telephone discussion, the NRC reviewer also requested a more current set of thermal shield neutron noise baseline data envelope curves for all eight detectors. A MacIntosh version of these curves, based on data taken on July 9, 1992, is provided as Enclosure 2. The earlier curves were generated on the personal computer software, Quattro Pro.
NRC REVIEW OF CRITERIA METHODOLOGY During the April 9, 1992 telephone discussion, the NRC also questioned the adequacy of the basis for the forcing function used by Westinghouse in developing the neutron noise monitoring acceptance criteria. This concern was further discussed during the May 22, 1992 telephone discussion. Since the Westinghouse forcing function had been previously reviewed by the NRC for Cycle 10 operation and for startup from the thermal shield repair outage, we committed to provide a chronology of NRC reviews in the May 22, 1992 telephone discussion.
We initially submitted the proposed final acceptance criteria for the reactor vessel thermal shield monitoring program on January 17, 1990. That submittal incorporated improvements to the criteria recommended by the NRC in their November 3, 1989 safety evaluation of the interim acceptance criteria. By letter dated May 11, 1990, the NRC approved the proposed final acceptance criteria being used for Cycle 10 operation.
The NRC also reviewed the thermal shield monitoring program as part of their review of the amendment application for thermal shield support system replacement design submitted on April 20, 1990. A detailed review of the thermal shield support system replacement design was conducted on June 25-27, 1990 and included presentations by Westinghouse and SMC O'Donnell. Amendment No. 140 was issued as a result of these reviews. The amendment requested that we submit revised final acceptance criteria and include additional information related to the development of the criteria. This information was included in our revised acceptance criteria submitted on September 20, 1991. Amendment No. 140 included an extension of the thermal shield monitoring program through Cycle 11.
Document Control Desk
-3 CONCLUSION The existing acceptance criteria for the neutron noise monitoring program are the current basis for Cycle 11 operation of SONGS 1. These criteria and the methodology used to develop the criteria have been reviewed and approved by the NRC with conditions. These conditions have been satisfied in the criteria submitted on September 20, 1991.
The enclosed revised curve for detector 7B alleviates previous concerns with regard to the neutron noise signal data for this detector. The NRC has indicated that the thermal shield neutron noise monitoring issue can be successfully resolved for Cycle 11 operation following submittal of the corrected curve for detector 7B, and that there will be no need to reduce the acceptance criteria by 25%.
If you have any question regarding this matter, or desire additional information, please contact me.
Very truly yours, Enclosures cc:
J. B. Martin, Regional Administrator, NRC Region V George Kalman, NRC Senior Project Manager, San Onofre Unit 1 J. 0. Bradfute, NRC Project Manager, San Onofre Unit 1 C. W. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2&3 aa) a)S W
w 0..
k..
b..
0 (0
0U) 0 0
1 )
U
</
I\\
CO~
O0-0 E
c:
.1 1
-.o 00 w
U U
LU U
(aSd) AT!SUaG IejloedS J9MOd Page 1
of 8
-0 COR (D
Ca eJ CO)
D 0
Z
)
O LL CDD omo uL) 0 0
Z VOO 2
L) 1 Cp C)
DE N
SQa cj)o U)
O C,
xO 0
(0J CO U-L
~
~
L co
)a~!ue Iepd JG a
m a
p
<U 0d o
Page 2 of 8 a)
CU Ca eJ (D
- 0) 00
-d-~
II 00C COD a) a
~.0LL E
LLL (DCO C.2 xnC Q wL nL 00 S S
C/)d A4ISU9 0eDd eo o
Page 3 of 8 0
COm CJ CO CO)
<<m I-1.i.
o-a r--
o o
c o
II (0
0 CV 3L LL N
E 0n au ca U-LL C
a) a)
r-I--
CD c
0 Cm, I
z
-(I)
CO w
(asd) A4!SU9O le4DeodS J~m~d 60-i Page 4 of 8 0
0 0
Q) wa (a
N' Co UQ)
M)U)
U C',
0.L
- 0.
o 0
CO D
0
- j
-j CO COO CCD Cfl'-C'J.-.JC.J CC 00 ZU 05,
.2 2
0 2 (C)
Eg O DED 0
CD Z
CD O
co oU C
~
~
)
0 f
W 0
.C3 m
- 5 0
0 I
I) 0ad
~!~OIeDd
~~
O Page 5 of 8 a
a~
a
- a.
0~ 00 CD) c 0 oo
_V_
- 0) a)
a)
.0 0
-OO 0
-0 0
0D 00 zm Z
ai g2d JQd Page 6 of 8 CJ o
.m
>(1)
CD C)
LDii
< )
a) 0)a
-0.
0-r --
o o
LUL 0
I 0
cmJ OO
- m. IL N
a)(
O E C/ o LL NO
~Oco C)OL >
a)
C. 2 5
a)
.J 6
a)U 0
LL CU CD Z)
U--
(11 o
0 o
0c C/)
Co 0
LO CO.
M)
- 0)
((]Sd) A4!SU90 liloa3dS JBmOd 60-1 Page 7 of 8 C'J C
<LUi O0 LUR a~
a 0O CL000
- 0.
0 r-0 0
<a a)a 0
0 LM 0
~
2u2 C
z71
)N CJ)O~LL C
a x W
0 0.oOO CUg wI (0U
)U
)
)
0 U
U) CZ 0
o U1i (OSd) A!SU90 i8ijo3dS J~mOd 60-1 Page 8 of 8 000 C'j zz
-D e'li c,<
w a) w OO o
O
- 0)
II 0
0
~cnw COOCU L
-O CO)
CO*
C)
U) 0 CD
- 0)
(DC0 E Z"3a.-C CO~ 0
_-C CD I
00 0D 0~N
~
~
i, 0
i) 0 U
CD6 0;
(GSd) A4SU9O lenoedS J~mOd 601