ML20086F720
| ML20086F720 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 01/30/1975 |
| From: | Utley E CAROLINA POWER & LIGHT CO. |
| To: | Knuth D, Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II), US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20086F722 | List: |
| References | |
| AO-50-261-75-2, NG-75-140, NUDOCS 8401040618 | |
| Download: ML20086F720 (3) | |
Text
i l
p e
U qq
\\
U #L~10 50--
Carolina Power & Light Company January 30, 1975 File: NG-3513 (R)
Serial: NG-75-140 Mr. Normcn C. Moseley, Director Directorate of Regulatory Operations
^
U. S. Nuclear Regulatory Commission g
Region II, Suite 818 l
I 230 Peachtree Street, N.W.
Atlanta, Georgia 30303 g,.
h,-
Mr. Donald Knuth, Director t
y
/ / i',i if Directorate of kegulatory Operations Office of Regulation U. S. Nucicar Regulatory Commission Washington, D. C.
20545
Dear Sirs:
i II.-B. -ROBI SON NNIT NO. 2 LICENSE NO. DPR-23 PRESSURIZER I;EVEL C'llANNEL NUMBER II Inaccordancewith65.2.aoftheTechnicalSpecifications
~
for 11. B. Robinson Unit No. 2, the attached Abnormal Occurrence Report l
is submitted for your information. This report fulfills the requirement l
for a written report within ten days of an Abnormal Occurrence and is in accordance with the format set forth in Regulatory Guideline 1.16, Revision 1.
Yours ves
- truly,
.-f, M&
WL I
E. E. Uticy Vice-President Bulk Power Supply JBM: TAW:mvp Attachment cc: Messrs. N. B.,Bessac W. E. Graham P. W. Ilowc J. B. McGirt D. B. Waters 8401040610 750130 PDR ADOCK 05000261 S
PDR 336 Fayettevine Street. P. O Gos 1551 Ralenjh. N C 2M02
_m
-1 m
~
O O
ABNORMAL OCCURRENCE REPORT 1.
Report No.
50-261/75-2 23.
Report Date January 28, 1975 2b.
Occurrence Date January 20, 1975 3.
Facility H. B. Robinson Unit No. 2 Hartsville, South Carolina 29550 4.
Identification of Occurrence Failure of pressurizer icvel channel II to generate a reactor trip signal or a safety injection signal upon insertion of simulated high and low levels.
5.
Conditions Prior to Occurrence The reactor was at 100% power with all parameters normal. A periodic test, P.T. 5.3 " Pressurizer Water Level Protection Channel Testing -
Protection Channel Set II," was in progress.
I 6.
Description of Occurrence p
u.
At 0,950 on January 20, 1975'," comparator LC-460A was removed from service for the performance of.P.T..5.3.
In the process of conducting the P.T.,
l an input signal for high pressurizer Icvel was inserted. The test signal of 4.64 volts did not result in a high level trip function. The test l
signal was increased to 5 volts, with no trip. A low level safety injection signal equivalent to 1.24 volts was then injected into the comparator with no safety injection function resulting. The test signal was then reduced to 1 volt with no response. Therefore, at 0956 it was determined that comparator LC460A had malfunctioned. The comparator was immediately removed and a replacement comparator calibrated and installed. Channel II was returned to service at 1050 hours0.0122 days <br />0.292 hours <br />0.00174 weeks <br />3.99525e-4 months <br /> January 20, 1975.
7.
Designation of the Apparent Cause of the Occurrence Bench testing of the defective comparator resulted in satisfactory operation.
However, reinsertion of the comparator into the control loop on January 23, 1975, resulted in a test failure.
Investigation revealed that filter capacitor C.3 had malfunctioned causing the +15 D.C. power supply to see an increased noise level.
This noisc lev'el combined with loop noise of this channel caused the comparator to be inoperative in the loop but functioned on the test bench.
A new 50 pf filter capacitor was placed in this comparator on January 23, 1975.
W
O O
4 i
l,
The comparator was then checked in the loop satisfactorily.
8.
Analysis of Occurrence i
l To obtain a reactor trip from high pressurizer 1cvel, inputs from two of the three channels are required.
Per tabic 3.5-2 of the Technical Specifications the minimum operable channels for this 4
i function is two with one degree of redundancy required. These conditions were met from the time the periodic test was commenced in that comparators 459A and 461A were functional, and the bistables associated with LC460A (BS 460-Al and BS 460-A2 - high level reactor trip and low level safety injection respectively) were placed in a tripped mode prior to testing the channel. Tripping of the bistables provided one of the two required inputs to initiate a reactor trip and thus, by definition, redundancy and operability requirements were met.
To obtain a safety injection signal due to low pressurizer level coincident with low pressurizer pressure only one of three channels is required. Table 3.5-3 of the Technical Specifications requires a minimum of two operable channels and one degree of redundancy for this function.
The operability of comparators. 459A and 461A in combination with the Lc460A tripped bistable-raet' the,se requirements.
~..
Therefore from the initiation of the periodic test, prior to any knowledge of the malfunctioned comparator, until completion of repairs all minimum channel availabilities were met and no limiting condition of operation requiring operator action existed.
Likewise there were no injuries, exposures, releases of radioactive materials, or other potential threats to the public health and safety involved with this occurrence.
1 I
9.
Corrective Action A new comparator was calibrated and placed in service at 1050 hours0.0122 days <br />0.292 hours <br />0.00174 weeks <br />3.99525e-4 months <br />, January 20, 1975.
The faulty comparator was bench tested satisfactorily, but reinsertion in its control loop again produced failure. The comparator was again removed from the loop and a 50 yf filter capacitor replaced.
Reinsertion in the loop resulted in satisfactory operation. The replacement comparator was placed back into normal service, and the repaired comparator will be rechecked and placed back in stock.
10.
Failure Dat_a A previous occurrence, October 3,1974, resulted from failure of a 50 pf capacitor. This was reported per abnormal occurrence report 74-22 and related the failure of overtemperature and overpower comparator TC-412C.
t
..m.
~,_, _ -... -. -
~
.m
-