ML19326B401
| ML19326B401 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 08/21/1974 |
| From: | Cavanaugh W, Phillips J, Rueter D ARKANSAS POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML19326B399 | List: |
| References | |
| NUDOCS 8004150767 | |
| Download: ML19326B401 (3) | |
Text
~
.?
- p.,
k.)
1.
Abnormal Occurrence Report No.
50-313/74-7
- 2. ' Report Date:
'8-19-74 3.
Occurrence Date:
8-12-74 4.
Facility:
Arkansas Nuclear One-Unit 1 5.
Identification of Occurrence:
Calibration procedural problem o:' the RC flow input to the RPS power / imbalance / flow trip reportable under Technical Specification 1.8.7.
6.
Conditions Prior to Occurrence:
Steady-State Power Reactor Power 0
MWth
~
Hot Standby Net. Output 0
MWe Cold Shutdown Percent of Full Power 0
t Refueling Shutdown Routine Startup Operation _
Routine Shutdown
~-
Operation i
~
Load Changes During Routine Power Operation Other (Specify) x Z ro Power Physics Testing following initial criticality.
5 7.
Description of Occurrence:
i A miscalibration of the RC flow 1'nput to the RPS power imbalance / flow trip was identified on the Duke Power Oconee 1 projec by the Babcock 6 Wilcox Company. This triggered a generic investigation and the evalua-tion which identified the design deficiency which caused the calibration
~
procedural problem.
The trip setting was based on a design flow of 131.3 x 106 lbm/hr; however, maximum flow has been determined to be approximately 136.4 x 106 lbm/hr which resulted in an upward shift of the power imbalance bistable
.setpoint.
f
(, -
8oo415o767 July S, 1974-NSP-10, Rev. O Page 1 of 3 w-
t v:
-Abnormal Occurrence Report No.
50-313/74-7 Sheet 2 8.
Designation of Apparent Cause of Occurrence:
Design y
Procedure x
Manufacture Unusual Service Condition Including i
Installation /
Environmental Construction Component Failurc Operator Other (Specify)
The calibration procedures for the reactor coolant flow instrumentation
'and RPS power / imbalance / flow channel did not specifically state the
-reactor coolant flow rate basis (design or actual flow) or the reactor coolant density conditions that should be used due to a design deficiency.
9.
Analysis of Occurrence;
,_s With the RPS flow channels miscalibrated, the ability of the RPS to
~
protect against central fuel melting caused by core axial imbalance could have been compromised. However, for the excessive imbalance condition to exist previous misoperation of the control rods would have to occur. Since the automatic reactor trip on high flux was set at 0.5%
of full power for the Zero Power Physics testing, no safety implications were involved.
5 i !
10.
Corrective Action:
Appropriate procedures have been revised to correct the calibration
-. i
- )
error and the bistables have been recalibraced.
O July 5, 1974 NSP-1D, Rev. O Page 2 of 3
_s,.
?
p,..
U Abnormal Occurrence Report No.
50-313/74-7 Sheet 3
- 11. Failure Data:
'Ihere have been no other occurrences of this type. No equipment mal-function was involved.
12.
Reviews and Approvals:
Reviewed and Approved by: Plant Safety Committee Yes No ( )
Plant Superintendent Yes (
No ( )
Reference:
T(AJ $ A/fh_ Date: h [6 7'[
4 Reviewed by:
~
Date: _[//
[
' ~ Licensing supdrvisor Approved byi_
,?/ y /
- 7. tjI f- )$$-N is Date:
'~~
a5 t 'Re' vie amDmttee e
/
Approved by:
m Date:
70 7
/,1 nager of Nuclear Serv Approved by:yfr///j/ffAn-t'[
Date:
' S$~~N
/ 'D'irec' tor'of'Po'we'r ' roduction '-
P I!?/!77-Approved by:
' /
. /'
m Date:
Senior Vice P/esident l
l D'
k_
~
July 5, 1974 NSP-10, Rev. O Page 3 of 3
.. _.