05000445/LER-2001-002
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4452001002R00 - NRC Website | |
I. DESCRIPTION OF THE REPORTABLE EVENT
A. REPORTABLE EVENT CLASSIFICATION
This Licensee Event Report is submitted to report a condition prohibited by plant's Technical Specification pursuant to the requirements of 10CFR50.73 (a)(2)(i)(B).
B. PLANT OPERATING CONDITIONS PRIOR TO THE EVENT
On March 7, 2001, when this issue was discovered, Comanche Peak Steam Electric Station (CPSES) Unit 1 was in Mode 1, Power Operations, and CPSES Unit 2 was in Mode 1, Power Operations.
C. STATUS OF STRUCTURES, SYSTEM OR COMPONENTS THAT WERE
INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED TO
THE EVENT
There were no other inoperable structures, systems or components that contributed to event.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND
APPROXIMATE TIMES
The Primary Plant Ventilation System (PPVS) serves the areas housing Engineered Safety Features (ESF) equipment as well as the radwaste areas and the fuel handling and storage areas. The PPVS supply consists of eight non-safety related, primary plant supply fans (30,000 scfm each) with individual intake dampers, and shares common discharge ductwork with two non-safety related, ventilation equipment room supply fans. The PPVS exhaust consists of twelve non-ESF filtration units and fans (15,000 scfin each), four ESF filtration units and fans (15,000 scfin each), and two non-safety related, ventilation equipment room exhaust fans. The PPVS is a normally operating system, aligned to bypass the ESF High-Efficiency Particulate Air (HEPA) filters and charcoal adsorbers. During emergency operations, the PPVS non-ESF fans are stopped and ESF fans are started to begin filtration. Upon receipt of the actuating signal, the stream of ventilation air discharges through the ESF filter trains. The demisters remove any entrained water droplets present, to prevent excessive loading of the HEPA filters and charcoal adsorbers.
On March 7, 2001 during a review of the PPVS engineering surveillance test procedures, surveillance testing personnel (utility, non-licensed) noted that PPVS was being tested with the PPVS supply fan pneumatic intake dampers in the "closed" position instead of the "open" position. The dampers are designed to "fail open on loss of instrument air" and, the PPVS has been tested with the dampers in the closed position since unit start-up.
Facility Name (1)
COMANCHE PEAK STEAM ELECTRIC STATION UNIT I
LER Number (6) Year Sequential 3 Revision Number 3 Number O1 M 002 3 00 Docket Page(3) Enclosure to TXX-01080 On March 8, 2001, the test was conducted with the correct line-up i.e., dampers in the open position. Results from the March 8, 2001, were acceptable and no system degradation was noted.
E. METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE OR
PROCEDURAL ERROR
On March 7, 2001 during a review of the PPVS engineering surveillance test procedures, surveillance testing personnel (utility, non-licensed) noted that PPVS was being tested with the PPVS supply fan pneumatic intake dampers in the "closed" position instead of the "open" position. The dampers are designed to "fail open on loss of instrument air" and, the PPVS has been tested with the dampers in the closed position since unit start-up.
II. ANLYSIS OF THE EVENT
A. SAFETY SYSTEMS THAT RESPONDED
Not applicable — there were no safety system responses associated with this event.
B. DURATION OF SAFETY SYSTEM INOPERABILITY
Not applicable — there were no safety systems rendered inoperable due to this event.
C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT
The purpose of negative pressure testing for the primary plant ventilation system is to verify the capabilities of the buildings and their components to maintain a negative pressure in the Auxiliary, Safeguards, and Fuel Buildings. During the post accident mode of operation, the PPVS is designed to maintain a slight negative pressure in the Auxiliary, Fuel and Safeguards buildings, with respect to adjacent areas, to prevent unfiltered leakage. The acceptance criterion of ± 0.05-inch water gauge relative to atmospheric pressure was selected as a reasonable measure of the integrity of the negative pressure boundary. The frequency of 18 months is consistent with the guidance provided in NUREG-0800, Section 6.5.1 and is performed on a staggered test basis.
Facility Name (1)
COMANCHE PEAK STEAM ELECTRIC STATION UNIT I
LER Number (6) Year Sequential � Revision Number � Number � 01 M 002 � 00 Docket Pagc(3) Enclosure to TXX-01080 Based on a review of test results with the PPVS supply fan and non-operating ESF filtration unit pneumatic dampers failed in the "open" position when compared to the historical results with the dampers tested in the "closed" position, the results were similar. Hence, it is reasonable to assume the PPVS system would have functioned as designed to maintain a negative pressure within the building structures and prevent radioactive contaminates from escaping the buildings to the outside atmosphere.
Therefore, it was concluded that this event did not adversely impact the safe operation of CPSES or the health and safety of public.
III. CAUSE OF THE EVENT
In the conservative accident analyses performed at CPSES, instrument air is not assumed to be available post accident. As such, the valves are assumed to fail open. The test configuration in the procedure did not recognize this conservative assumption and tested with the valves closed. Hence, the cause of the subject reportable event was deemed to be less than adequate procedures.
IV. CORRECTIVE ACTIONS
Immediate actions were to perform the test with the dampers in the in the correct position. The applicable procedures will be revised to require the dampers to be in the open position when the test is to be performed.
V. PREVIOUS SIMILAR EVENTS
There have been other previous events which resulted in less than adequate surveillances. However, the causes of those events are sufficiently different than this such that the corrective actions taken for the previous events would have not prevented recurrence.