05000388/LER-2006-001
| Susquehanna Steam Electric Station - Unit 2 | |
| Event date: | 01-25-2006 |
|---|---|
| Report date: | 03-23-2006 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3882006001R00 - NRC Website | |
EVENT DESCRIPTION
On January 25, 2006 with Unit 2 in Mode 1 at 100% power, concerns were raised about the potential for interaction between an installed scaffold and Unit 2 'D' Residual Heat Removal (RHR; EIIS Code: BO) pump instrument tubing. The tubing feeds two Automatic Depressurization System (ADS; EIIS Code: B) pressure switches that provide an ADS initiation permissive signal when the 2 'D' RHR pump is running. Analysis has conservatively concluded that scaffold movement during a dynamic event would have challenged the function of the ADS pressure switches. Accordingly, it was assumed that the ADS pressure switches were inoperable from the time of scaffold installation on February 1, 2005 to the time the scaffold was removed on January 27, 2006. This duration exceeds the Technical Specification 3.3.5.1 allowable completion times for inoperable Emergency Core Cooling System (ECCS; EIIS Code: B) Instrumentation and is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as a Condition Prohibited by Technical Specifications.
CAUSE OF EVENT
Two root causes have been identified for this event:
Less than adequate scaffold program design — PPL Susquehanna's scaffold control program contains elements, such as procedural inconsistencies and insufficient training, that inhibit flawless execution.
Less than adequate reinforcement by supervision and management of administrative requirements — Supervisors and Managers of scaffold installation and inspection personnel were not reinforcing the need for workers to perform scaffold installation per procedural requirements.
ANALYSIS / SAFETY SIGNIFICANCE
Function of the Unit 2 'D' RHR pump discharge (ADS permissive) pressure switches was conservatively considered suspect because of the scaffolding in the RHR pump room. Loss of these switches removed one "pump running" permissive signal from the ADS initiation logic. However, this logic incorporates multiple redundancies (any RHR pump or Core Spray loop (CS; EIIS Code: BM) in either division) that are capable of producing the pump running permissive for ADS initiation. As such, ADS would have initiated, if called upon to do so, even if a seismic event would have rendered the subject switches inoperable. The scaffold did not pose any operability concerns for the RHR system itself.
Weak programmatic controls regarding the potential impact of scaffolding on safety-related equipment did create the potential to render multiple safety-related systems, structures, and components inoperable concurrently.
CORRECTIVE ACTIONS
The following cDrrective actions have been completed:
- A site-wide inspection of accessible areas was initiated to identify, inspect, rework or remove scaffolding at Susquehanna.
Over 100 scaffold installations were reviewed. While numerous non-compliances with scaffold procedure requirements were identified, only the situation identified in this report rendered safety-related equipment inoperable.
- The applicable procedure was revised to provide clearer guidance regarding long-term scaffolding installatiol and inspection requirements.
- Stand-down meetings were conducted and written communications were issued to reiterate expectations regarding use of the scaffold procedure.
- Efforts were undertaken to ensure scaffold installers and inspectors were properly trained and qualified to perform such cuties.
The following corrective actions are planned:
- A cross-discipline team will evaluate and revise Susquehanna's scaffold control program.
- Training will be completed for designated scaffolding installation and inspection personnel on the revised programmatic requirements of Susquehanna's scaffold control program.
- A Maintenance management, in-plant observation process will be implemented to reinforce administrative requirements, provide coaching, and to document and trend observations.
ADDITIONAL INFORMATION
None