05000387/LER-2004-004
| Susquehanna Steam Electric Station - Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material |
| 3872004004R00 - NRC Website | |
EVENT DESCRIPTION
On 8/20/2004, while performing a surveillance on the Railroad Access Shaft Radiation Monitors (EIIS Code:
IL), Instrumentation & Control (I&C) technicians (Utility, Non-Licensed) discovered that the Secondary Containment Zone III isolation relays (EIIS Code: JM) of both process radiation monitors in the Railroad Access Shaft were disabled. Investigation determined that the instrumentation trip outputs had been bypassed on 7/16/2004 through inappropriate jumper installation. I&C technicians tasked to defeat the local audible alarm on a separate area radiation monitor mistakenly executed steps of a plant procedure that also defeated the trip outputs of the two process radiation monitors in question. This discovery was significant because two Spent Fuel Storage Casks (EIIS Code: DF) containing irradiated fuel had been lowered from the Refueling Floor during this period of time (8/2/2004 and 8/16/2004). Plant Technical Specifications (TS) 3.3.6.2 and 3.3.7.1 require the Railroad Access Shaft radiation monitors to be operable during movement of irradiated fuel assemblies within the Railroad Access Shaft. Because actual transfer times for both lifts were less than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, TS Required Action completion times were not exceeded. In the event of an actual radioactive material release, the disabled radiation monitors would not have, however, initiated automatic re-alignment of the Reactor Building Zone III Ventilation System (EIIS Code: VA), automatic start of the Standby Gas Treatment System (SGTS; EIIS Code: BH) and automatic start of the Control Room Emergency Outside Air Supply System (CREOASS; EIIS Code: VI). The inability of these systems to respond to radiological conditions in the Railroad Access Shaft constitutes a condition that could have prevented the fulfillment of safety functions needed to control the release of radioactive material and is reportable per 10 CFR 50.73(a)(2)(v)(C). Actual radiological conditions observed in the Railroad Shaft during movement of the casks did not approach levels necessary for system actuation. All other Reactor Building ventilation instrumentation capable of actuating these systems was operable as required by TS. The jumpers that defeated the actuation capability of the Railroad Access Shaft Process Radiation Monitors were removed on 8/20/2004. No radioactive releases resulted from this event.
CAUSE OF EVENT
Two root causes have been identified for this event:
- Less-Than-Adequate Work Practices — Bypass of the process radiation monitor trip functions was outside the scope and instructions of the work plan. Neither a pre-job walkdown nor a supervised pre job briefing was conducted.
- Less-Than-Adequate Procedural Direction — The controlling procedure assumes that the local alarm horn on the area radiation monitor must be disabled during movement of the Spent Fuel Cask and incorporates a prerequisite to confirm task completion. This prerequisite is not confirmed by the work group that performs the task but by an operator (Utility, Licensed) who verifies work completion through status control logs.
When work was performed beyond the intended work scope, the occurrence was not adequately captured in the status control log. Further, the need to bypass the local alarm is suspect as observations made during actual cask movement suggest that radiation levels do not approach the area radiation monitor alarm setpoint.
ANALYSIS / SAFETY SIGNIFICANCE
This event was determined to be reportable under 10 CFR 50.73(a)(2)(v)(C) in that safety functions needed to control the release of radioactive material would not have functioned automatically in response to radiological conditions in the Railroad Access Shaft.
Actual Safety Significance: Automatic isolation of the Railroad Access Shaft would not have occurred in response to radiation conditions in the shaft. The output trip signals of two radiation monitors were defeated during a plant evolution requiring their presence per Technical Specifications. No actual radiological challenge arose during the Spent Fuel Cask movement that necessitated automatic system response.
Potential Safety Significance: Defeating the auto initiation and isolation capability provided by the radiation monitors compromises the protection afforded to the general public in the event of an actual fuel handling accident.
CORRECTIVE ACTIONS
The following corrective actions have been completed:
- Individuals and supervisory personnel involved in this event were coached and counseled. Expectations were reviewed.
The following corrective actions are planned:
- Work standards related to this event will be reaffirmed with affected personnel.
- A maintenance stand-down, emphasizing human performance tools and lessons learned from this event, will be conducted.
- Maintenance workers will complete training on the station's Human Performance Simulator.
The need to bypass the Area Radiation Monitor local alarm will be evaluated. If bypass is deemed necessary during future Dry Fuel Storage Cask transfer efforts, controls will be incorporated into the primary evolution procedure to ensure that the Area Radiation Monitor local alarm is the only function bypassed.
ADDITIONAL INFORMATION
Failed Component Information:
None
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