05000400/LER-2005-004
| Harris Nuclear Plant - Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4002005004R00 - NRC Website | |
I. DESCRIPTION OF EVENT
From the end of Refueling Outage 12 (RFO-12) on November 5, 2004, through March 5, 2005, the plant increased to and operated at 100 percent power. On July 12, 2005 it was recognized that specific guidance for operator manual actions related to the ability to respond to a loss of pressure in the Essential Services Chilled Water System (ESCW) [KM] expansion tank, in the event of a sustained loss of Service Air (SA) [LF], was not sufficiently detailed to ensure operability for the period from November 5, 2004 through March 5, 2005.
During RFO-12, Engineering Change (EC) 51444, was installed to improve plant reliability by replacing active solenoid valves with passive check valves. The purpose of this EC was to ensure that adequate pressure and inventory would be maintained in the ESCW during accident conditions.
This improvement was accomplished by installing new check valves on both the Demineralized Water System (DW) [KC] and SA supply lines to the ESCW expansion tank and extending the class boundary to those valves. The previous solenoid operated (Target Rock) isolation valves were removed from the SA supply lines. EC 51444 allowed the SA system to be in constant communication with the ESCW Expansion tank such that as long as the SA header remained pressurized, the ESCW expansion tank would be pressurized. In the event of an extended loss of SA, EC 51444 added actions to plant procedure APP-ALB-002 to direct plant response on a loss of expansion tank pressure. These actions were to ensure that pressure in the expansion tanks was monitored and action initiated in the event that SA header pressure could not be immediately restored. However, specific guidance on how the ESCW expansion tank pressure was to be maintained was not adequately documented in accordance with IN 97-78.
The manual actions added to APP-ALB-002 did not fully address the considerations identified in Information Notice (IN) 97-78, "Crediting of Operator Actions in Place of Automatic Actions and Modifications of Operator Actions, Including Response Times." The 10 CFR 50.59 evaluation did not adequately address the guidance provided in Nuclear Energy Institute (NEI) 96-07 "Guidelines for 10 CFR 50.59 Implementation." When temporary modification EC 60425 was approved on March 5, 2005 to address the premature failure of the SA check valves installed by EC 51444, the considerations of IN 97-78 and NEI 96-07 were adequately addressed.
Although both trains of ESCW were fully functional, both trains of ESCW are considered to have been inoperable from the implementation of EC 51444 at the end of RFO 12 on November 5, 2004, until the approval of temporary modification EC 60425 on March 5, 2005. This time is longer than the time allowed by Technical Specification (TS) 3.7.13.
The instrumentation and controls for the ESCW System are designed for automatic operation after manual starting of the pumps and water chillers. Makeup water level in the system is automatically controlled. The pressure reducing regulator valves in the SA and DW connections at the expansion tank normally regulate the ESCW System and internal pressure. Neither the SA nor the DW supply lines to the ESCW expansion tank are safety related.
Energy Industry Identification System (EllS) codes are identified in the text within brackets [ ].
II. CAUSE OF EVENT
The root cause of this event was that site personnel failed to recognize that the plant had inadvertently introduced reliance on an operator manual action to ensure operability, in the event of a sustained loss of SA, without fully documenting actions taken to meet the guidance of IN 97-78 and NEI 96-07.
III. SAFETY SIGNIFICANCE
There were no actual significant safety consequences as result of this condition. Both ESCW trains were functional during this period of time, except for periods of maintenance when the train was under clearance or identified by operators as unavailable. There were no losses of SA during the period from November 5, 2005 to March 5, 2005 which would have required implementation of the manual actions.
For potential safety significance, the ESCW System is composed of two redundant safety trains. It is assumed that the non-safety portion of the system would be unavailable resulting in a loss of SA to the ESCW expansion tanks. It is possible that over a period of time the expansion tanks could become depressurized and void formation could occur. However, based on the instructions provided in APP-ALB-002 by EC 51444, on a SA Low Pressure alarm, Operations would monitor ESCW surge tank pressure and initiate actions as necessary to keep surge pressures at or above 3 psig. While the actions were not specific, it is reasonable to conclude that the potential safety significance would be minimized by the following: the time delay in the decrease in expansion tank pressure is significant, and additional resources would be called in to assist in recovery of SA or to respond to an ESCW trouble alarm.
This condition is reportable as a condition prohibited by Technical Specifications pursuant to 10 CFR 50.73(a)(2)(i)(B) since the condition existed for a time longer than its allowed outage time. This condition was neither recognized nor discovered until after the allowed outage time for this condition had elapsed, and the condition had already been rectified by the approval of temporary modification EC 60425 on March, 5 2005.
IV. CORRECTIVE ACTIONS
As immediate corrective action, the temporary modification, which adequately addressed the required manual actions to repressurize the tank in the event of an extended loss of SA pressure, was approved on March 5, 2005. The corrective action to prevent recurrence will be to provide 10 CFR 50.59 refresher training specifically covering the guidance for operator manual actions to the Harris Engineering Support Services 10 CFR 50.59 qualified personnel and to those pursuing near term qualification. A second corrective action to prevent recurrence will be to provide Real Time Training to the Harris Engineering Support Services personnel on considerations when adding or revising an operator manual action. Additionally, procedure EGR-NGGC-0005 "Engineering Change" will be revised to include requirements for operator manual actions.
V. PREVIOUS SIMILAR EVENTS
No previous HNP events or conditions are known within the last three years related to declaring a system inoperable for a period longer than allowed by Technical Specification due to inadequate evaluation and implementation of operator manual actions.