05000255/LER-2007-004

LER-2007-004,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2552007004R00 - NRC Website

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) Palisades Nuclear Plant 05000-255 2007 -- 004 -- 00

EVENT DESCRIPTION

In the period between April 25, 2006, and April 30, 2006, maintenance was performed on a valve that necessitated the isolation of shutdown cooling heat exchanger (SDCHX) [HX;BP] E-60B to facilitate the work. At the time, the plant was initially in Mode 6, with Technical Specification (TS) Limiting Condition For Operation (LCO) 3.9.5, "Shutdown Cooling (SDC) and Coolant Circulation - Low Water Level," being applicable. Later in the period, Mode 5 was entered with TS LCO 3.4.8, "PCS Loops — Mode 5, Loops Not Filled," being applicable. Each TS LCO required two SDC trains to be operable.

Isolating one SDCHX was considered to have no effect on the requirement to maintain two operable SDC trains. The two SDCHXs were considered to operate as a single heat exchanger comprised of two partial capacity units. A single SDCHX was allowed to be credited to both operable SDC trains, provided that sufficient heat removal capacity could be obtained with one SDCHX.

Subsequently, on March 5, 2007, it was determined that the practice of simultaneously crediting a single SDCHX to both operable SDC trains was not supported by the plant licensing bases, and that a distinct SDCHX is required for each operable SDC train. Therefore, during the time SDCHX E-60B was isolated in April 2006, one train of SDC was inoperable when two trains were required, and action to immediately restore the inoperable SDC train to operable status in accordance with TS 3.9.5 Condition A and TS 3.4.8 Condition A was not taken.

This occurrence is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.

CAUSE OF THE EVENT

The occurrence resulted from a long-standing interpretation of Custom Technical Specifications, Improved Technical Specifications and the plant's design and licensing bases, which led to the belief that it was permissible to credit one SDCHX to either or both SDC trains if sufficient heat removal capacity existed.

CORRECTIVE ACTIONS

Procedures and design documents will be revised to clarify that a distinct SDCHX is required for each operable SDC train.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Palisades Nuclear Plant 05000-255 2007 -- 004 -- 00

SAFETY SIGNIFICANCE

The safety significance of this occurrence is considered to be minimal. The one operating SDCHX was providing sufficient heat removal capacity throughout the period, requiring no active response to fulfill its safety function in either SDC train.

PREVIOUS SIMILAR EVENTS

None