05000400/LER-2001-004

LER-2001-004,

Docket Number
Event date:
Report date:
4002001004R00 - NRC Website

SUMMARY:

On December 25, 2001 at 0503, with the Harris Nuclear Plant (HNP) shutdown for Refueling Outage 10 (RF010), the plant entered Mode 4 from Mode 3 without satisfying Technical Specification (TS) 3.4.1.3. The TS requires at least two reactor cooling loops operable with one of these loops in operation. Two residual heat removal loops were operable but not in operation and no reactor coolant loops were operable since all steam generator levels indicated below the TS Mode 4 operability limit of 74% wide range. The TS 3.4.1.3 was revised as part of the Steam Generator (SG) replacement in RF010. The requirement to maintain Wide Range (WR) SG level greater than or equal to 74% in Mode 4 was added as a result of the license amendment to replace SGs.

Previously, SG level was monitored using narrow range level with an operability limit of 10% narrow range. Therefore, this event was the initial failure to meet this operability requirement.

With no RHR loops in operation, Technical Specification 3.4.1.3 requires at least one operable reactor coolant loop and its associated operable steam generator to be in operation. Surveillance Requirement 4.4.1.3.2 requires wide range (WR) level to be greater than 74% in order to have the steam generator considered OPERABLE. The TS 3.4.1.3 Action statement requires immediate initiation of corrective action to return the required loops to OPERABLE status.

Contrary to these requirements, during this event, the plant entered Mode 4 from Mode 3 with no operating reactor coolant loops operable, since all steam generator levels were less than 74%. Both RHR loops were operable but neither was operating. This condition was unrecognized, and uncorrected, for about four hours after entry into Mode 4.

A root cause investigation of the event identified the root cause to be a failure to accurately read and apply the surveillance criteria given in the surveillance procedure.

This failure was caused by habit intrusion among the main control room staff. Based on their pre-refueling outage 10(RF010) experience, no one in the control room expected that SG water inventory would have to be increased above the normal operating band in order to maintain SG operability in going from Mode 3 to Mode 4.

Event Summary:

The plant entered Mode 4 from Mode 3 without satisfying Technical Specification 3.4.1.3 that requires at least two reactor coolant loops operable with one of these in operation.

Two RHR loops were operable but not in operation and no reactor coolant loops were operable since all steam generator levels indicated below the Technical Specification Mode 4 operability limit of 74% wide range.

Prior to Mode 4 entry, plant procedure GP-007 requires the operator to "verify Mode 4 portion of OST-1022 is performed SAT." The unit senior control operator (USCO) directed the reactor operator (RO) to check the Mode 4 surveillance requirements in parallel with performance the routine surveillance requirements for Mode 3. The RO misinterpreted the SG level criteria for Mode 4 and reported that reactor coolant loop surveillance requirements for Mode 4 were satisfied. Additionally, GP-007 requires completion of the Minimum Equipment List (MEL) to ensure the status of required components is known. The GP-007 MEL does not contain specific SG operability criteria, so when the Shift Supervisor - Operations (SSO) completed the MEL, he assumed the reactor coolant loop operability and operation were requirements for Mode 4 were met since no related equipment had been identified in Mode 3 as being Inoperable.

FACILITY NAME (1) DOCKET LER NUMBER (6) PAGE (3) Harris Nuclear Plant, Unit 1 05000 0 YEAR SEQUENTIAL NUMBER REVISION OF 0 3 mi WRFC?

II. CAUSE OF EVENT

that SG water inventory would have to be in order to maintain operability in going consequences from this event. The intent adequate reactor coolant loops were in surveillance was not adhered to. The actual always well above 30% NR which is the backup if the WR level instrument is inoperable.

of TS in accordance with 10 CFR to clarify Mode 4 steam generator operator supervisors and reactor replacement in RF010. The requirement to 74% in Mode 4 was added as a result SG level was monitored using of 10% narrow range. Therefore, this operability requirement.

cognitive errors resulting in TS or corrective actions resulted from as it pertained to this event.

Mindset. No one in the control room anticipated increased above the normal NR operating band from Mode 3 to Mode 4.

III. SAFETY SIGNIFICANCE

There were no adverse plant safety or equipment of the Technical Specification was met in that operation although the specific text of the steam generator level during this event was instrumentation specified by TS to be used This event is being reported as a violation 50.73(a)(2)(1)(B).

IV. CORRECTIVE ACTIONS

Corrective actions:(1) Revise plant procedures operability requirements. ( (2) Coached licensed operators on this event.

V. PREVIOUS SIMILAR EVENTS

The TS 3.4.1.3 was revised as part of the SG to maintain WR SG level greater than or equal of the license amendment to replace SGs. Previously, narrow range level with an operability limit event was the initial failure to meet this There have been other events at HNP where personnel violations. However, no other additional causes this review of previous operating experience