05000317/LER-2009-001
| Calvert Cliffs Nuclear Power Plant, Unit 1 | |
| Event date: | 03-06-2009 |
|---|---|
| Report date: | 05-04-2009 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3172009001R00 - NRC Website | |
A. PRE-EVENT PLANT CONDITIONS
Unit 1 was operating at 100 percent of rated thermal power on March 6, 2009, prior to the discovery of the subject events.
B. EVENT
On March 6, 2009, we discovered that procedural requirements for starting Reactor Coolant Pumps (RCPs) were not consistent with the pump start requirements contained in the Technical Specifications. As a result, RCPs on Unit 1 were started outside of the requirements of Technical Specifications 3.4.5 (RCS Loops — MODE 3). Specifically, there is a Note in the Technical Specification Limiting Condition for Operation that states the following:
2. No RCP shall be started with any Reactor Coolant System (RCS) cold leg temperature 365 degrees F (Unit 1), 5 301 degrees F (Unit 2) unless:
a. Pressurizer water level is 5 170 inches; b. Pressurizer pressure is 5 300 psia (Unit 1), 5 320 psia (Unit 2); and c. Secondary side water temperature in each steam generator is 5 30 degrees F above the RCS temperature.
The Technical Specification Bases states that "Ensuring the above conditions are satisfied will preclude a power-operated relief valve (PORV) from opening as a result of the pressure surge in the RCS, when an RCP is started.
In contrast, the RCP start requirements contained in Operating Instruction (01)-01A, Reactor Coolant System and Pump Operations, stated that the above requirements only applied to the first RCP started. The requirements differed for subsequent RCP starts in that restrictions were removed for pressurizer pressure and steam generator secondary side water temperature.
C. INOPERABLE STRUCTURES, COMPONENTS, OR SYSTEMS THAT CONTRIBUTED
TO THE EVENT
The event involved a difference in requirements between Technical Specifications and operating procedures. No equipment contributed to this event.
In all instances, the first two RCPs were started in accordance with Technical Specifications requirements. For subsequent RCP starts (the remaining two RCPs), pressurizer pressure was in excess of 300 psia. The PORV did not open during any RCP start.
A review was performed for Unit 2 RCP starts during the previous three years. There were no violations of the Technical Specification requirements.
E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED
No other systems or functions were affected.
F. METHOD OF DISCOVERY
The site Nuclear Regulatory Commission Senior Resident Inspector questioned the Technical Specification requirements associated with RCS loop operability. While performing research into that issue, engineering and operations personnel discovered that a procedure deficiency existed in the RCP start requirements contained in Operating Instruction 01-01A.
G. MAJOR OPERATOR ACTION
No major operator actions were taken as a result of this condition. Procedural deficiencies contributed to the events. Operating procedures did not contain correct RCP starting requirements in accordance with Technical Specifications 3.4.5, Note 2, 3.4.6, Note 2, and 3.4.7, Note 3. Appropriate procedures were corrected prior to starting the RCPs during the Unit 2 refueling outage.
H. SAFETY SYSTEM RESPONSES
No safety systems actuated as a result of the event.
II. CAUSE OF EVENT:
The apparent cause of this event is a failure to recognize that, when Improved Technical Specifications were adopted at Calvert Cliffs in 1998, the Notes to Technical Specifications 3.4.5, 3.4.6, and 3.4.7 changed the number of RCPs to which the RCP start criteria applied. These criteria, instead of applying to only the first RCP to be started, now applied to any RCP started within the applicability of the Note. This procedure deficiency has been entered into the site corrective action program (CR-2009-002841).
This new criteria should have been incorporated into the operating procedures governing RCP starts. The affected procedures are being updated to accurately reflect the Technical Specification requirements. This failure to recognize the change in RCPs to which the start criteria applied is believed to involve a human performance issue that may have been caused by human performance error traps, such as time pressure, multiple tasks, and vague or interpretative guidance related to the Improved Technical Specifications conversion project.
Current human performance error prevention tools, which were not required or in use at the time when Improved Technical Specifications changes were being made, are expected to prevent similar issues from occurring in the future. The use of human performance tools is outlined in fleet administrative procedure CNG-HU-1.01-1003, Human Performance Tools for Non-Field Technical Activities.
These RCP start criteria are included as part of the low temperature over-pressure (LTOP) controls. Only the LTOP RCP start criteria in procedure 01-1A were initially found to be outside the criteria allowed by the Technical Specifications. After discovery and prior to the next start of the RCPs, additional affected procedures are being revised to encompass all of the Technical Specification RCP start criteria. A review of all LTOP operational criteria will be performed to ensure that related Ols and other procedures accurately reflect the appropriate LTOP controls.
III.� ANALYSIS OF THE EVENT:
On March 6, 2009, Calvert Cliffs Nuclear Power Plant discovered that procedural requirements for starting a RCP were not consistent with the pump start requirements contained in the Technical Specifications 3.4.5, Note 2, 3.4.6, Note 2, and 3.4.7, Note 3. These notes provide RCS criteria, such as pressure and level, acceptable for starting any RCP when the RCS temperature is less than 365 degrees F. Contrary to these pump start requirements, RCPs were started on April 6, 2006, December 20, 2006, and March 11, 2008 without meeting the RCS pressure requirement of Technical Specification 3.4.5, Note 2. Therefore, the Technical Specifications were violated for each of these RCP starts. This event is reportable per 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's technical specifications.
The procedural error existed since the Technical Specification RCP start requirements were modified in 1998. The opportunity for a Technical Specification violation existed since that time until the error was identified in March 2009. A historical review determined that RCP starts at three different times in the past three years, as noted above, did not meet the RCP start requirements in the Technical Specifications.
The plant's safety analysis does not specifically include RCP start criteria. However, these criteria are included as part of the LTOP controls. The potential consequence of starting RCPs outside of the Technical Specification criteria would be the possible overpressurization of the RCS during LTOP conditions. Ensuring that the conditions listed in Technical Specifications are satisfied will preclude a PORV from opening as a result of the pressure surge in the RCS, when an RCP is started. Plant logs were reviewed to determine if a pressure transient occurred as a result of starting an RCP outside of Technical Specification guidelines. No pressure transient was noted. There were no actual safety consequences as a result of this condition.
Realizing that a PORV could have lifted if challenged, a qualitative probabilistic risk assessment evaluation was performed. During the subject RCP starts, the recorded pressures at the associated temperatures were well within the Technical Specifications Figure 3.4-12-1 maximum PORV lift setting requirements, therefore, precluded challenging the PORVs. The risk incurred due to the subsequent RCP pump starts in violation of the Technical Specifications requirements was considered to be small.
The RCP starts had no affect on Nuclear Regulatory Commission Reactor Oversight Process Performance Indicators.
IV. CORRECTIVE ACTIONS:
A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL
STATUS:
No actions were required to return systems to pre-event normal status. Appropriate procedures were revised to incorporate the Technical Specification requirements for starting RCPs prior to its use on Unit 2 during the spring 2009 refueling outage.
B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE
Revise affected procedures to accurately reflect Technical Specification RCP start criteria.
A comparison of LTOP controls in the Technical Specifications with the associated implementing procedures will be performed to ensure LTOP controls are accurately reflected in the appropriate procedures.
V. ADDITIONAL INFORMATION
A. FAILED COMPONENTS:
There are no failed components associated with this event.
B. PREVIOUS LERs ON SIMILAR EVENTS
A review of Calvert Cliffs' events over the past four years was performed. Previous LERs on similar events are as follows:
Setpoint.
scope of this corrective action did not include LTOP provisions and Operating Instructions and would not have identified the procedure deficiency in Operating Instruction 01-01A.
C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EllS) COMPONENT
FUNCTION IDENTIFIER AND SYSTEM NAME OF EACH COMPONENT OR SYSTEM
REFERRED TO IN THIS LER:
� IEEE 803 IEEE 805 � Component EllS Function System ID Power-Operated Relief Valves� 20� AB Reactor Coolant Pumps� P AB
D. SPECIAL COMMENTS
None