05000483/LER-2002-008
| Callaway Plant Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| 4832002008R00 - NRC Website | |
I. DESCRIPTION OF THE REPORTABLE EVENT
A. REPORTABLE EVENT CLASSIFICATION
This event is reportable per 10 CFR 50.73(a)(2)(ii)(B), an unanalyzed condition.
B. PLANT OPERATING CONDITIONS PRIOR TO THE EVENT
Callaway Plant was in Mode 1 at 100 percent power.
C. STATUS OF STRUCTURES, SYSTEMS OR COMPONENTS THAT WERE INOPERABLE AT THE START
OF THE EVENT AND THAT CONTRIBUTED TO THE EVENT
There were no structures, systems, or components inoperable at the time of discovery and that contributed to this event.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE TIMES
On 4/18/2002, during an extent of condition review concerning the neutron flux positive rate trip function, a concern was identified where Technical Specification (T/S) Table 3.3.2-1, Allowable Value for the Steam Line Pressure Negative Rate - High (HNPR), is less restrictive than the Safety Analyses Limit (SAL) credited in the Callaway Mode 3 Main Steam Line Break (MSLB) analysis.
T/S lists the Allowable Value for the HNPR function as less than or equal to 124 psi. T/S Bases lists the Nominal Trip Setpoint (NTS) for the HNPR function as less than or equal to 100 psi. The Safety Analysis Limit (SAL) for the HNPR function is 100 psi. Consequently, the T/S allow the HNPR function to be set at a value less conservative than the value assumed in the safety analysis.
During startup or shutdown evolutions when safety injection on low Pressurizer pressure or low steamline pressure is blocked below Permissive P-11 (Pressurizer pressure less than 1970 psig), the HNPR rate signal is enabled by P-11 to provide steamline isolation. With Reactor Coolant System (RCS) Tavg greater than 450 degrees F, steamline isolation will be provided by the HNPR signal for break sizes greater than or equal to 0.02 sq. ft. Final Safety Analysis Report (FSAR) Steam System Piping Failure Analysis credits main steamline isolation on two out of three HNPR signals in any one loop during cooldown and heatup operations below P-11.
Corrective actions being evaluated include either decreasing the T/S Allowable Value from less than or equal to 124 psi to less than or equal to 100 psi or revising the Callaway Mode 3 MSLB analysis to credit a HNPR SAL greater than or equal to 124 psi.
Because the plant was operating in Mode 1, there were no immediate operability concerns. A Generic Letter 91-18 Operability Determination was completed. This evaluation included the required compensatory actions for T/S compliance if the plant is taken to Mode 3 with reactor coolant system pressure below the P-11 setpoint of 1970 psig.
E. METHOD OF DISCOVERY OF EACH COMPONENT, SYSTEM FAILURE, OR PROCEDURAL ERROR
This condition was identified during a review concerning the neutron flux positive rate trip function.
II. � EVENT DRIVEN INFORMATION
A. SAFETY SYSTEMS THAT RESPONDED
Not Applicable.
B. DURATION OF SAFETY SYSTEM INOPERABILITY
This T/S item is applicable in Mode 3 below the P-11 (Pressurizer pressure less than or equal to 1970 psig) interlock.
At the time of discovery, Callaway Plant was in Mode 1, and thus there was no immediate inoperability. During past plant shutdowns, this situation would have been applicable while below P-11 until the Main Steam Isolation Valves were closed. This typically is of a short duration while the plant transitions between Modes.
C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT.
This does not pose a significant safety consequence due to the plant parameters necessary to render this circumstance applicable. Typically, this unique combination of plant pressure and system lineups is only experienced while transitioning between Modes and is of a short duration. Additionally, a historical review of related surveillance documents revealed that the electronic circuitry associated with the T/S HNPR setpoint is extremely reliable. This review, consisting of sixty-nine surveillance documents, found that the HNPR setpoint bistables were always within calibration tolerances. Based upon the demonstrated reliability of the electronic circuitry and the rarity of operating the plant within the limited conditions necessary for this scenario, this does not pose a significant safety consequence.
III. � CAUSE OF THE EVENT Generic evaluations conducted by Westinghouse led to the incorrect selection of 124 psi as the T/S Table 3.3.2-1 Allowable Value for Steam line pressure high negative rate.
IV. � CORRECTIVE ACTIONS Corrective actions being evaluated include either decreasing the T/S Allowable Value from less than or equal to 124 psi to less than or equal to 100 psi, or revising the Callaway Mode 3 MSLB analysis to credit a HNPR SAL greater than or equal to 124 psi.
A Generic Letter 91-18 Operability Determination was completed. This evaluation included the required compensatory actions for T/S compliance if the plant is taken to Mode 3 with reactor coolant system pressure below the P-11 setpoint of 1970 psig.
V. � PREVIOUS SIMILAR EVENTS A review was conducted of LERs and Callaway Corrective Action Requests (CARs) covering the period of 4/18/99 to 5/29/02. There were no previous LERs or CARs documenting a similar event or occurrence.
VI. A ADDITIONAL INFORMATION are from the IEEE Standard 805-1984 and IEEE Standard 803A-1984 was no faulted component.
The system and component codes listed below respectively.
System: JG Component: Not Applicable — there