05000315/LER-2001-004
| Donald C. Cook Nuclear Plant Unit 1 | |
| Event date: | 09-27-2001 |
|---|---|
| Report date: | 11-21-2001 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3152001004R00 - NRC Website | |
2001 004 00 17. TEXT (If more space is required, use additional copies of NRC Form (366A) Conditions Prior to Event Unit 1, Mode 4, Hot Shutdown
Description of Event
On September 27, 2001, during Unit 1 startup activities, the unit was taken from Mode 4 to Mode 3 with the remote shutdown pressurizer (EIIS:AB) level instrument inoperable. The inoperable instrument was identified in Mode 4, during performance of normal control room panel walkdowns, when shift personnel found that pressurizer level instrument, 1- NLP-151, that also provides readout display on the Remote Shutdown Panel, was indicating a difference of 7 percent compared to level instruments 1-NLP-152 and 1-NLP-153. This exceeded the acceptance limit of 4 percent contained in procedure 01-OHP-4030-STP-030, "Daily and Shiftly. Surveillance Checks," and the instrument was declared inoperable.
Despite this discovery, the unit entered Mode 3 with an inoperable remote shutdown instrument channel contrary to Technical Specification (TS) 3.0.4. This LER is being submitted in accordance with 10 CFR 50.73(a)(2)(i)(B) for an operation or condition, which is prohibited by plant Technical Specifications.
Unit 1 TS 3.3.3.5, "Remote Shutdown Instrumentation," requires that the remote shutdown instrumentation channels listed in TS Table 3.3-9 to be operable with readouts displayed external to the control room in Modes 1 through 3. The actions for TS 3.3.3.5 state that, "With the number of OPERABLE remote shutdown monitoring channels less than required by Table 3.3-9, either: a) Restore the inoperable channel to OPERABLE status within 30 days, or b) Be in HOT SHUTDOWN within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />." In addition, TS 3.0.4 requires that entry into an operational mode or other specified applicability condition shall not be made unless the conditions of the limiting condition for operation are met without reliance on provisions contained in the action statements unless otherwise excepted. Because Unit 1 entered Mode 3 with 1-NLP-151 inoperable, the TS 3.3.3.5 Limiting Conditions for Operation was not met and thus is a violation of TS 3.0.4.
During the extent of condition review for this event, it was also identified that the surveillance requirement to perform a monthly channel check for the remote shutdown pressurizer pressure instrument channel could not be performed prior to Unit 1 entering Mode 3. Because the pressurizer pressure instrument has a range of 1,700 pounds per square inch gauge (psig) to 2,500 psig, the channel check must be performed at a pressurizer pressure of at least 1,700 psig. However, Mode 4 operation at a pressure at or above 1,700 psig is prohibited by the current operational limitations on primary-to- secondary steam generator tube differential pressure. In addition, it was noted that Unit 2 TS 3.3.3.5 includes a statement that the provisions of TS 3.0.4 are not applicable. It was identified that during Unit 1 startup activities on December 12, 2000, the required monthly channel check had not been performed for the pressurizer pressure instrument prior to the mode transition. This condition was also determined to be reportable in accordance with 10 CFR 50.73(a)(2)(i)(B).
Cause'of Event The apparent cause for the September 2001 event was human error. When the pressurizer level instrument was declared inoperable, operations personnel improperly focused on operability requirements for the reactor protection instrumentation specification TS 3.3.1.1, instead of the remote shutdown instrumentation specification TS 3.3.3.5. Instrument specification TS 3.3.1.1 is only applicable in Modes 1 and 2.
A leaking Swagelock connection (EIIS:CPLG) was found to be the cause of the pressurizer level instrument inoperability.
Regarding the December 2000 event for failure to perform the required monthly channel check of the remote shutdown pressurizer pressure instrumentation prior to entering Mode 3, the cause was incorrect procedure guidance. Procedure 01-OHP-4030.STP.031, "Operation Weekly Surveillance Checks," incorrectly stated that the Hot Shutdown Panel channel check for pressurizer pressure instrument 1-NPP-151 was not applicable in Mode 3.
2001 � 004 � 00 17. TEXT (If more space is required, use additional copies of NRC Form (366A)
Analysis of Event
The Remote Shutdown System provides the control room operator with sufficient instrumentation and controls to place and maintain the plant in a safe shutdown condition from a location other than the control room. This capability is necessary to protect against the possibility that the control room becomes inaccessible. If the control room becomes inaccessible, the operators can establish control at the Hot Shutdown Panel, and place and maintain the plant in Mode 3.
Performance of scheduled channel checks ensures that a gross failure of the Remote Shutdown System instrumentation has not occurred. A channel check is the quantitative assessment of channel behavior during operation by observation.
This determination includes, where possible, comparison of the channel and/or status with other indications and/or status derived from independent instrument channels measuring the same parameter.
TS 3.0.4 requires that entry into an operational mode or other specified applicability condition shall not be made unless the conditions of the limiting condition for operation are met without reliance on provisions contained in the action statements unless otherwise excepted. The Applicability section of the TS Bases for TS 3.0.4 describes that the intent of this provision is to insure that facility operation is not initiated with either required equipment or systems inoperable or other specified limits being exceeded. This section further states that exceptions to this provision have been provided for a limited number of specifications when startup with inoperable equipment would not affect plant safety. This exception is stated in the action statements of the appropriate specifications. This exception is not presently applicable for the Unit 1 TS 3.3.3.5. However TS.
The significance of the TS violations is considered minimal since the probability of an event requiring the Remote Shutdown System is low, and because the equipment can generally be repaired during operation without significant risk of spurious trip.
Corrective Actions
The leaking Swagelock fitting on Unit 1, that caused the level deviation on the remote shutdown pressurizer level instrument, was tightened, successfully tested and returned to service. The Unit 2 pressurizer level instrumentation was also inspected and no indicated level deviations were identified.
The involved individuals have been counseled and a lessons learned memorandum has been issued to appropriate personnel. The personnel performance aspects of this event are being addressed in accordance with plant practices and procedures and will be tracked as part of Donald C. Cook Nuclear Plant's corrective action process.
A proposed amendment to the Unit 1 TS 3.3.3.5 has been submitted to include an exception for the remote shutdown instrumentation from the provisions of TS 3.0.4. Specifically, the amendment proposes to revise the action statements for TS 3.3.3.5 to add a statement that the provisions of TS 3.0.4 are not applicable in Modes 1 through 3. The proposed change is being requested to allow entry into Mode 3 under the provisions of the action statements for TS 3.3.3.5. In the interim, a Unit 1 Mode 3 constraint has been generated in lieu of a procedure revision and will prevent additional violations until the TS change is approved. This TS change will make the action requirements consistent between Units 1 and 2 and will prevent recurrence of similar events involving the remote shutdown instrumentation.
Previous Similar Events
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