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| Quarter | Site | Title | Description | |
|---|---|---|---|---|
| 05000483/FIN-2015002-01 | 2015Q2 | Callaway | Failure to Properly Implement Compensatory Actions as Directed by Procedure | The inspectors identified a non-cited violation of 10 CFR Part 50, Appendix B, Criterion V, Instructions, Procedures, and Drawings, for the licensees failure to properly implement procedure directed compensatory actions necessary for operability of safetyrelated equipment. Specifically, when the train B class 1E switchgear air conditioning unit (SGK05B) was taken out of service for maintenance, compensatory measures to open all of the doors between both trains of engineered safety feature ac and dc switchgear and batteries were not implemented correctly. This resulted in less than calculated minimum cooling air flow required under accident conditions to support operability of the associated switchgear. The licensee entered this issue into their corrective action program as Callaway Action Request 201503501. The corrective actions include revising the compensatory action procedures and providing training on the issue. The licensees failure to properly implement compensatory actions necessary to maintain operability of safety-related equipment in accordance with plant procedures was a performance deficiency. The performance deficiency is more than minor, and therefore a finding, because it is similar to examples 3.i, 3.j, and 3.k in Inspection Manual Chapter 0612, Appendix E, Examples of Minor Issues, and it is associated with the equipment performance attribute of the Mitigating Systems Cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences (i.e., core damage). Specifically, between May 6 and 7, 2015, when the train B class 1E switchgear air conditioning unit (SGK05B) was taken out of service for maintenance, compensatory measures to open all of the doors between both trains of vital batteries, chargers, and engineered safety feature switchgear were not implemented correctly and when discovered required significant evaluation to determine the operability status of the supported equipment during the maintenance. Using Inspection Manual Chapter 0609, Appendix A, Exhibit 2, Mitigating Systems Screening Questions, the finding was determined to be of very low safety significance because it did not affect system design, did not result in a loss of system function, did not represent a loss of function of a single train for greater than its technical specifications allowed outage time, and did not cause the loss of function of one or more non-technical specification trains of equipment designated as high safety-significance. This finding has a cross-cutting aspect of Challenge the Unknown in the human performance cross-cutting area because individuals did not stop when faced with uncertain conditions and risks were not evaluated and managed before proceeding. Specifically, operations personnel did not question why they were only opening one door of a double door set when implementing the compensatory measures to allow cool air in the air conditioned rooms to cool the rooms without air conditioning (H.11) |
| 05000483/FIN-2015002-02 | 2015Q2 | Callaway | Inadequate Operability Evaluation When Taking Emergency Diesel Generator Support Equipment Out of Service | The inspectors identified a non-cited violation of 10 CFR Part 50, Appendix B, Criterion V, Instructions, Procedures, and Drawings, for the licensees failure to perform an adequate operability evaluation on the train A emergency diesel generator when required support equipment was taken out of service for maintenance. This resulted in necessary compensatory actions not being in place when the support equipment was taken out of service. The immediate corrective action taken by the licensee was to perform a prompt operability determination and implement compensatory measures. The licensee plans to evaluate the current planned maintenance process for safety related support equipment. The licensee entered this issue into their corrective action program as Callaway Action Request 201502708. The licensees failure to perform a prompt operability determination after bounding conditions were applied to the immediate operability determination per plant procedures was a performance deficiency. The performance deficiency is more than minor, and therefore a finding, because it is associated with the equipment performance attribute of the Mitigating Systems Cornerstone and adversely affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences (i.e. core damage). Specifically, the failure of the licensee to perform an adequate operability evaluation resulted in the failure to implement required compensatory actions to maintain operability of the train A emergency diesel generator. Using Inspection Manual Chapter 0609, Appendix A, Exhibit 2, Mitigating Systems Screening Questions, the finding was determined to be of very low safety significance because it did not affect system design, did not result in a loss of system function, did not represent a loss of function of a single train for greater than its technical specifications allowed outage time, and did not cause the loss of function of one or more non-technical specification trains of equipment designated as high safety-significance. This finding has a work management cross-cutting aspect in the human performance cross-cutting area because the licensee did not appropriately implement a process of planning, controlling, and executing work activities such that nuclear safety is the overriding priority. Specifically, not having a clear work process for assessing operability of technical specification components when support systems are taken out of service for planned maintenance led to operators failing to adequately evaluate the operability of the train A emergency diesel generator (H.5). |
| 05000483/FIN-2015002-03 | 2015Q2 | Callaway | Inverter NN11 Inadvertently Transferred to its Alternate AC Source | On June 9, 2014, the Callaway Plant was in Mode 1 operating at 100 percent rated thermal power when, during a maintenance activity, inverter NN11 unexpectedly transferred from its normal direct current (dc) source to its bypass alternating current (ac) source. This inverter provides power to the NN01 bus which is one of four vital 120 Vac instrument buses at the Callaway Plant. The transfer of inverter NN11 to its bypass source was caused by a momentary loss of power to bus SB038 which supports instrumentation and controls for systems such as the reactor trip system and the engineered safety feature actuation system. This momentary loss of power caused the following plant impacts: Control rod insertion 612 steps, with an associated pressurizer level and pressur perturbation and subsequent Xenon transien Opening of valve BNLCV0112D, centrifugal charging pump A suction fro refueling water storage tank isolation valve, due to momentary loss of th associated volume control tank level channe Actuation of the steam generator environmental allowance modifier circuit resulting in resetting of the low level setpoint trip from 17 to 21 percent narro range leve Numerous momentary partial trip actuation The NRC inspectors responded to the control room and verified that the plant system responded as designed and that the operators stabilized the plant in accordance wit plant procedures Investigation identified a loose mounting screw that secures disconnect switch NN01-11 to NN01. Maintenance work in the area of the loose termination led to a momentary interruption of power to cabinet SB038, which appeared as a fault condition to the inverter, thus causing the inverter to transfer to its alternate power source. The cabinet, bus, and inverter are seismically qualified and are required to be capable of performing their design basis accident functions following a safe shutdown earthquake. With the degraded electrical termination, which existed for an extended period of time before discovery and repair, the inverter and SB038 loads would not have been capable of performing their design basis function following a safe shutdown earthquake, thus rendering the components inoperable. The direct cause of this event was inadequate thread engagement of the screw securing disconnect switch NN01-11 to the NN01 bus. However, the presence of threads in the switch mounting hole (which is not intended to engage with the bus bar termination screw) introduced the potential for binding during screw installation. The detail of this mounting configuration is not identified on plant drawings of the cabinet or switch provided by the vendor and nothing in the work control process required a detailed comparison of the switch to the work procedures and, as such, it was reasonable that this potential vulnerability was not identified and addressed in the procedure or pre-job walkdown. During the actual installation of the screw, the screw appeared flush and tight with the switch mounting board, meeting the requirements of the work package. The equipment was successfully post-maintenance tested and technical specification surveillance tested for a period of 6 years. There was also no industry or vendor operating experience describing this vulnerability. Based on this information, the inspectors concluded that no performance deficiency existed since it was not reasonable for Callaway Plant personnel to foresee and correct this condition. The licensees root cause analysis determined that the root cause of the event was that work instructions did not include direction to remove the back panel cover of the cabinet to support alignment and thread engagement of the mounting screws during switch installation. Corrective actions taken by the licensee included changes to job planning aids and the maintenance procedures associated with the replacement of this type of switch. The inspectors determined during their review of Licensee Event Report 2014-003-01 that traditional enforcement applies in accordance with Inspection Manual Chapter 0612, Appendix B, Figures 1 and 2, Issue Screening, Inspection Manual Chapter 0612, Section 9, and NRC Enforcement Policy, Section 2.2.4.d, because a violation of NRC requirements existed without an associated Reactor Oversight Process performance deficiency. This issue is considered to be a Severity Level IV violation of 10 CFR Part 50, Appendix B, Criterion V, Instructions, Procedures, and Drawings, based on a conservative bounding evaluation performed using Callaways SPAR model which determined the condition was of very low safety significance (Green) and was similar in significance to NRC Enforcement Policy example 6.1.d.2. This issue was entered into Callaway Plants corrective action program as Callaway Action Request 201403898. Licensee Event Report 2014-003-01 was submitted pursuant to 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Callaway Technical Specification 3.8.7, Inverters Operating, based on the period of past inoperability of the NN11 inverter and SB038 loads. The inspectors reviewed the licensees submittal and determined that the report included the potential safety consequences and necessary corrective actions, but it did not thoroughly document the event, in that the effects on the plant from the inverter transfer to its alternate ac power source were not described. The licensee entered the licensee event report completeness issue into their corrective action program as Callaway Action Request 201504217 and initiated a corrective action to submit a revision of the licensee event report at a later date. Because it was not reasonable for the licensee to have been able to foresee and correct the condition that caused the switch failure, the NRC determined that no performance deficiency existed. Thus, the NRC is exercising enforcement discretion in accordance with Section 3.5 of the NRC Enforcement Policy and is not issuing enforcement action for the violation (EA-15-152). Further, because the licensees action and/or inaction did not contribute to this violation, it will not be considered in the assessment process or the NRCs reactor oversight process action matrix. This licensee event report is closed. These activities constitute completion of one event follow-up sample, as defined in Inspection Procedure 71153. |