05000321/LER-2012-001
| Edwin I. Hatch Nuclear Plant Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3212012001R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor Energy Industry Identification System codes appear in the text as (EIIS Code XX).
DESCRIPTION OF EVENT
On 2/25/2012, with the unit in Mode 5 for refueling, the control rod "full-in" indication for Control Rod 22-27(AA) seen by the Rod Position Indicating System (RPIS) was noted to be inoperable, and a RAS for TS 3.9.4 was entered. In accordance with TS RAS 3.9.4.A.2.2 for the Condition in which one or more required control rod position indication channels is inoperable, action was taken to electrically disarm the Control Rod Drive (CRD) associated with Control Rod 22-27 after visual verification that the control rod drive was fully inserted. A suitable tag-out was conducted to assure the continuation of the disarming of CRD 22-27.
Subsequently, a modified probe buffer card was installed to bypass the "full-in" indication signal in order to remove the associated rod blocks to facilitate appropriate outage activities.
Notation of the use of the modified probe buffer card in the RPIS for Control Rod 22-27 was added to an existing TS RAS which was being used to track the loss of RPIS indications and similar buffer card installations for other control rods.
After completion of the associated work, at approximately 2121 EST on 2/28/2012, the tag- out described above was cleared (i.e., removed) without removing the modified probe buffer card and without performing a functional test of the RPIS full-in indication prior to moving fuel in the reactor vessel, as required. Fuel movement occurred from the time the tag-out was removed until 0817 EST on 3/2/2012 when the error was discovered, resulting in a condition prohibited by TS LCO 3.9.4 for Control Rod 22-27 position indication,
CAUSE OF EVENT
The cause of this event was attributed to less than adequate procedural controls with respect to other administrative control documents (tag-outs, for example) for which credit is taken to ensure tag-outs are not removed prior to clearing the conditions required by the associated required action statements. This lack of effective procedural control was exacerbated by the failure of involved personnel to effectively "self check" as a human error prevention technique. These concurrent deficiencies resulted in the failure of the on-shift management to account for the prior installation of the modified probe buffer card on Control Rod 22-27 RPIS when considering the removal of the tag-out for the CRD 22-27. Thus, the resultant failure to remove the modified probe buffer card inadvertently potentially impacted the "Refueling Equipment Interlocks" and the Refuel Position One-Rod-Out Interlock" and was contrary to TS LCO 3.9.4.
REPORTABILITY ANALYSIS AND SAFETY ASSESSMENT
Assessment Information:
Refueling equipment interlocks restrict the operation of the refueling equipment or the withdrawal of control rods to reinforce unit procedures that prevent the reactor from potentially achieving criticality during refueling. The refueling interlock circuitry senses the conditions of the refueling equipment and the control rods. Depending on the sensed conditions, interlocks are actuated to prevent the operation of the refueling equipment or the withdrawal of control rods.
information to the refueling interlocks to prevent such inadvertent criticalities during refueling operations. During refueling, the refueling interlocks (reference LCO 3.9.1 and LCO 3.9.2) use the full-in position indication channel to limit the operation of the refueling equipment and the movement of the control rods. The absence of the full-in position channel signal for any control rod removes the "all-rods-in" permissive for the refueling equipment interlocks and prevents fuel loading. Also, this condition causes the refuel position "one-rod-out interlock" to disallow the withdrawal of any other control rod.
The inoperability of the "control rod full-in indication" for Control Rod 22-27 which resulted from the failure to properly remove the modified probe buffer card on Control Rod 22-27 RPIS did not result in any personnel injuries, offsite radiological releases, or damage to safety- related equipment. During the time frame that fuel was moved in the reactor vessel without having operable position indication for Control Rod 22-27, the installation of the probe buffer card would physically allow that control rod to be withdrawn with the reactor in a mode where this is not allowed, However, administrative controls were in place to preclude the withdrawal of any control rod and additional TS required action statements would have to be cleared as well to allow movement of a control rod. Even though this "as found" condition was contrary to the TS requirements, no change in reactivity resulted and no movement of the control rod occurred. Based on this information this reported condition had low safety significance.
These events comprised an operation or condition which was prohibited by TS 3.9.4, and are thus reportable under the requirements of 10CFR50.73(a)(2)(i)(B).
CORRECTIVE ACTIONS
Short-term corrective actions included "Beginning-of-Shift-Training", where direction was given in BOST 12-12, "Tag-out Released with Technical Specification RAS Still Active", that the Unit Shift Supervisor should sign as a "Tag-out Holder" for any tag-out being used for Technical Specification RAS configuration control compliance and should list the RAS number as a reason for being a "Tag-out Holder" on the tag-out.
Long-term corrective actions include the revision of procedure 31GO-OPS-006-0 "Conditions, Required Actions, and Completion Times" and form OPS-1349 "Required Action Sheet" to include specific directions to reference and list Administrative Control Documents such as tag-outs or other required action tracking sheets on OPS-1349 "Required Action Sheet" to preclude an oversight such as that which occurred in the subject event.
Additionally, the shift supervisor will signora as the document holder for the tagout or "locked" the tagout as directed by procedure as an additional administrative control to preclude recurrence.
ADDITIONAL INFORMATION
Other Systems Affected: None Failed Components Information: None Commitment Information: This report does not create any new permanent licensing commitments.
Previous Similar Events: No similar events have been noted.