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 Start dateReporting criterionTitleEvent descriptionSystemLER
ENS 5538026 July 2021 22:31:00NonReactor Shutdown Due to Control Rod Drive FailureOn July 26, 2021 at 1731 CDT, while the reactor was subcritical during a reactor startup, the University of Missouri-Columbia Research Reactor (MURR) was manually shut down due to the failure of the control rod drive mechanism for shim control blade B. MURR was not in compliance with one (1) Limiting Conditions of Operations (LCO). TS 3.2.a states, 'All control blades, including the regulating blade, shall be operable during reactor operation.' A spare control rod drive mechanism was installed for control blade B, post-installation operability testing was conducted satisfactorily, and permission from the Reactor Facility Director was obtained prior to the reactor returning to operation later on July 26, 2021. Currently, MURR is operating at 10 MW (full power). A detailed event report will follow within 14 days.Control Rod
ENS 546609 April 2020 19:32:00NonAbnormal OccurrenceOn 4/9/20, at 1432 CDT, the University of Missouri-Columbia Research Reactor (MURR) was shut down due to the failure of the geared rotary limit switch assembly to move with corresponding regulating blade drive mechanism movement. This email is a required notification per MURR Technical Specification (TS) 6.6.c(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by MURR TS 1.1, had occurred. MURR was not in compliance with one (1) Limiting Conditions of Operations (LCO). TS 3.2.f states, 'The reactor shall not be operated unless the following rod run-in functions are operable.' Specifically, the rod run-in function that occurs when regulating blade position is less than or equal to 10 percent withdrawn was not operable as required by TS 3.2.f.8. The regulating blade drive mechanism was repaired, post-maintenance operability testing was conducted satisfactorily, and permission from the Reactor Facility Director was obtained prior to the reactor returning to operation later on 4/9/20. Currently, MURR is at 10 MW. A detailed event report will follow within 14 days as required by MURR TS 6.6.c(3).
ENS 546538 April 2020 06:00:00NonResearch and Test Reactor Forced Shutdown Due to Failure of Regulating Blade Drive MechanismOn 4/8/20 at 0100 CDT, the University of Missouri-Columbia Research Reactor (MURR) was shut down due to a failure of the regulating blade drive mechanism to move the regulating blade during reactor operation. This email is a required notification per MURR Technical Specification (TS) 6.6.c.(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by MURR TS 1.1, had occurred. Specifically, MURR was not in compliance with all Limiting Conditions for Operations (LCOs). MURR was not in compliance with two (2) LCOs: 1. TS 3.2.a states, 'All control blades, including the regulating blade, shall be operable during reactor operation,' and 2. TS 3.2.f states, 'The reactor shall not be operated unless the following rod run-in functions are operable.' Specifically, the rod run-in function that occurs when the regulating blade position is less than or equal to 10 percent withdrawn was not operable as TS 3.2.f.8 requires. The regulating blade drive mechanism was repaired, post-maintenance operability testing was conducted on the regulating blade, and permission from the Reactor Facility Director was obtained prior to the reactor returning to operation later on 4/8/20. Currently, MURR is at 10 MW. A detailed event report will follow within 14 days as required by MURR TS 6.6.c.(3).
ENS 5445320 December 2019 03:21:00NonTechnical Specification Deviation

On December 19, 2019, at 2121 CST, the University of Missouri-Columbia Research Reactor (MURR) was shut down due to a seized servomotor on the regulating blade drive mechanism during reactor operation. This notification is required per MURR Technical Specification (TS) 6.6.c(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by TS 1.1, had occurred. MURR was not in compliance with all Limiting Conditions for Operations (LCOs), specifically TS 3.2.a, which states, 'All control blades, including the regulating blade, shall be operable during reactor operation.' The regulating blade drive mechanism was removed, a new motor installed, and then the regulating blade drive mechanism was reinstalled and all its functions were tested satisfactorily. Permission from the Reactor Facility Director was obtained per TS 6.6.c(4) prior to starting up the reactor later on December 20.

A detailed event report will follow within 14 days as required by TS 6.6.c(3).

ENS 5443610 December 2019 06:12:00NonTechnical Specification Violation Requiring Shutdown

The following information was received via phone and email. On December 10, 2019, at 0012 CST, the University of Missouri-Columbia Research Reactor (MURR) was shut down due to a failure of the regulating blade drive mechanism during reactor operation. MURR was not in compliance with all Limiting Conditions for Operations (LCOs), specifically S 3.2.a, which states, 'All control blades, including the regulating blade, shall be operable during reactor operation.' The regulating blade drive mechanism was removed, repaired, reinstalled, and all its functions were tested satisfactorily. Permission from the Reactor Facility Director was obtained per TS 6.6.c(4) prior to starting up the reactor later on December 10." Notification to the NRC Operations Center is required per TS 6.6.c(1) to report that an Abnormal Occurrence, as defined by TS 1.1.b, occurred. MURR was not in compliance with all of the Limiting Conditions for Operations as established in TS Section 3.0.

A detailed event report will follow within 14 days as required by TS 6.6.c(3).

ENS 5418730 July 2019 00:03:00NonTechnical Specification DeviationThe following information was received via email: On July 29, 2019, at 1903 CDT, the University of Missouri-Columbia Research Reactor (MURR) was shut down due to a failure of the regulating blade drive mechanism during reactor operation. This email is a required notification per MURR Technical Specification (TS) 6.6.c(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by TS 1.1, had occurred. MURR was not in compliance with all Limiting Conditions for Operations (LCOs), specifically TS 3.2.a, which states, 'All control blades, including the regulating blade, shall be operable during reactor operation.' The regulating blade drive mechanism was removed, repaired, reinstalled, and all its functions were tested satisfactorily. Permission from the Reactor Facility Director was obtained per TS 6.6.c(4) prior to starting up the reactor later on July 29. Currently, MURR is at 10 MW. A detailed event report will follow within 14 days as required by TS 6.6.c(3). The licensee has notified the NRC Research and Test Reactor Project Manager.
ENS 541491 July 2019 16:00:0010 CFR 50.72(b)(1), 50.54(x) TS DeviationNon-Power Reactor Report - Technical Specification DeviationThe following was received via e-mail: On July 1, 2019, sometime between 1100 and 1200 CDT with the reactor shut down and during performance of electrical preventative maintenance, the University of Missouri-Columbia Research Reactor (MURR) deviated from Technical Specification (TS) 3.4 because reactor containment integrity did not exist for approximately ten (10) minutes while the reactor was not secured, as defined by TS 1.26. During this event time, two (2) shim control rod drive mechanisms were not installed because scheduled work was in progress on these drive mechanisms. Therefore, the reactor was not secured per TS definition 1.26, but the reactor was shut down per TS definition 1.27. Also during this time, and unknown to the Control Room operators, an Electronics Technician opened the two (2) electrical motor breakers to the reactor containment system's two (2) automatically-closing doors one at a time for approximately 5 minutes each. Though this event happened on July 1, no NRC-licensed operator knew that the automatically-closing door motor breakers had been opened on July 1 until mid-day on July 3. Once the abnormal occurrence was realized, the Reactor Facility Director was briefed on the situation on the afternoon of July 3, and he gave permission to continue reactor operation in accordance with TS 6.6.c.(4). This email is a required notification per TS 6.6.c.(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by TS 1.1.b, has occurred. MURR was not in compliance with all of the Limiting Conditions for Operations as established in TS Section 3.0. A detailed event report will follow within 14 days as required by TS 6.6.c.(3).Control Rod
ENS 5403428 April 2019 11:33:00NonControl Blade InoperableOn April 28, 2019, at 0633 CDT, with the University of Missouri-Columbia Research Reactor (MURR) operating at 10 MW in the automatic control mode, the Lead Senior Reactor Operator (LSRO) was conducting surveillance Technical Specification (TS) 4.2.a, which states, 'All control blades, including the regulating blade, shall be verified operable within a shift.' During this verification of control blade operability, shim control blades 'A,' 'B,' 'C,' and the regulating blade were verified operable. However, shim control blade 'D' would not move in the inward direction. The LSRO then immediately shut down the reactor by initiating a manual scram by placing Master Control Switch 1S1 to the 'TEST' position. The LSRO completed all immediate and applicable subsequent actions of reactor emergency procedure REP-8, 'Control Rod Drive Mechanism Failure or Stuck Rod,' and verified all shim control blades were fully inserted. This email is a required notification per TS 6.6.c(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by TS 1.1.b, has occurred. MURR was not in compliance with all of the Limiting Conditions for Operations (LCOs) as established in TS Section 3.0. The failure of the control rod drive mechanism to insert shim control blade 'D' is a deviation from TS 3.2.a, which states, 'All control blades, including the regulating blade, shall be operable during reactor operation.' In addition, shim control blade 'D' would not have inserted during the activation of any rod run-in function listed in TS 3.2.f - shim control blades 'A,' 'B,' and 'C' would have inserted. All reactor safety system scram functions were unaffected and remained operable during this event. Troubleshooting revealed a broken wire to the inward motor winding of shim blade 'D' control rod drive mechanism. The wire was repaired, and the shim control blade 'D's operability was tested satisfactorily. Permission from the Reactor Facility Director was obtained prior to reactor startup per TS 6.6.c(4), and the reactor returned to 10 MW operation at 1319 CDT on April 28. A detailed event report will follow within 14 days as required by TS 6.6.c(3).Control Rod
ENS 5384928 January 2019 01:13:00NonControl Blade InoperableOn January 27, 2019, at 1913 CST, with the University of Missouri-Columbia Research Reactor (MURR) operating at 10 MW in the automatic control mode, the Lead Senior Reactor Operator (LSRO) was conducting surveillance Technical Specification (TS) 4.2.a, which states, 'All control blades, including the regulating blade, shall be verified operable within a shift.' During this shiftily verification of control blade operability, all blades were initially verified operable. However, when banking the control blades to their final position after all blades were satisfactorily tested a few seconds earlier, shim control blade 'A' would not move in the inward direction. The LSRO then immediately shut down the reactor by initiating a manual scram by placing the Master Control Switch 1S1 to the 'TEST' position. The LSRO completed all immediate and subsequent actions of reactor emergency procedure REP-2, 'Reactor Scram,' and verified all shim control blades were fully inserted. The inability to manually insert shim control blade 'A' with Control Rod Operate Switch 1S4, which inserts and withdraws the control blade, is a deviation from TS 3.2.a, which states, 'All control blades, including the regulating blade, shall be operable during reactor operation.' Troubleshooting revealed a problem with an electrical contact on Control Rod Operate Switch 1S4, and it has since been replaced. The reactor has not returned to operation at the time of this email. However, permission from the Reactor Facility Director has been obtained to restart the reactor once scheduled maintenance activities have been completed. A detailed event report will follow within 14 days as required by MURR TS 6.6.c(3).Control Rod
ENS 5384121 January 2019 18:35:00NonDeviation of Ts 3.3.A(1) for Anti-Siphon Device Found InoperableOn January 21, 2019 at approximately 1235 CST, with all four (4) shim control rods fully inserted into the reactor core during performance of a pre-startup checklist, the University of Missouri-Columbia Research Reactor (MURR) deviated from Technical Specification (TS) 3.3.a(1) due to test jumpers being installed while electrical power was available to the shim rod drive mechanism electromagnets. Prior to this event, the reactor was shut down for a regularly-scheduled maintenance period. A required notification per TS 6.6.c(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by MURR TS 1.1, had occurred. Specifically, MURR was not in compliance with all TS Limiting Conditions for Operations, specifically TS 3.3.a(1). For about ten (10) seconds at approximately 1235 CST, power was available to the shim rod drive mechanism electromagnets while electrical test jumpers, which hold anti-siphon system isolation valves V543A and V543B closed, were inserted. In effect, the anti-siphon system was not operable while the reactor was technically operating for ten (10) seconds per the following definitions: 1. TS 1.23 Reactor in Operation - The reactor shall be considered in operation unless it is either shutdown or secured. 2. TS 1.27 Reactor Shutdown - The reactor is shutdown when: All four (4) of the shim blades (rods) are fully inserted and power is unavailable to the shim rod drive mechanism electromagnets. 3. TS 1.26 Reactor Secured - MURR did not meet the definition of Reactor Secured during the event. Though all four shim rods were fully inserted and a reactor startup had not commenced, electrical power being available to the shim rod drive mechanism electromagnets caused the reactor to technically be in Operation for a very brief period. Though this event happened at approximately 1235 CST, it was not fully identified as an abnormal occurrence per TS 1.1.b until approximately 1625 CST, after a reactor startup was performed to 10 MW operation. Once the abnormal occurrence was realized, the Reactor Facility Director was immediately notified at 1715 CST, and he gave permission to continue reactor operation. A detailed event report will follow within 14 days as required by MURR TS 6.6.c(3).Control Rod
ENS 5343330 May 2018 12:10:00NonTechnical Specification DeviationOn May 30, 2018, at 07:10 CST, with the reactor operating at 10 MW in the automatic control mode, MURR (University of Missouri Research Reactor) was shut down due to a failure of the Control Rod Operate Switch 1S4 to move the shim control blades in the inward direction. The Reactor Safety (Scram) and Rod-Run-In Systems were unaffected by this failure and remained operational and would automatically and manually initiate, if required. This email is a required notification per MURR TS (Technical Specification) 6.6.c(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by MURR TS 1.1.b, has occurred. MURR was not in compliance with all of the Limiting Conditions for Operations (LCOs) as established in Section 3.0. Specifically, MURR was not in compliance with TS 3.2.a, which states, All control blades, including the regulating blade, shall be operable during reactor operation. Control Rod Operate Switch 1S4 was replaced and retest was conducted satisfactorily, which included verifying inward and outward movement of all 4 shim control blades. Authorization was received from the Reactor Facility Director, as required by TS 6.6.c(4), to restart the reactor and resume 10 MW operation. A detailed event report will follow within 14 days as required by MURR TS 6.6.c(3). The failure was identified during scheduled testing and the reactor was shutdown by manual Scram in accordance with procedures. The licensee notified the NRC Research and Test Reactor Project Manager (Wertz).Control Rod
ENS 532444 March 2018 09:08:00NonTechnical Specification DeviationOn 3/4/17 at 0308 CST, the MURR (University of Missouri Research Reactor) emergency power generator was switched out of automatic control for approximately 10 to 15 seconds while the reactor was operating due to human error. With the emergency power generator in manual control, the emergency electrical power system is considered inoperable because the emergency electrical power system would not have supplied power in the event of a loss of normal electrical power. This email is a required notification per MURR Technical Specification (TS) 6.6.c.(1) to report to the NRC Operations Center that an Abnormal Occurrence as defined by MURR TS 1.1 happened. Specifically, MURR was not in compliance with the Limiting Condition for Operation TS 3.6.a which states, 'The reactor shall not be operated unless the emergency electrical power system is operable.' When the emergency power generator was switched out of automatic control, a Control Room alarm notified the Console Operator. Another operator placed the emergency power generator back into automatic mode which was the quickest way to regain compliance with TS 3.6.a. The MURR continued to operate at 10 MW. A detailed event report will follow within 14 days as required by MURR TS 6.6.c.(3). The licensee notified the NRC Research and Test Reactor Project Manager (Wertz).
ENS 5314230 December 2017 13:17:00NonTechnical Specification Required Report for an Abnormal OccurrenceOn 12/30/17 at 0717 CST, the University of Missouri-Columbia Research Reactor (MURR) was shut down due to the loss of negative pressure in the reactor containment building. Prior to the shutdown, the reactor was operating for a period of time during the loss of negative pressure which is a deviation from MURR Technical Specifications (TS). This email is a required notification per TS 6.6.c.(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by MURR TS 1.1, had occurred. Specifically, MURR was not in compliance with all TS Limiting Conditions for Operations (LCOs). MURR was not in compliance with TS's 3.4.b and 3.4.a.(6). TS 3.4.b. states, 'Reactor containment integrity shall be maintained at all times except when: (1) The reactor is secured...' TS. 3.4.a.(6) states, 'For reactor containment integrity to exist, the following conditions shall be satisfied:...(6) The reactor containment building is at a negative pressure of at least 0.25 inches of water with respect to the surrounding areas: and...' While on Routine Patrol on the morning of 12/30/17, an operator noted that the differential pressure gauge between the reactor containment building and the MURR laboratory building was reading zero (0.0) inches of water vacuum. The operator on Routine Patrol radioed the Lead Senior Reactor Operator in the Control Room, and the reactor was shut down. The cause of the loss of negative pressure was the closing of a backup ventilation exhaust door from the reactor containment building. With the backup ventilation exhaust door closed, the ventilation system was only supplying air to the reactor containment building, not allowing a balanced air recirculation to maintain a negative pressure. The backup ventilation exhaust door actuator was found to be inoperable. The backup ventilation exhaust door operation was repaired by melting ice that had formed in the air supply lines to the door's operating air cylinder. Condensation that had formed in the air lines was removed, and heat trace and insulation were installed around all the backup door air supply lines. The compliance procedure for verifying backup ventilation doors' operability was conducted satisfactorily as post-maintenance testing. Permission from the Interim Facility Director was obtained prior to the reactor returning to operation later on 12/30/17. A detailed event report will follow within 14 days as required by MURR TS 6.6.c.(3).
ENS 528415 July 2017 05:00:00NonAbnormal Occurrence Due to Source Range Inoperability During Reactor Start-UpOn 7/4/17 at 0232 CDT, the University of Missouri-Columbia Research Reactor (MURR) was shut down due to the suspected inoperability of the Source Range Nuclear Instrument Channel during reactor startup. This is a required notification per MURR Technical Specification (TS) 6.6.c.(1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by MURR TS 1.1, had occurred. Specifically, MURR was not in compliance with all Limiting Conditions for Operations (LCOs). MURR was not in compliance with TS 3.5.a.3. and its associated note (1). TS 3.5.a.3 states, 'The reactor shall not be operated unless the following instrument channels are operable: ...3. Source Range Nuclear Instrument Channel...'. Note (1) clarifies that the Source Range Nuclear Instrument Channel is 'required for reactor startup only.' During the first rod withdrawal of the reactor startup, the Source Range Nuclear Instrument Channel indication was erratic. Therefore, it was decided to shut down the reactor. The Source Range Nuclear Instrument Channel was repaired by replacing two power supplies in its instrument drawer, the required compliance procedures were conducted on the nuclear instrument, and permission from the Facility Director was obtained prior to the reactor returning to operation later on 7/4/17. Currently, MURR is at 10 MW. A detailed event report will follow within 14 days as required by MURR TS 6.6.c.(3).
ENS 5270220 April 2017 19:49:00NonTechnical Specification Required Report for an Abnormal OccurrenceOn 4/20/17 at 1449 CDT, the University of Missouri-Columbia Research Reactor (MURR) was shut down due to a failure of the regulating blade drive mechanism to move the regulating blade during reactor operation. This email is a required notification per MURR Technical Specification (TS) 6.6.c. (1) to report to the NRC Operations Center that an Abnormal Occurrence, as defined by MURR TS 1.1, had occurred. Specifically, MURR was not in compliance with all Limiting Conditions for Operations (LCOs). MURR was not in compliance with two (2) LCOs: 1. TS 3.2.a states, 'All control blades, including the regulating blade, shall be operable during reactor operation' and 2. TS 3.2.f states, 'The reactor shall not be operated unless the following rod run-in functions are operable.' Specifically, the rod run-in function that occurs when the regulating blade position is less than or equal to 10% withdrawn was not operable as TS 3.2.f.8 requires. The regulating blade drive mechanism was repaired, the required compliance procedure was conducted on the regulating blade, and permission from the Acting Facility Director was obtained prior to the reactor returning to operation later on 4/20/17. Currently, MURR is at 10 MW. A detailed event report will follow within 14 days as required by MURR TS 6.6.c.(3). The cause of this event is not related to the cause of the earlier regulating blade drive mechanism failure on 1/17/17.
ENS 525363 February 2017 06:00:00Research And Test Reactor EventAir Effluent Concentration Exceeded Technical Specifications(The following) is a required notification per MURR (University of Missouri Research Reactor) Technical Specification (TS) 6.6.c.(1) to report to the NRC Operations Center that an Abnormal Occurrence as defined by MURR TS 1.1.b occurred on February 3, 2017. Specifically, MURR was not in compliance with the Limiting Condition for Operations TS 3.7.b. On February 3, 2017, MURR released the radioisotope Iodine-131 from the ventilation exhaust stack at a concentration equal to 1.07 times AEC (Air Effluent Concentration) which exceeds the one (1) AEC Maximum Controlled Instantaneous Release Concentration for 'Particulates and halogens with half-lives greater than 8 days'. The Iodine-131 originated from the MURR Iodine-131 Processing Hot Cells, not from the reactor. By February 4, 2017, the ventilation exhaust stack radioisotope concentration was within TS limits. Currently, all Iodine-131 processing activities have ceased and will not resume until corrective actions are implemented and permission from the Facility Director is obtained. MURR has convened an Event Review per MURR procedure AP-RR-026 to identify the causes and corrective actions for this departure from specification. A detailed event report will follow within 14 days as required by MURR TS 6.6.c.(3).
ENS 5249518 January 2017 03:30:00Research And Test Reactor EventFailure of the Regulating Blade to MoveOn 1/17/17 at 2130 CST, the MURR (University of Missouri Research Reactor) was shut down due to the failure of the regulating blade to move. This email is a required notification per MURR TS 6.6.c.(1) to report to the NRC Operations Center that an Abnormal Occurrence as defined by MURR TS 1.1 happened. Specifically, MURR was not in compliance with all Limiting Conditions for Operations (LCOs). MURR was not in compliance with the LCO TS 3.2.a. which states, 'All control blades, including the regulating blade, shall be operable during reactor operation.' The regulating blade was repaired, and the required compliance procedure was conducted on the regulating blade prior to the reactor being started up on 1/18/17. Currently, MURR is again at 10 MW. A detailed event report will follow within 14 days as required by MURR TS 6.6.c.(3). The reactor was at 10 MW power when this event occurred. The cause of this event is under investigation. The licensee notified the NRC RTR Project Manager.
ENS 524799 January 2017 06:00:00Research And Test Reactor EventAbnormal Occurrence During Movement of a Regulating BladeOn Jan 09, 2017, during movement of a reactor regulating blade, an expected annunciator did not occur. This required entry into Technical Specification 3.2.F.8. The rod run in relay and contact block were replaced and the system tested satisfactorily. Technical Specification 3.2.F.8 was subsequently exited. The licensee will be notifying the Research and Test Reactor Project Manager.
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