ML15209A890
| ML15209A890 | |
| Person / Time | |
|---|---|
| Site: | University of Missouri-Columbia |
| Issue date: | 07/27/2015 |
| From: | Rhonda Butler Univ of Missouri - Columbia |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML15209A890 (8) | |
Text
UNIVERSITY of MISSOURI RESEARCH REACTOR CENTER July 27, 2015 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P 1-37 Washington, DC 20555-0001
REFERENCE:
Docket No. 50-186 University of Missouri-Columbia Research Reactor Amended Facility License R-103 Written communication as required by University of Reactor Technical Specification 6.1.h(2) regarding Technical Specifications 3.2.a
SUBJECT:
Missouri Research a deviation from The attached document provides the University of Missouri-Columbia Research Reactor (MURR) Licensee Event Report (LER) for an event that occurred on June 29, 2015, that resulted in a deviation from MURR Technical Specification 3.2.a.
If you have any questions regarding this report, please contact John L. Fruits, the facility Reactor Manager, at (573) 882-5319.
Sincerely, CRalph ?A.utler, P.E.
Director RAB:jlb Enclosure MARGEE P. STOUT Z..NOTAJRY'n My Comd on E*ms March 24, 2016 "SEAL ntgoey county Commission #12511436 1513 Research Park Drive Columbia, MO 65211 Phone: 573-882-4211 Fax: 573-882-6360 Web: www.murr.missouri.edu Fighting Cancer with Tomorrow's Technology
Licensee Event Report U.S. Nuclear Regulatory Commission July 27, 2015 Licensee Event Report No. 15 June 29, 2015 University of Missouri Research Reactor Introduction On June 29, 2015, with the reactor operating at 10 MW in the automatic control mode, the control room operator initiated a manual rod run-in to shut down the reactor as part of performing compliance procedure CP-10, "Rod Drop Times." Immediately after the rod run-in was initiated, the control room operator noted that shim control blade 'A' was not driving in the inward direction. The reactor was immediately shut down by placing Master Control Switch IS I in the "Test" position in accordance with reactor emergency procedure REP-8, "Control Rod Drive Mechanism Failure or Stuck Rod." Operation of Master Control Switch IS I removes the holding current from the four control rod drive mechanism (CRDM) electromagnets, thus allowing all of the control blades to drop to their fully inserted positions without inward movement of the CRDMs. All immediate actions of REP-8 were completed.
Failure of the CRDM to move control blade 'A' in the inward direction resulted in a deviation from Technical Specification (TS) 3.2.a, which states, "All control blades, including the regulating blade, shall be operable during reactor operation. "
Description of the Rod Control System The reactivity of the reactor is controlled by five neutron absorbing control blades. Each control blade is attached to a CRDM by means of a support and guide extension (offset mechanism).
Four of the control blades, referred to as the shim blades, are used for coarse adjustments to the neutron density of the reactor core. The fifth control blade is a regulating blade. The low reactivity worth of this blade allows for very fine adjustments in the neutron density in order to maintain the reactor at the desired power level. The nominal speed of the shim blades is one inch per minute in the outward direction and two inches per minute in the inward direction.
Nominal speed of the regulating blade is 40 inches per minute in both the inward and outward directions. The speed of the control blades cannot be adjusted without physically altering the system. The four shim blades are actuated by electro mechanical CRDMs that position, hold, and scram each shim blade. Each CRDM consists of a 0.02-HP, 115-volt, one-amp, single-phase, 60-cycle motor connected to a lead screw assembly through a reduction gearbox and overload clutch. The reactivity worth and speed of travel for the control blades are sufficient to allow complete control of the reactor system from a shutdown condition to full power operation.
The insertion rate of the control blades is adequate to ensure prompt shutdown of the reactor in the event a scram signal is received.
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Licensee Event Report U.S. Nuclear Regulatory Commission July 27, 2015 Control blade movements, interlocks and bypasses, and control modes are managed by the Rod Control System. The Rod Control System is a relay and switch logic system used to prohibit accidental or incorrect operation which could result in an unsafe condition.
During normal operation, Master Control Switch IS1 allows the shim blades to be withdrawn or inserted manually by a three-position ("In-Normal-Out") switch (1S4) located on the reactor control console. The switch is spring return to the mid-position ("Normal") when released. A five-position ("A-B-C-D-Gang") selector switch (1S 3) enables the reactor operator to select the shim blades individually or as a group. 115 VAC power is supplied to the CRDM motor windings through motor relays (see Attachment 1); KI for shim control blade insertion and K2 for shim control blade withdrawal.
Detailed Event Description On June 29, 2015, at 02:00 with the reactor operating at 10 MW in the automatic control mode, the control room operator initiated a manual rod run-in as part of performing compliance procedure CP-10, "Rod Drop Times." Immediately after the rod run-in was initiated, the control room operator noted that shim control blade 'A' was not driving in the inward direction. The reactor was immediately shut down by placing Master Control Switch 1S I in the 'Test' position in accordance with reactor emergency procedure REP-8, "Control Rod Drive Mechanism Failure or Stuck Rod." Operation of Master Control Switch ISI removed the holding current from the four CRDM electromagnets, thus allowing all of the control blades to drop to their fully inserted positions without inward movement of the CRDMs. All control blades were verified to be fully inserted. All immediate actions of REP-8 were completed. Failure of the CRDM to move shim control blade 'A' in the inward direction resulted in a deviation from TS 3.2.a, which states, "All control blades, including the regulating blade, shall be operable during reactor operation."
After the reactor was secured, the CRDM was removed for inspection. Troubleshooting efforts revealed an intermitted failure of CRDM 'A' motor relay KI. Relay contacts 6 and 10 would intermittently not make sufficient contact to allow current flow with the relay coil energized; thus preventing the motor inward direction windings from being energized.
Safety Analysis The basis for TS 3.2.a is to ensure that the normal method of reactivity control is used during reactor operation. When operating the reactor at 10 MW in the automatic control mode, the control blades are routinely shimmed in the outward direction as a result of poison buildup and fuel depletion. Shimming of a control blade in the in-ward direction after initial reactor startup is not a routine occurrence and therefore it is difficult to postulate at what time the failure occurred and how long the reactor may have been in operation with the failed relay. A review of the Page 2 of 4
Licensee Event Report U.S. Nuclear Regulatory Commission July 27, 2015 Nuclear Instrumentation (NI) power level strip-chart recorders indicated conditions consistent with steady-state operation for the entire week. While the ability of inward movement of control blade 'A' may have been unavailable sometime during this period, at no time was the ability to scram the reactor, either through automatic initiation or manually by the control room operator, affected by this failure. CRDM motor relays KI and K2 are not a part of the Reactor Safety System.
Corrective Actions When the control room operator discovered that CRDM 'A' would not move the shim control blade in the inward direction, he immediately initiated a reactor scram by placing Master Control Switch I SI in the "Test" position and completed the immediate actions of reactor emergency procedure REP-8, "Control Rod Drive Mechanism Failure or Stuck Rod," to ensure the reactor was in a safe shutdown condition. All four shim control blades were verified to be fully inserted.
Troubleshooting efforts identified the failure of CRDM motor inward relay K1. The relay was bench tested to identify the single component intermittent failure of contacts 6 and 10. A visual inspection of the relay internals also revealed some discoloration on contacts 8 and 12, which can be associated with a high resistance connection (Attachment 1). This type of relay, Magnecraft 782HXDXH21-120A, has been used at MURR for many years and has proven very reliable in the past. However, a similar event occurred on April 23, 2014 (see LER 14-02, letter dated May 16, 2014). As a result of that event, all Magnecraft relays of that lot number were removed from service and a new lot of relays were installed. At that time the relay manufacturer (Schneider Electric) was contacted and MURR was assured that the failure was an isolated instance and not an identified deficiency.
Because this June 2 9 th occurrence is a similar repeat failure, the Magnecraft relay has been replaced with an equivalent relay from a different manufacturer (Allen Bradley) (Attachment 2). In addition to replacing the failed relay, all Magnecraft relays have been removed from the remaining CRDMs and replaced with Allen Bradley relays.
MURR electronic maintenance procedure EMP-12, "Drive Mechanism," was completed on CRDM 'A.'
Additional post maintenance testing included bench testing to ensure correct operation of the CRDM relay contacts, monitoring CRDM run current and speed over the full length of travel, and performing multiple cycles of the CRDM motor relay to ensure proper operation.
Additionally, this event was entered into the MURR Corrective Action Program as CAP entry No. 15-0057 and any additional information or corrective actions will be considered and documented.
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Licensee Event Report U.S. Nuclear Regulatory Commission July 27, 2015 If there are any questions regarding this Licensee Event Report, please contact me at (573) 882-5319. 1 declare under penalty of perjury that the foregoing is true and correct.
Sincerely, John L. Fruits Reactor Manager ENDORSEMENT:
Reviewed and Approved, Ralph A. Butler, P.E.
Director xc:
Reactor Advisory Committee Reactor Safety Subcommittee Dr. Garnett S. Stokes, Provost Dr. Henry C Foley, Senior Vice Chancellor for Research Mr. Geoffrey Wertz., U.S. NRC Mr. Johnny Eads, U.S. NRC Attachments:
- 1. Control Rod Drive Mechanism Motor Relay KI
- 2. 700-HC Miniature Ice Cube Relay v~Y PgRGEE P.
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ATTACHMENT 1 Magnecraft 782H Hermetic Ice Cube Relay Relay Contacts 6-10 Control Rod Drive Mechanism Motor Relay Ki
ATTACHMENT 2 Bulletin 700-NC Miniature Ice Cube Relay Product Selection Bulletin 700-HC Miniature Square Base with Blade Terminals Description Contact Rating 2PDT 2-Pole 2 Form C Contacts:
ID A - AgNi Contacts IDA C300 C300 Low energy rating; II0V, 10 mA) 100 mw PA Low energy rating:
(5V, 10 mA or 25V, 2 mA) 50 mW Wiring Diagrams U.S./Canada International 1-1.1
,C-i2.
AInpl 4
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700 HN128 700-HN103 700-HN104
-. Input u
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Coil Voltage Cat. No.
4PDT 4-Pole 4 Form C Contacts:
7A = AgNl*A Gold Plated Contacts 4PDT 4-Pole 4 Form C Contacts:
7A - AgNi Silver Contacts 12V DC 24V DC 24V AC 120V AC 240V AC 6V AC 12V AC 24V AC 120V AC 240V AC 6V DC I ZV DC 24V DC 48V DC 1 V DC 6V AC 12V AC 24V AC 120V AC 240V AC 6V DC 12V DC 24V DC 48V DC I IOV DC 700-HC22Z12 700-HCZ2Z24 700-HC22A24 700-HC22Ai 700-HC22A2 700-HC 14A06 700-HC14AI 2 700-HC14A24 700-HC14A1 700-HC14A2 700.HC14Z06 700-HC 14212 700-HC 14Z24 7D0,HC 14Z48 700-HC14Z1 700-HC24A06 700-HC24A12 700-HC24A24 700-HC24A1 700-HC24A2 700-HC24206 700-HC24Z12 700-HC24Z24 700-HC24Z48 700-HC24Z1 7A C300 R300 Low energy rating; i0 V, 10mA) 100 mW 700-HNN103 700-11M28T 700-HN104-
- LED Option: Add suffix (-4) to the selected Bulietin 700-NC Relay Cat. No. eLrept for the 240V AC units, add i-411.
t Push-to-Test arid LEl) Option: Add suffix (-3-4) to the selected Bultletin 700-HC Retay Cat. No., except for the 240V AC units, add (-3-41Ll.
Copyright0 2015 Rockwell Automation, Inc All Rights Reserved
Cat. No. 700-HC..
Electrical Ratings PiLot Duty Rating 4 Rated Thermal Current /skh)
Rated Insulation Voltage (U,)
ATTACHMENT 2 NEMA C300, R300 7 A and 10 A 250Y IEC - 300V UL/CSA Contacts Inductive 120V AC 240V AC General Purpose Resistive Min. Low Energy Permissible Load Permissible Coll Voltage Variation 700-HC-4 15 4 7.5 A 7 A, 277%'
.4111l 1.5 A 0.75 A Hp 1/8 1/3 700-HC22 IS A 7.5 A 10 A, Z77V AC 10 A, 24V DC 1.5 A 0.75 A Hp 1/3 3/4 7 A, 30V DC 100 mW (10V, 10 mA)
- Sliver Contacts 50 mW ISV, 10 mA or 25V, 2 mA) - Gold Contacts Pickup:
80..110W. of Nominat Voltage at 50 Hi 80... 110 5 of Nominal Voltage at 60 H-00.110.. of Nominal Voltage at DC Must Dropout Voltage:
20O of Nominal Voltage at AC 1W, of Nominal Voltage at DC 5O Hz Coil AC Inrush 2.2 VA Consumption Coils
.lot.
Seated 1.3 VA DC CoIls 1.0 W Max. AllOwable Leakage 20': of VA IAC) 10,X of W (DC)
Design Specification/Test Requirements Electrical Dielectric Withstand Pote-to-Poee 200V Voltage 60 Hz 1.6 VA 1.1 VA Contact to Colt Electrical Life (Cycles)
Mechanical Degree of Protection (Open Type) IEC 529 Mechanical Life Cycles Swritching Frequsency OperaUons Coil Voltages Operating Time (ms)
Maa. Pickup Max.
Dropout 4000V 100 020 minimum IP 20 (Guarded Terminal Sockets) 20 x l6 JAC)50 x Io D (DCI 1800/HR See Product Selection 10 3
Maximum Operating Rate Environmental Termperature Altitude Insulating Material EnclosuIre Contact Material Terminal Markings on Sock Sockets Certifications Standards 0 cycles/s Operating
-30...5 C
(-22...1}31 "FI Storage 55...-85 'C t-67...,`185 "Fl, 2000 m f6560 ft)
Molded High Dielectric Mateliat Transparent Dust Cover
,gSi )700-HC21 Agili -. 5 itm All (700-1101) et In accordance with ENS0 0005 700-.11103, -HN51289, -iI,104 cURus Recognized (I'le No. E14843, Guide NRNT2fNRNTB), cULus Listed wshen used with Bulletin 700-HNI03, 11104, and -HN128 sockets iile No. E14843, Guide IRNT/NRNT7), CE Marked, LP Certified UL 508. CSA Z2.2 No. 14, EN 61810-1
- SWe Performance Date.
t NEMA Rating Chart is in publication 700-SG003"