Information Notice 2018-10, Thermal Sleeve Flange Wear Leads to Stuck Control Rod at Foreign Nuclear Plant
| ML18214A710 | |
| Person / Time | |
|---|---|
| Issue date: | 08/29/2018 |
| From: | Chris Miller, George Wilson Division of Inspection and Regional Support, Division of Materials and License Renewal |
| To: | |
| Croon G | |
| References | |
| IN-18-010 | |
| Download: ML18214A710 (3) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
OFFICE OF NEW REACTORS
WASHINGTON, DC 20555-0001 August 29, 2018 NRC INFORMATION NOTICE 2018-10: THERMAL SLEEVE FLANGE WEAR LEADS TO
STUCK CONTROL ROD AT FOREIGN NUCLEAR
PLANT
ADDRESSEES
All holders of an operating license or construction permit for a nuclear power reactor under
Title 10 of the Code of Federal Regulations Part 50, Domestic Licensing of Production and
Utilization Facilities, except those who have permanently ceased operations and have certified
that fuel has been permanently removed from the reactor vessel.
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform
addressees about recent operating experience (OE) related to Westinghouse (WEC) nuclear
steam supply system plants that have thermal sleeves in the control rod drive mechanism
(CRDM) penetration tubes. The available OE demonstrates the potential for these components
to experience wear of the thermal sleeve flange from contact against the CRDM penetration
tube. The resulting wear can have significant consequences which were not previously
considered for WEC designed pressurized water reactors (PWRs). The purpose of this IN is to
raise industry awareness regarding this issue for similar designed PWRs. The NRC expects
that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. Suggestions contained in this IN are not NRC
requirements; therefore, no specific action or written response is required.
DESCRIPTION OF CIRCUMSTANCES
In December 2017, following a refueling outage at an Electricite de France (EDF) facility, the
French plant identified one stuck control as part of the rod control rod drop and stepping tests, which precluded the plant from starting up. The plant returned to mode 6, removed the vessel
head and determined by visual inspection that the CRDM thermal sleeve flange in the
centermost location was completely worn through. This resulted in a loose part that lodged in
the path of the CRDM shaft, thereby precluding motion of the control rod. Within the same time
frame, another stuck control rod occurred at another French plant. Due to the common wear
issue observed at these two plants, EDF notified the French Nuclear Safety Authority in
February 2018 of the significant safety events.
Due to similarities in design it is reasonable to assume that over time US plants may also
experience similar wear. Additional information is available in WEC letter Nos. LTR-NRC-18-34 and LTR-NRC-18-53, dated May 23, 2018, and July 17, 2018, respectively. These documents
can be found on the NRCs public Web site under Agencywide Documents Access and
Management System Accession Nos. ML18143B678 and ML18198A275.
BACKGROUND
There have been no prior NRC Generic Communications related to the issue of CRDM thermal
DISCUSSION
The above operating experiences illustrate that unexpected wear could occur in certain thermal
sleeves during normal operating conditions. Therefore, facilities that have similarly designed
thermal sleeves may consider monitoring for thermal sleeve flange wear and if needed consider
taking corrective action(s) to mitigate any potential safety consequences that can result from the
noted wear.
CONTACT
S
This information notice does not require any specific action or written response. Please direct
any questions about this matter to the technical contacts listed below.
/RA/ /RA by Michael King for/
George A. Wilson, Director Christopher G. Miller, Director
Division of Materials and License Renewal Division of Inspection and Regional Support
Office of Nuclear Reactor Regulation Office of Nuclear Reactor Regulation
Technical Contact:
David Rudland, NRR
301-415-1896 E-mail: David.Rudland@nrc.gov
ML18214A710 *email concurrence
NRR/DMLR/
OFFICE
MPHB
OIP/ICAB RI* RII* RIII* RIV*
NAME RKalikian SWittick MFerdas* SSandal* AStone* GGeorge*
DATE 8/27 /18 8/28/18 8/09/18 8/03/18 8/13/18 8/04/18 NRR/DIRS/IRGB NRR/DIRS/IRGB/ NRR/DIRS/IRGB/L NRR/DIRS/IRGB/
OFFICE NRR/DMLR/D NRR/DIRS/D
CMiller*
NAME GCroon BBenney ELee BPham* GWilson*
/RA by MKing for/
DATE 8/27 /18 8/27 /18 08/21/18 8/27/18 8/29/18 8/29/18 OFFICE NRO/DCIP/D
NAME TMcGinty*
DATE 08/29/18