Information Notice 2018-10, Thermal Sleeve Flange Wear Leads to Stuck Control Rod at Foreign Nuclear Plant

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.

ML18214A710

BACKGROUND

There have been no prior NRC Generic Communications related to the issue of CRDM thermal

sleeve flange wear.

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

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

/PM PM A BC

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