CNS-17-021, Special Report 2017-01 for the Units 1 and 2 Loose Parts Monitoring System Non-Functional for Greater than 30 Days

Special Report 2017-01 for the Units 1 and 2 Loose Parts Monitoring System Non-Functional for Greater than 30 Days

ML17111A963
Person / Time
Site:	Catawba
Issue date:	04/20/2017
From:	Simril T Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2017-01, CNS-17-021
Download: ML17111A963 (5)

Text

. .

ef~DUKE Tom Simril

~JENERGY~ Vice President Catawba Nuclear Station Duke Energy CN01 VP I 4800 Concord Road York, SC 29745 o: 803. 701.3340 f: 803. 701.3221 Tom.Simril@duke-energy.com CNS-17-021 April 20, 2017 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001

Subject:

Duke Energy Carolinas, LLC (Duke Energy)

Catawba Nuclear Station, Units 1 and 2 Docket Numbers 50-413 and 50-414 Special Report 2017-01 for the Units 1 and 2 Loose Parts Monitoring System Non-Functional for Greater than 30 Days In accordance with Required Action A.2 of the Catawba Nuclear Station Selected Licensee Commitment (SLC) 16-7.4, "Loose-Part Detection System," attached is Special Report 2017-01 concerning an occurrence of the Units 1 and 2 Loose Parts Monitoring System having Collection Regions which were non-functional for a period of greater than 30 days. SLC 16-7.4 states that if all channels of one or more Loose-Part Collection Region(s) are non-functional for greater than 30 days, then prepare and submit a Special Report to the Commission outlining the cause of the malfunction and the plans for restoring the channel(s) to FUNCTIONAL status within 40 days.

This occurrence is considered to be of no significance with respect to the health and safety of the public. There are no new regulatory commitments contained in this letter.

Questions on this special report should be directed to Sherry Andrews at 803-701-3424.

Sincerely,

-iOYY\~

Tom Simril Vice President, Catawba Nuclear Station Attachment

Document Control Desk Page 2 April 20, 2017 xc:

Catherine Haney Regional Administrator U.S. Nuclear Regulatory Commission - Region II

• Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, GA 30303-1257 Joseph D. Austin Senior Resident Inspector (Catawba)

U.S. Nuclear Regulatory Commission Catawba Nuclear Station Michael Mahoney (addressee only)

NRC Project Manager (Catawba)

U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 0-8H4A 11555 Rockville Pike Rockville, MD 20852-2738 S.E. Jenkins Manager Radioactive and Infectious Waste Management Division of Waste Management South Carolina Department of Health and Environmental Control 2600 Bull St.

Columbia, SC 29201

,i.

Attachment Catawba Nuclear Station, Units 1 and 2 Special Report 2017-01 BACKGROUND Catawba Nuclear Station Units 1 and 2 each have a Loose Parts Monitoring System (LPMS) in order to meet Regulatory Guide 1.133, Rev 1, as described in the UFSAR.

The LPMS is an electronic system that monitors the Reactor Coolant System for metal-to-metal impacts in the primary coolant loop. Accelerometer sensors are mounted at various collection regions on the exterior surfaces of the upper reactor vessel, lower reactor vessel, reactor coolant pumps, and steam generators. The signal information from these sensors are amplified and then routed out of containment to the LPMS cabinet mounted in the Control Room.

Selected Licensee Commitment (SLC) 16.7-4 "Loose-Part Detection System" states the requirements of the LPMS. SLC 16.7-4 requires at least one channel in a Collection Region to be functional when in Modes 1 and 2. The SLC defines a Loose-Part Collection Region as "an area within the reactor coolant system where loose parts can possibly collect and which is monitored by the Loose-Part Detection System." The SLC lists the Collection Regions:

1) Lower reactor vessel (3 SLC sensor channels)

2) Upper reactor vessel (3 SLC sensor channels)

3) Primary side of steam generator A (2 SLC sensor channels)

4) Primary side of steam generator B (2 SLC sensor channels)

5) Primary side of steam generator C (2 SLC s_ensor channels)

6) Primary side of steam generator D (2 SLC sensor channels)

The SLC states the secondary side of all the steam generators and reactor coolant pumps channels (each having 1 non-SLC sensor channel) are not in a Collection Region required by Regulatory Guide 1.133.

Each steam generator has two SLC and one non-SLC sensor channels. The sensor channel locations are close to each other, and if one detects a loose part, it is expected that the other channels in that area would also detect the loose part, regardless of the channel being SLC or non-SLC related. Because the steam generator channels located on secondary side are excluded from the Collection Region, if one SLC steam generator channel fails, orily the remaining SLC channel can be used to meet the SLC.

As described in the LPMS User Manual, the LPMS uses a feature called Single Channel Alarm Inhibit (SCA lnh) to reduce false alarms on the system. This feature prevents an event from being reported if only a single channel alarms. This method is based on the assumption that any true loose part would trigger more than one sensor. This feature requires more than one channel to meet the alarm criteria at the same time in order for the LPMS to generate a Control Room alarm. This feature can be activated or overridden on a per channel basis by user-specified settings. The default is that SCA lnh is active. Therefore, if only one SLC channel is active in a Collection Region, in order for the channel to be considered functional per the SLC, that channel's SCA lnh Override must be selected so that the LPMS will trigger an alarm with only one SLC channel alarm from that Collection Region.

A channel check is performed every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> per SLC Surveillance 16.7-4-1 of each Collection Region channel. The audio check is performed each night shift per the Mode 1 Periodic Surveillance Items procedure.

DESCRIPTION OF OCCURRENCE The Unit 1 LPMS did not meet SLC requirements for the 1C Steam Generator Collection Region from 12123115 to 3116117.

For the 1C Steam Generator, the sensor channels are:

Channel 7 - 1C SIG Manway (SLC)

Channel 8 - 1C SIG Hot Leg (SLC)

Channel 16 - 1C SIG Secondary (non-SLC)

Channel 8 (SLC) for the 1C SIG region was disabled on 12123115 due to a problem on the channel. This resulted in the 1C SIG region having one SLC and one non-SLC channel active.

While this is sufficient for the Unit 1 LPMS to detect a loose part in this region, this does not meet SLC requirements. Channel 7 (SLC) would need the SCA lnh Override setting enabled to meet SLC requirements to allow the single active SLC channel to alarm. This was performed on 3116117. During this time, it is expected that the Unit 1 LPMS would have detected a loose*

part in that area due to the non-SLC required Secondary Channel 16 in the area remaining functional. Also, the nightly audio channel checks did not observe any unusual noises during this time.

The Unit 1 LPMS did not meet SLC requirements for the 1A Steam Generator Collection Region from 2118116 to 3116117.

For the 1A Steam Generator, the sensor channels are:

Channel 9 - 1A SIG Manway (SLC)

Channel 10 - 1A SIG Hot Leg (SLC)

Channel 18 - 1A SIG Secondary (non-SLC)

Channel 9 (SLC) for the 1A SIG region was disabled on 2118116 due to a problem on the channel. Channel 18 (non-SLC) for the 1A SIG region was also disabled during this time due to a previous modification to a circuit card. With both of these channels disabled, only Channel 10 (SLC) was active for the 1A SIG region, and required the SCA lnh Override setting ~nabled to be able to detect loose parts in the region. The Override setting was enabled on 3116117.

During this time, the nightly audio checks did not detect any unusual noises. Additionally, the LPMS has not detected a loose part on Channel 10 after activation of the SCA lnh Override on 3116117. Therefore, there is no concern of an unidentified loose part in this region.

The Unit 2 LPMS did not meet SLC requirements for the 2D Steam Generator Collection Region from 11114116 to 3116117.

For the 20 Steam Generator, the sensor channels are:

Channel 20 - 2D SIG Secondary (non-SLC)

Channel 21 - 2D SIG Manway (SLC)

Channel 22 - 20 SIG Hot Leg (SLC)

On 11/14/16, Channel 21 (SLC) developed a problem which was discovered 11/16/16 during monthly channel functional test. The channel was disabled per procedure. On 3/7/17, Channel 22 (SLC) developed a field problem and was disabled per procedure. On 3/9/17, the problem on Channel 21 cleared, and the channel was re-enabled. When both of these channels were disabled, the system was not able to detect loose parts in the 20 SIG region. When only one of these channels was disabled, the system could detect a loose part in this region, but the SCA lnh Override setting would need to be enabled to meet SLC requirements. The Override setting was enabled on 3/16/17. With the exception of the time period between 3/7/17 and 3/9/17, it is expected that the Unit 2 LPMS would have detected a loose part in the 20 SG Collection Region due to the non-SLC required Secondary Channel 20 in the area remaining functional.

Also, the nightly audio channel checks did not observe any unusual noises.

CAUSE OF THE NON-FUNCTIONALITY For both Units 1 and 2, a legacy deficiency was identified with the Loose Parts Monitoring System Channel Functional Test procedure on 3/14/17. The procedure did not provide guidance to activate the Single Channel Alarm Inhibit (SCA lnh) Override in the case of only one SLC channel active in a region. In addition, the procedure allowed all SLC channels in a region to be disabled (Unit 2 SLC Channels 21 and 22 were both disabled from 3/7/17 to 3/9/17).

CORRECTIVE ACTIONS

• 1) The Loose Parts Monitoring System Channel Functional Test procedure was updated to include instructions for the following:

a. Direction to activate Single Channel Alarm Inhibit Override, if the channel in question is the only SLC channel in a region, or when disabling a collection channel.

b. Steps to prevent all SLC channels in a region from being inadvertently disabled.

c. Additional guidance for monthly testing to ensure that if a channel has its SCA lnh Override enabled, it remains enabled after testing is complete. Testing currently enables and disables SCA lnh Override as part of the testing, and the new instructions prevent this setting from accidentally being changed.

2) Restore Units 1 and 2 LPMS to functionality:

a. After the Loose Parts Monitoring System Channel Functional Test procedure was updated, the SCA lnh Override feature was enabled for Unit 1 Channels 7 and 10, and Unit 2 Channel 21 on 3/16/17.

b. Portions of the procedure were used as a functional test to ensure the channels would alarm as expected.