ML21025A421
| ML21025A421 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 01/25/2021 |
| From: | Laura Smith Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML21025A421 (3) | |
Text
Larry D. Smith Regulatory Assurance Manager Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657 410 495 5219 Office 410 610 9729 Mobile www.exeloncorp.com larry.smith2@exeloncorp.com TS 3.3.10 and 5.6.7 January 25, 2021 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Calvert Cliffs Nuclear Power Plant, Unit No. 2 Renewed Facility Operating License No. DPR-69 NRC Docket No. 50-318
Subject:
Reactor Vessel Level Monitoring System and Wide Range Pressurizer Pressure System Special Report This special report is submitted in accordance with Calvert Cliffs Nuclear Power Plant Technical Specification 3.3.10. The report is required due to the Unit 2 Reactor Vessel Level Monitoring System (RVLMS) and Wide Range Pressurizer Pressure System having less than the required minimum number of operable channels.
ACTION TAKEN On December 23, 2020 at 0315, Unit 2 Control Room received an unexpected alarm at window E-10 on 2C06, "RVLMS [Reactor Vessel Level Monitoring System] CH A 2C144A and responded in accordance with the applicable alarm response procedure. The Channel A Post-Accident Monitoring Display at 2C06 System Health screen indicated a fan malfunction, and showed a Fan Fail Red light illuminated at the same time. In accordance with site procedure the associated cabinet (2C144A) should be considered inoperable. This rendered both Channel A RVLMS and Channel A Wide Range Pressurizer Pressure inoperable. Calvert Cliffs Technical Specification "Post-Accident Monitoring (PAMS) Instrumentation,"
Table 3.3.10-1, Functions 5 and 10, require two channels of RVLMS and Wide Range Pressurizer Pressure to be operable. Because of the subject failure, Calvert Cliffs entered Technical Specification 3.3.10, Condition A. When the Completion Time of Condition A expired on January 22, 2021 at 0315, Calvert Cliffs entered Technical Specification 3.3.10, Condition B, which requires submission of this report in accordance with Technical Specification 5.6.7.
PREPLANNED ALTERNATE METHOD OF MONITORING The RVLMS instrumentation is designated for post-accident monitoring use. It provides the plant operator with information to assess void formation in the reactor vessel head region and the trend of liquid level in the reactor vessel plenum. The RVLMS consists of two redundant channels. Unit 2 RVLMS Channel B remains operable with all eight of its sensors functioning normally. The removal of Channel A
Document Control Desk January 25, 2021 Page 2 from operable status eliminates a means of redundant indication. However, alternate methods of monitoring for core and Reactor Coolant System voiding, using pressurizer level, Reactor Coolant System subcooling, hot and cold leg temperature, and core exit thermocouple instrumentation, were initiated as required by plant procedures.
The Wide Range Pressurizer Pressure System is designated for post-accident monitoring use. It is used by Operations to monitor the cooldown of the Reactor Coolant System following a loss of coolant accident and other design bases accidents. The Wide Range Pressurizer Pressure System consists of two redundant channels. Unit 2 Wide Range Pressurizer Pressure System Channel B remains operable. The removal of Channel A from operable status eliminates a means of redundant indication. Alternate methods of monitoring Pressurizer pressure are 2PI103A-D, 2PI103 or 2PI105AA.
CAUSES OF INOPERABILITY The cause of inoperability is the failure of channel A RVLMS cabinet cooling fan. The most probable cause of this failure is age-related degradation.
PLANS AND SCHEDULES FOR RESTORING THE SYSTEM TO OPERABLE STATUS Currently, Maintenance is waiting on the replacement fan assembly to arrive onsite. The expected return to service date is mid-October 2021 due to a lengthy lead time for fan assembly delivery.
There are no regulatory commitments contained in this correspondence.
Should you have questions regarding this matter, please contact me at (410) 495-5219.
Respectfully, Larry D. Smith Regulatory Assurance Manager LDS/KLG/lmd cc:
NRC Project Manager, Calvert Cliffs NRC Regional Administrator, Region I NRC Resident Inspector, Calvert Cliffs S. Seaman, MD-DNR
Document Control Desk January 25, 2021 Page 3 bcc:
D. T. Helker F. Mascitelli T. P. Haaf J. A. Dullinger R. C. Jones D. M. Fiore H. M. Crockett D. J. Hild L. D. Smith K. L. Greene L. Day P. Beavers E.R. Kreahling D. R. Sheets EDMS NRC 21-005