ML21022A419
| ML21022A419 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 01/22/2021 |
| From: | Laura Smith Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML21022A419 (3) | |
Text
Exelon Generation~
January 22, 2021 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Calvert Cliffs Nuclear Power Plant, Unit No. 1 Renewed Facility Operating License No. DPR-53 NRC Docket No. 50-317 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
Subject:
Reactor Vessel Level Monitoring System and Wide Range Pressurizer Pressure System Special Report
Reference:
(a) Letter from L. D. Smith (Exelon) to Document Control Desk {NRC), dated January 13, 2021, Reactor Vessel Level Monitoring 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 1 Reactor Vessel Level Monitoring System (RVLMS) and Wide Range Pressurizer Pressure System_having less than the required minimum number of operable channels. This report supersedes the report submitted in Reference (a) as Reference (a) did not include the Wide Range Pressurizer Pressure System_having less than the required minimum number of operable channels in its report.
ACTION TAKEN On December 10, 2020 at 1517, Unit 1 Control Room received an unexpected alarm at window E-10 on 1C06, "RVLMS [Reactor Vessel Level Monitoring System] CH A 1C144A" and responded in accordance with the applicable alarm response procedure. The Channel A Post-Accident Monitoring Display at 1C06 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 {1Cl44A) 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, Calvert Cliffs entered Technical
Document Control Desk January 22, 2021 Page 2 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 1 RVLMS Channel B remains operable with all eight of its sensors functioning normally. The removal of Channel A 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 1 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 1-PD-102A-D at normal operating pressure, Channel B PAMS Wide Range Pressurizer Pressure 1PT105B, 1-Pl-103, or 1-Pl-103-A at low pressure, and 1P105B on the Plant Process Computer.
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-April 2021 based on 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.
- b~
Larry D. Smith Regulatory Assurance Manager LDS/KLG/lmd
Document Control Desk January 22, 2021 Page 3 cc:
NRC Project Manager, Calvert Cliffs NRC Regional Administrator, Region I NRC Resident Inspector, Calvert Cliffs S. Seaman, MD-DNR