05000400/LER-2016-003
| Shearon Harris Nuclear Power Plant - Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4002016003R00 - NRC Website | |
comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Inf000llects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
Note: Energy Industry Identification System (EllS) codes are identified in the text within brackets [ ].
A. Background
Event Date: September 21, 2016 Mode: 1 Reactor Power: 100 percent No change in plant mode or in reactor power occurred as a result of the conditions described in this report.
On February 17, 1998, the NRC issued Information Notice (IN) 97-45, Supplement 1, to alert licensees of the potential of erratic indications from high-range radiation monitors as result of a problem with their associated coaxial cables. These erratic indications could mislead operators assessing radiation levels in the containment building during accident scenarios. The erratic indications result from positive and negative current flow when exposed to transient temperature conditions, such as those postulated during a loss-of-coolant accident or a main steamline break. This phenomenon is known as temperature induced current (TIC), and could result in false high radiation readings for approximately 15 minutes following a design basis accident.
B. Event Description
On September 21, 2016, Shearon Harris Nuclear Power Plant, Unit 1, (Harris) declared both Containment High-Range Radiation Monitors (CHRRMs) [RIT] inoperable following a review of the previous actions taken in response to IN 97-45, Supplement 1, and determining them to be inadequate. The CHRRMs utilize Rockbestos cables [CBL1] similar to those described in IN 97-45, Supplement 1. The use of these cables by Harris is historical, going back at least 20 years.
The CHRRMs are part of the Radiation Monitoring System [IL] and provide an estimate to operations personnel of radioactivity inside containment for the purpose of detection of, or verification of, a breach of fission product barriers, and for monitoring and accessing conditions following an accident. This is a safety-related function that is required for Technical Specification (TS) operability. This is a monitoring function only, and does not initiate any specific control actions or provide an actuation signal for other equipment.
For inoperable CHRRMs, TS requires "either restore the inoperable channel(s) to OPERABLE status within 7 days or prepare and submit a Special Report to the Commission, pursuant to Specification 6.9.2, within the next 14 days." The cables have been installed for at least 20 years, with none of the TS-prescribed actions occurring. Thus, this condition is reportable as a condition prohibited by TS per 10 CFR 50.73(a)(2)(i)(B). In addition, the CHRRMs will not be restored to operable in 7 days, thus the TS 6.9.2 Special Report is required. This LER is being submitted to address both reporting requirements.
The potentially impacted components are coaxial cables manufactured by RSCC under the name Rockbestos, model RSS-6-104/LD.
C. Causal Factor The cables were installed in accordance with Harris' design configuration. The use of these cables by Harris is historical, going back at least 20 years.
comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Inf000llects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
D. Safety Analysis
The CHRRMs provide a monitoring function only, and do not initiate any specific control actions or provide an actuation signal for other components. These monitors do not perform a specific function in mitigating the consequences of an accident, and are not modeled per Probablistic Risk Assessment. Alternate means of monitoring conditions in containment are available to the operators. This condition does not render the CHRRMs inoperable for all conditions, but only for a period of about 15 minutes immediately following a loss-of-coolant accident or a main steamline break.
Periodic testing of the CHRRMs has not revealed any other conditions that would challenge the monitor's accuracy or reliability. Therefore, this condition represents a degradation of low safety significance.
At no point in the potentially impacted period were the CHRRMs required to provide information during a design basis accident. Thus, there is no consequence to the health and safety of site personnel or to the public.
E. Corrective Actions
Completed Actions:
Information regarding this condition has been added to the Operations' Turnover sheet to ensure adequate awareness by operations.
Planned Actions:
Either (1) perform site specific testing on the currently installed cables to implement a correction factor for use with the radiation monitoring system, (2) replace the affected cables with cables not impacted by TIC, or (3) gain NRC approval of a License Amendment Request to restore compliance.
F. Additional Information
There have been no previous Licensee Event Reports due to the impact of TIC on the CHRRMs.