ENS 46354
ENS Event | |
|---|---|
22:51 Oct 22, 2010 | |
| Title | Potential Inoperability of Oscillation Power Range Monitors |
| Event Description | {{#Wiki_filter:At 1751 [CDT] on Oct 22, 2010, Dresden Nuclear Power Station (DNPS) determined that current Oscillation Power Range Monitors (OPRM's) setpoints, as outlined in the Core Operating Limits Report (COLR), for Dresden U2 are non-conservative. This renders the Technical Specification (TS) function of the OPRM's in the Reactor Protection System (RPS) inoperable.
This event was initiated as a result of notification by Westinghouse Nuclear Fuels (NF-BEX-10-157) that an error exists in the McSLAP computer code which affects the Safely Limit Minimum Critical Power Ratios (SLMCPR) for Dresden. Currently the COLR and installed, amplitude setpoint (Sp) is 1.13 and the confirmation count setpoint (Np) is 15. This is required to be adjusted to 1.12 (Sp) and 14 (Np). Alternative methods to detect and suppress thermal hydraulic instabilities were initiated as required by Technical Specifications. This non-conservative computer code error could potentially have prevented fulfillment of the OPRM system's safety function and is therefore reportable per 10 CFR 50.72(b)(3)(v)(A), 'An event or condition that could have prevented the fulfillment of a safety function - shutdown the reactor and maintain it in a safe shutdown condition.' Corrective actions include the following: 1. Revise U2 Core Operating Limit Report (COLR) to reflect correct values as determined by Westinghouse Nuclear Fuels Letter (NF-BEX�l0-157). 2. Adjust OPRM setpoints to comply with COLR values. The licensee will notify the NRC Resident Inspector.
On October 22, 2010, Dresden Nuclear Power Station was notified by Westinghouse that an error in McSlap computer code resulted in a non-conservative MCPR safety limit. The preliminary results of the Westinghouse evaluation concluded that the setpoints for the Oscillation Power Range Monitors were also non-conservative. As a result of the notification, Dresden declared all channels of OPRM inoperable and took the required action of the plant's technical specifications. This was considered a loss of function. This condition was reported as a condition that could have potentially prevented the fulfillment of the OPRM system's safety function in accordance with 10 CFR 50.72(b)(3)(v)(A), an event or condition that could have prevented the fulfillment of a safety function - shutdown the reactor and maintain it in a safe shutdown condition. However, subsequent evaluation of the preliminary result determined that the original conclusions were overly conservative and the OPRM setpoints did not require revision. Based on the later evaluation, the function of the OPRMs was not adversely impacted by the installed setpoints. Thus, the system was always capable of performing its intended safety function. Therefore the notification associated with Event Number 46354 is being retracted. The licensee notified the NRC Resident Inspector. The R3DO (Ring) was notified. }}[[Event description::Description::{{#Regex_clear:At 1751 [CDT] on Oct 22, 2010, Dresden Nuclear Power Station (DNPS) determined that current Oscillation Power Range Monitors (OPRM's) setpoints, as outlined in the Core Operating Limits Report (COLR), for Dresden U2 are non-conservative. This renders the Technical Specification (TS) function of the OPRM's in the Reactor Protection System (RPS) inoperable. This event was initiated as a result of notification by Westinghouse Nuclear Fuels (NF-BEX-10-157) that an error exists in the McSLAP computer code which affects the Safely Limit Minimum Critical Power Ratios (SLMCPR) for Dresden. Currently the COLR and installed, amplitude setpoint (Sp) is 1.13 and the confirmation count setpoint (Np) is 15. This is required to be adjusted to 1.12 (Sp) and 14 (Np). Alternative methods to detect and suppress thermal hydraulic instabilities were initiated as required by Technical Specifications. This non-conservative computer code error could potentially have prevented fulfillment of the OPRM system's safety function and is therefore reportable per 10 CFR 50.72(b)(3)(v)(A), 'An event or condition that could have prevented the fulfillment of a safety function - shutdown the reactor and maintain it in a safe shutdown condition.' Corrective actions include the following: 1. Revise U2 Core Operating Limit Report (COLR) to reflect correct values as determined by Westinghouse Nuclear Fuels Letter (NF-BEX�l0-157). 2. Adjust OPRM setpoints to comply with COLR values. The licensee will notify the NRC Resident Inspector.
On October 22, 2010, Dresden Nuclear Power Station was notified by Westinghouse that an error in McSlap computer code resulted in a non-conservative MCPR safety limit. The preliminary results of the Westinghouse evaluation concluded that the setpoints for the Oscillation Power Range Monitors were also non-conservative. As a result of the notification, Dresden declared all channels of OPRM inoperable and took the required action of the plant's technical specifications. This was considered a loss of function. This condition was reported as a condition that could have potentially prevented the fulfillment of the OPRM system's safety function in accordance with 10 CFR 50.72(b)(3)(v)(A), an event or condition that could have prevented the fulfillment of a safety function - shutdown the reactor and maintain it in a safe shutdown condition. However, subsequent evaluation of the preliminary result determined that the original conclusions were overly conservative and the OPRM setpoints did not require revision. Based on the later evaluation, the function of the OPRMs was not adversely impacted by the installed setpoints. Thus, the system was always capable of performing its intended safety function. Therefore the notification associated with Event Number 46354 is being retracted. The licensee notified the NRC Resident Inspector. The R3DO (Ring) was notified. }}| ]] |
| Where | |
|---|---|
Dresden  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor | |
| Time - Person (Reporting Time:+0.23 h0.00958 days <br />0.00137 weeks <br />3.15054e-4 months <br />) | |
| Opened: | Phillip Prater 23:05 Oct 22, 2010 |
| NRC Officer: | Vince Klco |
| Last Updated: | Dec 3, 2010 |
| 46354 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 529642017-09-12T16:31:00012 September 2017 16:31:00
[Table view]10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Standby Liquid Control System Piping Failure ENS 463542010-10-22T22:51:00022 October 2010 22:51:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor Potential Inoperability of Oscillation Power Range Monitors ENS 446652008-11-03T16:42:0003 November 2008 16:42:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor Control Rods Drift Out While Shutdown 2017-09-12T16:31:00 | |