05000369/LER-2005-005, Re Inoperable Source Range Neutron Flux Monitors During Mode 6 and Core Alterations
| ML053330126 | |
| Person / Time | |
|---|---|
| Site: | McGuire  |
| Issue date: | 11/21/2005 |
| From: | Gordon Peterson Duke Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 05-005-00 | |
| Download: ML053330126 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3692005005R00 - NRC Website | |
text
,
Duke GARY R.
PETERSON 1 Power.
Vice President A Duke Energy Company McGuire Nuclear Station Duke Power MGOI VP/ 12700 Hagers Ferry Road Huntersville, NC 28078-9340 704 875 5333 704 875 4809 fax grpeters @duke-energy. corn November 21, 2005 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555
Subject:
McGuire Nuclear Station, Unit 1 Docket No. 50-369 Licensee Event Report 369/2005-05, Revision 0 Problem Investigation Process (PIP) M-05-04437 Pursuant to 10 CFR 50.73, Sections (a)(1) and (d), attached is Licensee Event Report (LER) 369/2005-05, Revision 0.
On September 21, 2005, while McGuire Nuclear Station Unit 1 was in Mode 6, all source range neutron flux monitors became inoperable when the annunciator alarm circuitry failed. In addition, core alterations commenced on September 22, 2005 while the source range neutron flux monitors were inoperable.
The inability of the required source range monitors to generate an audible high flux at shutdown alarm was not discovered until September 23, 2005.
All other Control room source range neutron flux indications were functioning properly during this period.
This report is being submitted in accordance with 10 CFR 50.73 (a)(2)(i)(B) as a condition prohibited by Technical Specifications (TS).
This event was determined to be of no significance to the health and safety of the public.
There are no regulatory commitments contained in the LER.
4PgAVIee /
G. R. Peterson Attachment www.duke-energy.comrn
U. S. Nuclear Regulatory Commission November 21, 2005 Page 2 of 2 cc:
W. D. Travers U. S. Nuclear Regulatory Commission Regional Administrator, Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, GA 30303 J. F. Stang, Jr. (addressee only)
NRC Project Manager (McGuire)
U. S. Nuclear Regulatory Commission Mail Stop 08H4A Washington, D.C.
20555-0001 J. B. Brady Senior Resident Inspector U. S. Nuclear Regulatory Commission McGuire Nuclear Site Beverly 0. Hall, Section Chief Radiation Protection Section 1645 Mail Service Center Raleigh, NC 27699-1645
bxc: Gary R. Peterson (MGOIVP)
Thomas P. Harrall Jr. (MGO1VP)
Scott W. Brown (MGOlVP)
Scotty L. Bradshaw (MGOIOP)
Scott B. Thomas (EC08G)
Ken D. Thomas (MG05EE)
Ken L. Evans (MG05SE)
Michael S. Kitlan (EC08I)
Dayna J. Herrick (EC08H)
Kay L. Crane (MGOlRC)
Berry G. Davenport (ON03RC)
Lisa F. Vaughn (ECliX)
Robert L. Gill (EC05P)
Randall D Hart (CNOIRC)
(NSRB Support Staff) (EC05N)
INPO Paper Distribution:
Master File (3.3.7)
ELL (ECO50)
RGC File
Abstract
Unit Status:
At the start of the event, Unit 1 was in Mode 6 (Refueling) at 0%
power, and Unit 2 in Mode 1 (Power Operation) at 100% power.
Event Description
On September 21, 2005, while Unit 1 was in Mode 6 all source range neutron monitors became inoperable when annunciator alarm circuitry failed.
Subsequently, on September 22, 2005 core alteration activities commenced with these monitors inoperable.
The inability of the required source range monitors to generate an audible high flux at shutdown alarm was not discovered until September 23, 2005.
All other Control room source range neutron flux indications were functioning properly during this period.
This event, which constitutes conditions prohibited by Technical Specifications, was determined to be of no significance to the health and safety of the public.
Event Cause
The causes of this event are attributed to an inadequate Operator Aid Computer (OAC) alarm response procedure, and the common alarm circuitry of the high flux at shutdown.
Corrective Action
Further core alterations were suspended while repairs were made to the annunciator system.
Procedural enhancements will be made to ensure a more prescriptive OAC alarm response.
Redundant and diverse alarms will be provided for the high flux at shutdown circuitry via the Operator Aid Computer.
The source range neutron flux monitor procedures will be enhanced to clarify required features for operability of the components, and Operations training will be strengthened to emphasize the importance of annunciators on operability of components.
NRC FORM 366 (6-2004)
v i en s.r*
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A)
- The COT procedure for the NIS source range neutron monitors will be enhanced to ensure acceptance criteria clearly states required functions for operability of the source range neutron flux channels.
- The Operations training program will be strengthened to emphasize the importance of annunciators on operability of components.
SAFETY ANALYSIS
UFSAR Chapter 15.4.6, "Chemical and Volume Control System Malfunction that Results in a Decrease in Boron Concentration in the Reactor Coolant", provides an analysis of a boron dilution event for the McGuire Nuclear Station while in Mode 6. The result of the analysis assumes that unborated water is delivered to the Reactor Coolant System and manual action terminates the event after receipt of a high flux at shutdown alarm.
The boron concentration in the Reactor Coolant System was verified to be within the COLR limits before and after the high flux at shutdown annunciator failure event.
During this period the Reactor Makeup water to NV isolation valve was procedurally locked closed.
Any other unborated water addition sources were under strict procedural control to ensure the required boron concentration stated in the COLR would not be violated.
The UFSAR analysis for dilution during refueling results in Table 15-19 show that a dilution in Mode 6 would progress over a time period of more than an hour.
The OAC was available during the event and would have provided the operator with multiple indications and diverse alarms.
Aside from high flux at shutdown annunciator, all other source range neutron flux monitoring indicators and alarms such as high flux at shutdown bistable, containment evacuation alarm, audible source range counts in the control room, and Gamma-Metrics high flux at shutdown LED were functioning properly.
Thus, considering the progression of a dilution over a time period of more than an hour, the operators would have had sufficient time to mitigate the dilution event.
In conclusion, the overall safety significance of this event was determined to be minimal and there was no impact on the health and safety to the public.
ADDITIONAL INFORMATION
A three year search of the McGuire corrective action database (PIP) and LER database revealed no other failure of the audible high flux at shutdown annunciator alarm circuitry; therefore, this event is not recurring.