05000456/LER-2003-003, Licensed Maximum Power Level Exceeded Due to an Error in a Westinghouse Supplied Calorimetric Calculation Constant
| ML032950548 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 10/03/2003 |
| From: | Pacilio M Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BW030082 LER 03-003-00 | |
| Download: ML032950548 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| 4562003003R00 - NRC Website | |
text
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Exelon Generation Company, LLC Braidwood Station 35100 South Rt 53, Suite 84 Braceville, IL 60407-9619 Tel. 815-417-2000 www.exelonCoTp.Com1 Nuclear October 3, 2003 BW030082 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Unit 1 Facility Operating License No. NPF-72 NRC Docket No. STN 50-456
Subject:
Submittal of Licensee Event Report Number 2003-003-00, "Licensed Maximum Power Level Exceeded Due To An Error In A Westinghouse Supplied Calorimetric Calculation Constant" The enclosed Licensee Event Report (LER) is being submitted in accordance with Braidwood Station Unit 1 License Condition 2.G due to violating license condition 2.C(1), "Maximum Power Level." License Condition 2.G requires an LER to be submitted within 30 days after discovery of the event; therefore, this report is being submitted by October 3, 2003.
Should you have any questions concerning this submittal, please contact Kelly Root, Regulatory Assurance Manager, at (815) 417-2800.
Respectfully, Michael J.Pacillo Site Vice President Braidwood Station
Enclosure:
LER Number 2003-003-00 cc:
Regional Administrator - Region IlIl NRC Braidwood Senior Resident Inspector
.-- I-G---aQ
Abstract
Braidwood Station received Nuclear Safety Advisory Letter (NSAL) 03-06, "High Net Heat Input," from Westinghouse informing the Station that an error had been found in calculations that may result in the use of a non-conservatively high Net Heat input value in the calorimetric calculations.
The Net Heat input is the difference between the reactor core power and the Nuclear Steam Supply System (NSSS) power.
It consists of energy provided by the reactor coolant pump to the reactor coolant, heat supplied by the pressurizer heaters, and other minor heat removal and additions such as the cooling provided by the reactor coolant pump seal injection.
The result of using a non-conservatively high Net Heat input value in the calorimetric calculations was that both Unit 1 and Unit 2 operated at higher than licensed core power levels on several occasions.
The Westinghouse evaluation determined that the increase in Net Heat input could be as much as 0.4 MWt.
This condition applies to both Unit 1 and Unit 2.
In accordance with Braidwood Station Unit 2 License Condition 2.G a notification was made to the NRC at 1557 CST on September 3, 2003, due to violation of license condition 2.C(l),
"Maximum Power Level."
NRC FORMN 366A U.S. NUCLEAR REGULATORY COMMIINSSION (1-2001)
LICENSEE EVENT REPORT (LER)
FACILITY NANIE (1)
DOCKET (2)
LER NUMBER (6)
PAGE (3)
YEAR SIQUENTIAL REVISION NUMBER NUMBER Braidwood, Unit 1 STN 05000456 l
2 of 3 2003 -
003 -
00 A.
Plant Operating Conditions Before The Event
Unit: 1 Event Date: September 3, Event Time: 0730 2003 MODE: 1 Reactor Power: 100 percent Reactor Coolant System [AB]:
Unit 1 and Unit 2 at normal operating temperature and pressure.
No structures, systems or components were inoperable at the start of the event that contributed to the event.
B.
Description of Event
There were no additional systems or components inoperable at the beginning of this event that contributed to the severity of the event.
Westinghouse issued NSAL 03-6, "High Net Heat Input" which described a minor and non-conservative error in the calculation of the Net Heat value provided by Westinghouse to a number of domestic and foreign nuclear power plants.
Braidwood Units 1 and 2 were listed as affected plants.
A review of data history indicated that there were several periods where both Unit 1 and Unit 2 operated at 100% power.
Adding the 0.4 MWt during these periods resulted in the Braidwood units exceeding 100% on these occasions.
The Net Heat value is the amount of heat, seen at the Steam Generators (NSSS Heat), which is not supplied by the reactor.
It consists of items such as the heat'suppl1iid'by the reaftorc1coolant pumpsi, the-heat su~plied'by'the'pressurizer' heaters, and other minor heat removals and additions such as the cooling provided by the reactor coolant pump seal injection.
The Net Heat value is used in the calorimetric calculation as follows:
Reactor Heat = NSSS Heat -
Net Heat A non-conservatively high Net Heat value used in the calorimetric calculation resulted in the reactor operating at higher than licensed power.
As discussed in the NSAL, heat removed from the NSSS via reactor coolant pump seal leak off, although small, was non-conservatively omitted.
The NSAL estimated that this error could be as high as a 0.4 MWt larger Net Heat value.
C.
Cause of Event
A Westinghouse calculation for the Net Heat input into the calorimetric calculation non-conservatively omitted the small amount of heat removed from the NSSS via the reactor coolant pump seal leak off flow.
D.
Safety Consequences
The safety analyses impact of the error is low.
The uncertainty calculation for the calorimetric yields a total uncertainty of 1.79% of rated thermal power (RTP).
The power-limited safety analyses assume a 2% RTP uncertainty.
NRC FORA 366A US. NUCLEAR REGULATORY COMMINIISON (1-2001)
LICENSEE EVENT REPORT (LER)
FACILITY NAMIE (I)
DOCKET (2)
LER NUIMBER (6)
PAGE (3)
YEAR SEQUETIAL REVISION NUMBER NUMBERI Braidwood, Unit 1 STN 05000456 l N
3 of 3
2003 -
003 -
00 Braidwood's licensed RTP is 3586.6 MWt.
The magnitude of the 0.4 MWt for Braidwood is less than 0.02% RTP.
Therefore, the safety analyses assumptions bounded the overpower condition.
This event did not result in a safety system functional failure.
E.
Corrective Actions
The immediate corrective action was to reduce and limit reactor power to 99.98%.
The Net Heat constant in the plant process computer, which is an input value into the calorimetric calculation, was conservatively reduced by 0.8 MWt.
The Net Heat input calculation is being revised to provide the appropriate Net Heat value to be used in the calorimetric calculation.
F.
Previous Occurrences
There have been no previous occurrences where incorrect calorimetric calculations resulted in exceeded licensed thermal power.
G.
Component Failure Data
Manufacturer Nomenclature Model Mfg. Part Number N/A N/A N/A N/A