05000457/LER-2009-001, Regarding Reactor Trip in Over Temperature Delta Temperature Due to a Signal Spike on One Channel with Another Channel Placed in the Tripped Condition for Surveillance Testing
| ML091740327 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 06/23/2009 |
| From: | Bryan Hanson Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BW090059 LER 09-001-00 | |
| Download: ML091740327 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4572009001R00 - NRC Website | |
text
10 CFR 50.73 June 23, 2009 BW090059 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Unit 2 Facility Operating License No. NPF-77 NRC Docket No. STN 50-457
Subject:
Licensee Event Report 2009-001 Reactor Trip on Over Temperature Delta Temperature due to a Signal Spike on One Channel With Another Channel Placed in the Tripped Condition for Surveillance Testing The enclosed Licensee Event Report (LER) is being submitted in accordance with 10 CFR 50.73, "Licensee event report system," paragraph (a)(2)(iv)(A), as an event that resulted in a valid actuation of the reactor protection system and auxiliary feedwater system. On April 24, 2009, Braidwood Station Unit 2 received an actuation of the reactor protection system (reactor trip) and the auxiliary feedwater system due to a momentary signal spike on one trip channel while a second channel was in a tripped condition in support of surveillance testing. 10 CFR 50.73(a) requires an LER to be submitted within 60 days following discovery of the event. Therefore, this report is being submitted by June 23, 2009.
There are no regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact Mr. David Gullott, Regulatory Assurance Manager, at (815) 417-2800.
Bryan Hanson Site Vice President Braidwood Station
Enclosure:
LER 2009-001-00
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC mey digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the informRtion r.nllMtion r*
PAGE Braidwood Station, Unit 2 05000457 1
of 3
- 4. TITLE Reactor Trip on Over Temperature Delta Temperature due to a Signal Spike on One Channel With Another Channel Placed in the Tripped Condition for Surveillance Testing
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIALIREV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.
MONTH DAY YEAR N/A N/A FACILITY NAME DOCKET NUMBER 04 24 12009 2009 - 001 00 06 23 2009 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 o 20.2201(b) o 20.2203(a)(3)(i) o 50.73(a)(2)(i)(C) o 50.73(a)(2)(vii) o 20.2201 (d) o 20.2203(a)(3)(ii) o 50.73(a)(2)(ii)(A) o 50.73(a)(2)(viii)(A) o 20.2203(a)(1) o 20.2203(a)(4) o 50.73(a)(2)(ii)(B) o 50.73(a)(2)(viii)(B) o 20.2203(a)(2)(i) o 50.36(c)(1)(i)(A) o 50,73(a)(2)(iii) o 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL o 20.2203(a)(2)(ii) o 50.36(c)(1)(ii)(A) 181 50.73(a)(2)(iv)(A) o 50.73(a)(2)(x) o 20.2203(a)(2)(iii) o 50.36(c)(2) o 50.73(a)(2)(v)(A) o 73.71(a)(4) 100 o 20.2203(a)(2)(iv) o 50.46(a)(3)(ii) o 50.73(a)(2)(v)(B) o 73.71(a)(5) o 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A) o 50.73(a)(2)(v)(C) o OTHER o 20.2203(a)(2)(vi) o 50.73(a)(2)(i)(B) o 50.73(a)(2)(v)(D)
Specify In Abstract below or in error, spurious transient, or channel failure in a coincident channel initiates an inadvertent reactor trip or safeguards actuation. This design has resulted in several events within the industry including unit trips while at power.
Therefore, the root cause of the Unit 2 reactor trip is determined to be the design of the RTS/ESFAS, which places a loop in a trip condition for testing, increases vUlnerability during testing conditions.
p.
Safety Consequences
There were no safety consequences impacting plant or public safety as a result of this event.
The OTDT function is a RTS function. The OTDT function is provided to ensure that the design limit departure from nucleate boiling ratio is met. This trip function also limits the range over which the overpressure delta-temperature trip function must provide protection.
The reactor trip system responded automatically due to the to the OTDT trip signal received. During the reactor shutdown, all required safety systems responded appropriately. There was no loss of any function that would have prevented fulfillment of actions necessary to 1) Shutdown the reactor and maintain it in a safe shutdown condition, 2) Remove residual heat, 3) Control the release of radioactive material, or 4) Mitigate the consequences of an accident.
This event did not result in a safety system functional failure.
E.
Corrective Actions
The corrective action to prevent recurrence is to pursue a modification which bypasses a tested channel rather than placing it in the tripped state during surveillances.
F.
Previous Occurrences
There have been no similar Licensee Event Report events at Braidwood Station in the last three years.
G.
Component Failure Data
Manufacturer NANomenclature NA NA Mfg. Part Number N/A PRINTED ON RECYCLED PAPER