05000277/LER-2017-001, Regarding Emergency Diesel Generator Exhaust Stacks Nonconforming Design for Tornado Missile Protection
| ML17068A019 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 03/08/2017 |
| From: | Pat Navin Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| CCN: 17-33 LER 17-001-00 | |
| Download: ML17068A019 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 2772017001R00 - NRC Website | |
text
Exelon Generation March 8, 2017 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Peach Bottom Atomic Power Station (PBAPS) Unit 2 Renewed Facility Operating License No. DPR-44 NRC Docket No. 50-277 Licensee Event Report (LER) 2-17-001 10CFR 50.73 Enclosed is a Licensee Event Report concerning a non-conforming condition associated with tornado missile protection for the emergency diesel generator exhaust stacks.
In accordance with NEI 99-04, the regulatory commitment contained in this correspondence is to restore compliance with the regulations. The specific methods that have been planned to restore and maintain compliance are discussed in the LER. If you have any questions or require additional information, please do not hesitate to contact Jim Armstrong at 717-456-3351.
Patrick D. Navin Plant Manager Peach Bottom Atomic Power Station PDN/dnd/IR 3961028 Enclosure cc:
US NRC, Administrator, Region I US NRC, Senior Resident Inspector R. R. Janati, Commonwealth of Pennsylvania S. Gray, State of Maryland B. Watkins, PSE&G, Financial Controls and Co-owner Affairs CCN: 17-33
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2018 (06-2016)
Estimated burden per response to comply with this mandatory collecfon request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br /> l~\\
Reported lessons learned are incorporated into the licensing process and fed back to industry.
LICENSEE EVENT REPORT (LER)
Send comments regarding burden estimate to the FOIA, Privacy and Information Collections
- ,~ ~l Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail (See Page 2 for required number of digits/characters for each block}
to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information ard Regulatory Affairs, NEOB-10202, (3150.0104), Office of Management and Budget, Washington, DC 20503. If a (See NUREG-1022, R.3 for instruction and guidance for completing this form means used to impose an information collection does not display a currently v<iid OMB control httg://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
number, the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Peach Bottom Atomic Power Station Unit 2 05000277 1 OF 4
- 4. TITLE Emergency Diesel Generator Exhaust Stacks Nonconforming Design for Tornado Missile Protection
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED I
SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR Peach Bottom APS Unit 3 05000278 FACILITY NAME DOCKET NUMBER 01 09 2017 2017 - 001 0
03 08 17
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 20.2201(b)
D 20.2203(a)(3)(i)
D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A) 1 D
20.2201(dl D
20.2203(a)(3J(iil
~ 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1J D
20.2203(a)(4l D
so.73(a)(2J(iiil D
50.73(a)(2)(ix)(A)
D 20.2203(a)(2Hil D
50.36(c)(1)(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. POWER LEVEL D
20.2203(a)(2)(iil D
50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(v)(A)
D 13.11(a)(4l D
20.2203(a)(2)(iiil D
so.3s(c)(2l D
50.73(a)(2)(v)(B)
D 13.11(a)(sJ D
20.2203(a)(2)(iv)
D so.4s(a)(3J(ii)
D 50.73(a)(2)(v)(C)
D 13.11(a)(1) 100%
D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
~ 50.73(a)(2)(v)(D)
D 13.11(a)(2)(i) 0 20.2203(a)(2)(vi)
~ 50. 73(a)(2)(i)(B)
~ 50.73(a)(2)(vii) 0 73.77(a)(2)(ii)
D 50.73(a)(2)(i)(C)
D OTHER Specify in Abstract below or in
- 3. LER NUMBER SEQUENTIAL NUMBER 001 REV NO.
0 d) Increasing the level of awareness and preparedness by communicating the issue to Operations personnel though shift manager turnover notes.
Analysis of the Event
Four emergency diesel generators are located on-site which provide backup power in the event of a loss of all offsite power. Each diesel generator is rated at 2,600 kW for continuous operation at 4, 160 volts.
The diesel generators provide sufficient power to safely shut down both units in the event of a design basis accident in one unit and a failure of one of the diesel generators. Each diesel generator is housed in a seismic Class I structure and designed to be protected against earthquakes, floods, tornadoes and other natural phenomena. However, the diesel engine exhaust stacks, which extend approximately seven feet above the roof of the building, are not protected against tornado generated missiles. The exhaust stacks are 24-inch diameter steel pipes with a 3/8-inch wall thickness. It was determined that, if the stacks were struck by a design basis tornado missile, they could be crimped in such a manner as to prevent the diesel generator from performing its design function. The design basis tornado missile for the site includes a wood plank that is 4 inches thick, 12 inches wide and 12 feet long traveling at 300 mph.
There were no actual consequences resulting from this non-conforming condition. A tornado that could produce the design basis missile is highly unlikely in the mid-Atlantic region. The probability of missiles causing more than one diesel generator to become inoperable is also very low.
This condition is being reported in accordance with the following criteria:
1 OCFR 50. 73(a)(2)(i)(B) for any condition which was prohibited by the plant's Technical Specifications.
1 OCFR 50. 73(a)(2)(ii)(B) for any event or condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degraded plant safety.
10CFR 50.73(a)(2)(v)(D) for any condition that could have prevented the fulfillment of the safety function of systems that are needed to mitigate the consequences of an accident.
1 OCFR 50. 73(a)(2)(vii)(D) for any event where a single cause or condition caused at least two independent trains to become inoperable in a single system designed to mitigate the consequences of an accident.
Cause of the Event
This condition was part of the original plant design and has existed since the initial construction and licensing of the plant. Peach Bottom Unit 2 and Unit 3 received their operating licenses in 1973 and 197 4, respectively, based in part on the design of the emergency diesel generators as described in the Final Safety Analysis Report (FSAR). This report did not address the fact that the exhaust stacks are not protected against tornado missiles and no other documented engineering analysis has been identified. It is not known if this was not evaluated at the time of the original design and licensing process, or if it was considered acceptable due to the low likelihood of damage to the exhaust stacks from tornado missiles.
SEQUENTIAL NUMBER 001 REV NO.
0 Past perception of this condition was that only one tornado generated missile needed to be considered and only one diesel exhaust stack would be impacted. Since only three emergency diesel generators are needed to safely shut down the plant, such a condition was considered to be included in the licensing basis of the plant. Additional industry and NRC information on this issue pointed to the need to have all diesel generators survive a tornado with the capability to perform their safety function intact.
Corrective Actions
Compensatory measures were implemented in accordance with NRC guidance contained in EGM 15-002 and DSS-ISG-2016-01 as described earlier. Enforcement discretion provided by EGM 15-002 remains in effect for five years for Peach Bottom, at which time modifications, license amendments or other actions must be implemented to fully resolve the issue. Peach Bottom intends to request a license amendment to allow for probabilistic methods to be applied to demonstrate that the risk associated with tornado missiles on specific components is sufficiently small such that plant modifications are not warranted.
Previous Similar Occurrences No previous similar events have occurred at the site. Page _4_ of _4_