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LER 50-387(388)/2017-007-00 Copy: NRC Region I Ms. T. E. Hood, NRC Project Manager Ms. L. H. Micewski, NRC Sr. Resident Inspector Mr. M. Shields, PA DEP/BRP NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017) Estimated burden per response to comply with this mandatory collection request: 80 hours. LICENSEE EVENT REPORT (LER) Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. (See Page 2 for required number of digits/characters for each block) Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects. ...... t-"' Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, (See NUREG-1 022, R.3 for instruction and guidance for completing this form NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, httQ://www. nrc.gov/readi ng-rm/doc-collections/nur§9s/staff/sr1 022/r3D the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. 1. FACILITY NAME DOCKET NUMBER .PAGE Susquehanna Steam Electric Station Unit 1 05000387 1 OF2 4. TITLE Secondary Containment Declared Inoperable Due to the opening of a plenum. 5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED SEQUENTIAL FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR REV MONTH DAY YEAR Susqueahanna Steam Electric Station Unit 2 NUMBER NO. 05000388 11 30 2017 2017 -007 -00 01 ..25 2018 FACILITY NAME DOCKET NUMBER 05000 9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: Check all that apply) 1 D 20.2201(b) D 20.2203(a)(3)(i) 0 50.73(a)(2)(ii)(A) D 50.73(a)(2)(viii)(A) D 2o.2201{d) D 20.2203(a)(3)(ii) D 50.73(a)(2)(ii)(B) D 50.73(a)(2)(viii)(B) D 20.2203(a)(1) D 20.2203(a)(4) D 50.73(a)(2)(iii) D 50.73(a)(2)(ix)(A) D 20.2203(a)(2)(i) 0 50.36{c)(1)(i)(A) 0 50.73(a)(2)(iv)(A) D 50.73(a)(2)(x) 10. POWER LEVEL D 20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A) D 50.73(a)(2)(v)(A) D 73.71(a)(4) D 20.2203(a)(2)(iii) D 50.36(c)(2) D 50.73{a)(2)(v)(B) D 73.71(a)(5) 100 D 20.2203(a)(2)(iv) D 50.46(a)(3)(ii) 1:81 50.73(a)(2)(v)(C) D 73.77(a)(1) D 20.2203(a)(2)(v) D 50.73(a)(2)(i)(A) D 50.73(a)(2)(v)(D) D 73.77(a)(2)(i) D 20.2203(a)(2)(vi) D 50.73(a)(2)(i)(B) D 50.73(a)(2)(vii) D 73.77(a)(2)(ii) D 50.73(a)(2)(i)(C) 0 OTHER Specify in Abstract below or in NRC Form 366A 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT NUMBER (Include Area Code) /Nicole PaQiiaro-LicensinQ Specialist-Nuclear Regulatory Affairs k570) 542-6578 13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT MANU-REPORTABLE CAUSE SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TOEPIX 14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR YES (If yes, complete 15. EXPECTED SUBMISSION DATE) D NO SUBMISSION 02 23 2018 DATE ft\BSTRACT (Umit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On November 30, 2017 at 1026, the Susquehanna Control Room received indication that a loss of Secondary Containment Zone 2 differential pressure had occurred. Control Room operators noted a differential pressure of 0" Water Column (WC) for several seconds, followed by a high differential pressure of 0.5" WC. System differential pressure was restored to normal in 3 minutes. The cause of the pressure swings is under investigation. Zone 2 differential pressures being less than 0.25" WC constitutes a loss of Secondary Containment based on not meeting requirements of Technical Specification (T.S.) 3.6.4.1 Surveillance Requirement 3.6.4.1.1 This condition is being reported in accordance with 10 CFR 50. 73(a)(2)(v)(C) as a condition that could have prevented fulfillment of safety function. This event was reported in ENS 53098 under 10 CFR 50.72(b){3)(v)(c) There is no redundant Susquehanna Secondary Containment system. There were no actual consequences to the health and safety of the public as a result of this event. NRC FORM 366 (04-2017) | LER 50-387(388)/2017-007-00 Copy: NRC Region I Ms. T. E. Hood, NRC Project Manager Ms. L. H. Micewski, NRC Sr. Resident Inspector Mr. M. Shields, PA DEP/BRP NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017) Estimated burden per response to comply with this mandatory collection request: 80 hours. LICENSEE EVENT REPORT (LER) Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. (See Page 2 for required number of digits/characters for each block) Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects. ...... t-"' Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, (See NUREG-1 022, R.3 for instruction and guidance for completing this form NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, httQ://www. nrc.gov/readi ng-rm/doc-collections/nur§9s/staff/sr1 022/r3D the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. 1. FACILITY NAME DOCKET NUMBER .PAGE Susquehanna Steam Electric Station Unit 1 05000387 1 OF2 4. TITLE Secondary Containment Declared Inoperable Due to the opening of a plenum. 5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED SEQUENTIAL FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR REV MONTH DAY YEAR Susqueahanna Steam Electric Station Unit 2 NUMBER NO. 05000388 11 30 2017 2017 -007 -00 01 ..25 2018 FACILITY NAME DOCKET NUMBER 05000 9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: Check all that apply) 1 D 20.2201(b) D 20.2203(a)(3)(i) 0 50.73(a)(2)(ii)(A) D 50.73(a)(2)(viii)(A) D 2o.2201{d) D 20.2203(a)(3)(ii) D 50.73(a)(2)(ii)(B) D 50.73(a)(2)(viii)(B) D 20.2203(a)(1) D 20.2203(a)(4) D 50.73(a)(2)(iii) D 50.73(a)(2)(ix)(A) D 20.2203(a)(2)(i) 0 50.36{c)(1)(i)(A) 0 50.73(a)(2)(iv)(A) D 50.73(a)(2)(x) 10. POWER LEVEL D 20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A) D 50.73(a)(2)(v)(A) D 73.71(a)(4) D 20.2203(a)(2)(iii) D 50.36(c)(2) D 50.73{a)(2)(v)(B) D 73.71(a)(5) 100 D 20.2203(a)(2)(iv) D 50.46(a)(3)(ii) 1:81 50.73(a)(2)(v)(C) D 73.77(a)(1) D 20.2203(a)(2)(v) D 50.73(a)(2)(i)(A) D 50.73(a)(2)(v)(D) D 73.77(a)(2)(i) D 20.2203(a)(2)(vi) D 50.73(a)(2)(i)(B) D 50.73(a)(2)(vii) D 73.77(a)(2)(ii) D 50.73(a)(2)(i)(C) 0 OTHER Specify in Abstract below or in NRC Form 366A 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT NUMBER (Include Area Code) /Nicole PaQiiaro-LicensinQ Specialist-Nuclear Regulatory Affairs k570) 542-6578 13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT MANU-REPORTABLE CAUSE SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TOEPIX 14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR YES (If yes, complete 15. EXPECTED SUBMISSION DATE) D NO SUBMISSION 02 23 2018 DATE ft\BSTRACT (Umit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On November 30, 2017 at 1026, the Susquehanna Control Room received indication that a loss of Secondary Containment Zone 2 differential pressure had occurred. Control Room operators noted a differential pressure of 0" Water Column (WC) for several seconds, followed by a high differential pressure of 0.5" WC. System differential pressure was restored to normal in 3 minutes. The cause of the pressure swings is under investigation. Zone 2 differential pressures being less than 0.25" WC constitutes a loss of Secondary Containment based on not meeting requirements of Technical Specification (T.S.) 3.6.4.1 Surveillance Requirement 3.6.4.1.1 This condition is being reported in accordance with 10 CFR 50. 73(a)(2)(v)(C) as a condition that could have prevented fulfillment of safety function. This event was reported in ENS 53098 under 10 CFR 50.72(b){3)(v)(c) There is no redundant Susquehanna Secondary Containment system. There were no actual consequences to the health and safety of the public as a result of this event. NRC FORM 366 (04-2017) | ||
NRC FORM 366A (04-2017) U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 LICENSEE EVENT REPORT (LER) CONTINUATION SHEET (See NUREG-1 022, R.3 for instruction and guidance for completing this form http://WoNV-J.nrc.gov/readinq-rm/doc-collections/nureas/staff/sr1 022/r3D 1. FACILITY NAME Susquehanna Steam Electric Station Unit 1 NARRATIVE CONDITIONS PRIOR TO EVENT Estimated burden per response to comply with this mandatory collection request: 80 hours. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Information SeiVices Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555*0001, or by e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104). Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. 2. DOCKET NUMBER YEAR 05000387 2017 3. LER NUMBER SEQUENTIAL NUMBER -007 REV NO. -00 Unit 1 -Mode 1, approximately 1 00 percent Rated Thermal Power Unit 2 -Mode 1, approximately 100 percent Rated Thermal Power There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event. EVENT DESCRIPTION On November 30, 2017 at 1026, the Susquehanna Control Room received indication that a loss of Secondary Containment Zone 2 differential pressure had occurred. Control Room operators noted a differential pressure of 0" Water Column (WC) for several seconds, followed by a high differential pressure of 0.5" WC. System differential pressure was restored to normal in 3 minutes. The cause of the pressure swings is under investigation. Zone 2 differential pressures being less than 0.25" WC constitutes a loss of Secondary Containment based on not meeting requirements of Technical Specification (T.S.) 3.6.4.1 Surveillance Requirement 3.6.4.1. There were no actual consequences to the health and safety of the public as a result of this event. The condition is being reported in accorance with 10 CFR 50.73(a)(2)(v)(C) as a condition that could have prevented fulfillment of a safety function. This event was reported in ENS 53098 under 10 CFR 50.72(b)(3)(v)(c). There is no redundant Susquehanna Secondary Containment system. CAUSE OF EVENT This event is still under investigation. The cause will be provided in the supplement. ANALYSIS/SAFETY SIGNIFICANCE This event is still under investigation. The safety significance will be provided in the supplement CORRECTIVE ACTIONS This event is still under investigation. The corrective action will be provided in the supplement. PREVIOUS SIMILAR EVENTS This event is still under investigation. Previous similar events will be identified under the supplement NRC FORM 3668 (04-2017) Page 2 of 2 | NRC FORM 366A (04-2017) U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 LICENSEE EVENT REPORT (LER) CONTINUATION SHEET (See NUREG-1 022, R.3 for instruction and guidance for completing this form http://WoNV-J.nrc.gov/readinq-rm/doc-collections/nureas/staff/sr1 022/r3D 1. FACILITY NAME Susquehanna Steam Electric Station Unit 1 NARRATIVE CONDITIONS PRIOR TO EVENT Estimated burden per response to comply with this mandatory collection request: 80 hours. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Information SeiVices Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555*0001, or by e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104). Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. 2. DOCKET NUMBER YEAR 05000387 2017 3. LER NUMBER SEQUENTIAL NUMBER -007 REV NO. -00 Unit 1 -Mode 1, approximately 1 00 percent Rated Thermal Power Unit 2 -Mode 1, approximately 100 percent Rated Thermal Power There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event. EVENT DESCRIPTION On November 30, 2017 at 1026, the Susquehanna Control Room received indication that a loss of Secondary Containment Zone 2 differential pressure had occurred. Control Room operators noted a differential pressure of 0" Water Column (WC) for several seconds, followed by a high differential pressure of 0.5" WC. System differential pressure was restored to normal in 3 minutes. The cause of the pressure swings is under investigation. Zone 2 differential pressures being less than 0.25" WC constitutes a loss of Secondary Containment based on not meeting requirements of Technical Specification (T.S.) 3.6.4.1 Surveillance Requirement 3.6.4.1. There were no actual consequences to the health and safety of the public as a result of this event. The condition is being reported in accorance with 10 CFR 50.73(a)(2)(v)(C) as a condition that could have prevented fulfillment of a safety function. This event was reported in ENS 53098 under 10 CFR 50.72(b)(3)(v)(c). There is no redundant Susquehanna Secondary Containment system. CAUSE OF EVENT This event is still under investigation. The cause will be provided in the supplement. ANALYSIS/SAFETY SIGNIFICANCE This event is still under investigation. The safety significance will be provided in the supplement CORRECTIVE ACTIONS This event is still under investigation. The corrective action will be provided in the supplement. PREVIOUS SIMILAR EVENTS This event is still under investigation. Previous similar events will be identified under the supplement NRC FORM 3668 (04-2017) Page 2 of 2}} | ||
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Revision as of 02:10, 18 May 2018
ML18025B210 | |
Person / Time | |
---|---|
Site: | Susquehanna ![]() |
Issue date: | 01/25/2018 |
From: | Berryman B Susquehanna, Talen Energy |
To: | Document Control Desk, Office of Nuclear Reactor Regulation |
References | |
PLA-7674 LER 17-007-00 | |
Download: ML18025B210 (3) | |
Text
JAN 2 5 2018 Brad Berryman Site Vice President U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Susquehanna Nuclear, LLC 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.2904 Fax 570.542.1504 Brad.Berryman@TalenEnergy.com SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-387(388)/2017-007-00 UNIT !LICENSE NO. NPF-14 UNIT 2 LICENSE NO. NPF -22 PLA-7674 TALEN-4 ENERGY 10 CFR 50.73 Docket No. 50-387 50-388 Attached is Licensee Event Repmt (LER) 50-387(388)/2017-007-00. The LER repmts an event which caused a loss of Secondary Containment differential pressure. This event was determined to be reportable in accordance with 10 CFR 50.73(a)(2)(v)(C) as a condition that could have prevented fulfilment of a safety function. There were no actual consequences to the health and safety of the public as a result of this event. This letter contains no new regulatory commitments. B. BenY"man
Attachment:
LER 50-387(388)/2017-007-00 Copy: NRC Region I Ms. T. E. Hood, NRC Project Manager Ms. L. H. Micewski, NRC Sr. Resident Inspector Mr. M. Shields, PA DEP/BRP NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017) Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. LICENSEE EVENT REPORT (LER) Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. (See Page 2 for required number of digits/characters for each block) Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects. ...... t-"' Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, (See NUREG-1 022, R.3 for instruction and guidance for completing this form NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, httQ://www. nrc.gov/readi ng-rm/doc-collections/nur§9s/staff/sr1 022/r3D the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. 1. FACILITY NAME DOCKET NUMBER .PAGE Susquehanna Steam Electric Station Unit 1 05000387 1 OF2 4. TITLE Secondary Containment Declared Inoperable Due to the opening of a plenum. 5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED SEQUENTIAL FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR REV MONTH DAY YEAR Susqueahanna Steam Electric Station Unit 2 NUMBER NO. 05000388 11 30 2017 2017 -007 -00 01 ..25 2018 FACILITY NAME DOCKET NUMBER 05000 9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: Check all that apply) 1 D 20.2201(b) D 20.2203(a)(3)(i) 0 50.73(a)(2)(ii)(A) D 50.73(a)(2)(viii)(A) D 2o.2201{d) D 20.2203(a)(3)(ii) D 50.73(a)(2)(ii)(B) D 50.73(a)(2)(viii)(B) D 20.2203(a)(1) D 20.2203(a)(4) D 50.73(a)(2)(iii) D 50.73(a)(2)(ix)(A) D 20.2203(a)(2)(i) 0 50.36{c)(1)(i)(A) 0 50.73(a)(2)(iv)(A) D 50.73(a)(2)(x) 10. POWER LEVEL D 20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A) D 50.73(a)(2)(v)(A) D 73.71(a)(4) D 20.2203(a)(2)(iii) D 50.36(c)(2) D 50.73{a)(2)(v)(B) D 73.71(a)(5) 100 D 20.2203(a)(2)(iv) D 50.46(a)(3)(ii) 1:81 50.73(a)(2)(v)(C) D 73.77(a)(1) D 20.2203(a)(2)(v) D 50.73(a)(2)(i)(A) D 50.73(a)(2)(v)(D) D 73.77(a)(2)(i) D 20.2203(a)(2)(vi) D 50.73(a)(2)(i)(B) D 50.73(a)(2)(vii) D 73.77(a)(2)(ii) D 50.73(a)(2)(i)(C) 0 OTHER Specify in Abstract below or in NRC Form 366A 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT NUMBER (Include Area Code) /Nicole PaQiiaro-LicensinQ Specialist-Nuclear Regulatory Affairs k570) 542-6578 13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT MANU-REPORTABLE CAUSE SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TOEPIX 14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR YES (If yes, complete 15. EXPECTED SUBMISSION DATE) D NO SUBMISSION 02 23 2018 DATE ft\BSTRACT (Umit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On November 30, 2017 at 1026, the Susquehanna Control Room received indication that a loss of Secondary Containment Zone 2 differential pressure had occurred. Control Room operators noted a differential pressure of 0" Water Column (WC) for several seconds, followed by a high differential pressure of 0.5" WC. System differential pressure was restored to normal in 3 minutes. The cause of the pressure swings is under investigation. Zone 2 differential pressures being less than 0.25" WC constitutes a loss of Secondary Containment based on not meeting requirements of Technical Specification (T.S.) 3.6.4.1 Surveillance Requirement 3.6.4.1.1 This condition is being reported in accordance with 10 CFR 50. 73(a)(2)(v)(C) as a condition that could have prevented fulfillment of safety function. This event was reported in ENS 53098 under 10 CFR 50.72(b){3)(v)(c) There is no redundant Susquehanna Secondary Containment system. There were no actual consequences to the health and safety of the public as a result of this event. NRC FORM 366 (04-2017)
NRC FORM 366A (04-2017) U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020 LICENSEE EVENT REPORT (LER) CONTINUATION SHEET (See NUREG-1 022, R.3 for instruction and guidance for completing this form http://WoNV-J.nrc.gov/readinq-rm/doc-collections/nureas/staff/sr1 022/r3D 1. FACILITY NAME Susquehanna Steam Electric Station Unit 1 NARRATIVE CONDITIONS PRIOR TO EVENT Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Information SeiVices Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555*0001, or by e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104). Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. 2. DOCKET NUMBER YEAR 05000387 2017 3. LER NUMBER SEQUENTIAL NUMBER -007 REV NO. -00 Unit 1 -Mode 1, approximately 1 00 percent Rated Thermal Power Unit 2 -Mode 1, approximately 100 percent Rated Thermal Power There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event. EVENT DESCRIPTION On November 30, 2017 at 1026, the Susquehanna Control Room received indication that a loss of Secondary Containment Zone 2 differential pressure had occurred. Control Room operators noted a differential pressure of 0" Water Column (WC) for several seconds, followed by a high differential pressure of 0.5" WC. System differential pressure was restored to normal in 3 minutes. The cause of the pressure swings is under investigation. Zone 2 differential pressures being less than 0.25" WC constitutes a loss of Secondary Containment based on not meeting requirements of Technical Specification (T.S.) 3.6.4.1 Surveillance Requirement 3.6.4.1. There were no actual consequences to the health and safety of the public as a result of this event. The condition is being reported in accorance with 10 CFR 50.73(a)(2)(v)(C) as a condition that could have prevented fulfillment of a safety function. This event was reported in ENS 53098 under 10 CFR 50.72(b)(3)(v)(c). There is no redundant Susquehanna Secondary Containment system. CAUSE OF EVENT This event is still under investigation. The cause will be provided in the supplement. ANALYSIS/SAFETY SIGNIFICANCE This event is still under investigation. The safety significance will be provided in the supplement CORRECTIVE ACTIONS This event is still under investigation. The corrective action will be provided in the supplement. PREVIOUS SIMILAR EVENTS This event is still under investigation. Previous similar events will be identified under the supplement NRC FORM 3668 (04-2017) Page 2 of 2