05000368/LER-1917-001, Regarding Inadequate Protection from Tornado Missiles Identified Due to Nonconforming Design Conditions
| ML17150A483 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 05/30/2017 |
| From: | Richard Anderson Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 2CAN051702 LER 17-001-00 | |
| Download: ML17150A483 (7) | |
| 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)(iii) 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)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation 10 CFR 50.73(b)(5) |
| 3681917001R00 - NRC Website | |
text
2CAN051702 May 30, 2017 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
Subject:
Licensee Event Report 50-368/2017-001-00 Arkansas Nuclear One, Unit 2 Docket No. 50-368 License No. NPF-6
Dear Sir or Madam:
Pursuant to the reporting requirements of 10 CFR 50.73, attached is the subject Licensee Event Report concerning the identification of inadequate protection from tornado missiles due to nonconforming design conditions for Arkansas Nuclear One, Unit 2.
There are no new commitments contained in this submittal.
Should you have any questions concerning this issue, please contact Stephenie Pyle, Manager, Regulatory Assurance, at 479-858-4704.
Sincerely, ORIGINAL SIGNED BY RICHARD L ANDERSON RLA/rwc Attachment: Licensee Event Report 50-368/2017-001-00 Entergy Operations, Inc.
1448 S.R. 333 Russellville, AR 72802 Tel 479-858-3110 Richard L. Anderson Vice President - Operations Arkansas Nuclear One
2CAN051702 Page 2 of 2 cc:
Mr. Kriss Kennedy Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339-5957 LEREvents@inpo.org
NRC FORM 366 (04-2017)
NRC FORM 366 (04-2017)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
LICENSEE EVENT REPORT (LER)
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 1. FACILITY NAME Arkansas Nuclear One - Unit 2
- 2. DOCKET NUMBER 05000368
- 3. PAGE 1 OF 5
- 4. TITLE Inadequate Protection from Tornado Missiles Identified Due to Nonconforming Design Conditions
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.
MONTH DAY YEAR FACILITY NAME N/A DOCKET NUMBER 04 06 2017 2017 001 00 05 30 2017 FACILITY NAME DOCKET NUMBER N/A
- 9. OPERATING MODE 6
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
- 10. POWER LEVEL 0
20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C) 73.77(a)(1) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) 73.77(a)(2)(i) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 73.77(a)(2)(ii) 50.73(a)(2)(i)(C)
OTHER Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT TELEPHONE NUMBER (Include Area Code)
Stephenie L. Pyle, Manager, Regulatory Assurance 479 858-4704 CAUSE SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX
CAUSE
SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED SUBMISSION DATE MONTH DAY YEAR YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
NO ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On April 6, 2017, as part of the closure of an Arkansas Nuclear One, Units 1 and 2 (ANO-1 & 2) Tornado Protection Study, a nonconforming condition in the plant design for a conduit that contains safety related cables for the ANO-2
- 1 Emergency Diesel Generator (EDG) meter and relay cabinets, was identified. The conduit did not meet current design basis for protection against a potential tornado missile impact. This vulnerability is similar to those previously reported in LERs associated with ANO-1.
On April 6, 2017, Operations declared the #1 EDG inoperable, implemented Enforcement Guidance Memorandum (EGM) 15-002, Enforcement Discretion for Tornado-Generated Missile Protection Noncompliance, along with necessary compensatory measures, and subsequently declared the affected equipment operable but non-conforming. Interim corrections include implementation of compensatory strategies. Plant modifications and license basis changes are being evaluated to resolve outstanding issues.
The cause of this issue was unclear and changing regulatory requirements during original plant licensing that led to an inadequate understanding of the regulatory guidance with respect to tornado missile protection design requirements.
A. BACKGROUND NRC DOCUMENTS Enforcement Guidance Memorandum (EGM) 15-002, Enforcement Discretion for Tornado-Generated Missile Protection Noncompliance, provides guidance to exercise enforcement discretion when an operating power reactor licensee does not comply with a plants current site-specific licensing basis for tornado-generated missile protection. Specifically, discretion would apply to the applicable Technical Specification (TS) Limiting Condition(s) for Operation (LCO) that would require a reactor shutdown or mode change in the event a licensee could not meet TS LCO required action(s) within the TS completion time.
Interim Staff Guidance DSS-ISG-2016-01, Clarification of Licensee Actions in Receipt of Enforcement Discretion Per Enforcement Guidance Memorandum EGM 15-002, provides interim staff guidance to facilitate staff understanding of expectations for consistent oversight associated with implementing enforcement discretion for tornado missile protection noncompliance(s) per EGM 15-002.
Appendix A of DSS-ISG-2016-01 provides guidance for acceptable initial and comprehensive compensatory measures for licensee use in implementing the enforcement discretion outlined in EGM 15-002. The licensee should declare (log) the utilization of EGM 15-002, inform the resident inspector, and enter the issue into the corrective action program. For initial compensatory measures, it is expected that the measures listed are already in place at sites that may be affected by severe weather, such as tornados and/or hurricane force winds.
The measures should be verified as current and readily deployable within a very short timeframe.
B. PLANT STATUS ANO-2 was operating at 0% rated thermal power in Mode 6 when this condition was discovered. There were no other structures, systems, or components (SSCs) that were inoperable at the time that contributed in the event.
C. DESCRIPTION OF EVENT
As a part of the closure of an ANO Tornado Protection Study, a tornado-generated missile vulnerability was identified on April 6, 2017. The vulnerability is associated with a conduit in the ANO-2 Fire Brigade Area on the 386 foot elevation of the ANO-2 Auxiliary Building. A western bound missile could strike the conduit in the Fire Brigade area above the ceiling tiles. Subsequent walk downs determined that only the western bound missile is creditable. This conduit contains the cables for instrumentation, controls, and interlocks for the #1 Emergency Diesel Generator (EDG)[EK].
The #1 EDG was declared inoperable and enforcement discretion per EGM 15-002 was implemented for the above issue and appropriate existing compensatory actions verified within the time allowed by the applicable LCOs. This condition has been entered into the ANO correction action program (CR-ANO-2-2017-1555). The guidance provided in EGM 15-002, with reference to Appendix A of DSS-ISG-2016-01, was utilized to address the compensatory measures that may be applicable to this condition.
This vulnerability is similar to the ones identified in ANO-1 LER 2016-002-00, dated August 11, 2016 (ML16224A767), and ANO-1 LER 2016-003-00 dated October 19, 2016 (ML16293A664).
Page 3 of 5 (04-2017)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 3. LER NUMBER Arkansas Nuclear One, Unit 2 05000-368 YEAR SEQUENTIAL NUMBER REV NO.
2017 001 00 D. EVENT CAUSES The identified condition is a design legacy issue. The cause of this issue was unclear and changing regulatory requirements during original plant licensing that led to an inadequate understanding of the regulatory guidance with respect to tornado missile protection design requirements.
E. CORRECTIVE ACTIONS
The following corrective actions were completed upon identification of each individual vulnerability:
The ANO directive (COPD-038) for implementing the respective enforcement discretion was completed for this condition. The actions completed ensure compliance with the requirements of EGM 15-002.
The status of the affected TS components was documented in the Station Log.
The NRC resident inspector and the ANO Operating crews were briefed with respect to the equipment that could be potentially affected during a site tornado event and the compensatory actions identified to both minimize the potential for tornado missiles during severe weather and to mitigate the consequences of potential tornado missiles.
The following corrective actions have been taken to further address the condition. Note that EGM 15-002 requires follow-up actions to be completed within 60 days following tornado vulnerability identification which resulted in application of the enforcement discretion. These actions are in addition to those established upon initial identification of tornado missile vulnerability and intended to provide a discernable, safety beneficial change, when compared with the initially established compensatory measures.
Appropriate procedures and directives have been revised to address the SSC impact per area identified above.
Operations personnel remain abreast of the tornado missile vulnerabilities and the established compensatory measures. Operations personnel are trained with respect to preparation for and the mitigation of natural events such as tornados. Procedures currently available cover events such as natural emergencies (includes tornado events), loss of offsite power, station blackout, and FLEX (diverse and flexible coping strategies) for beyond design basis events, along with the aforementioned ANO directive (COPD-038).
Additional longer term corrective actions are being considered. Options include the development and installation of a plant modification which bring affected areas into compliance with tornado missile protection standards as applicable to the ANO-2 licensing basis. Additional options include the application of Revision 1 of Regulatory Guide 1.76 or the use of other evaluation methods such as the Tornado Missile (TORMIS) code or the Tornado Missile Risk Evaluator (TMRE), either of which would require a license amendment request and subsequent NRC approval.
Page 4 of 5 (04-2017)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 3. LER NUMBER Arkansas Nuclear One, Unit 2 05000-368 YEAR SEQUENTIAL NUMBER REV NO.
2017 001 00
F. SAFETY CONSEQUENCES
This condition had no actual safety consequences impacting plant or public safety since ANO-2 has not experienced a tornado missile event.
As documented per EGM 15-002, tornado missile scenarios that may lead to core damage are very low probability events because safety-related SSCs are typically designed to withstand the effects of tornados. For a tornado missile-induced scenario to occur, a tornado would have to impact the site and result in the generation of missiles that would contact and fail vulnerable, unprotected safety-related equipment and/or unprotected safety-related subcomponents in a manner that is non-repairable and non-recoverable. In addition, because plants are designed with redundancy and diversity, the tornado missiles would have to affect multiple trains of safety systems and/or means of achieving safe shutdown.
The NRC has completed a generic risk analysis of potential tornado missile protection non-compliances to examine the risk significance for plant facilities. The generic analysis assumed that core damage would occur if a tornado hit a plant located in the most active tornado region in the country and that it caused a tornado-generated missile to fail all emergency core cooling equipment at the plant with no ability to recover. Given this conservative assumption, the staffs study established that the core damage frequency (CDF) associated with tornado missile-related non-compliances are well below CDFs requiring immediate regulatory action. In summary, the generic bounding risk analysis performed by the NRC concluded that this issue is of low risk significance.
During a postulated design basis tornado, the conditions documented could have resulted in a loss of the safety function for the EDGs, assuming the #2 EDG was already inoperable for a reason unrelated to tornado missile.
This system is used to mitigate the effects of a loss of offsite power by providing an emergency AC power source.
G. BASIS FOR REPORTIBILITY This event is reportable pursuant to the following criteria:
Any operation or condition which was prohibited by Technical Specifications 10 CFR 50.73(a)(2)(ii)(B)
Any event or condition that resulted in the nuclear plant being in an unanalyzed condition that significantly degraded plant safety.
Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident Page 5 of 5 (04-2017)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 3. LER NUMBER Arkansas Nuclear One, Unit 2 05000-368 YEAR SEQUENTIAL NUMBER REV NO.
2017 001 00 The guidance provided in NUREG 1022 states under 10 CFR 50.73(a)(1):
The holder of an operating license for a nuclear power plant (licensee) shall submit a Licensee Event Report (LER) for any event of the type described in this paragraph within 60 days after the discovery of the event.
H. ADDITIONAL INFORMATION
10 CFR 50.73(b)(5) states that this report shall contain reference to any previous similar events at the same plant that are known to the licensee. NUREG 1022 reporting guidance states that term previous occurrences should include previous events or conditions that involved the same underlying concern or reason as this event, such as the same root cause, failure, or sequence of events.
A review of the ANO corrective action program and LERs for the previous three years was performed. Aside from LERs 2016-002-00 and 2016-003-00 mentioned previously, there were no other similar events identified at ANO during this time period.
No components failed due to this condition. The conditions identified herein were a result of extent of condition evaluation with respect to potential tornado design vulnerabilities. These vulnerabilities are legacy issues which are being addressed in accordance with EGM 15-002.
Energy Industry Identification System (EIIS) codes and component codes are identified in the text of this report as [XX].