05000483/LER-2019-006, Unrecognized Inoperability of Boron Dilution Mitigation System (Bdms) Train B
| ML19295D510 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 10/22/2019 |
| From: | Wink R Ameren Missouri, Union Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| ULNRC-06537 LER 2019-006-00 | |
| Download: ML19295D510 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)() 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), 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) |
| 4832019006R00 - NRC Website | |
text
AIIIeI8fl Callaway Plant MISSOURI October 22, 2019 ULNRC-06537 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-000 1 10 CFR 50.73 Ladies and Gentlemen:
DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.
RENEWED FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2019-006-00 UNRECOGNIZED INOPERABILITY OF BORON DILUTION MITIGATION SYSTEM TRAIN B The enclosed licensee event report is submitted in accordance with 10CFR5O.73(a)(2)(i)(B) to report discovery of conditions and operations prohibited by Technical Specification (IS) 3.3.9, Boron Dilution Mitigation System (BDMS), and TS Limiting Condition of Operation (LCO) 3.0.4, LCO Applicability, due to unrecognized inoperability ofBDMS Train B.
This letter does not contain new commitments.
Sincerely 7
Roger C. Wink
(
Manager, Regulatory Affairs Enclosure LER 20 19-006-00 83 15 County Road 459 Steedman, MO 65077 AmerenMissouri.com
ULNRC-06537 October 22, 2019 Page 2 cc:
Mr. Scott A. Morris Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman,MO 65077 Mr. L. John Klos Project Manager, Callaway Plant Office ofNuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 09E3 Washington, DC 20555-000 1
ULNRC-06537 October 22, 2019 Page 3 Index and send hardcopy to QA File A160.0761 Hardcopy:
Certrec Corporation 6100 Western Place, Suite 1050 fort Worth, TX 76107 (Certrec receives ALL attachments as long as they are non-safeguards and may be publicly disclosed.)
Electronic distribution for the following can be made via LER ULNRC Distribution:
F. M. Diya B. L. Cox F. J. Bianco T. E. Herrmann S. P. Banker R. C. Wink T. B. Elwood J. C. PiUs
- i..j. Hutchison M. D. Hudson J. Joos Corporate Oversight NSRB Secretary Performance Improvement Coordinator Resident Inspectors (NRC)
STARS Regulatory Affairs Mr. Jay Silberg (Pillsbury Winthrop Shaw PiUman LLP)
Mr. Dan Beck (Missouri Public Service Commission)
frelephone Number (Include Area Code) 314-225-1905 Failure of the switch contacts to close on May 10, 2019 has been attributed to either a stack misalignment or mechanical binding. Corrective actions to prevent recurrence include establishing requirements to verify continuity through the Flux Double Test Bypass Switches for both BDMS trains when the switches are manipulated, and to replace the affected switch at the next available opportunity.
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 0313112020 (04-2018)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. Page Callaway Plant Unit I 05000483 j
i OF 4
- 4. Title Unracoanized moD rabilitv ofBoianflflutio dvlitioationSvstem_(BDMSEanB
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved MonthJ Dj Year YEAR Year FaciIit Name 05 10 2019 2019
- - 006
- - 00 10 22 2019 DoCkffltNumber
- 9. Operating Mode
- 11. This Report is Submitted Pursuantto the Requirements oflO CFR: (Check all that apply)
D 20.2201(b)
D 202203(a)(3)(i)
Q 5073(a)(2)(ii)(A)
Q 50.73(a)(2)(viii)(A) 5 D 20.2201(d) 0 20.2203(a)(3)(ii)
Q 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B) i: 20.220(a)(1)
- 20.2203(a)(4)
Q 50.73(a)(2)(iii)
Q 50.73(a)(2)()x)(A) 11 20.220(a)(2)(i) 0 50.36(c)(1)W(A)
C 5073(a)(2)(iv)(A)
Q 50.73(a)(2)(x)
- 10. PowerLevel Q 20.2203(a)(2)(ii)
Q 50.36(c)(1)(ii)(A)
Q 50.73(a)(2)(v)(A) 0 73.Z1(a)(4)
D 20.2203(a)(2)(iii)
Q 50.36(c)(2)
U 5073(a)(2)(v)(B)
Q 73Z1(a)(5)
C 20.2203(a)(2)(iv) 50.46(a)(3)(ii) ll 50.73(a)(2)(v)(C) 0 73.77(a)(1) 0%
D 20.2203(a)(2)(v)
Q 50.73(a)(2)(i)(A)
Q 50.73(a)(2)(v)(D)
Q 73.77(a)(2)(i) 0 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B)
Q 50.73(a)(2)(vii)
U 73.77(a)(2)(ii)
D 50.73(a)(2)(i)(c)
D OTHER Specify in Abstract below or in NRC Form 366A
- 12. Licensee Contact for tnis LER
_icensee Contact Engieer,ReguIatoryAffah-sandUcensing
- 13. COMPLETE ONE UNE FOR EACH COMPONENT FI6JLURE DESCRIBED IN ThIS REPORT
Cause
System f
Component J
Manufacturer Reportable to ICES
Cause
f SysJ Component Manufacturer J Reportable to ICES B
j JC j
HIS Jyhill Y
j J
- 14. Supplemental Report Expected Day J
Year E Yes(Ifyes, complete 15. EXPECTEDSUBMISSION DATE)
No Expected Submission Date BSTRACT (Limitto 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)
On August 23, 2019, it was discovered that Flux Doubling Test Bypass Switch 5604 had failed to close when it was placed n its Normal position at I 543 on May I 0, 201 9. This failure would have prevented train B of the Boron Dilution Mitigation System from performing its required safety function when required to be Operable in accordance with Technical Specification (IS) 3.3.9, Boron Dilution Mitigation System (BDMS), for the periods from I 543 on May 1 0, 201 9 to 2259 on May 16, 2019, and from 2301 on May 16, 2019 to 1212 on May 17, 2019. Due to the unrecognized inoperability of BDMS rain B, the TS 3.3.9 Limiting Condition of Operation (LCO) requiring two trains of BDMS to be Operable was not met during these periods, and the applicable Required Actions were not completed within their specified Completion Times.
In addition, Mode changes were performed during these periods of BDMS train B inoperability without satisfying the provisions of TS LCO 3.0.4.a, thereby resulting in a violation of TS LCO 3.0.4. Following discovery of the failure on August 23, 2019, remedial actions were taken to close the affected switch in its Normal position.
NRC FORM 366 (04-2018)U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 313112020 (04-2018)
, the NRC may not conduct or hffp://wwiv.nrc.gov/reading-rm/doc/collections/nuregs/staff/sM022/r3/)
sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME
- 2. DOCKETNUMBER
- 3. LERNUMBER YEAR E
SEIAJ[
REV Callaway Plant Unit I 05000-483 NUMBER NO.
2019 L
- - 006
- - 00 INMlM I Vt 1.
DESCRIPTION OF STRUCTURE(S), SYSTEM(S) AND COMPONENT(S):
The event reported in this LER involves the Boron Dilution Mitigation System (BDMS). The function of the BDMS [EIIS System: JCJ is to mitigate the consequences of the inadvertent addition of unborated primary grade water into the Reactor Coolant System (RCS) [EllS System: AB] when the plant is in Modes 2 (below the P-6 bistable [EIIS System: ABJ interlock setpoint), 3, 4, and 5. The addition of unborated primary grade water into the RCS results in boron dilution and the otential for an inadvertent boron dilution event.
The BDMS utilizes two channels of source range instrumentation. Upon detection of a flux multiplication by either source range instrumentation train, an alarm is sounded to alert the operator and valve movement is automatically initiated to terminate the dilution and start boration of the RCS.
Technical Specification (TS) 3.3.9, Boron Dilution Mitigation System (BDMS), provides the Limiting Condition for Operation, Conditions, Required Actions, and Surveillance Requirements for the BDMS.
2.
INITIAL PLANT CONDITIONS
At the time of the event, Callaway was in Mode 5 at 0% power with RCS loops filled following completion of core reload and prior to ascension to higher Modes in Refuel 23.
3.
EVENT DESCRIPTION
TS Limiting Condition for Operation (LCO) 3.3.9 requires two (i.e., both) trains of BDMS to be Operable when the plant is in Modes 2 (below P-6 setpoint), 3, 4, and 5.
At 1543 on 05/10/2019, Flux Doubling Test Bypass Switch 5604 [EIIS Component: HIS] was repositioned from its Alternate Source position to its Normal position. As the plant was in Mode 5 at the time, the affected BDMS train B was required to be Operable per TS LCO 3.3.9. However, on 08/23/201 9, it was discovered that there was a lack of continuity through the 5604 switch.
It was then concluded that the lack of continuity must have existed since the switch was repositioned on 05/1 0/201 9. This unrecognized failure of the switch to close would have prevented BDMS train B from performing its required safety function.
During the period that BDMS train B was inoperable, a change from Mode 5 to Mode 4 occurred at 1217 on 05/11/2019, a change from Mode 4 to Mode 3 occurred at 1951 on 05/14/2019, and a change from Mode 3 to Mode 2 occurred at 2224 on 05/1 6/201 9. The Modes of applicability for TS LCO 3.3.9 were briefly exited at 2259 on 05/1 6/201 9, when the permissive P-6 (flux doubling) interlock channels changed to a Set status during the first approach to criticality in Mode 2.
At 2301 on 05/1 6/201 9, the permissive P-6 interlock channels cleared, causing re-entry into the Modes of applicability for TS 3.3.9. Subsequently, a high source range neutron flux trip (which had not been blocked in a timely manner due to human error) caused an unplanned transition from Mode 2 to Mode 3 at 2303 on 05/16/2019. A second approach to criticality began at I I I 5 on 05/1 7/201 9, followed by a change from Mode 3 to Mode 2 at 1 1 23. The permissive P-6 interlock channels changed to a Set status again at I 21 2 on 05/1 7/201 9, exiting the Modes of applicability for TS 3.3.9.
Between I 21 2 on 05/1 7/201 9 and discovery of the failure on 08/23/201 9, BDMS was not required to be Operable, as Callaway remained in Mode I
, which is outside the Modes of applicability for TS 3.3.9.Page 2 of 4U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 313112020 (04-2018)
, the NRC may not conduct or hftp://www.nrc.gov/reading-rm/dodcollections/nuregs/staff/srl 0221r3/)
sponsor, and a person is not required to respond to, the information collection.
tFACJTYNAME 2.DOCKETNUMBER YEAR SEQUENTIAL REV Callaway Plant Unit I 05000-483 NUMBER NO.
2019
- - 00 4.
ASSESSMENT OF SAFETY CONSEQUENCES
The operations involving positive reactivity additions and Mode changes during the periods when train B of BDMS was inoperable did not significantly degrade plant safety. The failure did not affect the independent and redundant BDMS train A, and during the periods when BDMS train B was incapable of performing its required safety function during applicable Modes, there were no instances when BDMS train A was removed from service. Therefore, the ability of BDMS to mitigale an inadvertent dilution of the RCS was never lost.
5.
REPORTING REQUIREMENTS
This LER is submitted pursuant to 10 CFR 50.73(a)(2)(i)(B) to report conditions and operations that were prohibited by TS 3.3.9 and TS LCO 3.0.4.
The inoperability of BDMS train B at 1543 on 05/10/2019 (though unknown at the time) should have caused entry into TS 3.3.9 Condition A, with Required Action A.1 in effectto restore the train to Operable status within a Completion Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Due to the failure to perform Required Action A.1 within its associated Completion Time, TS 3.3.9 Condition B should have been entered at 1543 on 05/13/2019, with the following Required Actions in effect:
Required Action B.1 to suspend operations involving positive reactivity additions within a Completion Time of Immediately, AND Required Action B.2 to perform TS Surveillance Requirement (SR) 3.1.1.1 [i.e., shutdown margin calculations]
within a Completion Time of I hour and once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> thereafter, AND I
Required Action B.3.1 to close and secure unborated water source isolation valves within a Completion Time of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, AND Required Action B.3.2 to verify unborated water source isolation valves are closed and secured within a Completion Time of once per 31 days.
Required Actions B.1, B.2 and B.3.1 were not performed within their specified Completion Times, thereby resulting in operations (i.e., positive reactivity additions) and conditions (i.e., sources of unborated water being unisolated and shutdown margin calculations not being performed at an increased frequency) that were prohibited by TS 3.3.9.
In addition, per TS LCD 3.0.4, when an LCO is not met, entry into a Mode or other specified condition in the Applicability shall only be made:
a.
When the associated Actions to be entered permit continued operation in the Mode or other specified condition in the Applicability for an unlimited period of time; or b.
After performance of a risk assessment addressing inoperable systems and components, consideration of the results, determination of the acceptability of entering the Mode or other specified condition in the Applicability, and establishment of risk management actions, if appropriate; exceptions to this Specification are stated in the individual Specifications; or c.
When an allowance is stated in the individual value, parameter, or other Specification.
TS LCO 3.0.4.a was applicable to the event, because once 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> have elapsed with an inoperable BDMS train, TS 3.3.9 Condition A is to be continued into Condition B, which provides Required Actions that permit continued operation in the Modes of applicability for an unlimited time. However, as the Required Actions of TS 3.3.9 Conditions A and B were not met, each of the Mode changes that occurred during the periods when BDMS train B was incapable of performing its required safety function during applicable Modes constituted operations that were prohibited by TS LCO 3.0.4.Page 3 of 4US. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 313112020 (04-2018)
, the NRC may not conduct or http://www.nrc.qov/readinq-rm/dodcollections/nuregs/staff/srl022/r3/)
sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME_______
- 2. DOCKET NUMBER
- 3. LER NUMBER SEQUENTIAL J
REV Callaway Plant Unit I 05000-483 NUMBER NO.
2jOO6J 6.
CAUSE OF THE EVENT
An equipment failure analysis identified the cause of the failure as an electrical contact failure due to stack misalignment or mechanical binding within the switch. However, the root cause of the event was the lack of an indication or test to verify continuity through the affected switch, which resulted in untimely discovery of the failure.
An extent-of-condition review determined that the corresponding switch in the alternate train may potentially be susceptible to the same failure mode, but it has been verified to be operating properly.
7.
CORRECTIVE ACTIONS
Remedial actions were taken on 08/23/201 9 to exercise the affected switch in order to correct the misaligned or bound condition and verify continuity through the switch. To prevent recurrence, the affected switch will be replaced and inspected at the next available opportunity. In addition, to ensure that any future failures of the switches within the extent-of-condition will be detected and corrected in a timely manner, procedures and written instructions are being revised to direct the performance of a continuity check after each time the switches are re-positioned. Until the revised procedures and written instructions are issued, guidance to perform these continuity checks is being provided in an Operations Information Report (O1R).
8.
PREVIOUS SIMILAR EVENTS
None.Page 4 of 4