ULNRC-06850, Special Report 2023-03 Pam Report Inoperability of a Post Accident Monitoring (Pam) Instrument
| ML23355A173 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 12/21/2023 |
| From: | Witt T Ameren Missouri, Union Electric Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| Shared Package | |
| ML23355A173 | List: |
| References | |
| ULNRC-06850 | |
| Download: ML23355A173 (1) | |
Text
Callaway Plant
.t December 21, 2023 ULNRC-06850 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Ladies and Gentlemen:
DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.
RENEWED FACILITY OPERATING LICENSE NPF-30 SPECIAL REPORT 2023 PAM REPORT INOPERABILITY OF A POST ACCIDENT MONITORING (PAM) INSTRUMENT The enclosed Special Report 2023-03 (PAM Report) addresses inoperability of the Reactor Vessel Level Indicating System (RVLIS) 'A' channel. Since the period of inoperability for the RVLIS 'A' channel has exceeded the Completion Time specified by Required Action A.1 within Technical Specification (TS) 3.3.3, "PAM Instrumentation," Required Action B.1 of TS 3.3.3 requires submittal of a report in accordance with TS 5.6.8, "PAM Report."
No new commitments are identified in this correspondence. None of the material in this report is considered proprietary by Union Electric (d/b/a Ameren Missouri).
If you have any questions or require additional information, please contact Mr. Thomas B. Elwood, Supervising Engineer, Regulatory Affairs and Licensing at 314-225-1905.
Sincerely, Todd A. Witt Manager, Regulatory Affairs Enclosure - Special Report 2023-03 (PAM Report)
.t 8315 County Road 459 : Steedman, MO 65077 : AmerenMissouri.com
.t
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ULNRC-06850 December 21, 2023 Page 2 of 3 cc: Mr. John Monninger 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. M. Chawla Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop O8B1A Washington, DC 20555-0001
ULNRC-06850 December 21, 2023 Page 3 of 3 Index and send hardcopy to QA File A160.0761 Hardcopy:
Certrec Corporation 6500 West Freeway, Suite 400 Fort Worth, TX 76116 (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 Other Situations ULNRC Distribution:
F. M. Diya K. C. Scott J. G. Beck W. A. Witt T. A. Witt B. L. Jungmann T. B. Elwood NSRB Secretary STARS Regulatory Affairs Mr. Jay Silberg (Pillsbury Winthrop Shaw Pittman LLP)
Ms. Kathleen McNelis (Public Service Commission)
Ms. Claire Eubanks (Public Service Commission)
Enclosure to ULNRC-06850 Page 1 of 2 Special Report 2023-03 PAM Report Requirement Callaway Plant Unit 1 Technical Speci"caon (TS) 3.3.3, "Post Accident Monitoring (PAM)
Instrumentaon," contains requirements for the Reactor Vessel Level Indicang System (RVLIS) instrumentaon. (The RVLIS channels correspond to Funcon 5 of TS Table 3.3.3-1.) TS 3.3.3 Liming Condion for Operaon (LCO) requires two channels of RVLIS instrumentaon to be Operable while in MODES 1, 2, and 3. With one of the required RVLIS instruments inoperable for more than 30 days, Required Acon B.1 speci"es, "Iniate acon in accordance with Speci"caon 5.6.8."
TS 5.6.8, "PAM Report," states, "When a report is required by Condion B or F of LCO 3.3.3, 'Post Accident Monitoring (PAM) Instrumentaon,' a report shall be submited within the following 14 days.
The report shall outline the preplanned alternate method of monitoring, the cause of the inoperability, and the plans and schedule for restoring the instrumentaon channels of the Funcon to Operable status."
Background
The RVLIS provides an indicaon of reactor vessel level from the botom of the reactor vessel to the top of the reactor under natural (narrow range) and forced (wide range) circulaon condions. In addion to the two dierenal pressure transmiters that support this funcon, resistance temperature detectors (RTDs) are provided on the sensing lines to these transmiters to allow for density compensaon of the "uid within the sensing lines. RVLIS employs dierent types of electronic cards in order to funcon properly. The cards of concern for this report include the Wesnghouse 7300 Series Summing Ampli"er (NSA) card and Wesnghouse 7300 Series Nuclear Mulplier/Divider (NMD) card, as issues with these cards are causing the 'A' RVLIS channel to be inoperable.
Summary of the PAM Instrument Inoperability On November 16, 2023, at 2100, BBLI1312 (Reactor Vessel Wide-Range Level Train 'A' Level Indicaon) was declared inoperable for intermitently failing high, thus requiring entry into Condion A, i.e.,
Required Acon A.1 of TS 3.3.3.3. The 30-day restoraon me speci"ed per Required Acon A.1 expired on 12/16/2023, which makes this 14-day PAM report due on 12/30/2023 per TS 5.6.8. A review of plant computer operaonal history for the 'A' and 'B' RVLIS channels iden"ed that the 'A' channel indicaon "rst began deviang from the 'B' channel indicaon on November 8, 2023, at 0700, with the deviaon becoming signi"cant enough to merit the determinaon that the channel was inoperable on November 16, 2023. From the start of the period where the 'A' RVLIS channel began displaying errac indicaon on November 8, through the date of this report, the 'B' RVLIS channel has remained operable.
Preplanned Alternate Method of Monitoring The 'B' RVLIS channel is sll operable to provide reactor vessel level indicaon. Also, an alternate means of monitoring has been implemented, as described in TS Bases 3.3.3, Required Acon F.1. the alternate means consists of monitoring the core exit thermocouples, pressurizer level indicaon, and Reactor Coolant System subcooling monitor indicaon. These three parameters provide diverse informaon for verifying adequate core cooling.
Enclosure to ULNRC-06850 Page 2 of 2 Cause of the Inoperability The cause of the inoperability is a combinaon of issues with the NSA and NMD cards. Speci"cally, the NSA card was producing errac readings that were being in"uenced by ambient temperature variaons in its cabinet, corresponding to the cabinet door being opened and closed. During invesgaon into the issue with the NSA card, a corresponding NMD card exhibited unacceptable signal dri. The signal dri from the NMD card alone would not have been sucient to cause the errac readings leading to the inoperable channel, but replacement of this NMD card has contributed to the overall duraon in restoring the 'A' RVLIS channel.
Plans and Schedule for Restoring the Instrumentaon Channel to Operable Status A replacement NSA card has been pre-tested sasfactorily, passed its burn-in tesng, and is ready for installaon. In addion, two replacement NMD cards have passed their pre-installaon tesng and are currently undergoing their burn-in tesng. During the burn-in of these NMD cards, each card has exhibited at least one anomalous data point. Further burn-in is required to ensure that either card will perform as expected if installed. If neither NMD card is approved for installaon, restoraon of the 'A' RVLIS channel will be conngent upon the availability of replacement parts being procured from Wesnghouse. Callaway has been experiencing long standing issues with parts quality with regard to Wesnghouse 7300 Series NMD cards that have not yet been resolved, with mulple new cards being unable to pass acceptance criteria. Callaway is acvely engaged with Wesnghouse to resolve these issues. Restoraon of RVLIS can be accomplished upon receipt of replacement cards that comply with Wesnghouse speci"caons.
Based upon discussions with Wesnghouse and the preliminary results of ongoing burn-in tesng for the NMD cards, Callaway ancipates that replacement of the cards and restoraon of the 'A' RVLIS channel to an operable status will take place during the "rst quarter of 2024. If unforeseen circumstances result in a delay in restoraon beyond March 31, 2024, Callaway will submit a supplementary report detailing the further plans for restoraon and any addional "ndings pernent to the system.