05000321/LER-1917-005, Regarding Automatic Scram Due to Intermediate Range Monitors Spiking Upscale

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Regarding Automatic Scram Due to Intermediate Range Monitors Spiking Upscale
ML17167A032
Person / Time
Site: Hatch Southern Nuclear icon.png
Issue date: 06/16/2017
From: Vineyard D
Southern Nuclear Operating Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-17-1110 LER 17-005-00
Download: ML17167A032 (6)
v • d • e


LER-1917-005, Regarding Automatic Scram Due to Intermediate Range Monitors Spiking Upscale
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(iv)(A), System Actuation
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)(x)
10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown
10 CFR 50.73(a)(2)(v), Loss of Safety Function
3211917005R00 - NRC Website
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text

David R. Vineyard

~ Southern Nuclear Vlca President-Plant Hall:h Hatx:h Nuclear Plant 11028 Halctl Patkv.'Cly North

~Y-~ 31513 June 16, 2017 Docket Nos.: 50-321 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant Unit 1 LEA 2017-005-00 912 537 5859 tel 912 366 2077 fax NL-17-1110 Automatic Scram Due to Intermediate Range Monitors Spiking Upscale Ladies and Gentlemen:

In accordance with the requirements of 10 CFR 50.73(a)(2)(iv)(A), Southern Nuclear Operating Company (SNC) hereby submits the enclosed Licensee Event Report.

This letter contains no NRC commitments. If you have any questions, please contact Greg Johnson at (912) 537-5874.

Respectfully submitted, David A. Vineyard Vice President - Hatch DAV(jcb Enclosure: LEA 2017-005-00

U. S. Nuclear Regulatory Commission NL-17-1110 Page2 Cc:

Regional Administrator, Region II NRR Project Manager-Hatch Senior Resident Inspector-Hatch RTYPE: CHA02.004

Edwin I. Hatch Nuclear Plant Unit 1 LER 2017-005-00 Automatic Scram Due to Intermediate Range Monitors Spiking Upscale

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 collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />

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LICENSEE EVENT REPORT (LER)

Reported lessons learned are incorporated into the licensing process and fed back to industry

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Send comments regarding burden estimate to the FOIA, Privacy and Information Collections (See Page 2 for required number of digits/characters for each block)

Branch (T-5 F53). 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 (See NUREG-1 022, R.3 for instruction and guidance for completing this form Affairs, NEOB-1 0202, (3150-01 04), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currenUy valid OMB control h!m:Jiwww. nrc. aov/reaging-rrn/doc:!<QIIectionslnur~~taff/sr1 022fr31) number, the NRC may not conduct or sponsor. and a person is not required to respond to, the information collection

.PAGE Edwin I. Hatch Nuclear Plant Unit 1 05000321 1 OF3

4. TITLE Automatic Scram Due to Intermediate Range Monitors Spiking Upscale
5. EVENT DATE
6. LER NUMBER
7. REPORT DATE
8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.

MONTH DAY YEAR 06 16 2017 FACILITY NAME DOCKET NUMBER 4

20 2017 2017

- 005
- 000
9. OPERATING MODE
11. THIS REPORT IS SUBMrrTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: Check all that apply)

D 20.2201(b)

D 20.2203(a)(3)(i) 0 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A) 2 D 20.2201(d)

D 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B) 0 20.2203(a)(1) 0 20.2203(a)(4) 0 50.73(a)(2)(iii)

D 50.73(a)(2)(ix)(A) 0 20.2203(a)(2){i) 0 50.36{c)(1)(i)(A)

~ 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) 0 73.71{a){5) 0 20.2203(a)(2)(iv)

D 50.46(a)(3)(ii) 0 50.73{a)(2)(v)(C) 0 73.77(a)(1) 001 0 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(D) 0 73.77(a)(2)(i) 0 20.2203(a)(2)(vi) 0 50.73{a)(2)(i)(B)

D 50.73{a)(2)(vii) 0 73.77{a)(2)(ii) 0 50.73{a)(2)(i)(C) 0 OTHER Specify in Abstract below or in NRC Form 366A

12. LICENSEE CONTACT FOR THIS LER ICENSEE CONTACT

~~LEPHONE NUMBER (Include Area Code)

Edwin I. Hatch/Jimmy Collins-Licensing Supervisor 912-537-2341

13. COMPLETE ONE UNE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT

CAUSE

SYSTEM COMPONENT MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX X

IG Jl GOBO y

14. SUPPLEMENTAL REPORT EXPECTED
15. EXPECTED MONTH DAY YEAR 0 YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

~NO SUBMISSION DATE ABSTRACT (Umit to 1400 spaces. i.e., approximately 15 single-spaced typewritten lines)

On April 20, 2017 at 0302 EDT with Unit 1 at approximately 1 percent rated thermal power due to a reactor startup from a planned maintenance outage, an automatic reactor scram was received due to the "A" and "8" Intermediate Range Monitors (IRMs) spiking upscale simultaneously. The instrument's set points for high-high neutron flux were reached, giving false trip signals to both channels of the reactor protection system (RPS) trip logic. Upon the automatic reactor scram signal, all control rods fully inserted appropriately. No primary containment isolation system (PCIS) actuations occurred and none were expected to occur based upon plant conditions following the reactor scram.

The cause of the event is due to the integrity of the IRMs signal cable connectors being in a degraded condition.

Degradation was found on "A" IRM at the detector connector, while the "8" IRM had connection issues between the penetration and the jumper connector. These IRM cable integrity issues allowed a signal path to exist between the cables' shielding and center conductors, causing the IRMs to spike upscale. The "A" and "8" IRM jumper cables and the associated connections were replaced and all Unit 1 IRM cables and associated trip logics were tested satisfactorily.

Event Description

On April 20, 2017 at 0302 EDT with Unit 1 at approximately 1 percent rated thermal power due to a reactor startup from a planned maintenance outage, an automatic reactor scram was received due to the "A" and "B" Intermediate Range Monitors (IRMs) spiking upscale simultaneously. The instrument's set points for high-high neutron flux were reached, giving false trip signals to both channels of the reactor protection system (RPS) trip logic. Upon the automatic reactor scram signal, all control rods fully inserted appropriately. No primary containment isolation system (PCIS) actuations occurred and none were expected to occur based upon plant conditions following the reactor scram.

Event Cause Analysis

The cause of the event is due to the integrity of the IRMs signal cable connectors being in a degraded condition. Degradation was found on "A" IRM at the detector connector, while the "B" IRM had connection issues between the penetration and the jumper connector. These IRM cable integrity issues allowed a signal path to exist between the cables' shielding and center conductors. The noise signal was magnified when the signal was transmitted to the instrumentation's amplifier, causing both the "A" and "B" IRMs to spike upscale and trip.

Safety Assessment

This event is reportable per 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in the automatic actuation of the reactor protection system (RPS).

The IRMs monitor neutron flux from the upper portion of the source range monitor (SRM) range to the lower portion of the power range neutron monitoring (PRNM) range. The IRM system has eight IRM channels, each of which includes one detector that can be physically positioned in the core by remote control. The detectors are inserted into the core for a reactor startup and are withdrawn after the reactor mode selector switch is turned to RUN. The IRM system is capable of generating a trip signal that can be used to prevent fuel damage resulting from anticipated operational occurrences (AOOs) that occur while operating in the intermediate power range. The independence and redundancy incorporated in the design of the IRMS are consistent with the safety design basis of the RPS.

The IRM system is divided into two groups of IRM channels arranged in the core. IRM channels "A", "C",

"E", and "G" are associated with trip system A of the RPS and IRM channels "8", "D", "F", and "H" are associated with trip system B. While the reactor mode switch is in REFUEL or STARTUP, an IRM upscale or inoperative trip signal actuates a neutron monitoring system trip of the RPS.

All control rods fully inserted and the plant responded as expected. Therefore, this event is considered to have very low safety significance.

Corrective Actions

As part of corrective actions, the "A" and "B" IRM jumper cables were replaced and all Unit 1 IRM cables Page 2 of3 (06-2016)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2018

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LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this fonn httoJ/www.nrc.gov/readinq-nn/doc-collectionslnureaslstaff/sr1 022/r3/)

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 teamed are incorporated into the licensing process and fed back to industry.

Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollecls.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

3. LER NUMBER Edwin I. Hatch Nuclear Plant Unit 1 05000-321 YEAR I SEQUENTIAL I REV NUMBER NO 2017
- 005
- 00 and associated trip logics were tested satisfactorily.

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