ML22154A550
| ML22154A550 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 06/07/2022 |
| From: | Robert Kuntz Plant Licensing Branch III |
| To: | Conboy T Northern States Power Company, Minnesota |
| Kuntz R | |
| References | |
| EPID L-2021-LLR-0083 | |
| Download: ML22154A550 (5) | |
Text
June 7, 2022 MONTICELLO NUCLEAR GENERATING PLANT - AUTHORIZATION AND SAFETY EVALUATION FOR ALTERNATIVE REQUEST NO. PR-02 (EPID L-2021-LLR-0083)
LICENSEE INFORMATION Recipients Name and Address:
Mr. Christopher P. Domingos Site Vice President Northern States Power Company - Minnesota Monticello Nuclear Generating Plant 2807 West County Road 75 Monticello, MN 55362 Licensee:
Northern States Power Company Plant Name(s) and Unit(s):
Monticello Nuclear Generating Plant Docket No.:
50-263 APPLICATION INFORMATION Submittal Date: November 1, 2021 Submittal Agencywide Documents Access and Management System (ADAMS) Accession No.: ML21305A067 Alternative Provision: The applicant requested an alternative under Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(z)(1).
Applicable Code Edition and Addenda: American Society of Mechanical Engineers (ASME),
Operation and Maintenance of Nuclear Power Plants (OM) Code, 2017 Edition with no Addenda.
Applicable Inservice Inspection (ISI) or Inservice Testing (IST) Program Interval and Interval Start/End Dates: Sixth 10-year IST interval currently scheduled to begin on October 1, 2022, and end on May 31, 2032.
IST Requirement: ASME OM Code, subsection ISTC, paragraph ISTB-3510, General, paragraph (b), Range, subparagraph (1) states, The full-scale range of each analog instrument shall be not greater than three times the reference value.
Brief Description of the Proposed Alternative: Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter, the licensee), hereby requests NRC authorization of this 10 CFR 50.55a request to support the implementation of the sixth 10-year IST interval for Monticello Nuclear Generating Plant (Monticello). Proposed Alternative No. PR-02 requests authorization for an alternative for determination of pump flow rate testing for Residual Heat Removal (RHR) and Residual Heat Removal Service Water (RHRSW) pumps.
Summary of Commitments: This submittal makes no new commitments and no revisions to existing commitments.
For additional details on the licensees request, please refer to the documents located at the ADAMS Accession No(s) identified above.
STAFF EVALUATION The RHR and RHRSW pumps with their instrument loops at Monticello must be tested by meeting the instrument accuracy requirements in accordance with the ASME OM Code, subsection ISTB, Inservice Testing of Pumps in Water-Cooled Reactor Nuclear Power Plants - Pre-2000 Plants, paragraph ISTB-3510(b), Range, subparagraph (1), which requires that the full-scale range of each analog instrument be no greater than three times the reference value, and table ISTB-3500-1, Required Instrument Accuracy, which requires the instrument accuracy for flow rate to be within +/- percent of full-scale. The combination of these two requirements results in an effective loop accuracy requirement of +/-6 percent of the reference value.
Alternative Request PR-02 proposed an alternative to the requirements in ASME OM Code, paragraph ISTB-3510(b)(1), for the Monticello existing flow transmitters FT-10-111A/B and FT-10-97A/B, flow isolators FY-4105 and FY-4106, and flow indicators FI-7188 and FI-7189, which are used for the loops of RHR pumps P-202A/B/C/D and RHRSW pumps P-109A/B/C/D.
The RHR and RHRSW pumps at Monticello are ASME OM Code Group A pumps, which are pumps that are operated continuously or routinely during normal operation, cold shutdown, or refueling operations. The instrument loops are each designed to indicate flow while two parallel pumps (RHR or RHRSW) are operating. During inservice testing, only one pump operates at a time. The existing instruments do not meet the ASME OM Code requirement. The reference value of flow for one pump is less than one-third of each instruments range.
The alternative proposes to use the existing station instruments to measure pump IST parameters. The licensee performed a loop check on each loop instrument as described in the submittal dated November 1, 2021, and determined that the installed RHR pumps in Divisions A and B, RHRSW pumps in Division A, and RHRSW pumps in Division B have as-found loop instrument accuracy of +/-0.84 percent, +/-1.21 percent, and +/-1.25percent, respectively. The instrument accuracies are within the percent requirements for Group A and Group B tests in table ISTB-3510-1. Paragraph ISTB-3510(b)(1) requires that the full-scale range of each analog instrument be not greater than three times the reference value. Thus, when combining the required level of accuracy with the allowed range for the reference value, the effective instrument accuracy is +/-6 percent of the reference value.
As shown below, table 1 summarizes submittal table PR-02-01, which specifies the ranges, equivalent references values, range to reference value ratio. Based on the information in submittal table PR-02-01 and the as-found loop instrument accuracy, calculated effective accuracies for the instruments in the RHR and RHRSW systems can be determined. The calculated effective instrument accuracies are less than the required effective accuracy of
+/-6 percent. Therefore, the NRC staff finds that these instruments yield readings at least equivalent to the reading achieved from instruments that meet ASME OM Code requirements.
Table 1 Instrument Loop Pumps Instrument Span (Range)
Equivalent Reference Value Range to Reference Value Ratio Effective Loop Accuracy with More Restrictive Instrument Accuracy A RHR Pumps FT-10-111A and FI-7189 loop P-202A 4-20 mA (16 mA)
(6.46-4) =
2.46 mA (16/2.46) =
6.50 (6.50 x 0.84%)
=
+/-5.46%
P-202C 4-20 mA (16 mA)
(6.59-4) =
2.59 mA (16/2.59) =
6.18 (6.18 x 0.84%)
=
+/-5.19%
B RHR Pumps FT 111B, FY-4106, and FI-7188 loop P-202B 4-20 mA (16 mA)
(6.43-4) =
2.43 mA (16/2.43) =
6.58 (6.58 x 0.84%)
=
+/-5.53%
P-202D 4-20 mA (16 mA)
(6.43-4) =
2.43 mA (16/2.43) =
6.58 (6.58 x 0.84%)
=
+/-5.53%
A RHRSW Pumps FT-10-97A and FI-7189 P-109A 10-50 mA (40 mA)
(18.44-10) =
8.44 mA (40/8.44) =
4.74 (4.74 x 1.21%)
=
+/-5.73%
P-109C 10-50 mA (40 mA)
(18.40-10) =
8.4 mA (40/8.40) =
4.76 (4.76 x 1.21%)
=
+/-5.76%
B RHRSW Pumps FT-10-97B, FY-4105, and FI-7188 P-109B 4-20 mA (16 mA)
(7.43-4) =
3.43 mA (16/3.43) =
4.66 (4.66 x 1.25%)
=
+/-5.83%
P-109D 4-20 mA (16 mA)
(7.42-4) =
3.42 mA (16/3.42) =
4.68 (4.68 x 1.25%)
=
+/-5.85%
Based on its review, the NRC staff finds that Alternative Request PR-02 will provide adequate accuracy of the instrumentation to be used for the flow testing of RHR pumps P-202A/B/C/D and RHRSW pumps P-109A/B/C/D at MNGP in demonstrating their operational readiness that will provide an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1).
CONCLUSION As discussed above, the NRC staff has determined that Alternative Request PR-02 will provide adequate accuracy of the instrumentation to be used for the flow testing of RHR pumps P-202A/B/C/D and RHRSW pumps P-109A/B/C/D at Monticello in demonstrating their operational readiness that will provide an acceptable level of quality and safety.
Therefore, the NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(1).
The NRC staff authorizes the use of Alternative PR-02 at Monticello for the sixth 10-year IST program interval currently scheduled to begin on October 1, 2022, and end on May 31, 2032.
All other ASME OM Code requirements for which relief or an alternative was not specifically requested, and granted or authorized (as applicable) remain applicable.
Principal Contributor:
Y. Wong G. Bedi Date: June 7, 2022 Nancy L. Salgado Chief Plant Licensing Branch IIII Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation cc: Listserv Joel S.
Wiebe Digitally signed by Joel S.
Wiebe Date: 2022.06.07 11:38:16 -04'00'
ML22154A550 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DEX/EMIB/BC NRR/DORL/LPL3/BC NAME RKuntz SRohrer SBailey NSalgado (JWiebe for)
DATE 6/2/2022 6/6/2022 6/2/2022 6/7/2022