ML18290A653

COL Docs - Clarification Topics for Vogtle Units 3&4 LAR 18-016, Rns Pump Testing ITAAC Changes

ML18290A653
Person / Time
Site:	Vogtle
Issue date:	10/17/2018
From:	NRC
To:	NRC/NRO/DLSE/LB4
References
Download: ML18290A653 (3)

Text

Vogtle PEmails From: Hoellman, Jordan Sent: Wednesday, October 17, 2018 10:40 AM To: Vogtle PEmails Cc: Patel, Chandu

Subject:

Clarification Topics for Vogtle Units 3&4 LAR 18-016, RNS Pump Testing ITAAC Changes Forwarding this to ADAMS for discussion at a future public meeting.

Jordan Hoellman Project Manager NRO / DLSE / LB4 U.S. Nuclear Regulatory Commission office: OWFN 08-C18 phone: (301) 415-5481 email: Jordan.Hoellman2@nrc.gov From: Patel, Chandu Sent: Monday, October 15, 2018 11:43 AM To: Chamberlain, Amy Christine <ACCHAMBE@southernco.com>; Sparkman, Wesley A. <WASPARKM@southernco.com>

Subject:

Clarification call for LAR 18-016 Hi Amy and Wes, Please see the topics we like to discuss to gain better understanding of LAR 18-016 before we prepare the RAIs. We may be able to arrange a call on this Thursday if you can support it. I will put this in ADAMS after you verify that there is no proprietary information.

LAR 18-016 proposes a change to the acceptance criteria for the RNS midloop flowrate ITAAC to clarify that the RNS pumps should be tested individually because operation of both RNS pumps at the same time with RCS hotleg water level at 50% is not advised as it imposes the risk of air entrainment due to vortexing at the common suction takeoff, which could damage the pumps

1) The staff would like to understand how this LAR is consistent with other sections of the FSAR. Specifically

• FSAR Section 19E, Shutdown Evaluation, Section 19E.2.1.2.2 RCS Hot Leg Level states that due to the low RCS drain rate and the RCS step nozzle (as discussed in 19E.2.1.2.3), the amount of air entrainment (and therefore RCS level perturbation during midloop) is negligible.

• TR 3.7.2 states that two trains of RNS RCS shutdown heat removal shall be FUNCTIONAL and one RNS pump in operation in MODE 5 with RCS pressure boundary open, which includes mid-loop operation.

• TRS 3.7.2.1 calls for the operator to verify one RNS pump is in operation and that the required RNS pump circulates reactor coolant at a flow > 1580 gpm, or verify both RNS pumps are in operation and circulating reactor coolant at a flow > 2000 gpm once applicability is reached.

1

APPLICABILITY: MODE 5 with RCS pressure boundary open (includes midloop operation)

MODE 6 with upper internals in place, MODE 6 with cavity level < 23 feet above the top of the reactor vessel flange.

• FSAR Table 19.59-18, AP1000 PRA-Based Insights does not mention that dual pump operation is not advised below 80% hotleg level.

o What procedures and alarms prevent the operator from using dual RNS pump below 80%

hotleg level?

o How was this condition modeled in the LPSD PRA?

2) To insert SG nozzle dams, FSAR Section 19E states that the RCS must be drained to a level sufficient to provide a vent path from the pressurizer to the steam generators so that the SG tubes can drain. The staff understands this level is 80% hotleg level. Is this level the same for SG nozzle dam installation?

3) Does any maintenance require hotleg level less than 80%, e.g., RCP maintenance?

4) Additionally, the staff notes that

• FSAR Chapter 19, page 19.59-18, states that initiating events during reactor coolant system drained conditions (includes midloop operation) contribute approximately 95 percent of the total shutdown core damage frequency.

• NUREG 1793 states, Inadvertent overdraining of the RCS while reducing inventory to reach midloop conditions has very high risk significance (initiating event IEV-RCSOD) (page 19-71).

Thanks, Chandu 2

Hearing Identifier: Vogtle_COL_Docs_Public Email Number: 378 Mail Envelope Properties (SN6PR0901MB2366FF1E98B061745EB84B41D5FF0)

Subject:

Clarification Topics for Vogtle Units 3&4 LAR 18-016, RNS Pump Testing ITAAC Changes Sent Date: 10/17/2018 10:39:34 AM Received Date: 10/17/2018 10:39:39 AM From: Hoellman, Jordan Created By: Jordan.Hoellman2@nrc.gov Recipients:

"Patel, Chandu" <Chandu.Patel@nrc.gov>

Tracking Status: None "Vogtle PEmails" <Vogtle.PEmails@nrc.gov>

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