ML112450479

Nine Mile Point, Unit No. 2 - E-mail from J.Dosa to R.Guzman NMP2 EPU SLC Piping/Component Rerating Modification

ML112450479
Person / Time
Site:	Nine Mile Point
Issue date:	09/02/2011
From:	Dosa J J Constellation Energy Nuclear Group, Nine Mile Point
To:	Guzman R V Division of Operating Reactor Licensing
Guzman R V, NRR/DORL, 415-1030
References
TAC ME1476
Download: ML112450479 (1)

Text

From: Dosa, John J [John.Dosa@cengllc.com] Sent: Friday, September 02, 2011 3:56 PM To: Guzman, Richard Cc: Darling, Theresa H Subject: RE: Quick Question - SLC piping/component rerating modification This was completed as stated. If there was a SAR change associated, it would have been discussed in the Fall 2010 50.59 report associated with the SAR update. I will need to review that document. From: Guzman, Richard [1] Sent: Friday, September 02, 2011 3:47 PM To: Dosa, John J Cc: Darling, Theresa H Subject: Quick Question - SLC piping/component rerating modification John - as we discussed, can you verify that the modification described below was indeed completed during the Spring 2010 outage? Is there a docketed document out there from NMPNS that states this. See below.

NMPNS 2/19/11 RAI Response The SLCS pump relief valve setpoint maintains a 31.6 psi margin to relief valve lift, in addition to the 3% set pressure tolerance (42 psi). Therefore, the combined margin is 73.6 psi. The overall combined accuracy of the test instrument is not accounted in the margin calculation. However, the instrument used for the set pressure determination meets the ASME OM CODE-2004, which is adopted in the NMP2 IST program. The gauge accuracy used in the set pressure determination is +/-0.5% compared to the code requirement of +/-1%. The combined margin of 73.6 psi is recognized to provide minimally sufficient margin for SLCS pump relief valves, at both CLTP and EPU conditions. As such, the piping design pressure is being rerated and the relief valve set pressure increased to provide additional margin. The margin of 73.6 psi was defined based on nominal relief valve setpoint of 1400 psi minus the pump discharge pressure of 1326.4 psi. This margin is 1 psi less than the existing margin that has been demonstrated effective at eliminating relief valve lift during surveillance testing. However, for the current operating condition the 75 psi margin to SLCS relief valve nominal setpoint has not prevented relief valve seat seepage during SLCS pump surveillance testing. To resolve this issue the SLCS relief valve vendor has recommended maintaining approximately a 10% margin between the maximum SLCS pump pressure pulsation and the nominal relief valve setpoint. To achieve this margin the SLCS piping and components are being rerated to 1600 psig. The setpoint for the relief valve will be established to include at least a 10% margin between the maximum SLCS pump peak pressure pulsation and the relief valve minimum setpoint, (1459 psi) or approximately a 133 psi margin. The rerating of the piping to 1600 psig will provide the ability to increase the relief setting to a maximum of 1600 psi providing approximately a 20% margin above the pump discharge pressure of 1326.4 psi. This modification is currently planned for implementation during the spring 2010 refueling outage.

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