ML102180069

Response to Precas Clarification Concerns from Phone Call

ML102180069
Person / Time
Site:	North Anna
Issue date:	07/06/2010
From:	Shaub T Dominion
To:	V Sreenivas Plant Licensing Branch II
Sreenivas V.NRR/DORL/LPL2-1 415-2597
References
Download: ML102180069 (2)

Text

From: Tom Shaub [tom.shaub@dom.com]

Sent: Tuesday, July 06, 2010 3:15 PM To: Sreenivas, V

Subject:

Response to PREACS clarification concerns from phone call V,

Here are the response to the clarifications you requested regarding the HHSI pump seals and operating conditions.

What is the HHSI pump seal model #?

10110534 FLOWSERVE - Seal, mechanical, size 3 1/4 , inboard, suction side, single pto, cartridge type, for a 2.5 rlij-11 pump consisting of the following: metal parts - 316 ss seal sleeve bore - chrome plated 316 ss rotating face - tungsten carbide stationary face - #5 carbon gland material - 316 ss gland connections - flush gland elastomer - epr sleeve elastomer - epr Our documented worst case seal leak was 1200 cc / hr. What was the cause of that seal leak? At what fluid temperature did this leak occur?

On 4 July 2005, leakage was identified from the outboard seal on U2 C HHSI pump, 2-CH-P-1C. The quantity of leakage was observed to be 20 ml/minute. A root cause evaluation was performed. It was determined that elevated vibrations caused the outboard seal leak on 2-CH-P-1C, and was not a fault with the manufacture or installation of the seal. A more extensive vibration analysis was performed and found the source of the elevated vibrations to be at the inboard end of the pump. Of the potential sources, only the gear-to-pump coupling would result in higher vibration readings at the outboard end of the pump. The elevated vibrations are a result of the gear-to-pump coupling. The gear-to-pump coupling had been installed in late December 2004 (six months prior to the seal leak). Installation was by skill-of-the-craft with no balance or alignment checks performed. Alignment checks are referring to the assembly of the coupling components to make the coupling, not alignment between the pump and gear. Corrective actions were implemented as a result of the root cause evaluation.

As far as the fluid temperature, the seal leak occurred during normal operation, and the HHSI pump suction temperature is approximately 100ºF. However, this seal leak was considered Accident Leakage, and therefore, the leakage that was logged in the ECCS Leakage Log, was 2928 cc / hr (1200 CC/hr x 2.44). See below for explanation of Accident Leakage.

What is the difference in this leakage at fluid temperature assumed in a design basis accident?

The North Anna ECCS Leakage Log, 1-LOG-20 and 2-LOG-20, accounts for the difference in leakage that could be expected if the ECCS system were in the recirculation mode following a DBA. During normal operations, the most conservative pressure seen by the seals of the High Head Safety Injection (HHSI) pumps is due to lowest allowed VCT pressure and weight of water due to height. This conservatively equates to the square root of 160.8 (Low Head Safety Injection (LHSI) system pressure during recirculation) divided by 27 (lowest normal operating pressure at the suction of the HHSI pumps due to VCT pressure and weight of water due height) which provides a conversion factor of 2.44. Only those leaks in the LHSI system from the discharge of the pumps to the LHSI containment penetrations and to the suctions of the HHSI pumps, including HHSI pump seal leakage, require this correction factor and an

ACCIDENT LEAKAGE entry in the ECCS Leakage Log. This conversion to accident leakage is dependent on pressure and not fluid temperature.

What is the mission time for the HHSI pumps?

In support of our GSI-191 containment sump effort we analyzed the operation of the all ECCS pumps and seals for 30 days. In all instances the pumps and associated seals were capable of performing their safety function i.e., provide the required flow and limit leakage to acceptable levels. The evaluation for the HHSI pumps concluded that there would be no noticeable change in leak rates until at least 60% of the carbon ring nose is worn away. This ring is checked periodically to ensure adequate seal life (30 days of operation) during a DBA.

Although the mission time is 30 days for the HHSI pumps, in both SBLOCA and LBLOCA scenarios, the HHSI pumps would mostly likely not be run for 30 days.

For the SBLOCA the HHSI pumps would supply water until the plant is depressurized. This could include the use of the HHSI pump and LHSI pump in piggyback mode of operation if the plant is not depressurized before the RWST is emptied. However, plant procedures require an aggressive plant depressurization; the plant can be easily depressurized within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and the HHSI pumps would no longer be necessary to provide core cooling.

For the LBLOCA the HHSI and LHSI pumps start and run on the SI. Both the HHSI and LHSI will continue to run through the injection phase into the recirculation phase (several hours). At that point core cooling is maintained by the flow from one HHSI and LHSI. If RCS pressure is low, one LHSI pump is sufficient to maintain adequate recirculation flow and cooling. (UFSAR 6.3.3.1.3)

Dominion Resources Services, Inc.

Thomas Shaub Technical Consultant Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060 Phone: (804) 273-2763 Fax: (804) 273-3715 E-mail: Tom.Shaub@dom.com (new e-mail address)

CONFIDENTIALITY NOTICE: This electronic message contains information which may be legally confidential and or privileged and does not in any case represent a firm ENERGY COMMODITY bid or offer relating thereto which binds the sender without an additional express written confirmation to that effect. The information is intended solely for the individual or entity named above and access by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution, or use of the contents of this information is prohibited and may be unlawful. If you have received this electronic transmission in error, please reply immediately to the sender that you have received the message in error, and delete it. Thank you.

April R. Thorpe, Contract Secretary Plant Licensing Branch 2-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Phone: 301-415-1688 Fax: 301-415-1222 April.Thorpe@nrc.gov E-mail Properties Mail Envelope Properties (1108E05267A25F458B14F9B1D036C5970E59EF62)

Subject:

Response to PREACS clarification concerns from phone call Sent Date: 7/6/2010 3:16:15 PM Received Date: 7/6/2010 3:16:15 PM From: Tom Shaub Created By: tom.shaub@dom.com Recipients:

V.Sreenivas@nrc.gov (Sreenivas, V)

Tracking Status: None Post Office:

DOM-MBX05.mbu.ad.dominionnet.com Files Size Date & Time MESSAGE 0 1/1/4501 Options Expiration Date:

Priority: olImportanceNormal ReplyRequested: False Return Notification: False Sensitivity: olNormal Recipients received: