ML102010679
| ML102010679 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 07/20/2010 |
| From: | Office of Nuclear Reactor Regulation |
| To: | Division of Operating Reactor Licensing |
| References | |
| Download: ML102010679 (4) | |
Text
WBN2Public Resource From: Poole, Justin Sent: Tuesday, July 20, 2010 3:48 PM To: wdcrouch@tva.gov Cc: WBN2HearingFile Resource
Subject:
RE: Draft Request for Additional Information Regarding Section 3.11
- Bill, By letters dated November 24, 2009, and January 11, 2010, the Tennessee Valley Authority (the licensee) submitted FSAR Amendments 95 and 97 for Watts Bar Nuclear Plant Unit 2 (WBNP2).
The Electrical Engineering Branch has reviewed the information provided for Sections 8 and Sections 9.2.1, and determined that in order to complete its evaluation, additional information is required. Please review to ensure that the RAI questions are understandable, the regulatory basis is clear, there is no proprietary information contained in the RAI, and to determine if the information was previously docketed. If not, we would like to discuss the questions, in draft form below, with you in a conference call. Please also let me know how much time Tennessee Valley Authority needs to respond to the RAI questions.
This e-mail aims solely to prepare you and others for the proposed conference call. It does not convey a formal NRC staff position, and it does not formally request for additional information.
Justin C. Poole Project Manager NRR/DORL/LPWB U.S. Nuclear Regulatory Commission (301)4152048 email: Justin.Poole@nrc.gov
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
DRAFT
- 1. Essential Raw Cooling Water (ERCW): FSAR Section 9.2.1.3 states ERCW system has eight pumps (four pumps per train). However, minimum combined safety requirements for one accident unit and one non-accident unit, or two non-accident units, are met by only two pumps on the same plant train. Sufficient redundancy, separation and independence of piping and components are provided to ensure that cooling is maintained to vital loads at all times despite the occurrence of a random single failure. Clarify the statement two pumps on the same plant train as related to the total number of pumps required for safe shutdown of both units. If the total number of pumps required for safe shutdown of two units is two on the same train, then provide information on how adequate separation (electrical and physical) is maintained between each pump and the associated power/control circuits for safe shutdown of both units following a plant fire.
For compliance with GDC 5, the following statement is made in FSAR Amendment 95:
Therefore, there are electric motors powered by the onsite distribution system of one unit that drive safety-related machinery (i.e., essential raw cooling water pumps, component cooling system pumps) required for safe shutdown of the other unit. For example, the ERCW system is arranged in two headers (trains) each serving certain components in each unit (see Section 9.2.1.2). There are eight ERCW pumps arranged electrically so that two pumps are fed from each shutdown board (1A-A, 1B-B, 1
2A-A, 2B-B). Only one pump per board can be automatically loaded on a DGU at any one time. The pumps supplied from the A boards pump into the A train header and likewise the B pumps.
Assuming that the operability of a ERCW pump will be dependent on operability of corresponding available power source(s) (power and control power), provide details on the minimum number of power supplies (emergency diesel generators) and corresponding ERCW pump/isolation valve combination required to be operable at all times to ensure that safe shutdown can be achieved on the unit with an accident and the non-accident unit assuming a simultaneous worst case single failure (including false or spurious accident signal) on each unit. Provide same level of details for the component cooling system pump combination.
- 3. FSAR Section 8.1.5.3 documents compliance with Regulatory Guides (RGs) and Institute of Electrical and Electronics Engineers (IEEE) Standards. For compliance with RG 1.81 Rev 1, the FSAR states Some plant common loads are supplied from Unit 1, channels I and II and other plant common loads are supplied from Unit 2. In no case does the sharing inhibit the safe shutdown of one unit while the other unit is experiencing an accident. All shared systems are sized to carry all credible combinations of normal and accident loads. Provide details on common loads supplied from each unit including the specific power sources.
- 4. FSAR Section 8.2.1.8 describes Conformance with Standards. For compliance with GDC 17, this section states The non-1E control power circuits from the vital battery boards to 6.9-kV common switchgear C and D have redundant protection (breaker and fuse) in the event of a failure. Selective coordination exists between the non-1E and Class 1E circuits that are fed from each of the vital battery boards. Thus, failure of all of the non-1E control power circuits on the vital battery boards will not have any effect on the 1E circuits or battery boards. For all AC (including 480V) and DC circuits that rely on molded case circuit breaker (MCCB) combinations or MCCB and fuse combinations or fuse/fuse combination to provide separation between common circuits or safety/non-safety related circuits, describe the protective devices/schemes used in each common or non 1-E circuit and provide coordination curves for the devices. Specifically provide details on the instantaneous region of the protective devices and available fault currents.
- 5. The FSAR Amendment 95 identifies cable splices in underground cable and low voltage power and control cable installations and penetrations. Position 9 of RG 1.75 states that cable splices in raceways should be prohibited. The NRC staffs prohibition against splices in raceways is centered on the prevention of fires caused by improper splices. Position 9 of RG 1.75 (Rev 2), states that if cable splices exist, the resulting design should be justified by analysis and that the analyses should be submitted as part of the safety analysis report. The NRC staffs review of the FSAR Amendment 95 and 97 did not find the necessary information for justifying splices in the cables that are being replaced for startup of WBN 2. In order to evaluate the use of splices in the new cables in raceways being installed for startup of WBN 2, the NRC staff requests TVA to provide additional information on the analysis/justification for use of splices in accordance with Position 9 of RG 1.75, which demonstrates compliance with the requirements of GDCs 2, 4, and 17.
- 6. The FSAR Amendment 95, Section 8.3.1.4.2 identifies fire resistance barriers installed between redundant division trays (open and enclosed trays) to maintain separation between them. The effects on cable ampacity due to environmental conditions and cable installation configuration are discussed in Section 8.3.1.4.1. The NRC staffs review of these two sections did not provide a description of the fire barriers or information on the effects of fire barriers on cable ampacity. The NRC staff requests TVA to provide additional information on the type of fire barriers and information on its effect on cable ampacity (derating) for the new cables being installed or replaced for startup of WBN 2.
- 7. Section 8.3.1.4.3 of the FSAR Amendment 95 (page 8.3-48) states that cables for non-safety related functions are not run in conduit used for essential circuits except at terminal equipment where only one conduit entrance is available. Also, FSAR Amendment 95 (page 8.3-49) states that a non-safety related cable may be routed with those of for essential circuits provided that the cable or any cable in the same circuit has not been subsequently routed onto another tray containing a different division of 2
separation of essential cables. The NRC staff requests TVA to provide a clarification of the above statements since they are contradictory.
- 8. In the original Safety Evaluation Report (NUREG 0847), the NRC staff concluded that the non-safety related cable must be treated as an associated cable if it was routed with essential circuits. An associated cable should only be routed with its associated safety related cables and be separated from other non-safety related cables as well as the redundant safety related cables. Thus the independence-of redundant cable systems cannot be compromised through the non-safety related cables sharing a common raceway. It is the NRC staffs position that any new non-safety related cables being installed or replaced for startup of WBN 2 and sharing a raceway with essential circuits should meet the guidelines of positions 4, 6, and 7 of RG 1.75 and Sections 4.5 and 4.6.2 of IEEE Standard 384-1974. The NRC staff requests TVA to provide an analysis of associated circuits for the new cables being installed or replaced for startup of WBN 2 in accordance with Section 4.6.2(1) of IEEE Standard 384-1974. The analysis should demonstrate that electrical faults, caused by failure of the associated cables, will not compromise the independence of redundant safety related cable systems. The analysis should verify that the cables associated protective device will clear the imposed fault condition (in an acceptable time period) without exceeding the I2t rating for the cable and without tripping the upstream breaker supplying the safety bus. The analysis should include sample coordination curves of the protective devices for each voltage level to show that a fault in the associated circuit will not result in a loss of the safety bus or the loss of redundant safety related cables.
DRAFT 3
Hearing Identifier: Watts_Bar_2_Operating_LA_Public Email Number: 47 Mail Envelope Properties (19D990B45D535548840D1118C451C74D5A4EB73233)
Subject:
RE: Draft Request for Additional Information Regarding Section 3.11 Sent Date: 7/20/2010 3:48:21 PM Received Date: 7/20/2010 3:48:22 PM From: Poole, Justin Created By: Justin.Poole@nrc.gov Recipients:
"WBN2HearingFile Resource" <WBN2HearingFile.Resource@nrc.gov>
Tracking Status: None "wdcrouch@tva.gov" <wdcrouch@tva.gov>
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