ML040300507

Memo Clarification of Licensee'S Response to NRC Request for Additional Information

ML040300507
Person / Time
Site:	Diablo Canyon
Issue date:	01/30/2004
From:	Donohew J NRC/NRR/DLPM/LPD4
To:	Stephen Dembek NRC/NRR/DLPM/LPD4
Donohew J N, NRR/DLPM,415-1307
References
TAC MB9476, TAC MB9477
Download: ML040300507 (4)

Text

January 30, 2004 MEMORANDUM TO: Stephen Dembek, Chief, Section 2 Project Directorate IV Division of Licensing Project Management Office of Nuclear Reactor Regulation FROM: Jack N. Donohew, Senior Project Manager, Section 2 Project Directorate IV-2 /RA/

Division of Licensing Project Management Office of Nuclear Reactor Regulation

SUBJECT:

DIABLO CANYON NUCLEAR POWER PLANT, UNITS 1 AND 2 -

CLARIFICATION OF LICENSEES RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION (TAC NOS. MB9476 AND MB9477)

By letter dated December 23, 2003 (DCL-03-178), Pacific Gas and Electric Company (the licensee) submitted its responses to the NRC request for additional information (RAI) dated September 25, 2003. The RAI was for the licensees license amendment request on Technical Specification (TS) 3.8.1 and 3.8.4 submitted by letter dated May 29, 2003.

In the response to NRC Question 3a on Surveillance Requirement 3.8.1.10, the licensee stated the following: "The degraded bus voltage relays (27HFB3 and 27HFB4) are set to drop out at 109.5 V (equivalent bus voltage of 3810 V) and 109 V (equivalent bus voltage of 3827 V),

respectively." The clarification needed for this sentence by the NRC staff was an explanation of why the bus voltage of 3810 V (for the 109.5 V) was smaller than the bus voltage of 3827 V (for the 109 V). 109.5 V is greater than 109 V.

This was discussed with the licensee on January 8, 2004. The clarification provided by the licensee was then incorporated into the attached e-mail sent to the NRC. The NRC staff decided that the clarification did not warrant the licensee providing the same information in a letter to the NRC. This memorandum is to docket the clarifying information provided by the licensee. Upon reviewing the information in the attached e-mail, the NRC staff had no further questions.

Docket Nos. 50-275 and 50-323

Attachment:

E-mail dated January 13, 2004

ML040300507 OFFICE PDIV-2/PM PDIV-2/LA EEIB PDIV-2/SC NAME JDonohew EPeyton GMorris SDembek DATE 1/21/04 1/21/04 1/21/04 1/22/04 E-MAIL DATED JANUARY 13, 2004 From: "Ketelsen, Stan C" <SCK3@pge.com>

To: <jnd@nrc.gov>

Date: 1/13/04 4:58PM

Subject:

DCL-03-178 Clarification This is in response to the telephone conversation between the submittal Project Manager, Jack Donahue, the NRR staff reviewer and Stan Ketelsen of PG&E on January 8, 2004, on the subject of the "Response to NRC Request for Additional Information Regarding License Amendment Request 03-07, Revision to Tech Spec 3.8.1 AC Sources- Operating & Tech Spec 3.8.4 "DC Sources -Operating Surveillance Requirements" in PG&E Letter DCL-03-178 on December 23, 2003.

In the phone call, Mr. Donahue questioned PG&Es response to NRC questions 3a and 3b relating to the equivalent bus voltage levels corresponding to the undervoltage relay setpoints provided in the response. The PG&E response to NRC questions 3a and 3b in PG&E Letter DCL-03-178, stated:

"The degraded bus voltage relays (27HFB3 and 27HFB4) are set to drop out at 109.5 V (equivalent bus voltage of 3810 V) and 109 V (equivalent bus voltage of 3827 V), respectively."

In the PG&E DCL-03-178 response, the bus voltages (3810 V and 3827 V) were calculated from the 109.5 V and 109 V undervoltage (UV) relay setpoints. In calculating these equivalent bus voltages, an equivalency of 119 V to the "nominal" bus voltage of 4160 V, as established during routine diesel generator surveillance testing, was used. However, the corresponding bus voltages were inadvertently switched in the above statement from DCL-03-178.

In reviewing the design calculation, however, it was determined that both the 109 V and 109.5 V undervoltage relay setpoints were based on the same equivalent bus voltage, 3831 V. The difference in the relay setpoints for the same equivalent bus voltage is explained as follows:

There are 2 UV relays associated with each vital 4kv bus degraded voltage bus transfer to the emergency diesel generators. Each UV relay is connected to its own potential transformer (PT) that has a "nominal" PT ratio of 35 to 1. One PT is connected across the A and B phases of the vital bus and the other is connected across the B and C phases of the vital bus. The slightly different relay setpoints (109.5V and 109V) account for a slight variation of the PT ratio due to different burden on the two PT circuits - the PT associated with relay 27HFB4 being more heavily loaded than that of relay 27HFB3. Thus, although the two setpoints are different, they both correspond to a bus dropout voltage for the degraded bus transfer of 3831 V. This value is also adjusted to account for instrument accuracy.

Based on the above, the first sentence of the last paragraph of PG&Es response to NRC questions 3a and 3b, as contained in PG&E Letter DCL-03-178, is revised to read as follows:

"The degraded bus voltage relays are set to drop out at 3831 V bus voltage."

1

This reference to only the bus voltage is consistent with the remainder of the paragraph and eliminates any confusion as to the two slightly different undervoltage relay setpoints that correspond to the same equivalent bus voltage. The rest of the response to NRC questions 3a and 3b in PG&E Letter DCL-03-178 remains unchanged.

If you have any questions, please dont hesitate to contact me at (805) 545-4720.

Stan Ketelsen Manager - Regulatory Services Diablo Canyon Power Plant 2