ML082600003

Public RAI - Request for Additional Information for Extended Power Uprate - Round 20 (TAC MD5262, MD5263, and MD5264) (TS-431 and TS-418)

ML082600003
Person / Time
Site:	Browns Ferry
Issue date:	09/16/2008
From:	Ellen Brown Plant Licensing Branch II
To:	Campbell W Tennessee Valley Authority
Brown Eva, NRR/DORL, 415-2315
Shared Package
ML082590704	List: ML082590709 ML082600003
References
TAC MD5262, TAC MD5263, TAC MD5264
Download: ML082600003 (2)

Text

REQUEST FOR ADDITIONAL INFORMATION EXTENDED POWER UPRATE ROUND 20 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN), UNITS 1 2, AND 3 DOCKET NOS.50- 259, 50-260 AND 50-296 The following requests for additional information (RAI) are based on the conference call with the Tennessee Valley Authority (TVA) regarding the Browns Ferry Nuclear Plant (BFN), Units 1 and 2, extended power uprate (EPU) review on August 15, 2008. During this conference call, TVA presented their proposed response to U.S. Nuclear Regulatory Commission (NRC)

Round 19 RAI Questions 180 (Unit 1) and 146 (Unit 2).

(Unit 1 Only) 194.

Provide the coherence between upper and lower main steam line (MSL) signals for 9-percent flow. It should be noted that only coherent background noise should be subtracted from coherent current license thermal power (CLTP) data.

195.

During the conference call on August 15, 2008, TVA explained that the possible reason for broad-band noise in MSL signals for 9-percent flow is up to 25 operating drywell cooling fans within containment. Provide the following fan specifications to support its explanation: sizes, flow rates, rpm, number of blades, and the proximity to the MSLs. TVA should also provide information about where peak frequencies of broadband fan noise mounds (broad humps of noise) are expected to occur and, based on the fan specifications, clarify whether the fan speeds change with plant power level. If available, provide other sensor spectra within containment that show mounded noise signals. Also, if available, TVA should provide the coherence between the other sensor spectra and the MSL spectra.

196.

Include the curves for low voltage input signals for strain gages (where mechanical signals are very low, and only electrical background noise is visible) on the plots showing MSL signals at 9-percent and 100-percent power (CLTP).

(Units 1 and 2) 197/153.

During the conference call on August 15, 2008, TVA explained, that the tones in the 19-percent power signal are probably due to switching frequencies in the Variable Frequency Drive (VFD) controller for circulation pumps, driven by Pulse Width Modulated inverters. TVA has surmised that the electrical signals in the drive cables generate an electromagnetic field around the cables, which corrupts the signals in surrounding strain gage cables. The containment exits of the power cables were identified by TVA to be closer to the exits of the strain gage cables in Unit 2 than in Unit 1. Therefore, these signals are not seen for Unit 1.

Provide the details on azimuth angles and elevations of the recirculation pump power cable penetrations and strain gage cable penetrations for both Units 1 and 2.

154.

TVA indicated that the pumps are run at minimum speed at 9-percent flow. As the VFD speeds up, it is expected that the tones should move up in frequency out of the range of interest. Provide the power spectral densities up to 500 Hz (or higher) that demonstrate the tones are moving up in frequency at higher speeds. Provide the correlation with the tones observed in the strain gages based on a characteristic signal (voltage or current) in the power cables supplying the pumps.

SRXB The following RAIs are based on proprietary draft responses provided during a public meeting held with the TVA regarding the BFN Units 2 and 3 EPU review on August 7, 2008. These questions focus on the proposed response to SRXB 106.

The draft response states that the calculation terminates in the calculated pressure exceeds the correlation bounds ((( ))). However, under anticipated transient without scram (ATWS) conditions the pressure is expected to exceed this value (([ )) pounds per square inch gage (psig)].

123.

Discuss what allows the code to continue its evaluation of the ATWS transient without terminating.

124.

Discuss how the core coolability under 10 CFR 50.46 is evaluated for this event.

125.

Assuming that the pressure is out of bounds, address how the code conservatively predicts the fuel temperature.

126.

If a fuel rod is predicted in dryout, address how the heat transfer is modeled.

127.

Discuss whether the heat transfer modeling approach is conservative in terms of the figure of merit (vessel pressure).