ML18033B500
| ML18033B500 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/22/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18033B499 | List: |
| References | |
| NUDOCS 9008280294 | |
| Download: ML18033B500 (4) | |
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UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 ENCLOSURE SAFETY EVALUATION REPORT HEATING VENTILATING'NDAIR CONDITIONING DUCTWORK AND SUPPORTS TENNESSEE VALLEY AUTHORITY BRONNS FERRY NUCLEAR PLANT llNIT'2 DOCKET NO. 50-260
1.0 BACKGROUND
Preliminary compari sons of the original amplified response spectra (ARS)
(without peak broadening as committed in the FSAR) obtained from El Centro ground motion time history and the new ARS (with peak broadening according to the agreement between NRC and TVA as summarized in Reference I) based on the artificial ground motion time history, identified significant differences where the new ARS exceeded the original.
TVA was required to assess the impact of these differences on the evaluation results based on the original ARS for miscellaneous steel frames, drywell access platforms, electrical conduit and supports, and HVAC ductwork and supports.
1f Through a series of on-site inspections conducted by NRC
( IRs 50-260/88-38, 50-260/88-39, 50-260/89-29, 50-260/89-32, and 50-260/89-42), all of the staff concerns were resolved and closed, except the structural integrity of HVAC ductwork and supports.
According to IR 50-260/89-32, TVA was required to complete the impact evaluation of the Class I ductwork and supports against the newly generated ARS in the diesel generator building (DGB), standby gas treatment building (SGTB),
and chimney before restart of Browns Ferry Nuclear Plant, Unit 2 (BFN-2).
As a result of the close-out inspection of the BFN-2 seismic design program conducted on November 6-10, 1989
( IR 50-260/89-42),
the staff closed all of its concerns relating to HVAC ductwork and supports for DGB and SGTB.
But, because the impact evaluation of Class I HVAC ductwork and supports inside the chimney was not available for review during the close-out inspection, this open item remained a restart issue for BFN-2 and was designated in the report as CSG-9.
On Nay 11, 1990, TVA submitted its final impact evaluation calculations of the HVAC ductwork and supports inside the chimney for staff review.
The purpose of this safety evaluation is to summarize the results and conclusions. from the staff's review of TVA's calculations.
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'4 2.0 EVALUATION TVA provided the following calculations for review:
1.
"Ductwork Stress Analysis for System O-SWHVAC-114-0, Rev. 1," Calculation No. CD-Q0031-885131 (RIM B22 900510 105) dated May 9, 1990.
2.
"Evaluation of Steam Packing Exhaust Duct Supports, Rev. 0," Calculation No. CD-00066-900240 (TIM 622 90059 141) dated May 8, 1990.
3.
"Qualification of Off Gas Duct Supports, Rev. 0," Calculation No.
CD-Q0066-900427 (RIM B22 900509 142), dated May 8, 1990.
4.
"Qualification of Class I HVAC Duct Support Number O-SWHVAC-114-29, Rev. 1," Calculation No. CD-Q0031-885345 (RIM B22 900509 139), dated May 8, 1990.
5.
6.
"Qualification of Class I HVAC Duct Support Number O-SWHVAC-114-24, Rev. 1," Calculation No. CD-Q0031-885030 (RIM 822 900509 138), dated May 8, 1990.
I "Qualification of Class I
HYAC Duct Support Nos.
O-SWHVAC-114-17, 18, 19,
'ev.
1," Calculation No. CD-Q0031-885337 (RIM B22 900509 140), dated May 8, 1990.
The review of Calculation B22 900510 105 which includes the ductwork stress analysis for System 0-SWHVAC-114-0 found that the duct system was analyzed by the use of TVA computer program TPIPE.
This duct system is composed of rectangular duct and round pipe sections.
The computer analysis results as contained in this calculation showed a maximum bending stress of 9,579 psi in the rectangular duct sections.
This stress is acceptable for interim operation since it is less than 12,000 psi, which has been accepted by the staff as the maximum allowable rectangular duct bending stress for interim operability (Reference 2).
The same calculation showed a maximum bending stress of 56,479 psi for the steel pipe sections of the duct system.
TVA used an allowable stress of 2.0Sy (60,000 psi for ASTM A106 Grade A piping material) for interim operation for the pipe sections in this duct system.
This interim operability allowable stress is the same as stated in paragraph 3.0 of TVA Pipe and Pipe Supports Operability Criteria BFN-50-C-7303 R2, which has been reviewed and approved by the NRC staff as documented in NUREG-1232, Vol. 3, Supp.
1 (Reference 3).
The impact evaluation of this ductwork system is therefore acceptable because both stresses in the rectangular duct and pipe sections were within the restart allowable stresses.
The review also covered duct support calculations performed by TVA as a part of the new spectra impact evaluation of HVAC ductwork system O-SWHVAC-114-0.
The review of TVA Calculations B22 900509 141 and B22 900509 142 showed that two new supports were added to this HVAC duct system.
Both supports were designed to meet long term criteria, and therefore acceptable.
From the review of Calculations B22 900509 139 and B22 900509 138 relating to the requalification
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I of two other existing HVAC supports on the same system, it was found both supports would not be qualified for the restart criteria in their original configuration.
Based on this finding, TVA upgraded these two supports to meet the long term operation criteria.
The review of TVA Calculation B22 900509 140 showed that duct supports O-SWHVAC-114-17, 18, and 19 located on the same duct system were qualified for the restart criteria without any modifications.
3.0 CONCLUSION
Based cn the review findings discussed
- above, the staff concludes that the new ARS impact evaluation performed by TVA for the Class I ductwork and supports inside the chimney meets the restart requirements.
Therefore, the issue related to the HVAC impact evaluation is resolved.
As such, open item CSG-9, "Impact of New ARS" as documented in IR 50-260/89-42 is considered closed for restart.
4.0 REFERENCES
(1)
Summary of meeting held on September 8 and 9, 1988 concerning the Resolution of IEB 79-14 Restart
- Issues, dated September 19, 1988.
(2)
Letter.from S. Black (NRC) to S. A. White (TVA), "Interim Operability Criteria for the Seismic Design Program for the Browns Ferry Nuclear Plant, Unit 2," dated July 26, 1988.
(3)
NUREG-1232, Vol. 3, Suppl.
1, "Safety Evaluation Report on Tennessee Valley Authority:
Browns Ferry Nuclear Performance
- Plan, Browns Ferry Unit 2 Pestart,"
October-1989.
Principal Contributor: T. Cheng Dated:
August 22, 1990