ML13333A459

Forwards Rept Re Analysis Methods to Determine That Fire in Hydrogen Seal Oil Unit Would Not Substantially Impact Structural Integrity of Steel in South End of Turbine Bldg

ML13333A459
Person / Time
Site:	San Onofre
Issue date:	12/26/1979
From:	Baskin K Southern California Edison Co
To:	Harold Denton, Ziemann D Office of Nuclear Reactor Regulation
References
NUDOCS 8001030648
Download: ML13333A459 (5)

Text

Southern California Edison Company P. 0.

BOX 800 2244 WALNUT GROV.E AVENUE ROSEMEAD, CALIFORNIA 91770 K. P. BASKIN TELEPHONE

MANAGER, GENERATION ENGINEERING December 26, 1979 213-572-1401 Director, Office of Nuclear Reactor Regulation Attention:

Mr. D. L. Ziemann, Chief Operating Reactors Branch #2 Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C.

20555 Gentlemen:

SUBJECT:

Docket No. 50-206 Fire Protection Program Review San Onofre Nuclear Generating Station Unit 1 During the review of the Fire Protection Program at San Onofre Unit 1, the NRC staff identified a concern regarding the effect on the structural steel of the south end of the turbine building, which would result from a fire in the hydrogen seal oil unit.

By letter dated May 15, 1979, we indicated that the result of our analysis determined that the conservatively assumed unmitigated fire will not'affect the structural integ rity of the turbine pedestal nor any of the individual structural systems surrounding it.

Subsequent to that submittal, we were requested to provide a report on the methods used to perform the analysis and this is provided as the enclosure to this letter.

The calculation determines the peak temperature for the hottest column to be 604 F. Based on Figure 6-7B, Section 6, Chapter 7 of the Fire Protection Handbook, 14th Edition, it is estimated that the compressive strength of the steel columns will be reduced by 20%.

Therefore, the loading capacity will be reduced from approximately 460 kips to approximately 370 kips, which is considerably greater than the maximum credible load of 150 kips for each column.

of&

FT

Mr. D. L. Ziemann

-2 It is concluded that the peak temperatures reached in the steel columns of the south turbine deck extension are not high enough to substantially impact the structural integrity of these supports.

These temperatures were recalculated and verified for submittal to your staff for review.

If you have any questions or desire additional infor mation, please contact me.

Very truly yours, encl.

ENCLOSURE AREA 9E FIRE STUDY ANALYSIS METHODS PURPOSE The purpose of this enclosure is to set forth the principal assumptions, methods, and conclusions of the calculation to determine the peak temperatures expected to occur at the steel support columns of the south turbine deck extension due to a fire in the hydrogen seal oil area (Area 9E).

ASSUMPTIONS The following assumptions were used in the calculation:

1. Maximum oil volume -

12,300 gal (Ref. 4).

2.

Air properties obtained from Reference 3.

3. Oil specific gravity - 0.85 (Spec.

2L-4140).

4. Heat load to steel columns is primarily due to radiation; heat load from conduction and convection is neglected.

5.

Heat loss from columns is convective and conductive; radiation is neglected.

6.

Flame temperature is assumed to be 2300 0F Most hydrocarbon fuels produce flame temperatures in the range of 25000-40000 F (Ref.

2, page 4-76) under ideal conditions. Choosing 23000 F compensates to some extent for temperature reductions due to uneven combustion, off-stoichiometric conditions & smoke.

7.

Emissivity for painted steel columns is E 12 0.90 (Ref.

1, Pg. 385).

8.

Small obstructions (pipes, conduits, etc.) are ignored in calculating configuration factors for radiation.

9. Air flow is assumed to be toward fire, past columns, @ 2 ft/sec.

10.

Air temperature is assumed to be 100 0 F @ Col. P, 150 0F @ Col. N and 200 0 F 0 Col. M.

11.

Columns @ Col. line P are least affected by the fire and will not be analyzed.

12. Pairs of columns are equally affected.

Only one column

@ each column line will be analyzed.

13. Since fire duration >> 8 brs, assume columns reach thermal equilibrium (Ref. 5,6).

14.

Assume conduction to the slab only, not to turbine deck.

-2 METHOD In order to calculate the peak temperatures, a heat balance is performed between the heat load on the columns due to radiation from the fire and the heat losses from the column due to conduction and convection. The.methodology and the associated references utilized in the calculation are listed below.

1. The heat load to the columns is primarily due to radiation. The radiation heat flux with associated shape factors was determined using the methods of Reference 1.

The heat loads from conduction and convection are neglected since the geometry of the area is such that air flow would be towards the north and away from the columns.

2. The heat loss fr3m the columns is convective and conductive.

Conduction losses are calculated by assuming each column to be a rectangular solid embedded in a semi-infinite medium with an isothermal surface at 100 0 F and using the methods of Reference 1 (See Ref. 1, Table 7-1, pg. 53).

The convective losses are determined assuming an air flow at 2 ft per sec, calculating appropriate dimensionless parameters from Reference 3, and determining the convective heat transfer coefficients as described in Reference 2.

3. Since it is assumed that the columns reach thermal equilibrium, a heat balance is performed using the previously obtained expressions for the heat loads input and the heat losses to determine the final equilibrium temperature.

CONCLUSION The peak temperature reached in any of the columns is determined to be 6040 F.

REFERENCES

1.

Holman, J.

P., Heat Transfer; 2nd Ed., McGraw Hill, 1968

2.

Baumeister, T., Marks' Handbook for Mechanical Engineers; 7th Ed.,

McGraw Hill, 1967

3.

Crane Technical Paper 410, Flow of Flids, 11th Ed.,

1970

4.

Dwg.

No. 567870

5.

Fire Study, Response to BTP APCSB 9.5-1, Docket 50-206 License DPR-13

6.

ASTiM Spec. E-119