ML20147E364
| ML20147E364 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 01/13/1988 |
| From: | Counsil W, John Marshall TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| CP-87-65, TXX-88082, NUDOCS 8801210089 | |
| Download: ML20147E364 (3) | |
Text
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e Log # TXX-88082
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File # 10110 t
.9 903.6 C
Ref. # 10CFR50.55(e)
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TUELECTRIC 1
January 13, 1987 w,,,iic.coimu Executtw Ysce President U. S. Nuclear Regulatory Commission Attn:
Document Control Desk Washington, D.C.
20555
SUBJECT:
COMANCilE PEAK STEAM ELECTRIC STATION DOCKET NOS. 50-445 AND 50-446 LOCA EFFECTS ON HVAC DUCT INSIDE CONTAINMENT SDAR: CP-87-65 (FINAL REPORT)
Gentlemen:
On August 24, 1987, we verbally notified your Mr. H. S. Phillips of a deficiency involving a postulated Loss of Coolant Accident (LOCA) effect on HVAC ducts inside the containment building.
The specific deficiency involves the ability of the HVAC duct system to maintain structural integrity during a differential pressure transient resulting from a LOCA. We have concluded that this condition is not reportable under the provisions of 10CFR50.55(e). Our last report was logged TXX-7010, dated November 30, 1987.
Upon review of the duct's layout, segment drawings, specification requirements and support information, three categories of duct segments were identified as being affected by this issue.
These categories are listed below:
Category 1: Straight segments of duct that have two adjacent longitudinal supports (which are not separated by flexible connectors) are likely to develop catenary action and were analyzed.
Category 2: Duct segments with a longitudinal support and an adjacent lateral support closely located on an elbow (without a separating flexible connector) may develop some catenary action and were addressed.
Category 3: Other segments of duct will not develop catenary action, therefore the duct's pressurization will not impose longitudinal loadings on the supports and the latter will remain intact.
No analysis for loadings on the supports was deemed necessary for this category.
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8801210089 880113 ADOCK 0500 5
i nruh olow Street LB 81 Dallas. Texas m01 O
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4 TXX-88082 January 13, 1988 Page 2 of 3 Nonlinear finite element modeling of the duct with large deformation capability, material nonlinearity and strain hardening was used to determine the duct's collapse pressure, the pertinent straining actions in_the duct, as well as its reactions on the supports.
This was performed for those duct cases identified in Categories 1 and 2 above.
The equalizing pressure was determined on the basis of the duct's defonnation.
The collapse pressure is defined as the external pressure at which the duct's deformation increases without bound, i.e. the pressure at which the duct cannot sustain any additional loadings.
Included in this stage were studies of the internal 3ressure buildup due to the volume decrease of the duct as determined from t1e non-linear finite element analysis.
The equalizing pressure is defined here as the pressure at which the internal pressure increase attributable to the volume decrease is equal to the duct's external pressure.
The purpose of the parametric studies was to evaluate the significance of the support stiffnesses, duct size and span on the collapse pressure as well as straining actions and reaction forces. Also included in this stage were support finite element calculations in order to determine the involved range of support stiffnesses.
The parametric studies provided a means by which the analyst could select analysis cases which encompassed more than one duct case.
Based on the results of the parametric studies of nonlinear finite element analyses, conclusions were drawn as to the acceptable duct parameters. Charts and/or formulas were developed in order to address any future analyses and/or any remaining analysis cases.
A review of the conclusions from these analyses shows that the ductwork will not fall catastrophically (i.e. the duct will collapse, but will not fall down nor will it cause a failure of the duct supports) due to a loss of Coolant Accident inside Containment.
Additionally, HVAC ductwork inside the Containment is not required to perfonn safety related functions af ter the event of a LOCA.
TXX-88082 January 13, 1988 Page 3 of 3 Records supporting these conclusions are available for review by your inspectors at the CPSES plant site.
Very truly yours, N $. (e te a re.l W. G. Counsil By:
J~. S. Marshall Supervisor, Generic Licensing MCP/mlh c-Mr. R. D. Martin, Region IV Resident inspectors, CPSES (3) i l
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