ML19329D704

Reactor Vessel Support Evaluation for LOCA Loadings.

ML19329D704
Person / Time
Site:	Crystal River
Issue date:	12/19/1975
From:	FLORIDA POWER CORP.
To:
Shared Package
ML19329D703	List: ML19329D702 ML19329D704
References
NUDOCS 8003160321
Download: ML19329D704 (3)

Text

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REACTOR VESSEL SUPPORT EVALUATION FOR LOCA LOADINGS m e _t y . m t* Y For loss of coolant conditions, the dynamic response of the reactor vessel supports was analyzed using the discrete planar nodel shown in Figure 1. This model was devised for the idealized structure shown in Figure 2.

The shells were represented by flexible, massless beam elements having the cross-sectional area, moment of inertia, etc. of uniform constant-thickness cylinders. An additional rotational s1 ring at the base of the model represented the flexibility of tie vessel foundation. In general., masses were placed at points of concentration of weight in the actual structure.

The reactor vessel is represented by masses 1,2, and 3. Mass 1

-includes the weight of the vessel skirt, lower vessel head, enclosed water, and a portion of the vessel shell. Mass 2, located at the.. elevation of the no::les, includes the weight of the central portion of the vessel shell, enclosed water, the plenum cover, and a portion of the core support structure shells. Mass 3 represeats the upper vessel head, enclosed water, and drive no::les.

The reac> w internals are represented by masses 4,5, and 18. Mass 4 is located at the upper grid and includes the weight of the grid, plenum cylinder, and 1/8 of the core. Mass 5, at the lower grid elevation, represents about 2/3 the weight of the core support structure; the remainder is included in Mass 2. Mass 18 is the concentrated weight of the lower grid and flow distributor, plus 1/8 of the core.

The entire core was modeled as a simply-supported beam having the natural frequency of a single fuel assembly (about 3 cps). Masses 6,7, and 8 each represent 1/4 core weight. The other 1/4 core weight is divided between masses 4 and 18.

Masses 9 through 12 represent the distributed weight of the drive support s tructures_(2-cy-1:ader -bolted-to the vesserhearpYbviding lateral support for the upper ends of the control rod drives).

The control and drives are represented by masses 13 through 17.

Mass.13 is located at the fringe between the core nozzle and the drive. Mass 14 represents the drive motors. Masses 15,16, and 17 represent the distributed weight of the drives and drive housings.

To evaluate the postulated LOCA condition, the applied thrust due to a pipe rupture was applied to the model in the form of a thrust versus time curve. The LOCA thrust force acting at thT reaEtor vessel's outlet nozzle was analyzed using the FLASil computer code and the relationship, thrust = pressure x area. A structural dynamics computer code was utilized to calculate the dynamic response of the planar model, i.e., the displacements, velocities, accelera-tions, and effective static forces at each time step. The time-varying effective . static forces were then used to determine the 8 foundation loads.  !

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