ML19309A933
| ML19309A933 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 11/17/1975 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8004010687 | |
| Download: ML19309A933 (5) | |
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_NRC DISTRIBUTION FOR PART 50 DOCKET MAT'iRIAL
- UEMPORARY FORM)
CONTROL NO ' 11111 FILE:
FROM: sacramento Municipal
. ' DATE OF DOC DATE REC'D LTR TWX RPT OTHER Utility Dist Sharamento, Calif 3.J.
Mattimoe 11-17-75 11-24-75 xxxx
- TO:
ORIG CC OTHER SENTNRC PDR vv.,
Mr. Robert W. Reid 1-sigqcd SENT LOCAL PD3 vvv CLASS UNCLASS PROPINFO INPUT NO CYS REC'D DOCKET NO:
xxxxx 1
50-312 DESCRIPTION:
ENCLOSURES Ltr re our 10-16-75 Itr...... trans the Attachment I-Reactor Vessellupport-followbng:
Evaluation.For LOCA Leadings... with fig 1 & 2......
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cv Mr. Robert W. Reid N
Chief, Operating Reactors, Branch No. 4 Division of Reactor Licensing U. S. Nuclear Regulatory Corr..iission Washington, D. C.
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Re:
Docket No. 50-312 Rancho Seco Nuclear Generating Station, Unit 1
Dear Mr. Reid:
In response to your letter of October 16, 1975 regarding the design of the reactor vessel support system at Rancho Seco Unit 1, the District provides the following information: to this letter shows the model used by Babcock and Wilcox to calculate the reactor vessel support system loads result-ing from = loss-of-coolant accident. These loads were then combined with nonnal operating loads and seismic loads to determine the resulting total stresses on the reactor vessel support system.
As noted in Attachment 1, the blowdown jet forces at the location of the break were considered in the design of the reactor vessel support system. The other two effects described in the enclosure to your October 16, 1975 letter - transient differential pressure in the annular region between the vessel and the shield wall and transient differential pressure across the core barrel within the reactor vessel - were not considered.
Very truly yours, b
d J' J. Mattimoe Assistant General Manager and Chief Engineer l
Attachment 13331 n wa, w,.n_ -, a ~ ~ ~, ~ -
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ATTACMENT 1 REACTOR VESSEL SUPPORT EVALUATION FOR LOCA LOADINGS For loss of coolant conditions, the dynamic response of the reactor vessel supports was analyzed using the discrete planar model 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 spring at the base of the model j
represented the flexibility of the 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 nozzles, 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 represents the upper vessel head, enclosed water, and drive nozzles.
The reactor internals are represented by masses 4, 5, and 18. Mass 4 is located at the upper grid and in::ludes the weight of the grid, plenum l
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 sup-port structure (a cylinder bolted to the vessel head support for the upper ends of the control rod drives)providing lateral The control rod drives are represented by masses 13 through 17. Mass 13 is located at the flange 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.
so evaluate the postulated LOCA condition, the applied thrust due to a i
pipe rupture was applied to the model in the form of a thrust versus time curve. The LOCA thrust force acting at the reactor vessel's outlet i
nozzle was analyzed using the FLASH 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, accelerations, and effective static forces at each time step. The time-varying effective static forces were then i
used to determine the foundation loads.
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