ML19095A257
| ML19095A257 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 05/05/1978 |
| From: | Stallings C Virginia Electric & Power Co (VEPCO) |
| To: | Case E, Stello V Office of Nuclear Reactor Regulation |
| References | |
| Download: ML19095A257 (2) | |
Text
e VIRGINIA ELECTRIC AND POWER C<>_M,~~~C'fST~;SIJ;IOH RicHMoNn,vx:aoxN.u. 23261
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- ):cE::3 u:~1r May 5, 1978'.
Mr. Edson G. Case, Acting Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory. Commission Washington, D. C.
20555 Attention:* Victor Stello, Jr., Director Division of Operati;ng Reactors
Dear Mr. Case:
RE
- 73 liAY 9 P~l 12 59 Serial No. *.Q67A/012578*
PO&M/DLB: dgt Docket Nosw 50-280 50-281 License Nos. DPR-32 DPR-37 This is in.response to your letter of January.25, 1978., concerning the design of the reactor vessel support system for* Surry.Power Station Unit Nos.
1 and 2. Your letter requested.that within 90 days.we submit our schedule for providing the required*. evaluation.. This letter is to inform you of the antici-pated. schedule.for this*evaluation.
Prior.to issuance of your letter of January.25, 1978, a tas~ group of utilities was formed and, with the assistance of Westinghouse. Electric Corpora-tion, has outlined the steps necessary to complete an. evaluation of the type you have requested.
The evaluation.program prepared by.the task group has been broken into three parts, or phases, to facilitate the. work. ef£ort and to. gain some advantage by performing generic analysis applicable to several plants of similar de~ignr Phase A, which is essentially complete, consists of. a detailed examination of primary loop characteristics for each plant involved in the task group effort to categorize and group the plants for the analyses.
Plant groupings are based on.plant characteristics such as reactor vessel. diameter, steam generator type, steam generator and reactor coolant pump support structures and primary loop temperatures.
Phase B will evaluate the postulated ruptures which have the greatest effect upon the steam generator and reactor coolant pump supports.
This evaluation will consist of ge~eric scoping analyses for the plant groupings determined in Phase A of the project using standard. loop analysis pro.cedures.
The. breaks. to be post-ulated for the analyses are the hot leg at the reactor outlet nozzle, the cross-over leg between the steam generator and the reactor coolant pump, and the cold leg at either the pump discharge or the reactor vessel inlet nozzle.
The results of these scoping analyses will be used to determine if specific plant analyses will be required to.better assess the adequacy of the support systems.
During this phase, bounding reactor coolant loop hydraulic forcing functions will be developed and generic subcompartment pressurization. studies will be performed.
,... 1.-:,noo:31 7~:., -* *-..
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VIRGINIA ELECTRIC AND POWER COMPANY TO Mr. Edson. G *. Case.
P_age 2 Phase C will address the reac.tor*vesselresponse for postulated pipe ruptures. at -the reactor_. vesseL inlet and outlet nozzle *... Analyses will.be
.performed on a.group basis where.asymmetric cavity*pressure loads, vessel internal.hydraul.ic loads, and vessel.support cbaraeteristic.s are similar.
The need for specific plant. analyses. wilL be. based on the. results of th_e generic. anal.yses.*
- Prior to** the ini.tiation
- of.. the* Phase C effort, studies will be performed to determine the effects of increased break.opening times, more detail.ed downcomer annulus nodalization and structural.. damping of the MULTIFLEX. calculations. Also, c.ertain reactor cavity pressurization studies and the development of. a mechanistic. crack opening analysis will.be performed.
The.anticipated. schedule. for the program is presented below:
- Program Effort
.Phase A Phase B Generic. Group Analyses Phase B RCL Hydraulic Forcing Functions.
Phase B Subc.ompartment Pressurization Phase B Specific. Plant Analyses.
Phase C Generic Group Analyses MULTIFLEX. Modifieatic:ms Reactor Cavity Pressurization.Studies Mechanistic. Pipe Break Analysis Phase C Specific Plant.Analyses Completion Date Complete June 15, 1978-June. 30, 1978-
- November 1, 1978 Early 1979*
First Quarter 197 9-January 1, 1979 January 1, :1979:
January 1, -1979:
January 1, *1980*
As explained in our letter of February-22, 1978, the concern over the reactor vessel supportsystem*is directly related to* the cone.em over the possibility of.the.reactor. vessel shield.ring or annulus. shielding.becoming a missile during a LOCA.. Accordingly, the *seal ring/shielding concern will be evaluated concurrent with the~ *eva-luation. of.. the reactor vessel support
_system.
Should. these analyses indicate: that seme c.01:rec.tive action is.necessary, potential plant modifications may be included in specific.plant.analyses. These modif.ications*may be later incorporated. in the plant, or augmented. in-service inspection or probability analyses may be proposed as an alternate solution. In either case, it is our intent to demonstrate the safety of.long-,.term continuous operation.
We trust this information is* suitable for your use.
Please inform us if you have additionar questions concerning. the program*outlined.above.
cc:
Mr. James P. O'Reilly Yours very truly, ZP,>>?. #~~-rv C. M *. Stallings Vice President-Power Supply and. Production Operations