ML20043B283
| ML20043B283 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 02/22/1978 |
| From: | Stewart W FLORIDA POWER CORP. |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20043B278 | List: |
| References | |
| NUDOCS 9005250200 | |
| Download: ML20043B283 (3) | |
Text
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W. P. STEWART. DIRECTOR -
POWER PRODUCTION 1
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February. 22,.1978-i i
Director
_ Office' of Nuclear Reactor Regulation i
~U.S. Nuclear Regulatory Commission Washington, D.C.'20555-L
Subject:
Crystal' River Unit 3 f
L Docket No. 50-302
--Operating License l
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Dear Sir:
On February'.7,1978 Florida Power Corporation received Mr. Stello's
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letter of February 2,1978 requesting us to submit to the Commission by.
February 22',?1978. additional information concerning the1 reactor cavity 1
. annulus seal. ring and~ associated biological shielding used at Crystal River Unit 3.
l In response to Mr. Stello's request, Florida: Power Corporation hereby-submits,three (3)-originals and forty (40) copies of the information-requested 1_n. items (a) through-(d) of Mr. Stello's letter.
' Please-contact.this office.should you-require additional discussion or-l
' clarification of our rosponse.
Very truly yours.
FLORIDA POWER CORPORATION
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'W. P. Stewart
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WPS/ECS/hw 2/6 cc:
File: 3-0-3-a-3
-9005250200 900518 PDR ADOCK 0500030')
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' General Office 3201 Thirty fourin street soutn. P O Box 14o42. St Petersburg. F!orida 33733 e 813-866 5151
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Response to Nuclear Regulatory Commission letter dated. February 2, 1978-
-A concerning the probability of the reactor vessel cavity annulus seal ring and/or.the biological shielding.becoming missles.
4 Concern (a):
Provide a statement as to whether the cavity annulus seal ring in your i
facility-is lef t in place during normal operation or if biological i
shielding iscinstalled in the reactor cavity annulus.
FPC Response:
The biological sand plug shielding and the reactor vessel cavity annulus seal ring remain in their respective design positions during normal.
operation at Crystal River Unit No. 3.
Concern (b):
If the answer to (a) is yes, when will you determine whether the cavity annulus seal ring er biological shielding would become a missile in your facility.
FPC Response:
H The design and construction of the biological sand plug shielding is l
such that the resulting pressure of a postulated rupture of high energy A
reactor coolant piping within the primary shield'would rupture the stainless steel shell of the sand plug. When the plug.shell is ruptured.
by the differential pressure, the sand contained within the shell is discharged in the form of a sand spray.
Thus, precluding the possibility of the biological sand plug shielding from becoming a missile. 'The postulated rupture of these sand plugs and associated sand spray will not effect the operation of the Decay Heat and Reactor Building Spray Systems.
For further discussion on the effects of, debris on these systems, refer to Section 6.2.2.1 of the FSAR.
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-Preliminary analyses indicate that there is a possibility of the cavity.
annulus seal ring becoming a confined missile and impat ting sufficient energy to the Control Rod Drive Mechanism (CRDM) shroud such that possible damage to the CRDM's may result, i
Concern (c):
Provide a-description of what you plan to do, and when, if the problem is found at your facility.
FPC Response:
- i By inherent design discussed in item (b) above, the biological sand plug 4
shielding cannot-become missiles during the postulated pipe rupture at Crystal River Unit 3.
Therefore, they require no additional consideration p
in regards to prevention of missiles.
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Florida Power Corporation has retained our Architect Engineer, Gilbert
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Associates, Inc. (GAI), to perform additional detailed analyses with regards'to the possibility of the cavity annulus seal ring becoming a missile during the postulated pipe rupture.
These detailed analyses are.
scheduled to be completed by March 31, 1978... Should the-seal ring missile probability be confirmed by these-additional analyses, the seal ring will either be relocated and restrained or removed from the af-fected area during normal, plant operation.. Design changes involving relocation' or removal of the seal ring will take place'during the first refueling outage for CRf3 which is currently scheduled for the fall.of f-1978.
Concern (d):
. Provide. justification for continued operation until the problem has been resolved, such justification to support why continued operation will not create undue risk to the health and safety of the public.
FPC Response:
. Florida Power Corporation believes that justification for continued operation of.CRf3 has as its basic foundation the fact that the event in question, i.e., a hypothetical double - ended instantaneous rupture of the main coolant pipe at-a particular location, has a very low prob-ability of occurrence.
A; Aconservativeprobabijityofgpipebreakintheprimarycoolantsystem is in the range of 10~
to 10- per reactor-year in large pipe This-estimate is supported by a recent publication by Dr. S;H. Bush ) as y
well as the' Commission's recently developed short-term interim criterion j
for determining an' acceptable level of. safety for operating PWAs under j
conditions of a postulated pipe break.
We conclude.that this estimated pipe break probability is considered 1
acceptably low to. justify continued operation of CR#3 until the sched-1' uled refueling-outage in the fall of 1978 and will in no way create undue risk to the health and safety of the public.
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(1) " Critical Factors in Blowdown Loads in the PWR Guillotine Nozzle Break (Volume 2 - the Asymmetric Load Problem)" dated June 6, 1977.
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DOCKET COPY ta=P-J. Cooper-Q. B. DuBois H..A.
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~ June 6, 1979 1;
ilr. Robe rt W. Reid Chief g
I 0perating Reactors Branch #4.
i Office of Nuclear-Reactor Regulation U.S. Regulatory. Commission Washington, DC 20555
. Subjects Docket.No. 50-302 Operating License No. DpR-72
. Reactor Cavity Annulus Seal Ring Support t
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Dear Mr. Reid:
-In resp' nse to an NRC letter dated February 2,1978, analyses weru per-'
o formed which showed that the seal ring, while positioned on! the original designed. seal ring" support, could become a missile during operation due to a LOCA pipe break inside the reactor cavity. - Additional calculat Lons were perinrmed to show that the seal ring missile could impact the CRDM shroud with sufficient energy to damage both the shroud and the control rods.-
Due to the above rete,renced analyses and calculations the design of a new seal ring support system is currently being< reviewed by Florida power Corporation. The new design holds the seal ring, during operation, in a raised position which would alleviate the seal ring f rom becoming 'a poten-tial missile in the event of a LOCA.-
Since ' the. seal ring 'is only used during ref ueling and until FpC and the NRC approve the new-seal ring support system. FPC will store the seal ring on -
the floor of the containment building (EL. 160'-0") during plant ope ra t ion'..
q Once the new support system is approved and installed the seal ring will be removed f rom the floor and placed on the new support system.
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Page Two June 6. 1979-Storing tl'ie sent ring on the floor will in no'way affect the safe and ef fi-etent operation of the plant.
Should' you'~have any questions coceerning this matter, please contact thlu-
. office.
- c Ve ry t ruly. yours,-
g FLORIDA POWER CORPORATION-
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September.11, 1979 i
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L DesetNo.s0.m DOCKET COPY nr. w. p. Stewart Manager, Nuclear. Operat18H400Cil0N DLl'AlugtgI i
. Florida Power Corporation L
Crystal River Nuclear Plant P. 0. Box 1240 Crystal River, Florida 32629
Dear Mr. Stewart:
RE:
REACTOR CAVITY SEAL. RING GENERIC ISSUE (PWR)
'Wo have reviewed your letter of June 6,1979, in regard to the potential l
for the reactor cavity annulus seal ring to become a destructive missile in the event of a loss-of-coolant accident pipe break inside the reactor cavity.
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Removal of the seal ring during operation at Crystal River Unit No. 3 is
. acceptable pending our approval and the installation of a. seal ring support system.
Sincerely,
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Robert.W. Reid, Chief Operating Reactors Branch #4 Division of Operating Reactors cc:- See next page t
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