ML20080D870
| ML20080D870 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 08/24/1983 |
| From: | Dixon O SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8308300615 | |
| Download: ML20080D870 (3) | |
Text
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SOUTH CAROLINA ELECTRIC & GAS COMPANY N>ST OP* ICE 7H CoLuusiA, south CAnoWNA 29218
~
O. W. DixON, Jn.
August 24, 1983 vic. e....os=T NUCLEAn OpenAtlONS 1
Mr. Harold R. Denton, Director
. Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington,ED.C. 20555
Subject:
Virgil C. Summer Nuclear Station Docket No. 50/395 Operating License No. NPF-12
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Cold Overpressure Protection s
Dear Mr. Denton:
South Carolina Electric and Gas Company (SCE&G) in a June 29, i
1983 letter to-the Staff, provided a preliminary design for a
-Cold Overpressure Mitigation System (OMS).
Following the issuance of the aforementioned letter, SCE&G identified a single failure associated with the automatic closure configuration of the Residual Heat Removal Systen (RHRS) suction isolation valves.
The text of this letter will address the single failure-in ~ addition to SCE&G's proposed solution.
Figure 1 of the. June 29, 1983 letter to the Staff is attached to provide the general arrangement of the RHRS suction isola-tion valves and relief valves.
The RHRS suction isolation valves receive a signal to close from two.(2) pressure transmitters in the Reactor Coolant System (RCS), PT-402 and-l
-PT-403.
If either of these pressure transmitters fail high, the RHRS will be isolated from the RCS,Ethus losing cold i
overpressurization protection.
For'. example, PT-402 on loop three (3)'of the RCS could fail high, close RHRS suction isolation valves 8702A/B 'and prevent the RHRS relief valves from performing their-intended function of cold overpressurization mitigation.
Similarly,1PT-403 on loop one (1) of the RCS could fail high', close RHRS suction isolation valves 8701A/B with the
- ~
same'results.
To correct the single failure described in the previous-para -
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L graph, SCE&G proposes to utilize the. design modification to.the RHRS suction isolation valves delineated by License Condition
'2.C.15.which' references Section 5.4.3Dof'the VirgilEC.
Summer
' Nuclear ' Station Saf ety ~ Evaluation Report -(CER). _ As stated in r
Section 5.4.3 of'the SER, SCE&G' committed, in a letter dated m
f j @ esog g p o g d g i
8
- e-I
' c.
l NN u e.(s n..
~
w Mr. Harold R.
Denton August 24, 1983 Page #2 November 6, 1981, to install power lockout devices in the control room by the first refueling.
This modification will allow the operator in the control room the capability to decnergize the motor operators of the RHRS suction isolation valves during power operation.
SCE&G proposes to extend the use of power lockout to encompass the second phase of cooldown and during initial heatup (RHRS operation).
In aligning the RHRS to l
take a suction from the RCS, the operator would restore power to the motor operators of the RHRS suction isolation valves, open the valves and remove power to the notor operators using the power lockout devices.
Consequently, the single failure of a pressure transmitter would not-isolate the RHRS from the RCS.
Administrative controls will be instituted to ensure that power is removed from the motor operators of the RERS suction isolation valves using power lockout devices during the second phase of cooldown and initial heatup with RHRS aligned to take suction from the RCS.
Based on the results of " worst case" mass i
input and heat input transient analysis provided in the June 29, 1983 letter to the Staff, Figures 2 and 3, RCS peak pressure would not approach the design pressure of the RHRS.
If you desire any additional information, please let us know, i
Ve tr
- yours, O. W.
D'x WRM:OWD/fjc cc:
V. C.
Summer T.
C. Nichols, Jr./O. W.
Dixon, Jr.
E. H. Crews, Jr.
E.
C. Roberts H.
N.
Cyrus J.
P.
O'Reilly Group / General Managers O. S. Bradham R. B.
Clary C. A.
Price A.
R.
Koon C. L. Ligon-(NSRC)
G. J.
Braddick J. C. Miller J. L.
Skolds J. B. Knotts, Jr.
'NPCF
. File:(Lic./Eng.)
.-_i.
m,.
Figure 1 1
i GENERAL ARRANGEMENT OF'ThE RHKS ISOLATION AND RELIEF VALVES
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TO PRESSURIZER RELIEF TANK l
A i
i
'"^'" ^
X X
l-8702A I-8701A 1-8708A LOOP 1 RilRS ISOLATION RilRS RELIEF ll0T VALVES VALVES LEC LOOP 1 COLD TO RiiRS '
bC PUMPS REACTOR I
VESSEL i
TO PRESSURIZER RELIEF TANK A
N E l
LOOP 3 110T LEG TRAIN B c
p.,
1-8702B 1-8701B 1-8708B INSIDE l0UTSIDE REACTOR REACTOR CONTAINMENT CONTAINMENT 4
v
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