ML19329A438
| ML19329A438 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 04/26/1978 |
| From: | Stello V Office of Nuclear Reactor Regulation |
| To: | NRC COMMISSION (OCM) |
| Shared Package | |
| ML19329A435 | List: |
| References | |
| NUDOCS 8001031002 | |
| Download: ML19329A438 (6) | |
Text
,-y 7590-01 v
UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of.
)
)
DUKE POWER COMPANY
)
Dockets Nos. 50-269
)
50-270 Oconee Nuclear Station, Units Nos.1, 2,
)
and 50-287 and 3 ORDER FOR MODIFICATION OF LICENSE I.
The-Duke Power Company (the licensee), is the holder of Facility Operating Licenses Nos. DPR-38, 47, and 55 which authorize the operation of the nuclear power reactors known as Oconee Nuclear Station, Units Nos.1, 2, and 3, (the facility) at steady reactor power levels not in excess of 2568 i
megawatts thermal (rated power) for each unit.
The facility consists of Babcock & Wilcox Company designed pressurized water reactors (PWR) located at the licensee's site in 0conee _ County, South Carolina.
II.
In accordance with the requirements of the Commission's ECCS Acceptance Criteria,10 CFR 50.46, the licensee submitted on July 9,1975, an ECCS evaluation for the facility. The ECCS performance submitted by the li-censee was based upon an ECCS Evaluation Model developed by the Babcock
& Wilcox Company (B&W), the designer of the Nuclear Steam Supply System 6
4 h
k b
dt o 8 001 ogy 99,
5
.m
~
~
7590-01 for this facility.
The B&W ECCS Evaluation Model had been previously found to conforn to the requirements of the Ccamission's ECCS Acceptance Criteria,10 CFR Part 50.46 and Appendix K.
The evaluation indicated that with the limits set forth in the facility's Technical Specifications, the ECCS cooling performance for the f acility would conform with the criteria contained in 10 CFR 50.46(b) which govern calculated peak clad temperature, naximum cladding oxidation, maximum hydrogen generation, cool-able geometry and long-term cooling.
On April 12, 1978, B&'J informed the NRC that it had determined that in the event of a small break LOCA on the discharge side of a reactor coolant pump, high pressure injection (HPI) flow to the core could be reduced somewhat.
Subsequent calculations indicated that in such a case the
~ '
calculated peak clad temperature might ex.ceed 2200F.
Previous small break analyses for B&W 177 fuel assembly (FA) lowered loop plants had identified the limiting sra'.1 br'eak to be in the suction line of the reactor coolant pump.
Recent analyses have shown that the discharge line break is more limiting tr. n the suction line break.
Each Oconee Nuclear Station unit has an ECCS configuration which consists of two high pressure injec. ion (HPI) trains which are supplied ~
t by three HPI pumps. Each train injects into two of the four reactor coolant system (RCS) cold legs on the discharge side of the RCS pump.
O s
9 d
-ss-g-
e The two' parallel HPI trains are connected Frt are kept isolated by manual valves (known as the cross-over valves) that are normally closed. '
Duke Power has proposed to naintain all three pumps in an operable status.
The O'conee cmergency power system is designed with sufficient capacity for this mode of operation. Upon receiving a safety injection signal the HPI pumps are sta'rted and valves in the injection lines are opened.
Assuming loss of offsite power and the worst single failure (the HPI pump C or the HPI va1Ye HP26), ~two HPI pumps would still be available and ~only one of the two injection valves would fail to open.
If a small break is postulated to occur in the RCS piping between the RCS pump discharge and the reactor vessel,' the high pressure injection flow injected into this line (about 50% of the output of.two high pres-sure pumps) could flow out.the break. Therefore, for the worst combination of break location and single failure, 50% of the flow rate of two high pressure ECCS pumpswould. contribute.to. maintaining the coolant inventory in the reactor. vessel. This situation had not been previously analyzed and B&W had indicated that the limits specified in 10 CFR '50.46 may be exceeded.
B&W has stated that they have analyzed a spectrum of small breaks in the pump discharge line and h;vb determined that to meet the limits of 10 CFR 50.46, operator action is required to open the.two manual operated e
<+
l.
n
-crassover valves and to manually align the motor driven isolation valve
[
n.hich had failed to open. This would allow the flow from the two 11PI -
pumps to ' feed all four reactor coolant legs.
BfM has assumed that 30%
of the flow would be lost through the break and 70% wou1'd refill the The licensee has committed to provide for the necessary operator core.
actions within the required time frame. That is, in the event of a i
small break and a limiting single failure, manual action will be taken to begin opening these valves within five minutes and have them fully opened and.an adequate flow split obtained within the following 10 minutes. The' analyses performed by B&W assumed that the flow split was established at 650 seconds by operator action. t!e conclude that the analyses are a reasonable approximation of the operator action that actually will be taken, rrovided specific procedures are prepared and 9
followed to assure such action.
B&W has stated that a.15 ft.2 discharge line break, with the afore-
. mentioned operator actions, is the most limitipg case. To arrive at this conclusion, B&W has performed analyses at break sizes of
.3,
.2,
.15,
.1, and.04 ft.2, using an approved Appendix,K'model for blowdown.
Additional analyses for the Oconee plants at 2568 R t indicate no core uncovery for the 0.15 ft.2 limiting break.
For this break size B&U has conservati.vely estimated the peak clad temperature to be well below the
. limits of 10 CFR 550.46(b).
~
O r--
1 i
u yy B&W has indicated the manner in which the calculational methods have been revised and has indicated that their revised calculations are 50.46. However, wholly in ct.'formance with the requirements of 10 CFR B&W has not yet had the opportunity to fully present the result of its calculations to the licensee for submittal to the NRC staff, and the staff has accordingly not had the opportunity to fully assess the f
new calculations.
Therefore, until the staff has had the opportunity to fully assess the B&W revised calculations, operation in accordance with the operating procedures specified in this Order, will assure that the ECCS will confom to the perfomance requirements of 10 CFR 50.46(b).
/
Accordingly, such procedures provide reasonable assurance that the public health and safety will not be endangered. Upon notification by the NRC staff, the licensee committed to provide the staff with B&W's reevaluation of ECCS.perfomance applicable to the licensee's facility as promptly as possible, and to submit a technical specificat' ion requiring appropriate operating procedures to assure required operator action as discussed herein.
Such procedures were described and the commitments confirmed,y the licensee's lettar of April 21, 1978.
b The staff believes that the licensee's action, under the circumstances, is appropriate r that this action should be confirmed by NRC Order.
Upon satisfactory completion of our assessment of the revised evaluation, we will accordingly modify the authorization to operate the facility.
J j *.
I V.
Copies of the following document are available for inspection at the Conmission's Public Document Room at 1717 H Street, Washington, D.C.
- 20555, and are being placed in the Commission's local public document room at the Oconee County Library, 201 South Spring, Walhalla, South Carolina 29691.
t (1) Letter fron Mr. Uilliam O. Parker, Jr. to Mr. Edson G. Case, Acting Director, Office of Huclear Reactor Regulation, dated April 21, 1978.
Accordingly, pursuant to the Atomic Energy Act of 1954, as amended, and the Commission's Rules and Regulations in 10 CFR Parts 2 and 50, IT 15 ORDERED THAT Facility Operating Licenses Nos. DPR-38, 47, and 55 are hereby amended by adding the following new provisions:
(1)
As soon as possible, the licensee shall submit a reevaluation wholly
~
in conformance with 10CFR50.46 of ECCS cooling performance calculated in accordance with the B&W Evaluation Model for operation with operating procedures describ'ed in its letter of April ~21, 1978, and (2)
Until further authorization by the Commissian,4he licen'see shall' operate in accordance with the procedures described in its letter of April 21, 1978.
FORTHENUCLEdRREGULATORYCOMMISSION
_V27 Vi or'Stello,
.I, D
- ec o r Division of Operating Reactors Office of Nuclear Reactor Regulation Dated at Bethesda, Maryland, this 26th day of April 1978.
h
_ J'
._