ML19322B467
| ML19322B467 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 04/26/1978 |
| From: | Stello V Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19322B464 | List: |
| References | |
| NUDOCS 7912030305 | |
| Download: ML19322B467 (6) | |
Text
a m
3
7590-01 O.
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 1
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 megawatts thermal (rated power) for each unit.
The facility consists of Babcock & Wilcoy Company designed pressurized water reactors (PWR) located at 1
the licensee's site in Oconee County, South Carolina.
l II.
i In accordance with the requirements of the Commission's ECCS Acceptance i
Criteria,10 CFR 50.46, the licensee submitted on July 9,1975, an ECCS i
evaluation for the facility.
The ECCS perfomance submitted by the li-censee was based upon an ECCS Evaluation Model developed by the Babcock l
& Wilcox Company (B&W), the designer of the Nuclear Steam Supply System i
N 912 03 0 ;O> O$
I
)
7590,
for this facility.
The B&W ECCS Evaluation Model had been previously found to confom to the requirements of the Commission'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 perfomance for the facility would confom with the criteria contained in 10 CFR 50.46(b) which govern calculated peak clad temperature, maximum cladding oxidation, maximun hydrogen generation, cool-able geometry and long-tern cooling.
On April 12,1978, B&W infomed the NRC that it had detemined that in the event of a small break LOCA on the discharge side of a reactor coolar.'.
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 exceed 2200F.
Previous small break analyses fo'r B&W 177 fuel assembly (FA) lowered loop plants had identified the l'imiting small break to be in the suction line of the reactor coolant pump.
Recent analyses have shown that the discharge line break is more limiting than the suction line break.
Each Oconee fluclear Station unit has an ECCS configuration which consists of two'high pressure injection (HPI) trains which are supplied
. 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.
9 g
g 4
O g
D g
~._my%%...w 7
3 Th3 two" parallel HPI trains are connected but are kept isolated by
~
manual valves (known as the cross-over valves) that are normally closed. -
Duke Power has proposed to maintain all three pumps in an operable status.
The O'conee emergency power system is designed with sufficient capacity for this node of operation. Upon receiving a safety injection signal the HPI pumps are started 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 valve HP26), two HPI pumps would still be availatite 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-f '.
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 punpwould 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 punp discharge line and have determined that to meet the limits of 10 CFR 50.46, operator action is required to open the.two manual operated 9
e i_
N 7590-01 3
4-q j
~
crossover valves and to manually align the motor driven isolation valve which had failed to open. This would allow the flow from the two HPI pumps to feed all four reactor coolant legs.
B&W has assumed that 30%
of the flow would be lost through the break and 70% would 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 small break and a limitina 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. We conclude that the analyses are a reasonable approximation of the operator action that actually will be taken, previded specific procedures are prepared and followed to assure such action.
B&W has stated that a.15 f t.2 discharce line break, with the afore-mentioned operator actions, is the most limitir.g 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 Mwt indicate no core uncovery for the 0.15 ft.2 limiting break.
For this break size bah has conservatively estimated the peak clad temperature to be well below the limitsof10CFR550.46(b).
.c s -Wee 1
e==wg.--- e %+ n
%gm egame.
gemm e e m mee -m,
.ww + we r
.eqya.m.
w
-,e+.=
w-ee.e6 4-.s.,
m h
o
~
]
7590-01 5-B&W has indicated the manner in which the calculational methods have been revised and has indicatc' that their revised calculations are wholly in confomance with the requirements of 10 CFR 50.46.
- However, B&W has not yet hao the opportunity to fully prerant the' result of
)
its calculations to the licensee for submittal to the NRC staff, and the staff h'as accordingly not had the opportunity to fully assess the new calculations.
Therefore, until the staff has had the opportunity to fully assess the B&W revised calculations, operatior in accordance with the operating procedures specified in this Order, will assure that the ECCS will confom to the performance 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 staf f, the licensee committed to provide the staf f with B&W's reevaluation of ECCS perfomance applicable to the licensee's facility as pronptly as possible, and to s'ubmit a technical specification requiring appropriate operating procedures to assure required operator action as discussed herein.
Such procedures were described and the commitments confirmed 'by the licensee's letter of April 21, 1978. '
The staff believes that the licensee's action, under the circunstances, is appropriate and 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.
+
+-..em..
e.,-
-_m.
7590-01
] -
IV.
1 Copies of the following document are available for inspection at the Comission's Public Document Room at 1717 H Street, Washington, D.C.
- 20555, and are being placed in the Comission's local public document room at the Oc'onee County Library, 201 South Spring, Walhalla, South Carolina 29691.
l (1 ) Letter fron Mr. William 0. Parker, Jr. to Mr. Edson G. Case, Acting Director, Office of Nuclear 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 IS 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 li.censee shall submit a reevaluation wholly in conformance with 10CFR50.46 of ECCS cooling performance calculated 1
in accordance with the B&W Evaluation Model for operation with operating procedures described in its letter of April 21, 1978, and (2) Until further authorization by the Commission,-the licensee shall operate in accordance with the procedures described in its letter, of April 21,1978.
FOR THE NUCLEAR REGULATORY C0ftMISSION VN dctor Stello,'erating Reactors JF, Director Division of Op Office of Nuclear Reactor Regulation Dated at Bethesda, Maryland, this 26th day of April 1978.