Duke Energy Corporation (Oconee Nuclear Station, Units 1, 2, and 3); Exemption

[Federal Register Volume 63, Number 224 (Friday, November 20, 1998)]
[Notices]
[Pages 64530-64531]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-31025]


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NUCLEAR REGULATORY COMMISSION

[Docket Nos. 50-269, 50-270, and 50-287]


Duke Energy Corporation (Oconee Nuclear Station, Units 1, 2, and 
3); Exemption

I

    The Duke Energy Corporation (Duke/the licensee) is the holder of 
Facility Operating License Nos. DPR-38, DPR-47, and DPR-55, that 
authorize operation of the Oconee Nuclear Station, Units 1, 2, and 3 
(Oconee), respectively. The licenses provide, among other things, that 
the facilities are subject to all rules, regulations, and orders of the 
U.S. Nuclear Regulatory Commission (the Commission) now or hereafter in 
effect.
    The facilities consist of pressurized water reactors located on 
Duke's Oconee site in Seneca, Oconee County, South Carolina.

II

    Title 10 of the Code of Federal Regulations (10 CFR) Part 50, 
Sec. 50.46(a)(1)(i), requires that each pressurized light-water nuclear 
power reactor must be provided with an emergency core cooling system 
(ECCS) that is designed so that its calculated cooling performance 
following postulated loss-of-coolant accidents conforms to the criteria 
set forth in paragraph 50.46(b). ECCS cooling performance must be 
calculated in accordance with an acceptable evaluation model and must 
be calculated for a number of postulated loss-of-coolant accidents 
(LOCAs) of different sizes, locations, and other properties sufficient 
to provide assurance that the most severe postulated small and large 
break LOCAs are calculated that will ensure adequate long-term cooling.
    By letter dated September 17, 1998, the licensee described a 
modification that would add voltage and frequency protection for the 
Oconee loads when they are supplied from a Keowee hydro unit. The 
protection would separate Oconee loads from a Keowee unit if that 
unit's voltage or frequency becomes greater than 110 percent or less 
than 90 percent of rated value at any time after loading. The planned 
design would also delay energizing the Oconee loads on the underground 
power path until the Keowee unit reaches greater than 90 percent 
voltage and frequency. The existing design allows early loading of the 
underground path Keowee unit at approximately 60 percent voltage. 
During the design phase of this modification, while considering the 
frequency overshoot that the Keowee units normally experience during an 
emergency start, questions arose concerning whether the emergency power 
system should be loaded at 60 percent or 90 percent. To provide needed 
data to resolve this question, the Keowee Emergency Power and 
Engineered Safeguards Functional (KEP/ESF) Test is planned.
    The test is scheduled during the Unit 3 outage, will be performed 
on the Keowee underground path, and will consist of two parts. One part 
will load the Keowee unit at its present design of approximately 60 
percent rated voltage

[[Page 64531]]

and frequency. The second part will use the same loads, but the Keowee 
unit will be loaded at approximately 90 percent rated voltage and 
frequency. Test data will be collected throughout the Oconee emergency 
power system (EPS) during the test. The licensee will then review this 
data to determine which delayed loading modifications should be 
implemented.
    In the September 17, 1998, letter, Duke explained it has determined 
that this test involves an unreviewed safety question, which, 
therefore, requires NRC approval prior to performing the test. This 
request is being processed separately. The licensee also indicated that 
in the extremely unlikely (probability, according to the licensee, of 2 
E-9) event that a real LOCA with loss of offsite power (LOOP) were to 
occur on either of the Oconee operating units (Unit 1 or 2) 
simultaneously when the test is initiated on Unit 3, the Oconee EPS 
would be placed in a condition outside the design basis. The EPS may 
not be capable of handling the electrical loading of two instantaneous 
LOCA/LOOP events without some safety related equipment being adversely 
affected. However, the EPS would be able to handle the electrical 
loading if the two events are offset in time by approximately 10 
seconds to allow the first unit's load to reach a steady-state 
condition prior to starting of the second unit's emergency loads. 
Therefore, this 10-second window of vulnerability causes an 
infinitesimally small, but non-zero, increase in the probability of a 
malfunction of equipment important to safety and increases the 
potential consequences of a LOCA/LOOP event during the performance of 
the test.
    The ECCS is designed to assure that the consequences of the 
spectrum of LOCA accidents, coincident with a LOOP, are within the 
performance criteria specified in 10 CFR 50.46(b). As explained in the 
licensee's letter dated October 21, 1998, the planned test on Unit 3 
could challenge this criteria in the extremely unlikely event that a 
LOCA and LOOP on Units 1 or 2 occurred coincident with the start of the 
test on Unit 3. Therefore, in the October 21 letter and pursuant to 10 
CFR 50.12, the licensee applied for an exemption from 10 CFR 50.46.

III

    Pursuant to 10 CFR 50.12, the Commission may, upon application by 
any interested person or upon its own initiative, grant exemptions from 
the requirements of 10 CFR Part 50, when (1) the exemptions are 
authorized by law, will not present an undue risk to public health or 
safety, and are consistent with the common defense and security; and 
(2) when special circumstances are present. The requested exemption 
meets the special circumstances of 10 CFR 50.12(a)(2)(iv) in that the 
exemption would result in benefit to the public health and safety that 
compensates for the small decrease in safety that may result from 
granting the exemption. The benefit is that this test will produce data 
to support a decision on implementation of proposed modifications to 
the loading methodology of the Keowee hydro unit to improve the overall 
reliability of the Oconee EPS, which supports the ECCS. The test is 
being conducted under a comprehensive test plan that includes special 
management oversight, ``just in time training'' for the operators, 
including power system failures, and detailed contingency plans. Other 
precautions to protect the power systems will be in place, which are 
described in more detail in the licensee's September 17, 1998, 
submittal. No other work will be allowed on the EPS of any unit during 
this test. A Lee gas turbine will be powering CT-5 to provide 
additional defense in depth for the EPS during the test. This minimizes 
the likelihood of a plant-centered LOOP occurring during the test 
period. Additionally, precautions have been taken so that the planned 
LOOP tests on Unit 3 will not propagate to the operating units. 
Therefore, the likelihood of two LOCA/LOOP events occurring within 
approximately 10 seconds of each other (one event being the LOCA/LOOP 
test on Unit 3 and the second event being an actual LOCA/LOOP on Unit 1 
or 2) is low during the postulated period of 24-hour duration of the 
KEP/ESF Test.

IV

    For the foregoing reasons, the NRC staff has concluded that the 
licensee's proposed exemption request from the requirements of 10 CFR 
50.46(b) for the KEP/ESF Test is justified. The probability of a 
coincident LOCA/LOOP on one of the operating units (approximately 2E-9, 
as estimated by the licensee) was calculated for the entire duration 
(24 hours) of the KEP/ESF Test. If a separation in time of greater than 
10 seconds exists between initiation of the test and a coincident 
event, the ECCS on the affected unit will be capable of performing its 
intended safety function. The benefit to the Oconee Emergency Power 
System from performing this test, along with the low probability of a 
concurrent LOCA/LOOP on one of the two operating Oconee units, provides 
justification for granting this exemption request. In addition, 
granting of the exemption to allow performance of the test will not 
present an undue risk to public health and safety and is consistent 
with the common defense and security. The NRC staff has determined that 
there are special circumstances present, as specified in 10 CFR 
50.12(a)(2)(iv), in that the exemption will result in a benefit to the 
public health and safety that compensates for the decrease in safety 
that may result from the granting the exemption because the exemption 
will allow the test to be performed that will produce data to support 
an implementation decision for a proposed modification that will 
improve the overall reliability of the Oconee emergency power system.
    Accordingly, the Commission has determined that, pursuant to 10 CFR 
50.12(a), the exemption is authorized by law, will not endanger life or 
property or common defense and security, and is, otherwise, in the 
public interest. Therefore, the Commission hereby grants Duke an 
exemption from the requirements of 10 CFR 50.46(b) for Units 1, 2, and 
3 during the 24-hour period when the tests are being conducted on Unit 
3 as requested in the submittal.
    Pursuant to 10 CFR 51.32, the Commission has determined that the 
granting of this exemption will not result in any significant effect on 
the quality of the human environment (63 FR 63754).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 16th day of November 1998.

    For the Nuclear Regulatory Commission.
Samuel J. Collins,
Director, Office of Nuclear Reactor Regulation.
[FR Doc. 98-31025 Filed 11-19-98; 8:45 am]
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