[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]
BILLING CODE 7590-01-P
