[Federal Register Volume 59, Number 134 (Thursday, July 14, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-17077]
[[Page Unknown]]
[Federal Register: July 14, 1994]
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NUCLEAR REGULATORY COMMISSION
Nebraska Public Power District; Cooper Nuclear Station
Environmental Assessment and Finding of No Significant Impact
[Docket No. 50-298]
The U.S. Nuclear Regulatory Commission (the Commission) is
considering the issuance of an exemption to Facility Operating License
No. DPR-46 to the Nebraska Public Power District (the licensee), for
the operation of the Cooper Nuclear Station (CNS), located in Nemaha
County, Nebraska.
Environmental Assessment
Identification of Proposed Action
The proposed action would grant an exemption from the requirements
of Section III.C.1 of Appendix J to 10 CFR Part 50, to allow Type C
testing (local leak rate testing) of four containment isolation valves
in the reverse direction.
The proposed action is in accordance with the licensee's
application for exemption dated June 29, 1994.
The Need for the Proposed Action
The purpose of Type C testing is to measure the leakage through the
primary reactor containment and thereby provide assurance that it does
not exceed the maximum allowable leakage rates. Prior to a recent
contractor review of local leakrate testing methodology, the licensee
had made the determination that reverse direction testing of the
subject containment isolation valves produced equivalent or more
conservative results than testing in the accident direction. The
contractor review disclosed that, while reverse pressure testing for
the subject valves (two globe valves and two stop-check globe valves)
was conservative with respect to measuring leakage past the valve
seating surfaces, such testing may be non-conservative with respect to
packing leakage and body-to-bonnet leakage. Packing and body-to-bonnet
leakage cannot be quantified by reverse pressure testing because the
physical configurations of the valves are such that valve packing and
the valve bonnets are not exposed to test pressure. The four valves are
not testable in the accident direction due to the inability to isolate
the valves from containment and the lack of test connections.
Several factors are cited by the licensee in its June 29, 1994,
request for exemption to demonstrate that a high level of confidence
exists that reverse direction pressure testing does not yield
significantly different results than what would be expected in the
accident direction. First, reverse pressure testing of globe valves
generally results in a conservative seat leakage measurement because
the pressurization test applies force in the direction that would
unseat the disk. Any increase in leakage attributable to this factor
would tend to offset the inability to measure packing and body-to-
bonnet leakage on the non-testable side of the valve. Second, all
subject valves are tested in the accident direction during integrated
leakrate tests, thus exposing all pressure retaining parts, including
the bonnet and packing, to the design basis pressure (58 psig).
Third, integrated leakrate test results historically have not
indicated any significant leakage through these two paths. As of June
22, 1994, total minimum path as-left leakage for all type B and C tests
measured 117.95 standard cubic feet per hour. The 1991 integrated
leakrate test yielded a total measured leakrate of 102.5 standard cubic
feet per hour. These results demonstrate that significant margin exists
with respect to the startup limit of 189 standard cubic feet per hour
and the total allowable limit of 316 standard cubic feet per hour.
Thus, there is confidence that the requirements of 10 CFR part 50,
appendix J, and the Cooper Nuclear Station Technical Specifications
continue to be met.
Fourth, valve packing and body-to-bonnet gaskets do not contain
materials that degrade as a result of the mild service conditions to
which they are subjected during normal operations and periodic
surveillance testing.
Finally, while the above factors may provide reasonable assurance
that leakage through the bonnet and the packing is not a problem for
the four subject valves, the licensee has proposed additional actions
in order to justify permanent exemptions from the ``equivalent or more
conservative'' results requirement of 10 CFR Part 50, Appendix J.
Specifically the licensee proposes to perform soap bubble tests to
detect body-to-bonnet or packing leakage while these pressure retaining
boundaries are pressurized in the accident direction during future
integrated leakrate tests. A ``zero bubble'' or zero detectable leakage
acceptance criteria would be satisfied to demonstrate the leak-
tightness of the packing and valve bonnets. Additionally, the licensee
proposes to specifically observe the two stop-check globe valves for
indication of leakage through the insulation during scheduled system
surveillance tests which subject the valves to pressurization.
Without the proposed exemption, the licensee would be forced, at
significant cost but without any significant increase in public health
and safety, to implement plant modifications to permit local leakrate
testing with test pressure applied in the accident direction. Further,
such actions would delay the restart date of the current outage, which
is currently scheduled for July 11, 1994.
Environmental Impacts of the Proposed Action
The Commission has completed its evaluation of the proposed action
and concludes that the proposed exemption would allow permanent
individual exemptions from Appendix J to 10 CFR Part 50 to allow Type C
testing of four isolation valves in the reverse direction.
The change will not increase the probability or consequences of
accidents, no changes are being made in the types of any effluents that
may be released offsite, and there is no significant increase in the
allowable individual or cumulative occupational radiation exposure.
Accordingly, the Commission concludes that there are no significant
radiological environmental impacts associated with the proposed action.
With regard to potential nonradiological impacts, the proposed
action does involve features located entirely within the restricted
area as defined in 10 CFR Part 20. It does not affect nonradiological
plant effluents and has no other environmental impact. Accordingly, the
Commission concludes that there are no significant nonradiological
environmental impacts associated with the proposed action.
Alternative to the Proposed Action
Since the Commission concluded that there are no significant
environmental impacts associated with the proposed action, any
alternatives to the exemption will have either no environmental impact
or greater environmental impact.
The principal alternative would be to deny the requested exemption.
Denial would not reduce the environmental impacts attributed to the
facility but would result in the expenditure of resources and increase
radiation exposures without any compensating benefit.
Alternative Use of Resources
This action does not involve the use of any resources not
previously considered in the Final Environmental Statement for the
Cooper Nuclear Station, dated February 1973.
Agencies and Persons Consulted
The NRC staff consulted with the Nebraska State official regarding
the environmental impact of the proposed action. The State official had
no comments.
Finding of No Significant Impact
Based upon the environmental assessment, the Commission concludes
that the proposed action will not have a significant effect on the
quality of the human environment. Accordingly, the Commission has
determined not to prepare an environmental impact statement for the
proposed action.
For further details with respect to this action, see the request
for exemption dated June 29, 1994, which is available for public
inspection at the Commission's Public Document Room, 2120 L Street,
NW., Washington, DC 20555, and at the local public document room
located at the Auburn Public Library, 118 15th Street, Auburn, Nebraska
68305.
Dated at Rockville, Maryland, this 8th day of July 1994.
For the Nuclear Regulatory Commission.
William D. Beckner,
Director, Project Directorate IV-1, Division of Reactor Projects--III/
IV, Office of Nuclear Reactor Regulation.
[FR Doc. 94-17077 Filed 7-13-94; 8:45 am]
BILLING CODE 7590-01-M
