[Federal Register Volume 70, Number 79 (Tuesday, April 26, 2005)]
[Notices]
[Pages 21447-21448]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E5-1968]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-368]
Entergy Operations, Inc.; Arkansas Nuclear One, Unit 2; Exemption
1.0 Background
Entergy Operations, Inc. (the licensee) is the holder of Facility
Operating License No. NPF-6 which authorizes operation of the Arkansas
Nuclear One, Unit 2 (ANO-2) nuclear power plant. The license provides,
among other things, that the facility is subject to all rules,
regulations, and orders of the Nuclear Regulatory Commission (NRC, the
Commission) now or hereafter in effect.
The facility consists of a pressurized water reactor located in
Pope County, Arkansas.
2.0 Request/Action
Title 10 of the Code of Federal Regulations (10 CFR), part 50,
appendix A, General Design Criterion (GDC) 57, regarding closed system
containment isolation valves (CIVs), states:
Each line that penetrates primary reactor containment and is
neither part of the reactor coolant pressure boundary nor connected
directly to the containment atmosphere shall have at least one
containment isolation valve which shall be either automatic, or
locked closed, or capable of remote manual operation. This valve
shall be outside containment and located as close to the containment
as practical. A simple check valve may not be used as the automatic
isolation valve.
By application dated October 30, 2003, and supplemented by a
letters dated July 1, November 15, and December 3, 2004, and March 3,
2005, the licensee requested a permanent exemption from 10 CFR part 50,
appendix A, GDC 57 for certain CIVs at ANO-2. Specifically, the
licensee requests an exemption for the applicable manual upstream CIV
associated with the emergency feedwater (EFW) system steam trap and the
applicable manual upstream CIV associated with the atmospheric dump
valve (ADV) drain steam trap. This will allow the plant to operate at
power with these CIVs open, rather than locked closed.
The CIVs under review are located on main steam lines outside
containment, but upstream of the main steam isolation valves (MSIVs).
The main steam and feedwater lines inside containment, in combination
with the secondary side of the steam generators, constitute closed
systems inside containment, so GDC 57 applies. The CIVs are not
automatic or capable of remote manual operation, and the licensee does
not wish to keep them locked closed.
3.0 Discussion
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.
Special circumstances, in accordance with 10 CFR 50.12(a)(2)(ii),
are present in that plant operation with the applicable manual upstream
CIV associated with the EFW system steam trap and the applicable manual
upstream CIV associated with the ADV drain steam trap in the closed
position is not necessary to achieve the underlying purpose of 10 CFR
part 50, appendix A, GDC 57. The staff's rationale is as follows.
Operation With the EFW Steam Trap CIVs and the ADV Drain Steam Trap
CIVs Open
The steam supply lines for the ANO-2 EFW pump and the ADVs tap off
of the ``A'' and ``B'' main steam headers outside containment and
upstream of the MSIVs. The steam supply from the ``B'' main steam
header has a steam trap upstream of the EFW pump turbine isolation
valve, which is a GDC 57 boundary valve. Therefore, the upstream CIV
for this steam trap is subject to GDC 57. The manual isolation valves
for this steam trap (which include the upstream CIV) are normally open
during power operation. Keeping the EFW steam trap isolation valves
closed during operation potentially threatens the operability of the
steam-driven EFW pump. It is noted that the EFW steam trap for the
``A'' EFW pump turbine is located downstream of the turbine isolation
valve. The ADV associated with the ``A'' main steam header has a drain
steam trap whose isolation valves are also maintained open during power
operation. The upstream CIV for this steam trap is also subject to GDC
57. Keeping the ADV drain steam trap isolation valves closed during
operation could cause the potential for waterhammer when an ADV line is
opened and damage the piping associated with the ADV, due to condensate
buildup. Since these applicable CIVs (associated with the EFW and ADV
drain steam traps) are manual CIVs and do not have remote closure
capability, GDC 57 requires that they be locked closed. Therefore, the
licensee requests an exemption from the requirements of GDC 57 to keep
these CIVs open during operation.
Operating with the ANO-2 EFW steam trap and ADV drain steam trap
CIVs open results in the secondary system pressure boundary inside
containment providing the only barrier against the release of
radioactivity to the environment through the steam trap piping.
However, the licensee has evaluated the effects of these valves being
open during power operation (provided below) and has shown this to have
no impact on the consequences of any of the events evaluated in the
Safety Analysis Report (SAR). Operating with the EFW steam trap CIVs
closed and the ADV drain steam trap CIV closed could compromise the
operability of the EFW pump turbine and damage the piping associated
with the ADV, due to condensate buildup.
Of the 36 events listed in Chapter 15 of the ANO-2 SAR, only ten
involve a radiation dose evaluation. The waste gas decay tank rupture
and the fuel handling accident need not be evaluated since they cannot
physically involve the EFW and ADV steam trap CIVs. Additionally, the
malfunction of the turbine gland sealing system can also be eliminated
from evaluation since it is bounded by the turbine trip event, which
will be discussed below. The remaining seven events are turbine trip,
loss of alternating current (AC) power, excess heat removal, main
steam/feed line break, loss of reactor coolant system (RCS) forced
flow, loss-of-coolant accident (LOCA), and steam generator tube
rupture.
For the turbine trip, loss of AC power, excess heat removal, and
main steam/feed line break, no post-event RCS activity is involved in
the dose estimate since the RCS integrity is not compromised. Having
the EFW and ADV steam trap CIVs open would not impact this event since
the containment isolation function is not a factor.
For the loss of RCS forced flow, only the reactor coolant pump
shaft seizure has a dose estimate, and that dose estimate is based on a
normal cool down to shutdown cooling with no secondary isolations
assumed. Therefore, having
[[Page 21448]]
the EFW and ADV steam trap CIVs open would not impact this event.
For the LOCA, activity in the secondary system is not considered in
the dose estimate because of the massive radioisotope inventories that
are conservatively and deterministically considered to be in the
containment building. No credit for the closure of the MSIVs or other
secondary system flowpaths is taken for this analysis unless a passive
failure of the secondary system pressure boundary inside containment is
assumed. Since the design and quality of the secondary system process
and drain lines inside containment is equivalent to that of the
containment liner, a passive failure of this piping is not considered
in the SAR analysis. Also, pertinent regulations (e.g., 10 CFR part 50,
appendix J, Option A, section II.H.4) assume that the closed system
inside containment remains intact during the accident. Therefore,
having the EFW and ADV steam trap CIVs open would not impact this
event.
For the steam generator tube rupture, no containment isolation
signal or main steam isolation signal would be generated. Manual
isolation of the affected steam generator is assumed to occur 60
minutes following a steam generator tube rupture, followed by cool down
to shutdown cooling conditions using the unaffected steam generator.
The isolation of the affected steam generator includes the local manual
isolation of the EFW and ADV steam traps. Therefore, the fact that they
are not equipped to be operated remotely has no effect on analyzed dose
consequences.
The staff has evaluated the licensee's analyses and makes the
following findings:
(a) Only 7 of the 36 Chapter 15 events need to be evaluated, for
the reasons given above.
(b) For the turbine trip, loss of AC power, excess heat removal,
and main steam/feed line break, the containment isolation function is
not a factor, so the position of the subject steam trap CIVs has no
effect on the consequences of the accidents.
(c) The loss of RCS forced flow event analysis does not assume
secondary system isolation (which includes the subject steam trap
CIVs), so the position of these CIVs has no effect on the analyzed dose
consequences.
(d) For the LOCA, secondary system isolation is not assumed in the
analyses, and pre-existing secondary system radioactivity is
insignificant compared to the analyzed releases, so the position of the
subject steam trap CIVs has no effect on the analyzed dose
consequences.
(e) For the steam generator tube rupture event, no containment
isolation signal or main steam isolation signal would be generated. The
analysis assumes the local manual isolation of the subject steam trap
CIVs. Therefore, the licensee's proposal, to allow the subject steam
trap CIVs to remain open during power operation, with only local manual
closure capability, is consistent with the event analysis.
Based on the above discussion, leaving the EFW and ADV steam trap
CIVs open during power operation would have no impact on the
consequences of any of the accidents evaluated in the SAR.
Alternate Solutions
The licensee has stated that operating with the EFW steam trap CIV
closed and the ADV drain steam trap CIV closed could compromise the
operability of the EFW pump turbine and damage the piping associated
with the ADV, due to condensate buildup. However, in its October 30,
2003, letter, the licensee did not explicitly address another possible
alternative to the requested exemption; that being, to bring the CIVs
(associated with EFW and ADV drain steam traps) into compliance with
GDC 57 by installing remote manual operators on the CIVs. The CIVs
could then be left open during plant operation. In its supplemental
letter dated July 1, 2004, the licensee stated again that leaving the
CIVs open during power operation would have no impact on the
consequences of any of the accidents evaluated in the SAR. Considering
this, the licensee believes that any potential benefit derived from
implementing a modification to install remote manual operators on the
subject CIVs would not be commensurate with the cost and resource
burden associated with preparing and implementing the modification.
Therefore, the licensee believes that the most expeditious, efficient,
and cost effective resolution of the nonconformance with GDC 57 is the
subject exemption request.
Although the staff considers there to be significant safety value
to the dual, redundant barrier concept of containment isolation, the
staff finds that, in this case, given the SAR analyses and the
assumption of an intact closed system inside containment during a LOCA,
it is not necessary to require compliance with the explicit
requirements of the regulation in order to achieve the underlying
purpose of the regulation, which is to ensure that the primary
containment serves as an essentially leak-tight barrier against the
uncontrolled release of radioactivity to the environment, because
leaving the EFW and ADV steam trap CIVs open during power operation
would have no impact on the consequences of any of the accidents
evaluated in the SAR. Thus, the staff finds that the safety benefits of
the modification are not commensurate with the cost.
Summary
The staff finds that, based on the above, it is not necessary, in
this case, for the subject CIVs to be locked closed, automatic, or
remote manual, as required by GDC 57, in order to achieve the
underlying purpose of GDC 57. Therefore, pursant to 10 CFR 50.12(a)(2),
the staff concludes that the operation of ANO-2 with the subject CIVs
open is acceptable, and that the requested exemption from GDC 57 is
justified.
4.0 Conclusion
Accordingly, the Commission has determined that, pursuant to 10 CFR
50.12(a), the exemption is authorized by law, will not present an undue
risk to the public health and safety, and is consistent with the common
defense and security. Also, special circumstances are present.
Therefore, the Commission hereby grants Entergy Operations, Inc. an
exemption from the requirements of 10 CFR part 50, appendix A, GDC 57,
to allow ANO-2 to operate with the applicable manual upstream CIV
associated with the EFW system steam trap and the applicable manual
upstream CIV associated with the ADV drain steam trap in the open
position.
Pursuant to 10 CFR 51.32, the Commission has determined that the
granting of this exemption will not have a significant effect on the
quality of the human environment (70 FR 19106).
This exemption is effective upon issuance.
Dated in Rockville, Maryland, this 15th day of April 2005.
For the Nuclear Regulatory Commission.
Ledyard B. Marsh,
Director, Division of Licensing Project Management, Office of Nuclear
Reactor Regulation.
[FR Doc. E5-1968 Filed 4-25-05; 8:45 am]
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