[Federal Register Volume 60, Number 36 (Thursday, February 23, 1995)]
[Notices]
[Pages 10122-10123]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-4383]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-352 and 50-353]
In the Matter of: Philadelphia Electric Company (Limerick
Generating Station, Units 1 and 2); Exemption
I.
Philadelphia Electric Company (the licensee), is the holder of
Facility Operating License Nos. NPF-39 and NPF-85, which authorize
operation of the Limerick Generating Station (LGS), Units 1 and 2. The
licenses provide, among other things, that the licensee is subject to
all rules, regulations, and orders of the Nuclear Regulatory Commission
(the Commission) now and hereafter in effect. The facilities consist of
two boiling water reactors located in Montgomery County, Pennsylvania.
II
Section 50.54(o) of 10 CFR Part 50 requires that primary reactor
containments for water cooled power reactors be subject to the
requirements of Appendix J to 10 CFR Part 50. Appendix J contains the
leakage test requirements, schedules, and acceptance criteria for tests
of the leak tight integrity of the primary reactor containment and
systems and components which penetrate the containment. Sections II.H.4
and III.C.2 of Appendix J to 10 CFR Part 50 require leak rate testing
of Main Steam Isolation Valves (MSIVs) at the calculated peak
containment pressure related to the design basis accident, and Section
III.C.3 requires that the measured leak rates be included in the
combined local leak rate test results. The proposed deletion of the
MSIV Leakage Control System (LCS), and proposed use of an alternate
leakage pathway affects the description of an existing exemption which
allows the leak rate testing of the MSIVs at a reduced pressure and the
exclusion of the measured leakage from the combined local leak rate
test results. The original exemption is contained in the LGS Safety
Evaluation Report (SER) (NUREG-0991, and its Supplement 3).
By letter dated December 22, 1994, the licensee requested an
exemption from the Commission's regulations. The subject exemption is
from the requirements of 10 CFR Part 50, Appendix J, ``Primary Reactor
Containment Leakage Testing for Water-Cooled Power Reactors,'' Sections
II.H.4, III.C.2, and III.C.3, to allow alternative testing pressure and
leakage limits for the MSIVs and to exclude MSIV leakage from the
combined local leak rate test results after deletion of the LCS.
The staff issued for LGS, Units 1 and 2, the current exemption from
10 CFR Part 50, Appendix J, Sections II.H.4, III.C.2, and III.C.3,
based on the conclusion that the LGS, Units 1 and 2, MSIV leak testing
methods were acceptable alternatives to the requirements. This
conclusion was included in the LGS SER (NUREG-0991, and its Supplement
3). The SER also described that in the event of a loss-of-coolant-
accident (LOCA), the MSIV LCS will maintain a negative pressure between
the MSIV and the effluent will be discharged into a volume where it
will be processed by the standby gas treatment system before being
released to the environment. The licensee had performed a radiological
analysis based on an assumed leak rate limit of 11.5 standard cubic
feet per hour (scfh), and the MSIVs were planned to be periodically
tested to ensure the validity of the radiological analysis. The staff
concluded that the current LGS testing procedure, where two valves on
one steam line are tested simultaneously, between the valves, utilizing
a reduced test pressure (i.e., half a peak containment pressure of 22
psig applied between the MSIVs) was acceptable. Also, the staff
excluded the MSIV test leakage rate from the combined local leak rate
because the MSIV leakage had been accounted for separately in the
radiological analysis of the site.
By letter dated January 14, 1994, the licensee submitted a
Technical Specifications (TS) amendment request for LGS, Units 1 and 2,
which supports the planned modification to eliminate the MSIV LCS and
utilize an alternate leakage pathway (main steam lines and condenser).
This proposal is based on the Boiling Water Reactor Owners Group
(BWROG) method summarized in General Electric Report NEDC-31858P,
Revision 2, ``BWROG Report for increasing MSIV Leakage Rate Limits and
Elimination of Leakage Control System.'' Therefore, the description of
the MSIV LCS and the assumed MSIV leak rate are no longer accurate once
the proposed TS modification is performed and implemented.
The licensee's January 14, 1994, TS (amendment) request states that
a plant-specific radiological analysis has been performed in accordance
with NEDC-31858P, Revision 2, to assess the effects of the proposed
increase to the allowable MSIV leakage rate in terms of Main Control
Room (MCR) and off-site doses following a postulated design basis LOCA.
This analysis utilizes the hold-up volume of the main steam piping and
condenser as an alternate method for treating MSIV leakage. The
radiological analysis uses standard conservative assumptions for the
radiological source term consistent with Regulatory Guide (RG) 1.3,
``Assumptions Used for Evaluating the Potential Radiological
Consequences of a Loss-of-Coolant-Accident for Boiling Water
Reactors,'' Revision 2, dated June 1974. The analysis results
demonstrate that dose contributions from the proposed MSIV leakage rate
limit of 100 scfh per MSIV, not to exceed 200 scfh for all four main
steam lines, and considering the proposed deletion of the MSIV LCS,
result in an acceptable increase to the LOCA doses previously evaluated
against the regulatory limits for the off-site doses and MCR doses
contained in 10 CFR Part 100, and 10 CFR Part 40, Appendix A, General
Design Criteria (GDC) 19, respectively. The proposed calculated off-
site and MCR doses resulting from a LOCA are the sum of the LOCA doses
previously evaluated (currently described in the Updated Final Safety
Analysis Report), and the additional doses calculated using the
alternate MSIV leakage treatment method. The method of calculating the
revised doses is conservative, since the LOCA doses
[[Page 10123]] previously evaluated already include dose contributions
from MSIV leakage at the maximum leakage rate currently permitted by
the TS. Appendix 2 of Attachment 3 of the January 14, 1994, submittal
shows the previously calculated doses and the new calculated doses
resulting from the proposed changes.
The staff concluded that the current exemption was acceptable based
on: The method of MSIV testing (i.e., 22 psig test pressure when
applied between MSIVs on a single steam line); a radiological analysis
that assumed a 11.5 scfh MSIV leak rate, and the licensee's commitment
that the MSIVs would be periodically tested to ensure the validity of
the radiological analysis (i.e., verify that the MSIV leakage rate
during testing is accounted for separately in the radiological analysis
of the site. The proposed changes do not affect the bases for the
current exemption. The modification and implementing TS change request:
Will not alter the procedure method of MSIV testing (i.e., test
pressure will remain at 22 psig when applied between MSIVs) and are
based on the results of a radiological analysis where the proposed
leakage rate and the resulting doses are still within regulatory
limits. Also, the MSIVs will be periodically tested to assure the
validity of the analysis (i.e., verify that the proposed MSIV leakage
rate assumed in the radiological analysis is not exceeded per proposed
TS 3.6.1.2.c), and the MSIV leakage will still be accounted for
separately in the radiological analysis of the site.
For the reasons set forth above, the NRC staff concludes that there
is reasonable assurance that: The current MSIV leak testing method
(i.e., test pressure of 22 psig when applied between MSIV) is an
acceptable method; the proposed alternate MSIV leakage pathway (main
steam lines and condenser), and the calculated doses obtained by
performing radiological analysis (calculated using an MSIV leakage rate
limit of 100 scfh per MSIV not to exceed 200 scfh for all four main
steam lines) are within the limits of 10 CFR Part 100 and GDC 19. The
staff finds it acceptable to continue to exclude the measured MSIV
leakage rate from the combined local rate, since the leakage is
accounted for separately and continues to meet the underlying purpose
of the rule. Therefore, the staff finds the requested exemption
presented in the licensee's December 22, 1994, submittal acceptable.
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 and
safety, and are consistent with the common defense and security; and
(2) when special circumstances are present. Special circumstances are
present whenever, according to 10 CFR 50.12(a)(2)(ii), ``Application of
the regulation in the particular circumstances would not serve the
underlying purpose of the rule or is not necessary to achieve the
underlying purpose of the rule * * *,''
The underlying purpose of the rule is to assure that the total
valve leakage is within the limits of 10 CFR Part 100 and GDC-19. The
licensee's analysis has demonstrated that an adequate margin can be
maintained even if leakage from the MSIV is considered separately and
subject to a leakage restriction of 100 scfh per MSIV, not to exceed a
total of 200 scfh for all four main steam lines.
IV
Accordingly, the Commission has determined that, pursuant to 10 CFR
Part 50.12, an exemption is authorized by law and will not present an
undue risk to the public health and safety, and that there are special
circumstances present, as specified in 10 CFR 50.12(a)(2). An exemption
is hereby granted from the requirements of Sections II.H.4, III.C.2(a),
and III.C.3 of Appendix J to 10 CFR Part 50. The exemption allows (1)
leakage testing of the MSIVs after deletion of the LCS, using a test
pressure of 22 psig applied between MSIVs and a leakage rate limit of
100 scfh per MSIV, not to exceed 200 scfh for all main steam lines, and
(2) exclusion of the measured MSIV leakage rate from the combined local
leak rate.
Pursuant to 10 CFR 51.32, the Commission has determined that the
granting of this exemption will have no significant impact on the
quality of the human environment (60 FR 7226).
The exemption is effective upon issuance and will be implemented
prior to startup of Cycle 4 for LGS, Unit 2, and prior to startup of
Cycle 7 for LGS, Unit 1.
Dated at Rockville, Maryland this 16th day of February 1995.
[FR Doc. 95-4383 Filed 2-22-95; 8:45 am]
BILLING CODE 7590-01-M
