ML20056C173
| ML20056C173 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 03/18/1993 |
| From: | Doris Lewis SHAW, PITTMAN, POTTS & TROWBRIDGE |
| To: | Mcgranery J MCGRANERY, J.P., JR. |
| References | |
| CON-#193-13753 DCOM, NUDOCS 9303300185 | |
| Download: ML20056C173 (10) | |
Text
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caviO w tc*ss March 18, 1993 By Hand Delivery James P. McGranery, Jr.,
Esq.
Suite 750 1255 Twenty-Third Street, N.W.
Washington, D.C.
20037 l
In the Matter of Sacramento Municipal Utility District (Rancho Seco Nuclear Generating Station)
Docket No. 50-312-DCOM
Dear Mr. McGranery:
The Commission's Memorandum and Order of March 3,
- 1993, (CLI-93-03) requires SMUD to provide ECO with the basis for the determination in the District's environmental report (ER) that the probability of a Loss of Offsite Power (LOOP) is less than once in twenty years.
This letter fulfills the Commission's requirement.
The basis for the statement in the ER on LOOP frequency is provided in the attached memorandum from the District.
The main references are also enclosed.
Pursuant to the Commission's Memorandum and Order, within fourteen days of service of this submittal, ECO may file an r
amended contention related to the LOOP issue as affected by the l
submittal.
Thus, any amended contention must be filed by April 1st.
Sincerely, David R.
Lewis Counsel for the Sacramento Municipal Utility District Enclosures cc:
Service List 9303300185 930318 PDR ADOCK 05000312 C
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$SMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT C P o. Box 15830, Sacramento CA 95852-1830,(916) 452-3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CALIFORNIA MEMORANDUM Subj:
Basis for LOOP Frequency Determination Date:
March 17, 1993 Section 5.3.1.2 of the Supplement to Rancho Seco Environmen-tal Report--Post Operating License Stage (ER) states:
During normal plant operations, it is important that elec-trical power be available to support equipment needed to operate the plant and mitigate the consequences of an acci-i dent.
During Custodial-SAFSTOR, a LOOP would result in the loss of the Spent Fuel Cooling System (SFC).
However, there is adequate time available to take corrective action without a safety consequence in the event of a LOOP.
RSNGS has six offsite power transmission lines and has the capability to receive power from either the District or Pacific Gas and Electric in less than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
An evalua-tion of the offsite electrical grid for RSNGS performed pur-suant to 10 CFR 50.63 " Loss of All Alternating Current Power" (Station Blackout) verified the stability of the Western grid.
The probability of a LOOP at RSNGS, as evaluated in accor-dance with the guidelines of Regulatory Guide 1.155, is less than once in 20 years.
Therefore the emergency diesel gen-erators are not required-to ensure power availability to support SFC equipment in the event of a LOOP.
An alterna-tive power supply can be made available well.within the min-imum time required to restore SFC.
A LOOP will not result I
in a release of any significant amount of SFP inventory of radioactivity.
The statement concerning-the probability of a LOOP at Rancho i
Seco in the third paragraph of section 5.3.1.2 of the ER relates l
to the Station Blackout evaluation identified in the second para-graph of this section, and more specifically, to the verification RANCHO SECO NUCLEAR GENERATING STATION D 14440 Twin Cities Road, Herald. CA 95638-9799;(209) 333-2935
.4 f
I of the stability of the Western grid.
Determination of LOOP fre-quency is one element of the Station Blackout evaluation required for light water reactors licensed to operate.
See 10 C.F.R.
S i
- 50. 63 (a) (1) (iii).
The Station Blackout evaluation for Rancho Seco, performed prior to the shutdown, was summarized in a letter from J.
Firlit to T. Murley, "10 CFR 50.63 ' Loss of'All Alternat-ing Current Power,'" CEO-89-161 (April 17, 1989) and is enclosed.
This evaluation determined that the " Expected frequency of grid-related Losses of Offsite Power (LOOPS) does not exceed once per 20 years."
Id.,,
page 1.
The Station Blackout evaluation was performed in accordance with NRC Regulatory Guide 1.155, " Station Blackout" (Aug. 1988),
j i
which is enclosed.
Reg. Guide 1.155 endorses NUMARC 87-00, l
" Guidelines and Technical Basis for NUMARC Initiatives Addressing i
e Station Blackout at Light Water Reactors" (Nov. 1987), also l
i i
~ ~y compliance l
enclosed hereto, as an acceptable method of show l
with 10 C.F.R. 50.63.
Reg. Guide 1.155 at 3.
The acceptability of NUMARC 87-00 is also reflected in the Statement of Consider-l' l
ations issued by the Commission in support of the Station Black-l out rule.
53 Fed. Reg. 23,203, 23,214 (1988).
a
]
Reflecting the requirements of the Station Blackout rule (10 l
i 4
l C.F.R.
S 50.63 (a) (1)), section 3.1 of Reg. Guide 1.155 calls for l
j specification of a minimum station blackout duration based on l
t several factors including the expected frequency of loss of
)
offsite power.
Reg. Guide 1.155 incorporates the factors into a 3
number of-tables which may be used to identify a facility's
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.t' Offsite Power Design Characteristic Group and Emergency AC Power Configuration Group.
These two groupings, coupled with the facility's average emergency diesel generator reliability, deter-i mine the acceptable blackout duration capability for an operating nuclear power plant.
LOOP frequency is considered in the tables l
identifying a facility's Offsite Power Design Characteristic Group.
See Reg. Guide 1.155, Tables 2 through 8.
Table 1 of Reg. Guide 1.155 cross-references section 3 of NUMARC 87-00 for l
these determinations.
NUMARC 87-00 breaks the step of determining the Offsite Power Design Characteristic Group into five parts.
NUMARC 87-00 at 3-2 to 3-3.
The first part of this step is to determine Site Susceptibility to Grid-Related Loss of Offsite Power Events.
Id.
at 3-2.
In this regard, NUMARC 87-00 states:
Grid-related loss of off-site power events are defined as l
LOOPS that are strictly associated with the loss of trans-mission and distribution system due to insufficient generat-1 ing capacity, excessive loads, or dynamic instability.
Although grid failure may also be caused by other factors, such as severe weather conditions or brush fires, these t
events are not considered grid-related since they were caused by external events.
t The industry average frequency of grid-related events is l
approximately 0.020 per site year, with most events isolated to a few systems.
According to NUREG-1032, the average
}
occurrence for the majority of systems is about once per 100 y
site-years.
NUREG-1032 notes sites having a frequency of i
grid-related events at the once per 20 site-year frequency are limited to St. Lucie, Turkey Point, and Indian Point.
1 Accordingly, no other sites are expected to exceed the Once per 20 site-year frequency of grid-related loss of off-site power events.
PLANTS SHOULD BE CLASSIFIED AS P3 SITES IF THE EXPECTED FREQUENCY BASED ON PRIOR EXPERIENCE OF GRID-RELATED EVENTS EXCEEDS ONCE PER 20 YEARS.
THIS DOES NOT l
INCLUDE EVENTS OF LESS THAN 5 MINUTES DURATION.
EVENTS i
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r
=_
i i M OF LONGER DURATION MAY BE EXCLUDED IF THE RESULTS OF ANALYSIS CONCLUDES THE EVENT IS NOT SYMPTOMATIC OF L
UNDERLYING OR GROWING GRID INSTABILITY.
Id. at 3-3 (footnotes omitted).
Applying this methodology, the District determined that the expected frequency of a grid-related LOOP affecting Ranch Seco is j
less than once per twenty years based on prior experience and the frequencies indicated in NUREG-1032, " Evaluation of Station Blackout Accidents at Nuclear Power Plants, Technical Findings Related to Unresolved Safety Issue A-44: Final Report" (June 1988) (pertinent portions enclosed).
Rancho Seco has never expe-rienced a LOOP in its 21 year operating history.
Based on empir-ical data, NUREG-1032 identifies only three plants (St. Lucie, f
Turkey Point, and Indian Point) having a grid-related LOOP fre-4 t
quency greater than once per twenty years.
NUREG-1032 at A-13.
l d
This conclusion and empirical data are in turn derived from NUREG/CR-3992, R.E.
Battle, " Collection and Evaluation of Con-2 l
plete and Partial Losses of Off-site Power at Nuclear Power i
Plants" (Feb. 1985), and NSAC/103, Electric Power Research Insti-tute, H. Wycoff, " Losses of Offsite Power at Nuclear Power Plants f
i All Years Through 1985" (May 1986).
-i The next two parts of the step of determining the Offsite I
i i
Power Design Characteristic Group involve estimating the esti-l mated frequency of LOOPS due to severe weather and extremely v
i severe weather.
These determinations are based on the calcula-f i
tions specified in Tables 6 and 8 of Regulatory Guide 1.155 and i
meteorological data.
NUMARC 87-00 tabulates Severe and Extremely j
i
-4 i
4
1 l
Severe Weather provided by the NRC Staff for each plant.
See NUMARC 87-00, Tables 3-2 and 3-3.
Utilizing this data, supplemented by meteorological data from the Updated Safety Analysis Report, and the methodology specified in Reg. Guide 1.155 and NUMARC 87-00, the District cal-culated an estimated frequency of a LOOP due to severe weather
~3 affecting Rancho Seco of less than 3.3 x 10 per site year, and the annual expectation of extremely severe weather in the range of 1 x 10~
to 3.3 x 10 These determinations, including the l
~
data and methodology, are documented in SMUD Calculation Z-EDS-E0817, which is enclosed.
In addition to grid-related and weather-related LOOPS, there i
is a possibility of a " plant centered" LOOP at operating nuclear plants.
Plant centered failures may involve hardware or design problems at a plant, human error in maintenance and switching, f
localized weather induced faults (lightening) or combinations of these failures.
As reported in NUREG-1032, there is no statisti-cally significant relationship between frequency of plant cen-tered losses of offsite power and design features analyzed; how-ever, the independence of power sources was found to be a deter-minant in the restoration time associated with a plant cer.tered 1
LOOP.
NUREG-1032 at 3-3 to 3-4, and A-5.
Of the total LOOPS at nuclear power plant sites through 1985, plant-centered LOOPS have i
occurred more frequently than grid and weather-related LOOPS, but recovery is typically accomplished within a few hours.
Id. at i
3-3 to 3-4.
l.
1 Reg. Guide 1.155 and NUMARC 87-00 do not require licensees to attempt to quantify a frequency of plant-centered LOOPS.
Instead, the possibility of such a LOOP is addressed indirectly by consideration of the Independence of offsite Power Sources (which as noted above is a determinant in the restoration time associated with such LOOPS).
This is the fourth part of deter-mining the Offsite Power Design Characteristic Group.
See NUMARC 87-00 at 3-2.
See also Reg. Guide 1.155 at 4 and Tables 4 and 5.
Although there is no requirement to estimate plant-centered LOOP frequency, it should be noted that during its 21-year oper-ating history, Rancho Seco has not experienced any plant-centered LOOP.
None of the plant-centered LOOPS reflected in the empiri-cal data analyzed in NUREG-1032 relate to Rancho Seco.
See NUREG-1032 at A-9.
Thus, there is no historic basis to expect more frequent plant-centered LOOPS at Rancho seco.1/
1/
lit should also be remembered that recovery from plant-centered LOOPS can be accomplished within a few hours.
In comparison, as of the June 7, 1991 decay. heat levels, 17.7 days is available to implement corrective action and spent-fuel cool-ing capability.
ER at 5-7.
Consequently, the possibility of a short-duration plant-centered LOOP is immaterial to a permanently shut down reactor such as Rancho Seco.
d 1
Enclosures:
f A.
Letter from J.
Firlit to T. Murley, "10 CFR 50.63 ' Loss of i
All Alternating Current Power,'" CEO-89-161 (April 17, 1989).
B.
Regulatory Guide 1.155, " Station Blackout" (Aug. 1988).
C.
NUMARC 87-00, " Guidelines and Technical Basis for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors" l
(Nov. 1987).
L D.
NUREG-1032, dtvaluation of Station Blackout Accidents at l
Nuclear Power Plants, Technical Findings Related to Unresolved Safety Issue A-44, Final Report," Chapters 1-3 and Appendix A (June 1988).
E.
SMUD Calculation Z-EDS-E0817.
i M:/0329/033D E.93 i
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION i
Before the Atomic Safety and Licensing Board In the Matter of
)
)
Docket No. 50-312-DCOM SACRAMENTO MUNICIPAL UTILITY
)
DISTRICT
)
(Decommissioning Plan)
)
(Rancho Seco Nuclear Generating
)
ASLBP No. 92-663-02-DCOM Station)
)
1 CERTIFICATE OF SERVICE I hereby certify that the foregoing Memorandum entitled
" Basis for LOOP Frequency Determination," dated March 17, 1993, was served upon the persons listed below by deposit'in the U.S.
Mail, first class, postage prepaid, or where indicated by an asterisk, by hand delivery, this 18th day of March, 1993.
The enclosures to the memorandum were provided only to James McGranery, Esq. and the Atomic Safety and Licensing Board.
Commissioner Ivan Selin, Chairman Administrative Judge U.S.
Nuclear Regulatory Commission Dr. Richard F.
Cole Washington, D.C.
20555 Atomic Safety and Licensing Board U.S.
Nuclear Regulatory Commission Commissioner Kenneth C.
Rogers Washington, D.C.
20555 U.S.
Nuclear Regulatory Commission Washington, D.C.
20555 Administrative Judge Mr. Thomas D. Murphy Commissioner James R. Curtiss Atomic Safety and Licensing Board U.S.
Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission l
Washington, D.C.
20555 Washington, D.C.
20555 i
commissioner Forrest J. Remick Charles A. Barth, Esq.
U.S.
Nuclear Regulatory Commission office of the General Counsel Washington, D.C.
20555 U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Commissioner E. Gail de Planque U.S.
Nuclear Regulatory Commission Jan Schori, Esq.
Washington, D.C. 20555 General Counsel Sacramento Municipal Utility District Administrative Judge P.o. Box 15830 Charles Bechhoefer, Esq., Chairman Sacramento, CA 95813 Atomic Safety and Licensing Board U.S. Nuclear Regulatory Commission office of the Secretary Washington, D.C.
20555 Attn:
Docketing and Service Branch U.S. Nuclear Regulatory Commission Washington, D.C.
20555 t
R a
\\",
Adjudicatory File
- James P. McGranery, Jr., Esq.
Atomic Safety and Licensing Board 1255 - 23rd Street, N.W.
U.S. Nuclear Regulatory Commission Suite 750 Washington, D.C.
20555 Washington, D.C.
20037 office of Commission Appellate Adjudication U.S. Nuclear Regulatory Commission Washington, D.C.
20555 P
i
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r-David R.
Lewis l
0124/030 tab.93
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