ML18046A497
| ML18046A497 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 03/11/1981 |
| From: | Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-02-02.A, TASK-2-2.A, TASK-RR NUDOCS 8103160501 | |
| Download: ML18046A497 (4) | |
Text
consumers Power company General Offices: 212 West Michigan Avenue, Jackson, Michigan 49201 * (517) 788-0550 March 11, 1981 Director, Nuclear Reactor Regulation Att Mr Dennis M Crutch.field, Chi.ef Operating Reactors Branch_ No 5 U S Nuclear Regulatory Commiss.ion Washington, DC 20555 DOCKET 50-255 - LICENSE DPR-20 ~ PALiqADEQ PLANT - SEP TOPIC II-2.A -
SEVERE WEATHEB PHENOMENA By letter dated Novemher 2.1, 1280., the. NRC transmitted its. evaluati_on of SEP Topic II-2.A,, Severe Weather Phenomena, for the Palisades Plant site.
Consumers Power Company has completed a revi.ew of this docUm.ent, and provides the following conrrnents for your considerati*on.
General:
The values selected by the NRC fer extreme.temperature, lightning strikes, snow and ice loads and wind and tornado loadings were verified against clima-tological data selected to be representative of site conditions-.
All parameters except the wind and tornado loading were verified against the climatological data recorded for the Benton Harbor FAA weather station.
Climatological data recorded for the Muskegon National Weather Service station were used to verify the wind loading value.
Current guidelines for estimating tornado and eXtreme wind characteristics were used to verify the tornado loading values.
Specific references are listed in Attachment 1.
Extreme Temperatures:
Normal daily temperatures at Benton Harbor range from a minimum of 14°F in January to a maximum of 80°F in July.
Measured extreme temperatures were 109°F and -21°F.
Based on these numbers, the extreme maximum and minimum temperatures of 90°F and -1°F selected by the NRC appear appropriate.
Lightning Strikes:
Thunderstorms occur an average of 42 days per year in the Benton Harbor area.
Using a strike factor of.37 strikes per sq mile per thunderstorm day, the calculated annual flash density is 6 strikes per sq kilometer.
8J0816050l
Mr Dennis M Crutchfield, Chief Palisades Plant March 11, 19 81 2
A structure such as a 160 ft (height above upper site grade) reactor building can be expected to be subjected to one strike every 3 years.
The strike re-currence frequency is highly dependent on the dimensions used for the structure.
Although the NRC did not state the dimension used in their analysis to get a strike recurrence frequency of 6 years, the difference between the two values can probably be attributed to the difference in structure dimensions used.
The NRC value of one strike every 6 years appears reasonable.
Ice Loanding:
Using local climatological data, we were unable to verify the values selected by the NRC of 2 days per year for hail storm occurrence, 12 days per year for freezing rain occurrence and 1.75 inches for maximum radial thickness of ice.
The values for hail and freezing rain are consistent with values determined for our Midland Plant site, and therefore appear to be acceptable. It is not apparent that the NRC value for maximum radial ice thickness was intended to take into account the local effects of the cooling towers.
In the past, some winter icing has been observed on the transmission lines and towers in the immediate vicinity of the plant.
As a result of these observations, the first two line towers adjacent to the plant were replaced in 1977 with stronger towers designed for radial ice thicknesses of up to five inches. It is believed that these towers are easily capable of withstanding any local ice loading which may occur in the future.
Except as discussed above, significant icing has not been observed on other local plant structures..
Design Wind Speed:
An acceptable site value for design wind speed, defined as the "fastest-mile" wind speed at a height of 30 feet above ground level with a return period of 100 years, should be 62 MPH.
This value was derived from the Muskegon National Weather Service station climatological data (annual extreme "fastest-mile" recorded wind speed) for the period 1960-1980.
The data were adjusted to the 30 foot level using a 1/7 power iaw exponent, and analyzed using a Fisher-Tippett Type I extreme value distribution.
The NRC value of 85 MPH is based on data collected from the Grand Rapids National Weather Service station.
The occurrence of the "fastest-mile" wind speed will generally be associated with thunderstorm activity which will intensify as the storm moves in-land from the lake shore.
Therefore, Grand Rapids would be expected to record a much higher wind speed than that recorded at the Muskegon station or at the Palisades site.
For this reason, it is felt that the value of 85 MPH is too extreme and the value of 62 MPH is more representative of Palisades Plant site conditions.
Snow Load:
Mean annual snowfall at Benton Harbor is 58.2 inches.
The heaviest single-day snowfall was 25.0 inches and occurred on December 6, 1937.
The largest recorded snow depth was 35 inches recorded on December 17, 1937.
The 100 year recurrence accumulated ground snowpack for Benton Harbor is 41 inches which corresponds to a snow load of 58 lb ft2.
This snow load value is based on a snowpack density of.25 gm/cm3 and maximum measured snow depth data at Benton
Mr Dennis M Crutchfield, Chief Palisades Plant March 11, 1981 3
Harbor for the period 1949-1977.
The cata were analyzed using a Fisher-Tippett Type I extreme value distribution.
Based on the 100 year recurrence accumul(~Jd ground snowpack and a suggested probable maximum winter precipitation value of 6.7 inches of equivalent water for the site region, the extreme winter pre-cipitation snow load at the plant site is 93 lb/~2. This value agrees with the NRC selected value of 90 lb/ft2.
Tornado Loading:
The NRC values of the design basis tornado parameters from Regulatory Guide 1.76 are not consistent with either the recorded tornado frequency and intensity data for the site region, or with the current state of knowledge or tornado and extreme wind characteristics.
More current guidance (1) for the characteristics of a design basis tornado for the site region suggest the following characteristics:
- 1.
Maximum wind speed of 300 MPH (combined rotational and translational).
- 2.
Maximum translational wind speed of 65 MPH.
- 3.
Maximum pressure change of 1.96 PSI.
The above design basis tornado characteristics are more representative of the site and should be used instead o~ the RG 1.76 characteristics.
Since the lake shore environment of the Palisades Plant site exerts an additional moderating influence on severe storm intensity which has not been taken into account, the above parameters are still considered to be conservative.
Rober A Vincent Staff Licensing Engineer CC JGKeppler, USNRC NRC Resident Inspector-Palisades Attachment ( 1 page)
ATTACHMENT l References
- l.
Guidelines for Estimating Tornado and Extreme Wind Characteristics at Nuclear Power Sites, ANSI N-l78, Draft 2, Revision 4 (l980), American National Standards Institute
- 2.
Local Climatological Data, Pellston, Michigan (1949-1977), US Department of Commerce, National Oceanic and Atmospheric Administration, Environmental Data Service
- 3.
Local Climatological Data, Muskegon, Michigan ( 1960-1980), US Department of Commerce, National Oceanic and Atmospheric Administration, Environmental Data Service
- 4.
Climate of Michigan by Stations, Michigan Department of Agriculture
- 5.
M A Bile. LLO, "Relationship Between Climate and Regional Variations in Snow-Cover Density in North America", Research Report 267 (December 1969),
Corps of Eng~neers, US Army, Cold Regions Research and Engineering Labora-tory, Hanover, NH
- 6.
"Seasonal Variations of the Probable Maximum Precipitation East of the l05th Meridian for Areas from lO to l,000 Square Miles and durations of the 6, 12, 24 and 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />", Hydrometeorological Report, No 33 (1956), US Weather Bureau
- 7.
NUREG/ CR-1389, "Estimating Water Equivalent Snow Depth from Related Metero-logical Variables", US Nuclear Regulatory Commission, Washington, DC
- 8.
D Bodle, Electrical Protection Guide for Land-Based Facilities.
JES-159-3-3M l/74 (.1971), Joslyn Electronic Systems