ML19350C883
| ML19350C883 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/06/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8104080390 | |
| Download: ML19350C883 (6) | |
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400 Chestnut Street Tower II April 6, 1981 Director of Nuclear Reactor Regulation Attention:
Mr. A. Schwencer, Chief Licensing Branch No. 2 Division of Licensing U.S. Nuclear Regulatory Cen=issicn Washington, DC 20555
Dear Mr. Schwer.c.er:
In the Matter of the Application of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 Ites 2.C(4) of the Sequoyah Nuclear Plant unit 1 operating license requires TVA to submit analyses of the vulnerability of the ERCW intake structure to barge collision. TVA submitted a response en Dece=ber 31, 1980, which has been reviewed by the NRC staff. A revised response is enclosed which addresses the NRC staff concerns defined in the meeting with TVA en March 26, 1981. Enclosure 1 is an analysis of the probability of a barge collisien, and Enclosure 2 is an analysis of the resulting explosion ha::ard.
Very truly yours, TENNESSEE VALLEY AUTHORITY N1h d
L. M. Mills, Fhnager Nuclear Regulation and Safety Sworn t and subsce.ibed, before ce this/h ti day ofbCuI.
1981
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My Ccmission Expires e
Enclosures 3
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81040 80 Mo 9
ENCLOSURE 1 SEQUOYAH NUCLEAR PLANT ERCW INTAKE PUMPING STATION PR03 ABILITY OF TOW COLLISION The collision of a tow with the ERCW intake pu= ping station is considered to be an unlikely event. The n6W intake structure is protected by location from collision with river traffic heading downstream for water surfaces up to elevation 705, which is 22 feet above maximum normal pool level and 15 feet above a ficod condition equivalent to one half the Probable Maximum Flood. As reported in a previous response, the probability per year of a collision with a drifting barge hea 4.4 X 10~ging downstream is conservatively estimated to be Theprobabilityofacollisiongnvolvingatowheading
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upstream has been determined to be 1.6 X 10 / year. The following considerations are applicable.
1.
Tow operators on the Tennessee River have been required to be licensed by the U.S. Coast Guard since 1972. A requirement for this license is that they must abide by the Western Rivers Rules of the Road. These rules provide that only tows having radar =ay proceed during inclement weather while those not having radar must tie up.
The U.S. Coast Guard has stated that the type of s
shoreline and mooring cells in the vicinity of Sequoyah Nuclear Plant afford excellent radar protection. The plant is located between Tennessee River Mile (TRM) 484 and 485; first class safety harbors are located near TRM 483 and 489. The Coast Guard has further stated that the present channel c:arkings are more than sufficient for a prudent navigator. The pumping station is well outside the navigation channel (approximately 300 feet from the boundary) and a daymarker and light is located on the far side of the channel directly opposite the. plant to guide upstream traffic away from the plant.
2.
Sequoyah Nuclear Plant is located on the convex bank of a bend in the Tennessee River channel. Upstream tows attempting to cut short the navigation of the bend would have a difficult angle of approach to the pumping station. As addressed in a previous response, tows losing power in the bend and drifting will drif t toward the shoreline opposite the intake structure.
The probability of 1.6 X 10~$ collisions / year was obtained using the following information. The calculation is believed to be conservative.
1.
Data available for the years 1945-1979 was searched for barge groundings on the Chickamauga Reservoir. Of the 10 groundings found, 7 were not applicable because of grounding during inclement weather before 1972 or because of intentional grounding caused by loss of power. A range of 40 35 miles (40.35 X 5280 X 2 feet) of shoreline and a total of 19,674 tows during these years were involved. This yields a probability of ggnding per tow per foot of shoreline on the reservoir of 3 6 X 10
2.
The target length of the intake structure susceptibility was conservatively taken as 200 feet.
(The intake structure is 118 feet by 67 feet.) The average nu=ber of tows heading upstrea: past the intake structure during 1974 to 1979 was approxi=ately 225 per year. The nulber of tows en the Chicka=auga Reservoir reached a peak in 1970, but has been roughly unifor: during 1974 to 1979 and is believed to be a good indication of the expected nu=ber of tows for the next sevegal years. The probability is therefore calculated as 3.6 x 10 groundings per tcw per foot of shoreline x 200 feet x 225 tows per year = 1.6 I 10" collisiens/ year.
An evaluation of the navigation capabilities and require =ents for navigation through this section of the river, =ile 484 to 4c5, was conducted. This evaluation provides a strong qualitative rationale that the expected rate of occurrence of an upstrea: barge i= pact On the ERC'4 pu= ping station is very unlikely ec= pared to the randc=
probability of a tcw grounding.
T7A is confident that the real expected rate of occurrence of barge,
i= pact en the ERC'4 is far less than the calculand value of 1.6 x 10-3 events per year. T7A's understanding of the inadequately docu=erted events has led to the conclusion that the calculated randc= probability of hitting a pcrtside bank (tow traveling upstrea=) at the Sequcyah river location is obviously very conserva*ive. TVA has atte=pted to develop quantitative =ethodology to represent the phenc=ena, but has been unable to achieve agree =ent with the NRC staff en this
=ethodology.
Discussiens with the U.S. Coast Guard revealed the following infor=a-tien about the potential for a barge tow to accidentally ecilide (direct impact er otherwise) with the ERC'4 pu= ping staticn.
The certified barge tug pilot pri=arily navigates in the traditicnal
" river-pilot" =anner, which is by (1) experience, (2) line of sight to land arks (3) U.S. Corps of Engineers chart (updated annually), and (4) the Coast Guard 'destern Rules of the Road. However, the codern (1981) river tus pilot is gen; rally equipped with depth finders (senar fatho:c=eters), range findig radars, electrcnics to define water and wind vectors, two-way radic, and electronic status indication of operational syste=s. The development and upgrade of =odern navigational aids, as well as a =cre reliable propulsion syste=, ensures an increasingly accurate, effective navigaticn of the river by targe pilots.
In all weather, the positien, without electronic aids, is known to less than 200 feet, and, with navigational electronics, to less than 50 feet. On Lake Chicka=auga, in the traverse by the Sequoyah Nuclear Plant, the position is very well defined because there are buoys every
.2 =ile en the port and starboard sides (a total of 14); there are five navigatica lights; the river and riverbank topographv is unusually distinctive; and there are distinctive land = arks (the Sequoyah cooling towers and power trans=issien lines). The radar equipped beat uses the trans=issicn lines as the pri=ary position locator. A river pilot going upstrea: by Sequoyah will choose to go en the starboard side because of courtesy ('destern Rules of the Road) and because of the need to efficiently and safely navigate an "s" curve through this traverse.
P l
The upstream barge is surprisingly maneuverable. A barge can =ake a 180 change in course without emergency measures in about twice the length or tow (i.e., within 400 to 800 feet). An upstream barge can a
make a 90 controlled turn in less than.2 =11e under typical conditions, i.e., current (2-1/2 knots), wind (10 knots), and power (single screw). If a tug loses propulsion in upstream traverse, he still has effective stearage for 1/4-1/2 mile (approximately 3-6 minutes, worst case). The pilot can make emergency stops by slipping an anchor or a, spud. An upstream barge can easily be piloted to hit a target area 90 to port or starboard within 25 feet under bad conditions and within 5 feet under good conditions. Therefore, a certified river pilot, even in extremis (defined as "must take emergency measures to avoid trouble or to ground his tow"), can and would avoid the ERCW.
The ERCW is a significant structure, which is well =arked and lighted as a navigation hazard. In extremis, a pilot will select the best course of action from an economic and safety standpoint. And, in a traverse by the Sequoyah ERCW, he will most likely attempt a grounding on an underwater shoal to his starboard side (the Denny Bluff Shoal).
The river barge pilot is a U.S. Coast Guard certified pilot, whose license is renewed annually and who has periodic physical and proficiency examinations. If a pilot is suspected of malfeasance, a suspension and relocation proceeding is conducted. No cases of malfeasance or of reported drunkenness have occurred on the north Tennessee River in the last five years.
0 i
ENCLOSURE 2 SECUOYAH NUCLEAR PLANT ERC'4 INTAKE STRUCTURE - EXPLCSION HAZARD In response to concerns raised by the ACRS, the possibility of a barge explosien in the vicinity of the new ERC'4 pu= ping station has been reviewed. Our respense is as follows:
(1) The ACRS identified liquid natural gas (LNG) as a substance to be considered in an exploding barge scenario. From our review of the barge shipments past Sequoyah for calendar year 1978, there were no shipments of LNG cn the Tennessee River. It should be noted that barge ship =ents of LNG past Sequoyah are not likely since natural gas transportation is handled almost entirely by pipeline in this regicn. Therefore, we do not censider the potential for an exploding LNG barge near the new ERC'4 pumping station to be a credible event.
(2) Contrary to the information in FSAR Table 2.2-1, there were, in calendar year 1978, shipments of unspecified fertilizers past the Sequoyah Nuclear Plant. Hence, the possibility of an accidental explosion =ust be considered.
In 1966, the U.S. Bureau of Mines issued a study entitled
" Explosion Hazards of Ac= onium Nitrate Under Fire Exposure,"
which exacined the deflagration and detonation hazards associated with Ac= onium Nitrate (AN). The study indicates:
(a) Ordinary fertilizer-grade AN requires strong overpressures to initiate detonation within the sixture.
(b) AN and AN-fuel =ixtures were exposed to fire with no transition from deflagration to detonation being observed.
(c) A combination of fire and overpressure results in transition to detonation. However.infree-ficwingbedsofgNand AN-fuel =ixtures, pressures as high as 8000 lb/in did not generate detonation. Only in experiments where the AN was not allowed to ficw freely was transition to detonation observed ip the AN-fuel =ixture at pressures above 1000 lb/in, but not with pure AN.
(d) It was fcund that hot AN (under fire exposure) readily detonated when impacted with a high velocity projectile or shock wave. Explosions in storage and ship =ents of AN have apparently resulted only when nearby explosions er structure collapse have occurred concurrent with fire in the AN.
I (e) Gas detonations have ceen shown 'ncapable of initiating detonation in AN sixtures. In general, fertilizers shipped on the Tennessee River employ diato=aceous earth and kaolin clay for anticaking dusts rather than using oil sealant, thus detonations are possible only in cargces where fire and missiles or external detonation are present. Most bulk fertilizers with earth or clay mixtures will not burn without mixing a considerable a=ount of paper or flac=able material into the fertilizer.
Based on the insensitivity to detonation exhibited by cost co==on fertilizers, the unlikely sequence of events required for detonation cust include: Barge collisien, fire in the fertilizer cargo, and concurrent detonation or missile-inducing event.
Therefore, given the low probability of a barge collision and the icw percentage of fertilizer shipments on the Tennessee River, it is concluded that, because of the very low probabilities associated with the event, no hazard exists to the intake pumping station from the transportation of fertilizers by barge en the Tennessee River system.
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