ML19290A342
| ML19290A342 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/26/1968 |
| From: | US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML19290A343 | List: |
| References | |
| NUDOCS 7911060581 | |
| Download: ML19290A342 (12) | |
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APR 2 61968 ADDENDUM TO THE SAFETY EVALUATION BY THE DIVISION OF REACTOR LICENSING U.S. ATOMIC ENERGY EMMISSION IN THE MATTER OF METROPOLITAN EDISON COMPANY (THREE MILE ISLAND NUCLEAR STATION UNIT 1)
DAUPHIN COUNTY, PENNSYLVANIA DOCKET No. 50-289 1556 001 7911060 D
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s P00RBR'8 NIL TABLE OF CONTENTS Page 1.0 INIRODUCTION 1
2.0 STATISTICAL ANALYSIS 2
3.0 IMPACT Al@ FIRE EFFECTS PROTECTION 5
4.0 REPORT OF THE ADVISORY COMMITTEE ON REACTOR SAFEGUARDS 9
5.0 CONCLUSION
9 Appendix A - Report of the Advisory Consnittee on Reactor Safeguards 10 Appendix B - Chronology of the Regulatory Staff's Review, continued 12 1556 002
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1.0 INTRODUCTION
This addendum to our Safety Evaluation In the Matter of Metropolitan rdison Company (Three Mile Island Nuclear Station, Unit 1) deals with the matter of proximity of the proposed facility to an airport which was the subject of Amendments 8, 9 and 10 to the application. The proposed Three Mile Island Nuclear Station would be located about 10 miles south of Harrisburg, Pennsylvania and about 2.5 miler southwest of the eastern end of Olmsted State Airport, formerly Olmsted Air Force Base. The plant is to be located about 1.4 miles from the center of the eastern instrument glide approach path to the runway. The runway length is 8000 feet with a 1000-foot extension on each end. The relation-ship of the proposed plant to the airport is shown on Figure A-1 of Supplement 5
( Amendment 8) to the applicant's Preliminary Safety Analysis Report (PSAR) which is a part of the application in this proceeding. Air traffic patterns near the site were described in answer to Question 2.6.3 of Supplement 1 ( Amendment 2) to the PSAR.
During the course of our review of Amendments 8, 9 and 10 to the application we have met with representatives of the U.S. Federal Aviation Agency (FAA) and the Bureau of Safety of the National Transportation Safety Board of the U.S.
Department of Transportation. The FAA administers U.S. air traffic and air safety regulations. The Bureau of Safety is responsible for the investigation of air crashes involving commercial aircraft and for making recommendations to the FAA on air safety matters.
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s 2-We have been assisted in this review by our consultants Mr. James Proctor of the U.S. Naval Ordnance Laboratory, Dr. Nathan M. Newmark of Newmark Consulting Engineering Services, and Mr. Irving Pinkel of the Lewis Research Center, U.S.
National Aeronautics and Space Administration.
2.0 STATISTICAL ANALYSIS The applicant has submitted in its application, and we have reviewed, statis-tical information relating to aircraf t crashes obtained from the Bureau of Safety.
In addition, the staff has obtained from the Bureau of Safety, as well as from the FAA, certain supplemental and confirmatory information. On the basis of this combined information we have concluded that the statistical data on commercial aircraft crashes for the years 1956-1965 inclusive submitted in Amendments 8, 9, and 10 is substantially correct. We have also examined records for 1966 and 1967 crashes and find that the statistics for these years are similar to the previous 10 year period.
In arriving at the probability of an aircraft strike on the facility, the applicant assumed that an aircraft crash could present a hazard to the facility if it involved one or more fatality and if it occurred on approach or takeoff within 5 miles of a commercial airport. Crashes not involving fatalities were not considered since they would be low energy strikes and the pilot would probably have enough control to avoid the facility. We agree that the selection of acci-dents is acceptable for the probability study since this type of accident is the type which might cause significant consequences if it occurred at this plant site.
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, As presented in Figure A-2 of Supplement 5 ( Amendment 8), the applicant's statistical study indicated that (1) most takeoff and landing crashes occurred within 2 miles of a runway (22 of 27 fatal crashes in the aforementioned 10-year period) and (2) about one-half the takeoff crashes and most of the landing crashes occurred within one-half mile of an extanded runway centerline. However, because the proposed Three Mile Island facility will not be located within one-half mile of the extended centerline of the Olmsted airport, only crashes occurring further than one-half mile from an extended runway centerline were considered in the applicant's statistical study. The cpplicant also excluded from the statistical study those crashes which occurred within 1 mile of the end of a runway since such crashes would be inapplicable to the present situation because the facility is located some 2-1/2 miles from the end of the Olmsted runway. The remaining crashes were assumed to have an equal probability of occurrence anywhere between 1 and 4 miles from the end of the airport runway. On this basis the applicant's calculations indicate a chance of one in one million per year that an aircraft of any size would crash on any given area the size of the reactor plant. These calculations assumed 80,000 movements (takeoffs or landings) per year at Olmsted which is four times the present rate. The basis for this assumption is presented in Supplement 5 (Amendment 10).
Based on the assumptions utilized by the applicant, we performed similar probability calculations. However, we assumed equal probability of occurrence of crashes within a 1-mile band between 2 and 3 miles from the end of the runway, including crashes within one-half mile of the extended runway centerline. Our method and the applicant's method give similar results (within a factor of 3).
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-4 As discussed in Tg 2; tan 3.0 of this addendum, the applicant has proposed to provide protection for vital systems against impact and fire effects of all potential crashes except those from very large aircraft (Boeing 707 or larger).
Since these aircraft will constitute only a portion (presently 3%) of the total traffic into the airport, we agree with the applicant that the probability of a strike on facility structures by an aircraft larger than that used as a design basis is very small.
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t It should be noted that the facility is designed to withstand the effects of other phenomena such as large floods and tornadoes which have a probability of occurrence between one chance in 10,000 and one chance in one thousand per year of occurring. This probability is about a factor of 100 greater than an aircraft strike on the facility.
The probability of a fatal caumercial aircraft crash on the facility if it were located in a " medium" ovarflight area (50 flights per day) away from an airport would be about one chance in 30 million per year if it is assumed that the plane could crash anywhere in a 20-mile wide band.
Similarly, the probability of a general aviation (private aircraft) fatal crash in such an overflight area would be about one in ten million per year. The general avia-tion aircraft are generally small and would probably not present an knpact problem but could cause a fire hazard to an unprotectsd plant.
As discussed in Section 3.0 of this addendum, the applicant has proposed to provide protection for vital systems against impact and fire effects of all potential crashes except those from very large aircraft (Boeing 707 or larger).
Since these aircraf t will constitute only a portion (presently 3%) of the total traffic into the airport, the probability for a strike on the facility by a very large plane is very small.
In summary, we agree with the applicant that the probability of a strike on facility structures by an aircraft larger than that used as a design basis is very small and is about the same as a strike by any aircraft at a nuclear facility away from an airport which does not have the special design provisions proposed for the Three Mile Island Station.
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% 3.0 IMPACT AND FIRE EFFECTS PROTECTION The applicant has performed impact calculations for several strike-related loadings which include small, high density, missiles and large, somewhat crushable missiles. The small missiles correspond to aircraft engines and the large missiles simulate the entire aircraft. Detailed calculations were performed, assuming a vertical impact at the apex of the dome at a speed of 200 knots. We believe that this is a representative speed since the aircraft speed limit in this area is 180 knots and since the worst noncontrolled dive reported as a fatal crash in the 10-year period reached a speed of about 200 knots.
The applicant has stated, and we agree, that a vertical strike on the dome will, be the worst angle of strike on the containment building. Detailed calcula-tions will be performed by the applicant during construction to illustrate the capability of the containment to withstand a strike on the cylinder wall.
We agree that the 200,000-lb plane, impacted as described in Supplement 5, is an acceptable design basis for this facility.
Mr. James Proctor of the Naval Ordnance Laboratory, and Dr. Nathan M. Newmark have reviewed the applicant's calculations. On the bais of their review, we conclude that the containment can withstand a 200,000-lb aircraft. The 200,000-lb missile would be representative of aircraft presently using the Harrisburg airport except the Boeing 707 and would include such aircraft as the Boeing 727.
Although calculations. have not been performed on an bepact on the flat surfaces of other critical structures, the applicant has stated' that the buildings will be designed to withstand the same design basis loads as the containment structure. We believe that these design bases are acceptable.
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. The applicant has stated, and we agree, that the effects on vital components within the containment would be less severe for the design aircraft impact than would be associated with the maximum aarthquake.
In addition, a loss-of-coolant accident would not be caused by the aircraft strike. We also conclude, on the basis of our consultants' evaluations, that the tnpact of the small, high density, missiles postulated would not result in penetration of the containment.
Extensive provisions for detection of and protection from fuel fire effects are proposed by the applicant. We asked Mr. Irving Pinkel of the Lewis Research Center, NASA, to review the practicability of the proposed fire protection measures.
On the basis of our review and taking Mr. Pinkel's comments into consideration, we believe that the proposed intake design will provide a significant degree of pro-tection against fuel fire effects after a strike on or near the facility.
The proposed ventilation intake for the auxiliary building and control room will be in a tunnel extending about 130 feet from the nearest building.
Since the velocity of air in the tunnel is about 1000 feet per minute, it would take several seconds for a combustible gas mixture to travel from the intake to the isolation dampers, located near the building. This will allow sufficient reaction time to detect combustible gases and to close the dampers.
Not only must a combustible gas mixture be prevented from reaching the building interiors, however, but an explosion in the entrance of the tunnel must be prevented since overpressures could damage the tunnel isolation dampers. The applicant has proposed a water deluge system and a gaseous explosion-suppression system to ensure that no explosion could take place in the tunnel.
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, In accordance with Mr. Pinkel's recommendations, we will require that the applicant take into consideration the following points in the design of the fire protection systems.
(1) The spray droplet size must be small to be effective and the spray must be checked for proper droplet size distribution periodically throughout the plant lifetLee.
(2)
Location of the spray nozzles through the length and height of the tunnel must be such as to assure the requisite distribution of water spray over the entire tunnel volume.
(3)
Stratification of gases must be allowed for in the placement of com-bustible. mixture detectors within the tunnel.
(4) Further studies to show whether collection and combustion of gases in the exhaust hood could cause an overpressure. which should be prevented by installation of a deluge system should be performed.
(5)
Attention must be given to obtaining and maintaining high quality detection instrumentation which would actuate the protective devices.
In addition to the above, we believe that attention must be given in the final design to assure that rapid actuation of the deluge system is not prevented by other crash effects, such as an aircraft Lapact on the water tower which would remove the static pressure head on the system. This could be accomplished either by a protected water source or by location of the water tower such that a crash could not affect both the tower and the air intake.
It should be noted that af ter the initiation of the spray deluge system, a pumping system, redundant in active components, would be actuated which would continue to supply water to the sprays and we believe this long-term arrangement is acceptable.
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s The applicant has provided examples of the means proposed to prevent air-craft fuel in liquid or vapor form from entering building doors and from gaining access to lower floors of the auxiliary building. These provisions are accept-able in concept.
We believe that all of the above points are anenable to design. We will review the proposed design provisions in detail at the tLme of the operating license review to ensure that the stated design criteria are met, that our requirements are satisfied and that inadvertent actuation of the protection systems will not present a hazard to plant equipment or personnel.
We also reviewed the redundancy of on-site and off-site power and decay heat removal systems and believe that the systems proposed provide reasonable assurance that a safe shutdown could be achieved after an aircraft strike on the facility. To ensure that feedwater for decay heat removal could be delivered to the steam generators even if all steam lines were broken (resulting in a loss of water inventory in the generators before the steam line isolation valves closed) one of the emergency steam driven feedwater pumps will be replaced by two 1/2-capacity electrical pumps. After the water inventory is restored by an electrical pump and the isolation valves closed, the steam-driven feedwater pump could again be used. We believe that this arrangement is acceptable. The appli-cant has calculated, and we agree, that the recctor will remain subcritical under all steam line break conditions.
It is unlikely that an aircraft strike would remove the access bridge to the site and at the same tLae present a fire hazard to the plant since the bridge is about 2000 feet away from the vital structures.
Immediate access to the site 1556 011
4 would not be required it the bridge were damaged since the plant has the capability to be shut down by the operators within the facility even if off-site power is not available as described in our Safety Evaluation. Since protection against fire effects is provided for the vital structures, fires caused by aircraft impacts which are externr1 the vital structures would not have to be immediately extinguished to accomplish the safe shutdown.
4.0 REPORT OF THE ADVISORY COMMITTEE ON REACTOR SAFEGUARDS The Advisory Committee on Reactor Safeguards ( ACRS), by letter to Chairman Seaborg dated April 6,1968, supplemented their report on the Three Mile Island Nuclear Station Unit 1.
A copy of the April 6, 1968, letter is attached as Appendix A to this report.
Amendments 8, 9, and 10 were submitted after the Committee issued its letter of January 17, 1968.
As a result of its review of these amendments, the Committee "... reaffirms its previous conclusion that, if suitable attention is given to the various items mentioned in the Committee's report of January 17, 1968, the proposed reactor can be constructed at the Three Mile Island site with reasonable assurance that it can be operated without undue risk to the health and safety of the public."
5.0 CONCLUSION
S We agree with the applicant that the probability of a damaging aircraft strike on the facility is very low and that the proposed protection against impact and fire effects significantly further reduces the probability of damage to the facility.
Our conclusions as set forth on pages 57 and 58 of the Safety Evaluation In the Matter of Metropolitan Edison Company, dated February 5,1968, which consti-tutes the staff's direct testimony in this proceeding, are not altered as a result of our review of Amendment 8, 9, and 10.
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