ML19253B718
| ML19253B718 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/23/1972 |
| From: | Maccary R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Deyoung R US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 7910180707 | |
| Download: ML19253B718 (7) | |
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Form AEC 388 IRev. 9-53) AECM 0240
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THREE MILE ISLAND UNIT NO. 1 Docket No. 50-289 Class I Seismic Structures and Containment FINAL STRUCTURAL EVALUATION FOUNDATIONS All Class I Seismic structures, except the diesel generator building, are founded on bedrock of Gettysburg shale. The diesel gene-rator building is founded on compacted backfill. During the cons truc-tion permit review a complete evaluation of the foundation conditions was made and the foundations were found structurally adequate to carry the applied loads. No new facts have been uncovered during construction which would affect the previous acceptance.
CLASS I SEISMIC STRUCTURES Class I Seismic structures, listed in the FSAR, section 5.1.1, are similar to Class I Seismic structure approved for previously licensed facili ties. All Class I Seismic structures are designed in accordance with the ACI-318-63 code for concrete structures and AISC Code for Steel S t ructures. In addition to dead, live, and DBA loads, all Class I Seismic structures are designed for the following environmental loads:
Tornado Loads - Tornado loads on Class I Seismic s tructures result from a 300 mph tangential wind with a 1.3 gus t factor, and a 3 psi pres-sure drop in 3 seconds. Although this tornado criterion is not s tand-ard, it is more conservative and therefore acceptable. The criteria for 1445 102
. tornado generated missiles have been re, viewed and found to be adequate as they are similar to those used for the previously licensed plants.
Seismic Loads - These loads re based on horizontal ground accele-rations of 0.06g for the OBE and 0.12 g for the DBE with vertical accelerations equal to two-thirds the horizontal ground accelerations.
These values have been evaluated by us and the AEC seismic consultants and found to be appropriate for this plant location.
All Class I structures which could be damaged by aircraft impact are lis ted in 5.1.3 o f the FSAR. They are designed for aircraft impact as described in Appendix 5A of the FSAR. The aircraf t for which these structures are designed to withstand the impact is identified as weigh-ing 200,000 lbs, and impacting at a velocity of 200 knots, with an effective impact area 19 feet in diameter. In addition, two smaller aircraft sections of 4,000 and 6,000 lbs were assumed to impact at 200 knots with respective effective impact areas o f 3 f t. and 5 ft. in dia-me ter.
These parameters have been reviewed by us and found to be appropriate, considering the existing local conditions and the exposure of the plant.
Other environmental loads such as snow, ice, and floods are also considered in the structural design. They are similar to the loads considered on previously licensed facilities and therefore acceptable to us.
To protect the personnel and equipment from the impact, the control building floors have been separated from the exterior walls exposed to kkk
,. an aircraft impact by a 2" wide joint., For the same reason the concrete floor slabs are supported on steel beams which rest on vibration dampen-ing elas tomeric pads. These arrangements and the justification for them presented by the applicants have been reviewed by us and the AEC consul-tants and found to be adequate for their purpose.
For the aircraft impact the applicants' general criterion that Class I Seismic structures, including the containment, be designed with the postulated impact loads as limits of s tructural functional integrity has been evaluated by us and AEC consultants -- Mr. J. Proctor of the Naval Ordnance Laboratory and Dr. N. Newmark of N. M. Newmark Consulting Engineering Services. It is our and AEC consultants' opinion that the impact design criterion is adequate and that the design is acceptable.
For all reinforced concrete Class I Seismic structures, the p-in-cipal methods of analysis have been the Working Stress and Ultimate Strength design methods as defined in ACI 318-63 "ACI Standard Building Code Requirements for Reinforced Concrete."
We have reviewed the design criteria and the design methods for the Class I Seismic structures as defined and listed by the applicants in the FSA2, and found them to b 2 in accordance with the pertinent codes and sound engineering practice; they are therefore acceptable to us.
The s tresses in Class I Seismic s tructures are below the allowable.
CONTAINMENT The primary containment is a prestressed concrete reacter building with 6 buttresses similar to containment structures previously licensed.
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. The structure is post-tensioned by means of BBRV tendons of 169-1/4-inch wires each. Each wire is " button-headed" at both ends of the tendon to anchorage hardware. This tendon system, which is the first nuclear application using such a large BBRV system, was evaluated on the basis of experimental and analytical information furnished by the applicants and found by us to be acceptable.
The liner design is typical for this type of containment. The choice of the materials, the arrangement of the anchors, the design criteria are similar to those evaluated for previously licensed plants and therefore acceptable to us.
The containment is designed in accordance with the applicable sec-tions of the ACI-318-63 code for concrete and the pertinent sections of the ASME Pressure Vessel Code,Section III, Division 1,1965 Edition for the liner.
The containment is designed for dead, live, DBA, OBE, DBE, environ-mental loads and aircraft impact loadings. Its structural design loads and design criteria are very similar to those previously approved and are acceptable to us.
Stresses in the shell, penetrations, and foundation resulting from static and dynamic loads were calculated by means of a well-known (KALNINS) computer program and were found to be below the allowable.
The method of analysis is in accordance with general engineering practice and acceptable for this type of structure.
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INTERIOR STRUCTURE The design pressure dif ferentials across walls of enclosed com-partments in the con.2inment internal structure as indicated by the applicants are: primary shield wall (reactor cavity), 200 psf; second-ary shield wall (steam generator ccmpartments),15 psf. For the DBA the primary shield loading will be such that the wall reinforcement will reach the yield point and the concrete will crack. We concur in the approach adopted.
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.. LTRESOLVED ISSUES ACCEPTANCE TESTING Structural proof testing will be accomplished by pressurization at 115% of the design pressure. However, the tes ts and acceptance criteria as described in the FSAR are different from those listed in Safety Guide 18.
Since compliance with Safety Guides is not mandatory, it is sug-ges ted that a meeting be arranged with the applicants to discuss the differences.
TENDON SURVEILLANCE As proposed by the applicants, tendon surveillance would be per-formed at intervals of 1 year, 5 years, and 20 ears after the initial structural proof test. Six vertical and nine hoop tendons would be inspected for broken wires. Two of the six vertical tendons would have lif t-off tests performed to verify pres tress levels. Five wires would be removed from five of the fif teen inspection tendons and subjected to visual, physical, and chemical tes ting.
It is our thinking at the pre-sent time that this program is not suf ficient and we intend to discuss with the applicants a modification of this program involving, among other chaagas, the increase of the number of inspected tendons from fif teen to twenty-one, and a frequency of inspection of 12, 24, and 36 months after the initial containment leakage test and every 5 years thereafter.
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