ML20039G820
| ML20039G820 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 12/18/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20039G819 | List: |
| References | |
| TAC-46519, NUDOCS 8201190181 | |
| Download: ML20039G820 (5) | |
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ENCLOSURE SAFETY EVALUATION OF RAriCHO SEC0 NUCLEAR GENERATING STATION UNIT 1 - TOWER CRANE DOCKET N0. 50-312 1.
Background and problem statement The proposed usage of the non-seismic Category I tower crane is for theconstructionoftheNuclearSerhiceElectricalBuilding(NSEB).
A PECCO f4odel PC 1400 tower crane is intended to be used for the construction cf the NSEB. The construction tower crane will be located adjacent to the existing Category I Auxiliary Building.
Two lh inch diameter safety cables are proposed for use in order to restrain and control the tower crane such that the collapse of the crane will not adversely effect safe shutdown equipment or the safety function of the existing Auxiliary Building. Administrative control measures are also proposed by the licensee to prevent dropping of crane loads on the Auxiliary Building to cause disfunctioning of the building.
1 The following evaluation is intended to ascertain that the specific measures proposed by the licensee are adequate for ensuring the structural integrity and function of safe shutdown equipment.
2.
Information used in review (1) Letter dated on November 10, 1981, from John J. Mattimoe of Sacramento Municipal Utility District to Mr. John Stolz, Chief, Operating Reactors Branch #4, USNRC.
(Safetycablerestrainsdesign calculations and drawings by Bechtel Power Corporation.)
0201190181 811218 PDR ADOCK 05000312 P
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(2) Information obtained during a conference call between the licensee and the staff on flovember 24, 1981.
(3) Letter dated on December 1, 1981, from Wm. C. Walbridge of Sacramento Municipal Utility District to Mr. John Stolz, Chief, Operating Reactors Branch #4, USNRC.
(Rehiseddesigncalculations andresponsestoquestionsidentifiedontheNohember 24, 1981, conference call.)
3.
Key area of review and discussion The proposed safety cables, their attachments to the tower crane, cable anchors, crane tower foundation and counterweight drop po-tential were reviewed for structural design adequacy. Applicable loads including wind and seismic loads were considered in a conser-hatihemanner. The review included following key items:
(1) We reviewed the design of the two 11c inch diameter safety cables. Each of the cables has a minimum breaking strength of 192,000 lbs. The two cables will be used to tie the tower crane to two G ft. diameter by 12 ft. deep deadman (casissons) located approximately 124 ft, south and east of the tower crane. Each dead-man can provide anchorage for a 34 uplift force of 13,800 lbs. with l
l a safety factor of 1.4 i
(2) TheeffectoftheherticalcomponentoftheSSEonthetension of safety cable was not considered in the original design loading i
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3-combinations (Ref. 1). We requested the licensee, during the conferencecallofreference2,toincludetheherticalcomponent of SSE on the calculation of cable tension. Bechtel pcwer cor-porationrehisedthecabletensioncalculationstoincludethe vertical compcnent of the SSE effect in reference 3.
Werehiewed the revised calculations and concluded that the proposed cable size of 1h inch diameter is adequate.
(3) The local stresses of tower crane column at the cable connection point were judged critical in dictating the manner of crane failure.
It is possible that the pcrtion of tower crane above the safety cable connection point could collapse under the SSE ehent in a way to cause damage to the Auxiliary Building. At our request, Bechtel Power Corporation staff checked the tower crane column stresses at cable connection point and found them to be acceptable, except that the splices between sections of the tower crane column were insufficient. The licensee proposed to reinforce the splice by two additional ik inch diameter high strength bolts. This strengthening proposal is acceptable.
(4)
In the licensee's original design of the 6 ft. diameter deadman (caisson) the stability under both the horizontal and herticalcomponentsofthecabletensionwasnotchecked. We requested the licensee to prohide a stability analysis to ensure that the deadman will not be pulled out by the uplift force. The
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licensee submitted the results of such an analysis on December 7, 1981, and demonstrated that the deacman was adequately designed to resist and anchor the safety cable force with a safety factor of 4.3.
(5) The tower crane foundation was checked for the addition of the two safety cable loads. Earthquake forces equivalent to SSE condition were used throughout the design of foundation. The licensee used the load factor method to combine three components of earthquake. Thesafetyfactoragainstcherturningforthecrane foundation under the SSE condition is determined as 1.4, which is acceptable.
(6)
In the submitted drawings, a portion of the Auxiliary Building is shown to be exposed under and within the crane counterweight radius of swing of 46 ft. DuringanSSEehent,itispossiblethat the counterweight could fall down and hit this portion of the existing Auxiliary Building. Thelicenseeresolhedthisconcernbyconfirming that within the counterweight radius the building houses only radwaste equipment which is non-Category I.
(7) Administratihecontrolswillbeimplementedduringtheperiod
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of the crane operation to limit its swing angle to that defined on the drawings of reference 1.
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Conclusion Basedonourdetailedrehiewofthelicensee'sdesigncalculations l
cf the s:fsty cables for the crane, cable attachments, cable anchors, l
i crane foundation stability, local stress calculations, and proposed administratihe controls, we conclude that in the ehent of a failure of the crane caused by a postulated design basis earthquake combined with applicable loads, the tower crane can reasonably be expected to fail l
l in a manner not to impair the structural integrity or effect the safety function of the Auxiliary Building. Therefore, the licensea's l
proposed operation of the tower crane after the implementation of the above described fixes and the necessary adninistrutive controls is acceptable.
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