ML20052G907
| ML20052G907 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 05/14/1982 |
| From: | Clemenson F, Emch R, Sargenct I, Sargent T, Vito D NRC, Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20052G904 | List: |
| References | |
| NUDOCS 8205190140 | |
| Download: ML20052G907 (25) | |
Text
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UNITED STATES OF' AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING'B0ARD In the Matter of CONSUMERS POWER COMPANY Docket No. 50-155 (Spent Fuel Pool Modification)
(Big Rock Point Plant)
)
JOINT TESTIMONY OF FRED CLEMENSON, IAN SARGENT, D.J. VIT0, AND RICHARD L. EMCH, JR. CONCERNING O'NEILL CONTENTION II.C Q.
What is your name?
A.
My name is Fred Clemenson.
Q.
By whom are you employed?
A.
I am a Principal Systens Analyst, Auxiliary Systems Branch Division of Systems Integration, U.S. Nuclear Regulatory Commission, Washington, D.C. 20555.
Q.
What is your educational background and professional qualifications?
A.
A description of my educational background and a statement of professional qualifications was previously filed in this proceeding.
Q.
What are your present duties?
A.
I am responsible for that part of the NRC Staff's review of the proposad modifications to the Big Rock Point Plant Spent Fuel Pool 8205190140 820514 PDR ADOCK 05000155 T
3, 4.
Expansion which deals with the remotely a'ctivated spent' fuel pool makeup water system, the spent fuel pool water level monitors and the control of heavy loads.
Q.
What is your name?
A.
My name is Richard L. Emch, Jr.
Q.
By whom are you employed?
A.
I am employed as a Project Manager in the Division of Licensing, Office of Nuclear Reactor Regulation, Nuclear Regulatory Commission, Washington, D.C. 20555.
Q.
What is your educational background and work experience?
A.
A description of my educational background and work experience was previously filed in this proceeding.
Q.
What are your present duties?
A.
As part of my responsibilities I supervise the licensing activities concerning the Big Rock Point Plant.
Q.
What is your name?
A.
My name is Ian Sargent. My professional qualifications will be filed subsequently.
Q.
What is your name?
e 4.
A.
My name is Dennis J. Vito. My' professional qualifications will be filed subsequently.
Q.
What is the purpose of your testimony?
A.
The purpose of this testimony is to address O'Neill Contention II.C, which reads as follows:
Is the spent fuel pool safe from a rupture which might be caused by a drop of a spent fuel transfer cask or of the overhead crane?
The response to this Contention is to be found in our response to subsequent series of questions that address the various aspects of spent fuel transfer cask load handling at the Big Rock Point Plant.
On December 22, 1980, the NRC Staff issued a generic letter dealing with the control of heavy loads which includes NUREG-0612. We received Consumer Power Company's Big Rock Point submittals during the period i
June 10, 1981 to September 23, 1981. We have also held telecons with the Licensee during the period March 5, 1982 to May 11, 1982. A site visit was made on March 23 - 24, 1982 to view the 24 ton Spent Fuel Transfer Cask safety slings and to obtain additional clarifications of several NUREG-0612. " Control of Heavy Loads at Nuclear Power Plants", issues.
Q.
Describe and discuss what measures are being taken by NRC to assure that the spent fuel transfer cask will not be dropped.
A.
The Staff's concern regarding a Spent Fuel Transfer Cask drop and with the handling of heavy loads in general was accentuated as a result of the many operating plants requesting license amendments to increase spent fuel pool storage capacity. A heavy load drop onto spent
o s.
fuel was a prime consideration in the dev'elopment of NUREG-0612.
NUREG-0612 sets forth the Staff's guidelines on the measures whfch should be' implemented at nuclear power plants in order to attain the appropriate level of safety in handling of heavy loads at nuclear power plants. As stated above, a generic letter dated December 22, 1980, which included NUREG-0612, was sent to all operating plants as well as to all applicants for operating licenses and holders of construction permits. For operating reactors, the generic letter requested each licensee to review its controls for the handling of heavy loads to determine the extent to which the guidelines are satisfied at its facility and to identify the changes and modifications that would be required in order to fully satisfy these guidelines.
Since it was realized that some of the requested information could more readily be provided while the rest could be time consuming, the Staff requested that the information be submitted in two stages, which are referred to as Phase I and Phase II.
Further, in order to provide sufficient technical support to complete these reviews in a timely manner, the staff has engaged Franklin Research Center (FRC) to provide technical assistance in these reviews.
Phase I, the earliest requested submittal, requires each Licensee to review its facility, to identify all heavy loao handling equipment at the facility which was within the scope of NUREG-0612, and to address specific areas of concern identified in NUREG-0612. These areas include safe load paths, procedures, crane operator qualification and training,
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special lifting devices, general purpose' lifting devices, crane inspection, testing and maintenance and crane design.
Phase II, the last requested submittal, requires each Licensee to address those handling system which when handling heavy loads in areas where their failure might result in significant consequences, (1) to provide features to ensure that the potential for a load drop is extremely small (e.g., a single-failure proof crane, or (2) to provide conservative evaluations of load handling accidents which show that the potential consequences of any load drop are acceptably small.
Q.
Does the 75 ton semi-gantry crane inside containment fall within the scope of review of NUREG-0612?
A.
Yes.
Q.
Please discuss your findings concerning the extent to which the Big Rock Point semi-gantry crane complies with the guidelines of NUREG-0612.
A.
In support of the Staff's review of Big Rock Point's sNnt fuel pool expansion program Franklin Research Center has prepared a draft Technical Evaluation Report that addresses all Phase I aspects of the NUREG-0612 review dealing with applicable load handling equipment, including the 75 ton rated capacity containment semi-gantry cranes, used in the load handling operations involving the 24 ton fuel transfer cask.
The pertinent portions of this review as it applies to the spent fuel transfer cask are as follows:
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4 Guidance 1
" Safe load paths should be defined for the movement of heavy loads to minimize the potential for heavy loads, if dropped, to impact irradiated fuel in the reactor vessel and in the spent fuel pool, or to impact safe shutdown equipment. The path should follow, to the extent practical, structural floor members, beams, etc., such that if the load is dropped, the structure is more likely to withstand the impact. These load paths should be defined in procedures, shown on equipment layout drawings, and clearly marked on the floor in the area where the load is to be handled.
Deviations from defined load paths should require written alternative procedures approved by the plant safety review committee."*
Licensee Response The Licensee has indicated that the safe load paths inside contain-ment have been selected to minimize the potential for damage to fuel and/or safe shutdown equipment should a heavy load be dropped in these areas. The safe load path for the fuel transfer cask is that path directly between the reactor vessel and the pool over which the operator moves the cask during the refueling operation. This path is clearly marked on diagrams within procedures which the operator is using to perform refueling activities. Deviations from the path specified in the refueling procedures occur only when transporting the cask to and from
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Quotes labled guidance are extrsted from NUREG-0612.
9
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its normal storage location and when activities associated with refueling dictate that the 5 ton auxiliary hook be used to light component's in other areas of containment.
Evaluation The licensee's actions concerning the establishment of safe load paths partially comply with the above guidance:
The designation of safe load paths for the 24 ton spent fuel transfer cask covers only its mavement between the reactor vessel and the storage pool. The movements of the 24 ton spent fuel transfer cask from its storage area to the refueling area and its travel path when the semi-gantry crane's 5 ton auxiliary hook is used is not treated as a safe load paths. The staff will require that (a) the additional regular movements of the 24 ton spent fuel transfer cask as defined above be provided with as safe load paths, (b) these load paths should minimize the movement of the transfer cask over the reactor vessel, (c) these safe load paths are to be marked to provide visual aids to operators and supervisors during load handling evolutions, and (d) Big Rock Point's Plant Safety Review Committee should designate those individuals which it believes are qualified to approve deviations from the written procedures and defined safe load paths.
Guidance 2
" Procedures,should be developed to cover load handling operations j
for heavy loads that are or could be handled over or in proximity to irradiated fuel or safe shutdown equipment. As a minimum, procedures I
should cover handling of those loads list'Ed in Table 3-1 of NUREG-0612.
These procedures should include: identification of required equipnent; inspections and acceptance criteria required before movement of load; the steps and proper sequence to be followed in handling the load; devining the safe load path; and other special precautions."*
Licensee Response The Licensee has stated that Standard Operating Procedure (50P) 43,
" Control of Heavy Load," generally covers handling operations for heavy loads that are or could be handled in proximity to irradiated fuel or safe shutdown equipment inside of containment. Procedures used specifically to prepare the spent fuel transfer cask for load handling operations include:
MFHS-1 Transfer Cask Preparation for Fuel Movement f1FHS-2 Fuel Handling Cables Inspection / Testing MFHS-4 Trip Testing and Resetting of the Fuel Handling Transfer Cask Evaluation Load handling procedures involving the spent fuel transfer cask comply with the above guidance. Procedures MFHS 1, 2 and 4 delineate the preparation, wire rope inspection / testing, and testing of the spent fuel transfer cask safety sling.
Additionally, the various refueling procedures provide specific reference to use of the cask during the refueling process.
Guidance 3
" Crane operators should be trained, qualified and cgnduct themselves in accordance with Chapter 2-3 of ANSI B30.2-1976, " Overhead and Gantry Cranes."*
Licensee Response The Licensee has stated that the Big Rock Point crane operator training, qualification, and conduct have been reviewed by the Licensee and found in compliance with the ANSI B30.2-1976 " Overhead and Gantry Cranes" require-ments with one exception: visual examinations. Big Rock Point crane operators are presently qualified in visual acuity to ANSI standards comparable to the the requirements of their normal job duties, whether they are auxiliary operators or mechanical repairmen. The Licensee intends to upgrade those standards as necessary to meet crane operator qualification of ANSI B30.2-1976.
Evaluation Our review of the Licensee's submittal concludes that Big Rock Point complies with the above guidance based on the Licensee's certification of compliance with Chapter 2-3 of ANSI B30.2-1976 and a commitment to upgrade visual testing. The Staff will require that the crane operators meet the visual requirements of ANSI B30.2-1976 before the next plant operation requiring the handling of spent fuel transfer cask.
Guidance 4 "Special lift'ing devices should satisfy the guidelines of ANSI N14.6-1978, " Standard for Special Lifting Devices for Shipping Containers 4
4 I
i l
Weighing 10,000 pounds (4500 kg) or More for Nuclear Materials." This standard should apply to all special lifting devices which carry' heavy loads in areas as defined above. For operating plants certain inspections and load tests may be accepted in lieu of certain material requirements in the standard.
In addition, the stress design factor stated in Section 3.2.1.1 of ANSI N14.6 should be based on the combined maximum static and dynamic loads that could be imparted on the handling device based on characteristics of the crane which will be used. This is in lieu of the guideline in Seciton 3.2.1.1 of ANSI N14.6 which bases the stress design factor on only the weight (static load) of the load and of the intervening components of the special handling device."*
Licensee Response Not Applicable.
Evaluation Since slings are used during the spent fuel transfer cask movements the above requirements are not applicable to the handling of the spent fuel transfer cask movements.
Guidance 5
" Lifting devices that are not specially designed should be installed and used in accordance with the guidelines of ANSI B30.9-1971, " Slings."
However, in seletting the proper sling, the load used should be the sum of the static and maximum dynamic loads. The rating identified on the sling should be in terms of the " static load" which produces the maximum static l
and dynamic load. Where this restricts slings to use on only certain cranes, the slings should be clearly marked as to the cranes wit'h which they may be used."*
Licensee Response The licensee has stated that slings used in the handling of heavy loads such as the spent fuel transfer cask are inspected periodically and prior to use in compliance with ANSI B30.9-1971.
Specifically, NX01 slings used to rig the spent fuel transfer cask and the reactor vessel head (designated as NX01 slings) comply with ANSI B30.9-1971, Chapter 9-2 (wire rope). These slings are stored and used on the reactor deck and comply with storage and temperature requirements of ANSI B30.9. These slings are inspected prior to use in accordance with MFHS-1 (Transfer Cask Preparation for Fuel Movement) and daily, using an inspection checklist.
Personnel performing rigging activities are trained with respect to inspection and acceptance criteria and proper rigging practices.
The spent fuel transfer cask sling assembly consists of two sling lines each rated at 12 tons and a turnbuckle rate at 13.8-tons. The entire sling assembly is certified to 28.6 tons. These sling assemblies are not marked with the maximum static load which produces the maximum static and dynamic loads.
Evaluation The Spent Fuel Transfer Cask slings comply with the requirements of ANSI B30.9-1971.
Furthermore, although the issue of dynamic loading has l'
\\
not been addressed, the slow hook speed ('6 ft./ min) of the Big Rock Point semi-gantry crane, the design factor of safety of 5 (based on ANSI B30.9 Tables), and the limited use of these sling assemblies should be considered adequate to show that the dynamic loads are insignificant in this application.
Additionally, considering that these slings are uniquely designed for a specific application, the licensee's decision not to mark the slings with the maximum combined static and dynamic loads is satisfactory.
However, the Staff will require that the slings either (a) be marked such that they will indicate exclusive use fo the movement of the reactor vessel head and spent fuel transfer cask within containment, or (b) be marked with the maximum static load which produces the maximum static and dynamic load within their rated capacity.
Guidance 6 "The crane should be inspected, tested, and maintained in accordance with Chapter 2-2 of ANSI B30.2-1976, " Overhead and Gantry Cranes," with the exception that tests and inspectioas should be performed prior to use where it is not practical to meet the frequencies of ANSI B30.2 for periodic inspection and test, or where frequency of crane use is less than the specified inspection and test frequency (e.g., the polar crane inside a PWR containment may only be used every 12 to 18 months during refueling operations, and is generally not accessible during power operation., ANSI B30.2, however, calls for certain inspections to be performed daily or monthly.
For such cranes having limited usage, the inspections, tests, and maintenance should be performed prior to their use.)"*
Response
The licensee has stated that the inspection, testing, and niaintenance on the semi-gantry cranes employed in the movement of the spent fuel transfer cask have been conducted in the past in accordance with Michigan Occupational Safety and Health Administration (MIOSHA) standards which are comparable to the standards in ANSI B30.P.-1976, Chapter 2-2 except for the inspection intervals.
Routine ii.c., monthly and yearly, inspection intervals for the semi-gantry crane have been revised to meet the requiremetns of ANSI B30.2. The Licensee has provided no information concerning the rated load test on the basis that this test is required for only new, reinstalled, alterer, extensively repaired, or modified cranes.
Crane maintenance as required by ANSI B30.2 has been included as part of the inspection program.
Evaluation Jur comparison of MIOSHA Standards, Part 18 " Overhead and Gantry Cranes", with ANSI B30.2-1976 verified the licensee's conclusion that the crane inspection, testing, and maintenance requirements are comparable.
Also, the licensee's decisions concerning inspection intervals comply with present requirements.
Big Rock Point complies with the above stated maintenance criteria on the basis of the licensee's certification of compliance with the maintenance criteria of ANSI 830.2-1976.
With reference to the rated load test criteria of ANSI B30.2-1976, insufficient information has been provided. The Staff will require the licensee to provide crane acceptance test data for our review.
4 Guidance 7 "The crane should be designed to meet the applicable criteria and guidelines of Chapter 2-1 of ANSI B30.2-1976, " Overhead and Gantry Cranes" and of CMAA-70, " Specifications for Electric Overhead Travelling Cranes."
An alternative to a specification in ANSI B30.2-1976 or CMAA-70 may be accepted in lieu of specific compliance if the intent of the specification is satisfied."*
Response
The Licensee has indicated that the reactor building semi-gantry crane was specified and designed to comply with specification #49 of the Electric Overh.ead Crane Institute Inc. (E0CI). A detailed comparison was made by the licensee between the requirements of that standard and those of the current standards referenced above. Additional information was provided by the licensee concerning the equivalency of actual design features, with the requirements of current standards, in areas associated with structural and mechanical reliability, where specific compliance was not apparent.
Evaluation The Big Rock Point semi-gantry crane was designed and produced prior to the publication of the above-referenced standards. Since these standards were not invoked in the original design specifications it is not feasible, in many cases, to determine unequivocally that a specific
[
requirement of these latter standards has been satisfied. Consequently, l
design features associated with load handling safety have been reviewed I
and compared with applicable current requirements employing engineering i
judgment where appropriate to determine ff the intent o'f the current standard has been satisfied.
The following discussion briefly identifies deviations noted in the course of this review where direct evidence of equivalency could not be established:
Welding Standards - CMAA-70 requires that welding design and procedures conform with the current issue of AWS D14.1 (American Welding Society Specification for Welding Industrial and Mill Cranes).
The semi-gantry crane specifications invoked AWS standards current at, the time of manufacture. AWS D14.1, copyrighted in 1970, represents the consolidation of various AWS welding design, workmanship, repair and inspection requirements for specific applications in load bearing weldments used in the manufacture of industrial and mill cranes.
This standard, in addition to consolidating welding requirements for specific applications in crane construction, provides some quality improvements by incorporating advances in welding technology over that existing in prior AWS standards. Such improvements are not expected to constitute a significant contribution to load handling reliability, particularly in the case of handling the spent fuel transfer cask where imposed stresses are substantially less than 4
design values. The Staff will require, however, that additional information demonstrating the equivalence of the welding standards used for fabrication of the 75 ton semi-gan ry with that provided in AWS D14.1 before loads in excess of 24 tons are handled.
O.
Girder Bending Stress - CMAA-70 requires that design loading combina-tions for Class A cranes includes an allowance for l'ateral ' load, due to acceleration or deceleration, equal to 2.5% of the live load plus the crane bridge (less end trucks and end ties). The Big Rock Point semi-gantry crar.e design included an allowance of 0.83% consistent with EOCI 49. The difference in bending stress between these two loadings is not substantial (approximately 600 psi at 2.5% and 200 psi at.83%).
Further, the principal issue is combined bending stress rather than the contribution from a specific force. The licensee has evaluated the combined bending stress for the load combination required to include lateral forces and found it to be less than 12,000 psi. This total stress is well within the allowable stress for the crane structural material (16,000 psi).
Girder Shear Stresses - CMAA-70 requires that torsional forces be calculated and included in the design loading combination used to determine maximum shear stress. Appropriate twisting moments were not required in such calculations under E0CI-49.
For cranes, in general, net twisting moment is not a substantial contribution to overall shear stretc (when considered in combination with shear stresses due to dead load, live load, rated loads, and impact allowance).
In the specific case of the Big Rock Point semi-gantry crane neither the licensee's review nor an independent evaluation of this crane indicated any design feature that would lead to substantial twisting due to lateral or over-hanging forces. The twisting moment due to starting and stopping of the bridge motor equal to 200% of full motor torque, as specified in CMAA-70,
has been estimated to be approximately 130-lb-ft. -The addition of moments of this order to the load combination used to estab'lish shear stress would not be of consequence.
Girder Proportions - CMAA-70 specifies an allowable web depth to thickness ratio (h/t) of 188 for girders with maximum compression stress equivalent to that allowed in the design of the Cig Rock Point semi-gantry crane. The girders used in this crane have an h/t ratio of 200 which, while significantly less than the E0CI-49 allowable of 240, exceeds the CMAA-70 limit. The difference between the actual and allowed h/t ratio is small. The actual compressive stress is less than the allowable stress (as discussed above the actual combined bending stress is on the order of 12,000 psi).
If the actual compressive stress is approximately this value, as is expected, an h/t ratio of 220 could be used in conformance with CMAA-70. There-fore, we conclude that the intent of this requirement has been satisfied.
Gantry Leg Structural Design - CMAA-70 requires that the design of leg, end tie, strut and sill members conform to the requirements of the current edition of the American Institute of Steel Construction (AISC) Manual of Steel Construction at a unit stress proportional to that used for girder design.
E0CI-49, the basis for the Big Rock Point semi-gantry crane, was prepared specifically for electrical overhead cranes and, consequently, did not identify any structural standards for gantry leg members. While no information has been provided by the licensee concerning design rules employed for the
. l gantry leg it is judged likely that' design rules similar to those contained in the Manual of Steel Construction were used by 'the manufacturer.
In the specific case of the spent fuel transfer cask, the fact that this lift is approximately 1/3 of the design rated load strongly indicates that no reduction in load handling reliability from that provided by strict conformance to CMAA-70 has been incurred. The Staff will require the licensee to submit additional information that will demonstrate the design rules employed on the semi-gantry leg meet the intent of CMAA-70 requirements before loads in excess of 24 tons can be handled by the semi-gantry cranes. The Staff will require the licensee to submit additional information that will demonstrate that the design rules employed for the gantry leg meet the intent of CMAA-70 requirements before loads in excess of 24 tons can be handled by the semi-gantry crane.
Fatique Considerations - CMAA-70 requires that fatique be considered in crane design and provides maximum allowable stress ranges for specific crane members subject to cyclic loading. No similar explicit require-ments were provided in E0CI 49. Our review revealed the following significant points which should be considered in determining equivalency of the Big Rock Point design to the requirements of CMAA-70.
In the case of the Big Rock Point semi gantry crane 1) no significant stress reversals are expected based on crane performancecharacteristics, 2) the number of lifts at or near design rated load is extremely small; and
- 3) the lift making a significant contribution to the overall duty cycle, the transfer cask, is approximately 1/3 of the design load. Therefore,
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we conclude that this crane is protected from fatique failure in a manner consistent with a crane whose design explicitly inci'uded the requirements of CMAA-70.
Gearing - CMAA-70 provides gearing design criteria based on American Gear Manufacturers Association (AGMA) standards. No similar specific criteria were provided in E0CI-49. The licensee has indicated that
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gearing for the semi-gantry crane is of steel construction and that L
good engineering practice was employed in the telection of the herring-bone and worm gear designs. While no specific design information has been provided concerning gear design it is judged likely that s
design rules similar to those incorporated in CMAA-70 concerning allo,able strength and durability horsepower were employed by the
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manulacturer.
In the specific case of the spent fuel transfer cask,
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the fact that this lift is approximately 1/3 of the design rated load is strongly indicative that no reduction in load handling reliability from that provided by strict conformance to CMAA-70 has been incurred.
The Staff will require the licensee to submit additional information that will demonstrate that the rules employed for gear design are equivalent to the AGMA requirements incorporated in CMAA-70 before loads in excess of 24 tons can be handled by the semi-gantry crane.
f Drum Design.- CMAA-70 specifies that "the drum shall be steel or minimum American Societyof Testing and Materials (ASTM) Grade A48-64 or later, Class 40 cast iron or equal material as specified by the crane i
manufacturer." The semi-gantry crane at Big Rock Point employs a drum fabricated from ASTM A48 Class 35. The use of a similar bu't lower tensile strength material, of composition based on ASTM standards and with appropriate properties used for design calculations, is judged to result in crane components, or structures, with overall factors of safety, and consequently, load handling reliability, equivalent to that produced with higher tensile strength material.
Conclusions and Recommendations The Big Rock Point semi-gantry crane was designed and fabricated in accordance with appropriate industrial standards existing at the time of manufacture. A detailed comparison of the requirements of those standards and actual design features with the requirements of CMAA-70 indicates that this crane substantially meets the intent of the crane design requirements with respect to load handling reliability. There are four items which require further information from the licensee in order to fully establish that the semi-gantry crane, under design rated load, possesses the degree of load handling reliability inherent in compliance with the above guidelines. The Staff will require the licensee to identify and submit for our review the following:
a.
Comparison of structural welding standard used with the requirements in AWS D14.1.
b.
Comparison of gear design criteria with the requirements of the AGMA standards invoked in CMAA-70.
c.
Comparison of gantry leg structural design rules with those required by CMAA-70.
d.
Documentation of intial load test or other testing equivalent to the rated load test specified in ANSI B30.2-1976, article 2-2.2.2.
While this information is necessary to establish full compliance with the above guideline it should be noted that the basic issue is the approach to allowable stresses and, consequently, its resolution is not judged to be crucial with respect to the reliable handling of smaller loads, such as the spent fuel transfer cask, where actual stresses are substantially less than design values.
Q.
Is the Big Rock Point semi-gantry crane designed in accordance with the guidance in NUREG-0554, " Single-Failure-Proof Cranes for Nuclear Power Plant", for a single failure proof crane when handling the 24 ton Fuel Transfer Cask?
A.
No. However, Big Rock Point has incorporated a device designated as a " safety sling" that has been designed to support the spent fuel transfer cask in the event of a hoist train failure.
Q.
Since Consumers Power Company has not demonstrated that the consequences would be acceptable should the spent fuel transfer cask be dropped and they also have not demonstrated that the Big Rock Point semi-gantry crane is single-failure-proof as set forth in NUREG-0554, present your reasons for concluding that the load handling equipment utilized in handling the 24 ton spent fuel transfer cask is acceptable.
A.
It is our understanding that the safe load handling of the spent fuel transfer cask was recognized as a significant issue during the original plant design. Therefore, Whiting Corporation provided an independent means to support the spent fuel transfer cask in the event a failure were to occur in of the semi-gantry crane main hoist system. This device is designated as the safety sling.
The safety sling consists of two lar'ge wire ropes suspended from the trolley of the semi-gantry crane. The upper portion-of the' spent fuel transfer cask is fitted with a structural device', two grippers that surround the two large wire ropes and a tripping mechanism that will activate the gripping device. The gripping devices are tripped or actuated by a tag line, attached to the trip mechanism bar on the spent fuel transfer cask, that runs to a small wire rope drum on the trolley. The design is such that the vertical motion of the tag line coincides with the motion of the spent fuel transfer cask suspended by the main hoist. Should the hoist fail in such a fashion that the downward movement of the main load block exceeds that of the tag line, due to a failure in the load carrying members of the main hoist mechanism, differential motion would exist with respect to the tag line. This differential motion would cause the tag line to trip the safety sling grippers surrounding the two large wire ropes attached to the trolley. Therefore, the weight of the spent fuel transfer cask would be rapidly transferred from the main hoist to the safety sling.
Consumers Power Corporation engaged MPR Associated Inc. to perform an evaluation of the adequacy of the safety sling. The MPR Associates Inc. evaluation and conclusions are restated here:
1.
"The maximum dynamic loading on the redundant support system for the nominal conditions is calculated to be 148 tons. This is less than the allowable load of 150 tons as discussed in Items 2 through 5 below and is there1 ore considered acceptable. The nominal conditions are as follows:
Wedge clearance - less than or equal to 0.050 inches radial.
Tag line slack and pin clearance - less than 0.37 inches.
" Trip arm position - within 0.25 inches of top dead center."
"In this regard we understand the following:
a.
Big Rock Plant personnel have reduced the
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wedge clearance to below 0.050 inches.
b.
Big Rock Point personnel have remachined the tag line drum to obtain a maximum mismatch between takeup of the tag line and main hoist that is less than 0.25 inches. Pin clearances in the tag line connections are assumed to be less than 0.12 inches for a total slack of less than 0.37 inches. An alternative method for obtaining effective tag line slack of 0.37 inches or less is to use the tag line snubber assembly shown nn enclosed MPR Drawing 1098-71-01 (Rev. B). This alternate method is not necessary if a total slack equal to or less than 0.37 inches can be maintained. We recommend that Big Rock Point personnel confirm that the total tag line slack and pin clearance is less than 0.37 inches.
c.
Based on discussions with Big Rock personnel, the angular position of the trip arm can be set to within 0.25 inches of top dead center with respect to the yoke. We recommend placing permanent cribe marks on the yoke at the 0.25 inch limit. Big Rock Point personnel agreed that this requirement will be included in the plant procedures.
2.
" Analyses performed by MPR of the cask safety lugs show that they are adequate for a 150 ton dynamic loading. The dimensions used by MPR in the analysis of the cask lugs have been verified by Big Rock Point personnel. The cask lug attachment welds were examined by the liquid penetrant method and found to be acceptable.
Either liquid or penetrant magnetic particle examination methods are satisfactory for examining the cask lug attachment welds."
3.
" Analyses performed by MPR indicate that the stresses in the cask shell at the load points exceed ~ yield for a 150 ton dynamic loading. How-ever, these stresses are considered acceptable for the following reasons:
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The maximum stresses are local bending stresses and will not affect the load capability of the attachment.
The stresses that do affect the load capability are the net tensile stresses averaged across the cross-section. These stress are less than one half yield.
Therefore, the cask shell at the attachments is considered adequate although some local yielding could occur in the event of a cask drop.
4
" Whiting has stated in their letter to CPCo dated November 10, 1980, that the cask handling safety device, trolley and bridge are adequate for a 150 ton dynamic loading."
5.
"The maximum calculated dynamic load on the safety slings, in the event of a cask drop, is 74 tons per sling. This load is about 65% of the minimum breaking strength (114 tons) of the sling.
The slings are considered satisfactory even though some yielding is predicted. Based on discussions with CPCo, we understand that the sling attachments have been tested to the full strength of the wire rope and are therefore considered acceptable."
FRC has performed an engineering evaluation of the safety sling assembly. This evaluation indicates that the safety sling assembly can be expected to terminate a spent fuel transfer cask drop following a failure of the hoist drive train. This drop termination is expected to take place after a short free fall and not impose unacceptable loads on the safety cables or crane structures. The licensee has agreed to provide a comprehensive maintenance and test program suitable to ensure that the safety sling assembly will be operable and able to perform within design limits whenever the transfer cask is being handled. This commitment is supported by written procedures which specify inspecting, rigging, adjusting, and testing requirements for the spent fuel transfer cask and safety slings prior to load handling. These procedures have
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been reviewed and found to be acceptable with the exception of adequate-cross referencing of the test tripping guidance in MFHS-4'. The licensee has agreed to revise MFHS-1 to require the safety sling trip test in MFHS-4 each time the spent fuel transfer cask is prepared for load handling.
Based on the foregoing, it is judged that design features provided' for the Big Rock Point 75 ton semi-gantry crane, when handling the spent fuel transfer cask, provides an additional level of protection against facility damage due to a cask drop similar to that which would be provided by a crane conforming to the requirements of NUREG-0554 for mechanical system failure.
In the case of the other load bearing members, such as girders, NUREG-0554 does not require redundency but provides an additional level of protection through conservative structural design reauirements imposing, as a design loading condition, the forces induced by a safe s
shutdown earthquake (SSE) with the crane carrying its design rated load.
s SeismicqualificationofthecraneisunderreviewintheSystematic
,s Evaluation Program and therefore is not discussed in this testimony.
s We find the Big Rock Point semi-gantry crane acceptable for handling the 24 ton spent fuel transfer cask.
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