ML20035H604
| ML20035H604 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 05/03/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20035H595 | List: |
| References | |
| NUDOCS 9305060061 | |
| Download: ML20035H604 (4) | |
Text
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SQQiGo It UNITED STATES.
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j NUCLEAR REGULATORY COMMISSION
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WASHINGTON. D.C. 20566 4 001 l
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RESOLUTION OF TWO UNRESOLVED ITEMS RELATING TO SPECIAL HANDLING DEVICE i
NORTHERN STATES POWER COMPANY j
PRAIRIE ISLAND NUCLEAR STATION. UNITS 1 AND 2 DOCKET NOS. 50-282 AND 50-306 l
1.0 INTRODUCTION
On October 4, 1991, Northern States Power Company (NSP), provided the outline of a design for a single-failure-proof heavy loads handling system for Prairie Island, Units 1 and 2.
This design is intended for use in handling l
Transnuclear TN-40 casks used in the Independent Spent Fuel Storage l
Installation.
Part of that design included a special lifting device (lift j
beam).
The safety evaluation for that design has two open items, both relating to the special lifting device. These open items require the following:
l (1) A test plan for the special lifting device, and (2) Justification for the use of the dynamic load factor used in design of the special handling device.
On January 25, 1993, NSP provided a submittal to resolve these outstanding concerns. This submittal is reviewed below in Section 2.0, " Evaluation."
Conclusions are provided in Section 3.0, " Conclusions."
2.0 EVALUATION I
2.1 Acceptance Testing for Special Lifting Device l
The licensee clarified the statement in the submittal dated October 4,1991, l
to specify that the special lifting device for the TN-40 casks would be designed in accordance with the requirements of ANSI N14.6-1986 instead of j
ANSI N14.6-1978. All further references to ANSI N14.6 will apply to the 1986
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Standard, unless otherwise stated.
l The licensee also stated that the special lifting device would be-load tested for acceptance prior to shipping with a lc J three times the weight of the
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load it is designed to support. Non-bearing t'ad members would be-tested in accordance with Section 6.2.3 of Standard 14.6 prior to initial use.
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i 9305060061 930503 i
PDR ADOCK 05000282 P
2.2 Testing to Verify Continuing Compliance for the purpose of testing to verify continuing compliance in accordance with Section 6.3 of the ANSI Standard, the licensee has elected to utilize the specifications of Section 6.3.l(2) which where surface cleanliness and conditions permit, allows the alternative of dimensional testing, visual inspections, and non-destructive testing of major load carrying welds and critical areas on a yearly basis in lieu of load testing. This section of ANSI N14.6 allows either alternative; i.e., load testing or dimensional testing to be conducted yearly with the time between tests to be extended to.a period not to exceed fourteen months. The specification continues to specify that, in the event the special lifting device has not been used for a period in excess of one year, such testing need not be performed until returning the device to service.
In lieu of the fourteen month period, however, the licensee proposes to allow adjustment of such testing, as required, to be completed every twelve months i 25% for consistency with other plant surveillance testing which is not controlled by Technical Specifications, thus allowing as much as 15 months and as little as nine months to elapse between testing periods.
The licensee expects to use the special lifting device on an average of about twice each year. On that basis, the licensee proposes to have the special lifting device visually inspected by maintenance or operating personnel prior to each use, thereby combining the requirement for visual inspections by operating personnel prior to each use (Section 6.3.6) with that requiring visual inspection by maintenance or non-operating personnel every period not in excess of three months (ANSI Section 6.3.7).
The functional testing of non-load bearing functioning parts of the lift beam, required in ANSI Section 6.2.3 as an acceptance test, will be conducted annually, as required by ANSI Section 6.3.4.
In the event, however, that the lift beam is not used for a period in excess of one year, the licensee proposes tc conduct the testing of non-load bearing functional parts prior to use.
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The lift beam will be load tested as prescribed in Section 6.2.1 following:
a.
Major maintenance or alterations as defined in Section 6.3.2 of ANSI N14.6, 1986; b.
An incident in which any of the load-bearing components of the TN-40 special lifting device may have been subjected to stresses substantially in excess of those for which it was previously qualified; or c.
An incident that may have caused permanent distortion of its load-bearing parts.
e
The licensee also proposes to repeat the functional testing required for initial acceptance of non-load bearing functional parts in ANSI Section 6.2.3 as prescribed in Section 6.3.5 following any event which requires repair or alteration of such parts, or which results in detectable distortion of the lift beam.
2.3 Justification for Dynamic Load Factor The licensee proposed to utilize a dynamic load factor of 0.05.
The proposed load factor was established by utilizing the hoist load factor recommended for cranes by the Crane Manufacturers Association of America (CM4A) Specification
- 70, " Specification for Electric Overhead Traveling Cranes," which specifies a facter of 0.005 times the hoisting speed in feet per second.
(Neither ANSI N14.6 nor NUREG-0612, " Control of Heavy Loads at Nuclear Power Plants" specifies any method for calculation of a dynamic load factor.) Utilizing this method, the licensee calculates a factor of 0.025 which the licensee doubles to a value of 0.05.
Th licensee notes that the CHAA specification specifies a minimum factor of 0.15 for crane design. The licensee states, however, that the minimum value of 0.15 does not apply because the special handling device will be designed for stress facters of 6 to yield and 10 to ultimate while the crane design stress factor is 5 to ultimate.
The licensee included other factors to show that the dynamic forces on the lift beam will be minimized. These factors are:
(1) The crane is equipped with a DC hoist control with a stepless drive which provides for smooth acceleration and deceleration.
It also requires less maximum motor torque than AC type drives.
(2) The maximum hoist speed that will be used when handling a TN-40 storage cask is very slow (5 ft/ min).
(3) The hoist is equipped with an energy absorbing torque limiter, which limits the torque to i30% of the design value.
(4) The hoist is equipped with a load cell which automatically stops the crane if a load of 125% of the rated static load is detected.
(5) Strict administrative controls are exercised over all crane operations.
Only qualified and trained operators will operate the crane.
(6) The crane wire cable will also provide damping effects which will reduce the dynamic load amplification factor.
1 (7) Two separate magnetic brakes are provided on the crane as well as regenerative braking.
Each magnetic brake provides a braking force of 15E of rated load and is tir,ed (soquenced) to act in series.
Thus, the sequenced magnetic brakes and the regenerative motor brake assures that smooth lowering and hoisting speeds can be maintained regardless of the load on the hook.
3.0 CONCLUSION
3.1 Test Plan for Special lifting Device The licensee's plans for testing are found acceptable since the program follows the ANSI Standard with few exceptions, as noted above. Those exceptions do not materially affect the test program.
The staff understands that all required load testing will be conducted with the test load three times the weight the lift beam is designed to support.
It should be noted that the two versions of ANSI N14.6 differ very little in context. Most changes add a sentence or paragraph for clarification.
3.2 Justification for Dynamic Load Factor The licensee utilized the methodology used by CHAA Specification #70 in the design of cranes. The crane specification notes, "This factor applies to the motion of the rated load in the vertical direction, and covers inertia forces, the mass forces due to the sudden lifting of the hoist load and the uncertainties in allowing for other influences. The hoist load factor is 0.5 percent of the hoisting speed in feet per minute, but not less than 15 percent or more than 50 percent, except for bucket and magnet cranes for which the impact value shall be taken as 50 percent of the rated capacity of the bucket or magnet hoist." __
The staff finds the licensee's justification acceptable, based upon the difference in safety factors between lift beam (10 to ultimate) and crane (5 to ultimate) and because of the other factors which result in minimizing the dynamic forces on the lift beam.
Principle Contributor:
N. Wagner Date: 9By 3,1993 l