ML18158A528

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EPRI Presentation_Heavy Loads
ML18158A528
Person / Time
Issue date: 06/07/2018
From: Steve Jones
NRC/NRR/DSS/SCPB
To:
Jones S, NRR/DSS/SCPB, 415-2712
References
Download: ML18158A528 (24)
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Text

EPRI Hoisting, Rigging and Crane User Group Presentation:

Control of Heavy Loads Steve Jones, Senior Reactor Systems Engineer Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission June 13, 2018 1

Purpose

  • Communicate operating experience important to NRC regulation and interface with industry initiative activities
  • Discuss relationship with ASME Cranes for Nuclear Facilities Committee 2

Heavy Load Issue Timeline GL 85-11 GSI-186 RIS GL81-07 Two Yellow Violations Opened 2008-28 RIS for Stator Drop GL 80-113 2005-25 Closure of GSI-186 Bulletin 96-02 Stator Drop NUREG 0612 and Temp Rig NUREG-1774 NUREG-0554 (Operating Collapse Task A-36 Experience)

ASME Issues NOG-1 ASME Issues Reactor Vessel Comparison Matrix Crane O&M First Dry Fuel Storage Head Lift Issues Standard?

Installation Licensed Industry Initiative 3

Analysis of Issue

  • Task A-36:

- Analyze current licensing criteria

- Analyze measures that ensure safe handling of heavy loads.

- Recommend changes

- Overview of potential consequences of a load drop

- Summary of current licensee programs

- Review of Historical Data

- Guidelines and Recommendations

  • Procedures and safe load paths
  • Consistency with industry standards
  • Assurance that critical SSCs adequately protected 4

Heavy Load Handling Program

  • Licensees review heavy load programs against NUREG-0612 guidelines
  • Requested responses in two phases to determine how NUREG-0612 guidelines would be met 5

Phase I and II Guidelines:

  • Phase I [prevention]:
  • Phase II [protection or

- Safe load paths consequence analysis]:

- Load handling procedures - Stops or interlocks prevent

- Periodic inspection and testing movement of load over critical

- Operator qualification SSCs, OR;

- Lifting device standard - Overhead crane and lifting devices designed to be single

- Sling standard failure proof, OR;

- Crane design standard - Load drop analyses

- Interim Technical Specifications demonstrate acceptable consequences.

6

Review of Phase I and II

  • All licensees submitted Phase I and II information
  • Resource intensive reviews confirmed conformance with Phase I guidelines
  • Phase II responses sampled
  • Phase II responses generally enhanced Phase I implementation through limited load drop analyses and administrative controls (where single-failure-proof cranes were not installed) 7

Resolution of Phase II (GL 85-11)

  • Greatest risk - heavy loads over irradiated fuel
  • Risk to safe-shutdown systems considered small
  • Full implementation of Phase II unjustified
  • Phase II responses did not identify additional concerns; no need for further generic action
  • However, Phase II responses captured in licensing basis 8

Bulletin 96-02

  • Handling of dry storage casks began after establishment of heavy load programs
  • Bulletin initiated because of proposed movement of dry storage casks at power in a BWR
  • Potential for cask drop to initiate transient and damage key equipment
  • Reinforced requirement to evaluate changes in operations through safety analysis report change process (10 CFR 50.59) 9

Heavy Load Generic Issue

  • Generic Issue 186 was opened in 1999 to determine the need for more regulatory action
  • Operating experience review published as NUREG-1774
  • RIS 2005-025 in October 2005 and Supplement in May 2007 reemphasized expectations regarding heavy load handling
  • Identified focus areas based on operating experience 10

Operating Experience Findings

  • Most heavy lift accidents due to below the hook issues (human errors, rigging failures, etc.) vice crane deficiencies
  • Industry standard provides clear single failure proof criteria for cranes
  • Consequence and load drop analysis methodologies vary between licensees
  • Three >30 ton load drops between 1980 and 2002, all due to rigging failures (not crane failures) 11

Key Insights

  • Three recurring causes of load drops at nuclear power plants:

- Two-blocking

- Intermediate hoists

- Inadequate sling protection

  • Human performance important to prevention
  • Additional measures can reduce risk

- Limit height of lift

- Redundant equipment available

- Use specially designed lift rigs 12

Two Blocking

  • Three drops due to cutting of wire rope

- 1970-Palisades (Polar Crane Aux Hoist; Prior to Operation; Limit Switch Bypassed)

- 1985-Browns Ferry (Unloaded Turbine Aux Hoist)

- 1993-Calvert Cliffs (Unloaded Turbine Aux Hoist)

  • Relationship to nuclear safety

- Aux hoist faster than main hoist; less time for operator action

- Main hoists carry heaviest loads

- Two Blocking is a credible cause of load drops 13

Intermediate Hoists

  • Hoist failure - Comanche Peak - 1999

- 20 foot drop of 45 ton motor

- Snag avoided RCS impact

- Plant was defueled

  • Chain failure - Peach Bottom - 2002

- 10 inch drop of 24 ton motor

- No damage to RCS; fuel in vessel

  • Load path issue - South Texas - 2003

- 50 ton motor moved over operating RHR heat exchanger (in containment)

- Double-capacity lift rig specified in heavy load program not used 14

Intermediate Hoists (Continued)

  • Relationship to nuclear safety

- Intermediate hoist increases failure probability

- Failures could threaten decay heat removal

  • Regulatory Insights

- Not addressed in heavy load guidelines

- Redundant capabilities unaffected by potential load drop should be available to manage risk pursuant to 10 CFR 50.65(a)(4) 15

Slings

  • Three drops of very heavy loads

- 2001 at San Onofre (mobile crane dropped from turbine bldg crane)

- 2001 at Turkey Point (mobile crane dropped form turbine bldg crane)

- 2005 at Browns Ferry (old trolley dropped from reactor building crane temp hoist)

  • All outside scope of heavy load program 16

Slings (Continued)

  • Nuclear safety insights

- Failed slings used in basket configuration

- Slings used as part of cask lifting device with special fittings

- Operating experience suggests synthetics more susceptible to cutting than steel

- Training and procedures may improve identification of incorrect sling usage

- Steel slings may allow more time to correct inadequate corner softening 17

Continued Heavy Load Issues

  • Mid-2000s: refueling delays
  • Regulatory Issue: unclear licensing bases (particularly reactor head lifts)
  • Safety Issue: potential damage that precludes adequate cooling of irradiated fuel
  • Desired Resolution: improved practices aligned with licensing basis 18

Industry Initiative

  • NEI proposed industry initiative related to heavy load handling:

- Safety basis for key heavy lifts

- Safety basis incorporated in FSAR

- Develop industry guidance for reactor head lifts (load drop analyses and single-failure-proof crane equivalence)

  • NRC held public meetings with NEI to speed guideline development 19

Industry Guidelines (NEI 08-05)

  • Realistic reactor head drop analysis methodology
  • Single-failure-proof handling system equivalence for head lifts
  • Maintenance rule risk management
  • NRC staff endorsed the NEI guidelines, with some exceptions 20

Safety Significance

- Significant portion of lift at height/location where drop could severely damage vessel

- High lift - increased potential for two-blocking, an important cause of drops

- Crane inspection/maintenance on or near critical path

- Vulnerable to single failures/operator error

  • BWR Cask Movements

- Potential for drops from high elevations over sensitive structures (e.g., spent fuel pool floor and torus)

- Often performed with reactor operating at power 21

Load Drop Probabilities

6.3 E-05 Drops/Lift

5.6 E-05 Drops/Lift

- Crane Failure (Navy Data):

2.5 E-06 Failures/Lift

- Human Error Probability (Failure of Lifting Device):

8 E-07 Failures/Lift

  • Estimates uncertain due to limited data 22

ANO Stator Drop

  • Collapse due to buckling of unstable column assembly

- New configuration

- Not load tested

  • Adverse impacts

- Loss of electric power

- Trip of adjacent unit

- Flooding

  • Safety Significance

- Mechanical damage and flooding impacted all sources of AC power except EDGs

- Unit 1 EDG work not coordinated with stator move 23

Ongoing Activities

  • Policy is to endorse consensus standards where appropriate
  • Participation with ASME for standards development

- ASME NOG-1, 2010 and later include matrix to NUREG-0554 guidelines for single failure proof cranes

- ASME HRT-1 addressed heavy component replacement activities following ANO stator drop

- ASME developing operation and maintenance standard addressing scope of NUREG-0612

  • Inspection and licensing

- Consolidated interim fuel storage license application

- At-reactor independent fuel storage facilities

- Reactor refueling activities 24

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