ML20203C371
| ML20203C371 | |
| Person / Time | |
|---|---|
| Site: | 07007001 |
| Issue date: | 12/08/1997 |
| From: | NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| Shared Package | |
| ML20203C294 | List: |
| References | |
| NUDOCS 9712150290 | |
| Download: ML20203C371 (10) | |
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p* UNITED STATES
- } NUCLEAR REGULATORY COMMISSION
, '# WASHINoToN, o,C. 205"M001
-December 8, 1997 DOCKET: 70-7001 CERTIFICATE HOLDER: Unite *J States Enrichment Corporatior.
Paducah Gaseous Diffusion Plant Paducah,KY
SUBJECT:
COMPLIANCE EVALUATION REPORT: APPLICATION DATED APRll 23,1997 AS REVISED JULY 31,1997, BUILDINGS C-331 AND C 335 SEISMIC UPGRADES (COMPLIANCE PLAN ISSUE 36)
BACK.CROUNQ
.ie Plan for Acnievino Comoliance with NRC Reaulations at the Paducah Gaseous Diffusion Plant (Compliance Plan), issue 36, " Seismic Capabilit, of Buildings C 331 and C 335", dest:ribes seismic noncompliances, pro' rides a justification for continued operation (JCO), and provides a plan of action and schedule for achieving compliance.
Structural seismic analyses have shown that significant plant damage could occur in two of the main cascade buildings, C-331 and C-335, be!ow the Evaluation Basis Earthquake (EBE), the seismic level established in the 1985 Safety Analysis Report (SAR) as the appropriate earthquake level for the site. The EBE corresponds to an earthquake with a 250-year return period. I he damage could involve the failure of the approximately 20-foot wide spans which treverse each building in three locations of each building's roof. Further, certain cascade piping attachments, known as 4
" expansion joints" or " bellows," were judged to fail in significant numbers at this earthquake level, in the JCO, United States Enrichment Corporation (USEC) committed to interim measures to maintain the cascade sub-atmospheric and to minimize the number of shift personnelin the affected buildings, until permanent corrective modifications are complete. The permanent modifications are to instail structural steel bracing to stiffen the structure, thereby reducing the displacements that cause the failures. The modifications would increase the capacity of the structures to a seismic level of 0.15g, the earthquake defined in the SAR Upgrade Program site specific hazmd curve associated with a 250-year return period. The Compliance Plan states that the modifications were to be completed by December 1997.
In a letter dated April 23,1997, USEC requested an amenoment to its certificate of compliance to: 1) obtain NRC approval of the resolution to three Unreviewed Safety Questions (USO4 associated with the seismic upgrades; 2) revise the completion date of the modifications from December 31,1997, to 15 months after NRC approves the amendment request; and 3) revise the JCO for the seismic issue S the Compliance Plan to include only sheltering in response to a UF6 release, rather than sheltering ard
. evacuation. Specifically, the three USQs identified by USEC are: 1) the increased stifiness of the buildings following completion of the modifications may increase the number and the probability of seismically-induced eqttipm9nt failures inside the buildings; 9712150290 971208'Su9 pcR ADOCK 0700 001
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- 2) the process of installing the new structural steel may temporarily make the buildings and the contained equipment more susceptib% to seismically-induced f ailure as the existing frames are altered and/or replaced; and 3) the process of installing the new structural steel may temporarily increase the probability of equipment f ailures due to postulated load handling accidents during construction. in that letter USEC provided information that addressed the USQs, in a letter dated June 30,1997, USEC indicated that they planned to submit a revised amendment request by July 31,1997, that further revises the seismic Compliance Plan issue commitments, in the letter, USEC also informed NRC that it was stopping work on the committed seismic modifications uritil NRC completes its review of the USCs, among other items. In response to USEC's letter, NRC informed USEC via letter dated July 24, 1997, that NRC still views December 31,1997, as the date to which USEC remains committed for completing the seismic modifications, and that any actions taken by USEC that may jeopardize meeting that date, are teken at USEC's own rist;.
By letter dated July 31,1997, USEC submitted a revised amendment request to:
- Obtain NRC approval of the resolution to three previously-identifie USOs.
- Revise the completion date for completing the seismic modifications from December 31,1997, to 18 months after completion of the following (assuming that analyses in progress, including the site specific seismic risk analysis, confirm the current modifications; otherwire new modifications and schedules will be proposed by USEC): (a) USEC submits, and NRC approves, the final design of the C 331 and C-335 structural modifications; (b) NRC completes its review of three USQs; (c) NRC completes its review of the seismic analysis included in USEC's upgraded SAR; (d) USEC submits, and NRC approves, an updated seismic risk analysis (scheduled to be submitted by December 1,1997).
- Revise the JCO in Compliance Plan issue 36 to only include sheltering, instead of sheltering and ovacuation.
- Revise the JCO in Compliance Plan issue 36 to reflect that the final design of the C 331 and C 335 structural modifications has been completed (current JCO states that the SAR upgraded seismic equipment analysis for Buildings C-331 and C-335 is not yet comp!cte).
- Revise the JCO to reference a DOE sponsored study performed by Lawrence Livermore National Laboratory which reviewed the health risks to workers and to the public from potential UF6 releases due to a seismic event.
By separate ietter dated July 31,1997, USEC provided drawings showing the final design for the planned structural modifications to Ruildings C-331 and C-335.
On July 23-25,1997, the staff conducted an onsite review of the facility, viewing areas where the seismic modifications will be installed, and discussed the modifications with
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- plant staff. NRC requested additionalinformation by letter dated August 20, t997; USEC provided the additionalinformation by letter dated September 19,1997.
DISCUSSION Each of the above 5 items it discussed in the following paragraphs.
'l.. USQ Resolution:
Question 1: The increased stiffness of the buildings following cumpletion of the modifications mr/ increase the number and the probability of seismicallv induced 4 equipment failures inside the buildings.
The certificate holder has identified.this issue as a USO because the probability of seismically-induced equipment f ailures may be increased by the stiffening of Buildings C-331 and C-335 and the equipment failures may be different from those currently identified in the SAR: however, the certificate holder conclude's that the consequences of such failures are bounded by the seismic failures evaluated in the JCO for Compliance Plan Issue 36. The staff review consisted of assessing the revised information, contained in the certificate holder's July 31,1997, subr..ittal, to the extent that it affects previous staff conclusions.
', The equipment failures were determined based on a structural analysis of the Paducah
_ '00' buildings, incorporating the structural mo6fications. - The modifications stiffen the buildings, which then changes the frequencies where amplificatice occurs. -Those equipment, piping systems, and components whose capacities are less than the EBE
- peak ground acceleration, were further evaluateo to determine possible failure modes and release of UF6 gas, if any, when ubjected to the EBE. The equipment f ailures were determined by analysis and by an experience-based methodology, codified in DOE Standard DOE STD 1020 94, " Natural Phenomena Hazards Design and Evaluation Criteria for Department of Energy Facilities."
In the July 31,1997, submittal, the certificate holder concludes that postulated equipment failures resulting from stiffening the buildings could result in a release of 45,920 pounds of UF6, assuming maximum power of 3040MW. In th : c.af f's iE Compliance Evaluation Report (CER) dated August 1996, it was ertimated that 64,000
_ pounds of UF6 would be released an s result of a seismic event, which envelopes the mine recently calculated value of 45,92O_ pounds. Therefore, the staff's previous conclusions in the CER, and the JCG, remain valid. The staff approves the resolution to
. USQ 1.
Question 2: The process'of installing the new structural steel may temporarily make the buildings and the contained equipment more susceptible to seismically-induced failure as the existing frames are altered and/or replaced.
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4 The certificate holder has identified this issue as a USO because:
- Temporary supports (shoring) used to support the structure, when existing steel is removed, will be designed for static and construction-activity dynamic loadings but will not be designed for seismic loadings. This increasas the probability of localized building and/or equipment f ailures above those evaluated in the SAR.
- As the project progresses, portions of the structure may be in a weakened state.
The various possible combinations of configurations have not been analyzed, and may result in an increased piobability of building and/or equipment f ailure should a seismic event occur, lhe certificate holder concludes that the probability, but not the consequences, associated with these potential failures willincrease as a result of the construction activities. The consequences remain bounded by the seismic failuies described in the JCO for Compliance Plan Icsue 36. The bounding case assumes 4 complete building collapse and the release of the entire contents of the cascade system.
The structural modifications consist of either removing existing steel bracing in a number of frame sections (i.e., bays), and replacing it with bracing whose capacity is higher, or adding bracing in bays where no bracing currently exisu. Each bay is two floors high and approximately 25 feet wide. The lower floor (ground floor) is approximately 20 feet from ground tu first floor; the upper floor (cell floor) is approximately 40 feet from floor to roof. The installation sequence that one should employ is not clear-cut. One would like to minimize both the time that the structure is degraded and the amount of degradation since risk is directly proportional to these parameters. Installing the structural modifications, however, ir a trade-off between minimizing the time that the structure ir, in a weakened state, both during construction and the total time that the structure is below its required capacity; and rainimizing the degradation to the structure during construction.
To minimize the time that the structure is below its required capacity, and also below its current capacity, on.e would attempt to install as much of the steel as possible in as short a time as possible (i.e., work in parallel e remove and replace ste,el bracing in many bays concurrently). However, doing so, would weaken the structure more during construction than if the steel were installed a little at a time (i.e., work in series - remove and replace steel bracing in one or only a few bays at a time before removing the bracing in the next bay). On the other hand, to minimize the degradation to the structure during construction, one would want to install the steelin series, but that would lengthen the total time that the structure is below it required capacity, and the time that it is degraded below w. aurrently exists. Considering that the structure contains some weak links that fail 5 % ;cantly below their required design capacity, it is important to promptly install the modifications.
A description of the construction sequence to be employed by the certificate holder is provided. Work will begin on the cell floor first and will be completed before beginning work on the ground floor. For bays where existing steel must first be removed, no more
5 than three bays will be disassembled concurrently. For these bays, the steel will be removed and replaced, starting at floor level and only removing steel in the lowest braced segment, before commencing work on the next higher adjacent braced elevation -
- simultaneous demolition of bracing from cell floor to building roof in a bay will not be permitted. Generally, there are three braced segments between the cell floor and the roof, resulting in two "X" braces. The work will normally begin in a centrally located t bay and proceed outward toward the perimeter of the building. On the cell floor, removal of existing steel will commence in some bays before installation of steelin bays whero no existing steelis prescnt. This w91 result in a local degradation of the structure, of short duration, below what cur ently exists. However, on the ground floor, work in all bavs where only new steel is to be added (i.e., no existing steel needs to be removed) will be completed before beginning work on tays where existing steel must be removed.
This sequence results in the ground floor stiffness always being greater than what currently exists. On the ground floor of each building (C-331, C-335) there are approximately 40 bays where the existing diagonal bracing will be removed and replaced with new bracing; and there are approximately 180 bays where new diagonal bracing will be added without removing existing steel. On the cell floor of each building, there are approximately 90 bays where existing diagonal bracing will be removed and replaced with new bracing; and there are approximately 35 bays where new diagonal bracing will be added without removing existing steel. The certificate holder estimates that the time that any given bay on a particular level will be in a degraded condition is 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
On the ground floor, the structure will not experience any global degradation since all bays that only require new steel (i.e., removal of existing steelis not necessary), will be completed first, before beginning work remnving existing steelin other bays. On the cell floor, the total time that the structure may experience some degradation is approximately 30 - 90 days per building, based on completing a bay in one day, working up to three bays concurrently. This time is not excessive and the degradation will be local. Therefore, the staff concludes that the degradation to the structure on the cell floor will be local and of short duration. The staff approves the resolution to USQ 2.
t Question 3: The process of installing the new structural steel may temporarily increase the probability of equipment f ailures due to postulated load handling accidents during construction.
The certificate holder has identified this as a USO because the projected plan for installing the steel will require approximately 2300 lifts of structural steel shapes and related materials in each building. Some of the lif ts will be over, or in proximity to, operating O or AQ equipment, including the cascade. A crane failure accident analysis for the cascade buildings in the SAR assumes that approximately 200 moves of major equipment are required each year and approximately 2% of the move time is over operating equipment. The analysis assumes a drop oi a '000' compressor (approximately 33 tons) onto cascade equipment that is running above atmospheric pressure.
The certificate holder concludes that the probability, but not the consequences, i
6 associated with the potential f ailure of equipment impo tant to safety, evaluated in the SAR, have increased as a result of the construction activities. The consequences remain bounded by the seismic failures in the JCO for Compliance Plan issue 36. The bounding case assumes a complete building collapse and the release of the entire contents of the cascado system. The certificatt holder concludes that the consequences are bounded by f ailures evaluated in the SAR and the JCO for Compliance Plan issue 36. In the SAR accident analysis, the weight of the dropped object is significantly more than the weight of er.ch lift associated with installation of the seismic modifications (33 tnns versus 5 tons). The lower weight would likely result in less damage than assumed in the SAR accident analysis. The bounding case in the SAR accident analysis assumes complete building collapse and release of the entire contents of the cascade system. These consequences exceed the estimated consequences of any equipment failures that may result due to postulated load handling accident. To further reduce the consequences, operation in Buildings C-331 and C-335 are restricted to subatmospheric pressure, which would decrease any release resulting from an equipment failure.
Other controls to be implemented by the certificate holder for each lift, to prevent and mitigate consequences associated with a potentialload handling accident, are:
. Lift time will be minimized;
- Rigging equioment will be inspected prior to each lif t; a Lift plans will be prepared and approved in accordance with plant procedures; a!!
lifts will require lif t specific rigging plans and will be approved by the steel installation contractor, plant construction engineering, and plant operations personnel;
- Each lif t will be planned from initial rigging, lift placement, stabilization, and rigging removal;
- Planning will include, for each lift, actions to be taken in response tc a postulated load handling accident;
- A construction engineer will be assigned to provide dedicated oversight;
- Work will be performed in accordar.,:e with approved work plans and the work control process;
- Hazardous equipment in the vicinity will be identified to construction personnel.
For lifts over, or in proximity to, O or AQ equipment, the following additional controls will be applied (these controls are consistent with TSR 2.4.4.13, Heavy Equipment Handling, which addresses movement of large process equipment):
- An operations representative will witness the lift and will maintain voice contact with the Area Control Room (ACR) throughout the lift to permit a rapid responso should a load handling accident occur.
. Facility owners will be notified prior to each lift.
+ important to safety equipment will be identified to construction personnel.
The staff concludes that the certificate holder has taken appropriate measures to prevent a load handling accident from occurring, and to mitigate the consequences should such an accident occur Consequences of a load drop accident have been previously evaluated in the SAR and bound potentialload handling accidents associated with installation of the structural steel. The staff's analysis did not include an evaluation of l
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Occupational Safety and Health Administration (OSHA) aspects of the instellation. The y
staff approves the resolution to USO 3.
- 11. Revise completion date for completing'the seismic moc'ifications from December 31,1997, to 18 months after completion of the following: (a) staff review of the final design of the structural modifications: (b) staff review of the
- three USO's; (c) staff review of the seismic analysis in the updated SAR: (d) staff approval of the updated seismic risk analysis for the Paducah site.
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.The certificate holder provided a schedule showing major milestones for completing the seismic upgrades. The certificate holder believes that personnel safety can be assured with their proposed schedule. The staff reviewed the schedule provided by the certificate holder and finds that it is reasonable and will not create excessive degradation
< of the structure as the existing steelis removed. Therefore, the staff concludes that 18 months to complete the structuralinstallation, after the USOs are approved, is
. reasonable. The Compliance Plan did not require the staff to perform the other items
- requested by the licensee before installing the modifications. Further, the staff believes that steelinstallation should begin promptly because of the existing weak structural compo..ents. Therefore, the staff recommends approval of the schedule to complete the
. modifications 18 months after the staff approves the USQs (ll(b)) and recommends denying that the schedule be based on satisfying conditions described in Sections ll(a),
ll(c), and ll(d) above. This recommendation requires that installation of the modifications be completed no lator than 18 months after the amendment is issued.
> Thu staff willimpose a condition to certificate GDP-1 as follows:
- _Notwithstanding sections 1(c),1(d),1(e), and 1(f) of the Plan of Action and
- Schedule in Compliance Plan issue 36, the structural modifications to Buildings C-
- . 331 and C-335, to upgrade their seismic resistance to resist the 0.15g EBE, equivalent to an approximate 250-year return period earthquake, will be completed no later than June 30,1999.
Ill. Change the JCO in issue 36 of the Compliance Plan to only include sheltering.
The current JCO includes both shelteting and evacuation as emergency preparedness actions to be potentidly employed of fsite in case of an accident. By removing evacuation, the JCO agrees with thc certificate holder's emergency preparedness plan and offsite actions within USEC's luthority. The NRC-approved Emergency Plan includes sheltering in-place. The staff does not object to revising the JCO in this regard.
IV. Change the JCO in issue 36 of the Compliance Plan to reflect that the final design of the C 331 and C-335 structural madifications and seismic equipment amlysis are complete.
Since the purpose of this JCO change is to reflect that the final design of the C-331 and C-335 structural modifications to raise the capacity of the structures to 0.15g
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curve, and the seismic equipment analysis have been completed by USEC, the staff does not object to revising the JCO as requested.
V. Chant,e the JCO in issue 36 of the Ccmpliance Plan to reference a DOE-sponsored study performed by Lawrenco Livermore National Laboratory.
The study that the certificate holder wishes to add to the JCO reviewed the health risks to workers and to the public from potential UF6 releases due to a seismic event. The staff did not review the report, nor was it requested to review the report. The staff has >
not relied on this report to reach its conclusions. Since the amendment request, as proposed, implies that the staff ceviewed and approved the. report as part of the JCO.
approval of the amendment will not include the reference to the report and this request is denied.
ENVIRONMENTAL REVIEW lsnuance of an amendment to the Certificate of Compliance GDP-1 to revise the Compliance Plan is subject to the categorical exclusion provided in 10 CFR 51.22(c)(19).
Therciore, neither an environmental assessment nor an environmentalimpact statement is required for the proposed action.
CONCLUSIOR For reasons discussed above, the staff recommends:
. Approval of the resolution to the three USQs.
. (at Approval of a completion date for completing the seismic modifications of 18 months after the staff issues the related amendment; (b) denial of the request to change the completion date for completing the seismic modifications from December 31,1997, to 18 months af ter completion of the following: (i) stsff review of the final design of the C-331 and C-335 structural modifications; (ii) staff review of the seismic analysis included in USEC's upgraded SAR; (iii) the t staff approves an updated seismic risk analysis submitted on December 1,1997.
- Approval of the change to the JCO in Compliance Plan Issue 36 to only include sheltering, instead of sheltering and evacuation.
= Approval of the change to the JCO in Compliance Plan issue 36 to reflect that the final design of the C-331 and C-335 structural modifications to raise the capacity of the structures to 0.15g magnitude earthquake, as defined in the SAR Upgrade Program site spee:fic hazard curve, and the seismic equipment analysis, have been completed by USEC (current JCO states that the SAR upgraded
9 seismic equipment analysis for Buildings C 331 and C 335 is not yet complete),
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Denial of the change to the JCO to reference a DOE-sponsored study performed by Lawrence Livermore National Laboratory which reviewed the health risks to workers and to the public from potential UF6 releases due to a seismic event.
The Region til Inspection staff has no objection to this proposed action. The staff discussed the Compliance Plan changes with the Department of Energy (DOE). DOE does not object to changes to the Compliance Plan that are recommended for approval in this CER.
Princioal Contributor
. Andrew Persinko J
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DISTRIBUTION NRC FILE CENTER PUBUC, NMSs r/f FCSS r/f SP8 r/f K'oBrien, Ritt PHdand. Rill NMsS Dir, off, rlf Rlll gnfrseis. pad
'See previous concurrence OFC 'SPB E 'beB E 'SPB E 'SPB E ER _ 8 NAME DPersinko/ij MHorn DHoad:ey DMartin / en DATE 11/2 A/97 11/26/97 11/26/97 11/26/97 /2# /97 C = COVER E = COVER & ENCLLSUhE N = NO COPY OFFICIAL. RECORD COPY 4
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iscussed the Compliance Plan changes with the Department of Energy (DOE). DOE do not object to changes to the Compliance Plan that are recommended for approval in this C .
Princioal Centribut Andrew Persinko I
"A DtSTR!BUTIGit NRC F4LE CENTER PUBLIC NMSS t/f FCSS r/f SPB r/f K'OBrien, Rlli PHiland, Rill NMSS Dir, Off. r/t R111 g:\_fraais. pad O F'J _ J('8 h SPB $PB b SPB h SPB NAME ersinkolii
n Hoadley i tin RPierson OATE \ h7 11 /$97 l' h/97 Ib7 / /97 C = COVER E = OOVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPV ;
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