ML20217L838

Rev 7 to DOE/ORO-2026, Plan for Achieving Compliance W/Nrc Regulations at Paducah Gaseous Diffusion Plant

ML20217L838
Person / Time
Site:	Paducah Gaseous Diffusion Plant
Issue date:	03/20/1998
From:	UNITED STATES ENRICHMENT CORP. (USEC)
To:
Shared Package
ML20217L825	List: ML20217L819 ML20217L838
References
DOE-ORO-2026, NUDOCS 9804070397
Download: ML20217L838 (8)

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DOE /ORO-2026 Plan for Achieving Compliance with NRC Regulations at the i

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Seismic Capability of Buildings C-331 and C-335 (new issue)

REQUIREMENTS -

10 CFR 76.35(a)(4), (6), and (8) "The application for an initial certificate of compliance must.

include the information identified in this section. (a) A safety analysis report which must include the

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following information:... (4) An assessment of accidents based on the requirements of f 76.85; j

... (6) A description of equipment and facilities which will be used by the Corporation to protect health and minimize danger to life or property (such as... provisions for protection against natural phenomena;... (8) A description of the plant site, and a description of the principal structures, systems, and components of the plant."

10 CFR 76.85 "The Corporanon shall perform an analysis of potential accidents and co-wes to establish the basis for limiting conditicns for operation of the plant with respect to the potential i

for releases of radioactive material. Special attention must be directed to assurance that plant i

operation will be conducted in _a manner to. prevent or to mitigate the consequences from a reasonable spectrum of postulated accidents which include... natural phenomena in order to ensure adequate protection of the public health and safety. Plant operating history relevant to the assessment should be included. In performing this assessment, the full range of operations should be considered including, but not necessarily limited to, operation at the maximum capacity contemplated. The i

assessment must be performed using an expected release rate resulting from anticipated operational occurrences and accidents with existing systems and procedures intended to mitigate the release consequences, along with site characteristics, including meteorology, to evaluate the offsite radiological consequences."

COMMITMENTS Source: Safety Analysis Report

2. Site Characteristics [Rev. 3, S/31/%]

This chapter provides information on the location and site characteristics of the facility to address 10 CFR 76.35(a)(8), including the historical basis for site characteristics in geology and seismology. This information is needed to support the assumptions that were used in determining the impacts of normal operation, the hazard and accident analysis as described in Chapter 4 of the application, and emergency operations, particularly with regard to the contribution of natural seismic

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phenomena to the initiation of events and the site related assumptions that were used in evaluating accident consequences.

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3. Facility and Process Descriptica [Rev. 3, $/31/96]

i This chapter provides information c4n the principal structures, systems, and components of the plant as well as information on the equipment and facilities that are used to protect health and minimize danger to life or property to address 10 CFR 76.35(a)(6) and 10 CFR 76.35(a)(8),

including (1) properties of uranium and uranium hexafluoride (UF) and the process and facilities used for enriching UF. in the 235U isotope; (2) UF, feed facilities and processes; _

PGDP Rev. 7.3/20/98

Issue 36, Page 2 Seismic capability of Buildings C-331 and c-335 1

I (3) UF. enrichment facilities and processes; and (4) UP. product withdrawal facility and pr'ocesses.

'Ihis information is needed to support the assumptions that were used in determming the impacts of normal operation, energency planmng, and the hazard and accident analysis as described in Chapter 4 of the application regarding the contribution of facility and process design to initiation of events

~and the design-related assumptions that were used in evaluating accident consequences."

4. Accident Analysis [Rev. 3,5/31/%]

This chapter provides a description of the accident analyses that were performed to address 10 CFR 76.35(a)(4) and 10 CFR 76.85. The accident analyses consisted of (1) review of operations including the history of failures and accidents; (2) discussion of the methodology used in determining the risk associated with hypothetical. accidents; (3) identification of accident scenarios; (4)

. consequences of accidents; and (5) determination of residual risk. The accident analyses considered -

natural phenomena including earthquakes.

i DESCRIPTION OF NONCOMPLIANCE In 1985, the PGDP was analyzed for a 0.18g peak ground acceleration canhquake loading corresponding to an approximate 250-year earthquake return interval, the. Evaluation Basis EartSquake (EBE) established in the 1985 Safety Analysis Report (SAR). Building capacities were -

- shown to be less than this eanhquake demand but only minor structural damage was estimated, and strucaral integrity was maintained. However, certain cascade piping anachments known as expansion joints or bellows were judged to fail in significant numbers within the buildings resulting

- in a substar:tial combined release of uranyl fluoride (UO F ) and hydrogen fluoride (HF) from the 22 cascade facihdes. Operations were limited to moderate power levels to keep the enrichment process sub-atmospheric until these expansion joints were improved.

Recently, structural seismic loading capacity analyses, performed as part of the general safety analyses update of the Paducah Gaseous Diffusion Plant (PGDP), have identified that significant plant damage could occur in two of the main cascade buildings, C-331 and C-335, below the Evaluation Basis Eanhquake. This damage could involve the failure of the approximately 20-foot s

wide spans which traverse each building in three locations of each building's roof. The similarly supported memnine and cell floor sections could also fail. The affected spans are attached at one column line and supported by a sliding support known as a " rocker arm." At a seismic loading

~ bove 0.05g, the building columns might be displaced out of phase to a distance greater than the a

available travel of the extension bracket support causing the spans to fall. Previous acceptance by DOE of the facility's seismic capability relied on the integrity of the buildings for events up to the.

o Evaluation Basis Earthquake. This potential for loss of the building integrity has been determined to be an unreviewed safety question and outside the plant's authorization basis.

JUSTIFICATION FOR CONTINUED OPERATION In response to the Unreviewed Safety Question, structural modifications to improve the bracing in the affected buildings have been developed and are in progress. Specifically, structural cross -

bracing will be added at specific column locations in the nonh-south and east-west directions in 1 Buildings C-331 and C-335 as identified in the detailed design which has been prepared to raise the capacity of the structures to a 0.15g magnitude canhquake as defined by the SAR Upgrade Program PGDP Rev. 7. 3/20/98

Seismic Capability of Buildings C-331 and C-335 Issue 36, Page 3

' site specific hazard curve. These modifications will reduce displacements thus ensuring the ove.sil building integrity. The modifications are scheduled for completion over an 18-month period concluding in July 1997. Completion of the modifications will bring the PGDP process building structures into compliance within the interpretation of the 1985 SAR and current seismic requirements for GDP hazardous facilities. However, the upgraded SAR seismic equipment analysis is not yet complete. Additional modifications to equipment could be recommended depending on the findings of the remaining equipment evaluations and the analyses of the HF and UO F2 Projected 2

releases.

PGDP plans to continue operatior. with two process buildings, C-331 and C-335, in a seismically weak condition until the completion of building reinforcement modifications. Continued l

operation of the processes in these buildings is justified in the interim since the increased risk to the general public and on-site workers is within an acceptable level. The risk increase to the public is a small increase in the chance of an exposure to UO:F and HF causing minor to moderate renal 2

injuries. The risk increase to some on-site workers is a moderate (factor of 2 to 3) increase in the chance of both exposure to toxic releases and physical injury. (See the "Paducah Gaseous Diffusion Plant Justification for Continued Operation: Temporary Operation of Buildings C-331 and C-335 with Potentially Severe Structural Damage Due to Evaluation Basis Earthquake Loads," prepared by the Department of Energy Regulatory Oversight, Oak Ridge, TN, dated May 17, 1996.)

Compensatory measures were initiated upon recognition of the structural deficiency and will remain in place until the corrective modifications are complete. These measures minimize the number of shift personnel in the affected buildings during the interim period, and the allowed power level in the two buildings is limited to maintain the cascade subatmospheric thereby minimizing the release after a seismic event.

The conclusion that the risk level is acceptable during the interim operating period is supported by evaluations of the consequences to the public and on-site workers from conservative release scenarios based on the projected and bounding building failures that are possible up to ^he evaluation basis earthquake. Physical effects such as the impact of a seismically induced fire also were examined as part of these scenarios.

The projected structural response of the two buildings up to an Evaluation Basis Earthquake (250-year return interval, peak ground acceleration equivalent: 0.15 g) is the inward collapse of three areas of each building's roof, mezzanines, and cell floor. These areas are about 20 feet wide and run the leng:h of each building in the direction of the structural expansionjoint between interna

structural units. The collapse could cause the release of UF., UO F, and HF. In addition, there is 2 2 s

probability that the buiMings could collapse in response to the loading of earthquakes that produce accelerations approaching 0.15g. Based on the possible structural response, four exposure cases were evaluated. A bounding case (Case 1) assumed that the building collapsed (i.e., the building fell over onto its side) and the entire contents of the cascade syen was released into the collapsed structures, it should be noted that the load bearing capacity of the converters located throughout the building on the cell floor would prevent the complete flattening cf the stmeture and provide a vertical air space approximately 8 feet high. The analyzed quantity of the UO F and HF 2 2 released was not reduced by physical considerations such as the material that would remain in the cascade piping and equipment or may deposit in the building or the vicinity of the building due to aerosol deposition. However, the effects of thermodynamics and the mixing of fluids (water vapor and R-114 Freon) in the building were considered. Case 2 used a conservative, but more realistic, engineering analysis basis that included an estimate of the UF. that would remain in the convertere following the cascade system ruptures. The amount of aerosol deposition that would occur during 1

PGDP Rev. 7. 3/20/98

Issue 36, Page 4 Seismic Capability of Buildings C-331 and C-335 the residence time of the release cloud in the buildings was also considered. This release dase is a conservative but defendable estimate of the bounding physical state of the building. Cases 3 and 4 3

are similar cases of the buildings' expected actual structural response to an Evaluation Basis Earthquake event (including the failure of areas of the buildings at the structural expansion joints).

Case 3 is based on a highly conservative estimate of the cascade damage that would be sustained if the roof, me=nine, and cell floor failed as predicted and no aerosol deposition occurred. Case 4 is the same 1 case 3 with consideration given to aerosol deposition.

The results of the four evaluation cases are summarized in the following table:

Table 1. Uranium Uptake and HF exposure

• to Individuals Evaluation Case Meteorology Maximum Maximum HF Exposure HF Exposure Class-Wind Uranium Inhaled Uranium Inhaled Concentration Concentration speed (m/sec)

Mass (mg) at 1 Mass (mg) at 5 (ppm)-1 mile (ppm)-5 miles mile miles I. Building Collapse-No retention in D-4 139 70 38 19 Cascade (Bounding Case)

II. Building Collapse-Conservative D-4 45 16 15 5

estimate of -

retention in Cascade III. Partial Building Failure F-3 32 7

17 3

with No Aerosol Deposition IV. Partial Building Failure F-3 20 4

11

'2 with Aerosol Deposition

• HF exposures are based an 1 bour average concentrations.

%e results of all but the bounding case (Case 1) show the potential for only a mild exposure, nearly within the accident evaluation guidelines. The bounding case consequences indicate the potential for significant renal injury, that would not be potentially life threatening at one mile distance from the release point.' One mile is essentially the distance to the site boundary from the buildings in question. The risk of exposure to the general public of moderate (uptake of 100-150 mg of uranium) and low (50-100 mg uptake) renal hijuries was estimated to be 0.15 injuries and 0.78' injuries / year, respectively, assummg no benefit from an emergency response. If emergency response

[ is considered and credited with a factor of 2 benefit due to sheltering, then the risk is essentially zero, at 0.15 low level renal injuries / year. Given the highly conservative nature of the evaluation --

of the release and the low consequences, continued operation does not pose a significant undue risk to the public during the period of operations until building modifications are completed.

The risk to workers in the buildites was estimated as well. Based on an assumed 5,wrcent chance of buikik.g collapse and a 50 percect chance of being present in the building (i.e., on shift),

PGDP Rev. 7,3/20/98

Seismic Capability of Buildings C-331 and C-335 Issue 36, Page 5 i

the inju'ry rate to individual workers was estimated at approximately 1 x 10-8 per year with a total injury rate risk estimated at 2.6x 10-3 injuries per year (for an operating staff of 26). This is judged to be acceptable and is no greater than the risk of general office work on-site. Injury from structures may even be higher in the office buildings, although the probability of exposure to HF and UO F 2 2 releases would be greater in the process buildings.

Therefore, it is concluded that the risk to the public and the on-site workers from the unmitigated response of Buildings C-331 and C-335 is not extreme and can be accepted without undue harm with the compensatory measures imposed on operations remaining in effect until the modifications are complete while the structural weaknesses are being corrected.

PLAN OF ACTION AND SCHEDULE The actions to upgrade the seismic capabilities of Buildings C-331 and C-335 are as follows:

1.

Based on a Directive for Information provided to USEC by DOE on September 22,1995, the USEC evaluation of the currently available information from the DOE safety analysis upgrade effort related to seismic capabilities at the facility completed on October 23,1995, the DOE evaluation of the USEC response dated October 31,1995, and USEC's proposed resolution documented on January 9,1996, the following actions are being implemented to ensure the protection of the workers and public health and safety:

Until the completion of modifications discussed below, operations in Buildings C-331 and C-335 will be limited to subatmospheric pressure within the enrichment cascade equipment.

Operations personnel will be instructed on the specific emergency procedures for shutting down the affected enrichment cascade equipment and building ventilation systems following a seismic event.

Building access will be limited to only those individuals essential to operations, inspections, or those personnel performing the modifications until they are complete.

Modifications to increase the seismic capability for floor and roof sections in Buildings C-331 and C-335 will be completed by June 30,1999.

l 2.

At the time of transition from DOE regulatory oversight to NRC regulatory oversight USEC.

will inform NRC of the interim meuures still in effect for the affected buildings and equipment

- and the current status of upgrading the seismic capabilities of the affected buildings and equipment.

3.

Documentation prepared for the design of the raodification and other relevant information concerning implementation will be provided to the NRC, upon issue, for information and review.

PGDP Rev. 7,3/20%

I I sue 36, Page 6 seismic capability of Buildings c.331 and c 335 4.

By December 1,1997 USEC shall submit for NRC approval an updated seistriic risk Analysis for the Paducah plant site. The analysis shall:

. Consider all available regional and site-specific data published by the U.S. Geological Survey.

Provide an estimate of the peak ground acceleration for a seismic event with a 250-year return period. If the estimate is greater than 0.15g, then the return period for a 0.15g event shall also be estimated.

Any proposed modifications that may result from this analysis shall be subject to a backfit analysis pursuant to 10 CFR 76.76(b).

SUMMARY

OF REQUIREMENTS, COMMITMENTS, AND NONCOMPLIANCES Issue: Seismic Capability of Buildings C-331 and C-335 Code of Federal Regulations Part Title 10 76.35(a)(4), 76.35(a)(6), 76.35(a)(8), 76.85 Application Cammitment Section Safety Analysis Report 2.1.1, 2.6, 3.1, 3.3, 3.4, 4.2.2.6, 4.6.1, 4.7, Table'4.9-1 Application Noncompliance Statement Section Safety Analysis Report 2.7, 3.16.1, 4.10 2

6 PGDP Rev. 7,3/20/98 1

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