ML20210F986

Compliance Evaluation Rept Accepting Amend to Coc GDP-1 Re Criticality Accident Alarm Sys Audibility Upgrades

ML20210F986
Person / Time
Site:	07007001
Issue date:	07/28/1999
From:	NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:
Shared Package
ML20210F982	List: ML20210F976 ML20210F986 ML20210F990
References
NUDOCS 9908020247
Download: ML20210F986 (3)

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• %q k UNITED STATES

[ ij NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. 20665-0001

/ July 28, 1999 DOCKET: 70-7001 CERTIFICATE HOLDER: United States Enrichment Corporation Paducah Gaseous Diffusion Plant Paducah,KY

SUBJECT:

COMPLlANCE EVALUATION REPORT: APPLICATION DATED MARCH 1,1999, CRITICALITY ACCIDENT ALARM SYSTEM AUDIBILITY UPGRADES BAQKGROUND Compliance Plan issues 46 and 50 require United States Enrichment Corporation (USEC) to upgrade audibility of the criticality accident alarm system (CAAS) alarm horns in certain areas of the plant process buildings. Since May 1998, the plant has experienced unreliability of the air sv9 ply system to power the CAAS horns. USEC reported several events dealing with the l inoput bility of the CAAS system due to the loss or degradation of the air supply. By a i certificate amendment request (CAR) dated November 5,1998, USEC indicated its plan to upgrade Paducah Gaseous Diffusion Plant (PGDP) CAAS system audibility, utilize a dedicated Jr system and air accumulators to supply the new CAAS horns to improve its reliability, and complete the upgrade project by January 18,2000. In the November 5,1998 CAR, USEC also requested NRC approval of its audibility determination criteria. NRC approved the CAR and issued the amended Certificate of Compliance on January 7,1999.

By letter dated December 4,1998, NRC granted USEC a CAAS audibility exclusion request for permit-required confined spaces and cell housings associated with cells that are running. In these areas, a " buddy system" is used to ensure that personnel working in these areas are notified to evacuate in the event of inadvertent criticality.

By letter dated March 1,1999, USEC submitted a CAR to revise the Technical Safety Requirements (TSRs) rclated to the audibility requirements for the CAAS at PGDP. This CAR also requests approval of a revision to related sections of the Safety Analysis Report (SAR).

By letter dated June 25,1999, USEC provided corrections and clarifications to the CAR.

DISCUSSION:

In the March 1,1999, CAR, USEC described its modification project to design and install an upgraded CAAS alarm system to ensure adequate audibility throughout the process buildir,gs and for una%rmed facilities within the evacuation area of buildings with CAAS clusters. In general, the overall new system is similar to the current system, except for the changes in the air supply and electrical circuits to increase system reliability.

Currently, the plant air system provides air supply for the CAAS horns and other plant needs.

The modification will improve the CAAS horns' reliability by providing a dedicated air supply system with air accumulators and air compressors to CAAS horns. For each new air horn, new air piping will be installed and routed through a main air supply header to an accumulator outside of the building. The accumulators will be maintained at the minimum air pressure 9909020247 990728 PDR ADOCK 07007001 C PDR

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necessary to blow the air horns for at least two minutes. The required minimum pressure varies for each system, depending on the number and size of accumulators and the number of horns.

The post-maintenance testing and the quarterly CAAS surveillance, both of which will sound all CAAS alarms, will deplete the CAAS accumulators below the pressure necessary to sound the air horns for two minutes. USEC has estimated that the time to recharge the accumulators above this pressure is greater than five hours using the perrnanently installed compressors alone. To reduce the recovery time and the time covered under TSRs, USEC will install a temporary connection to allow the connection of a portable air compressor with enough capacity to recharge the accumulators in approximately one hour. Under both the current and the new TSRs, PGDP will enter the Limiting Condition for Operation (LCO) when an area dces not have an audible CAAS. The LCO calls for immediate actions to restrict operations, rc;trict access to the affected areas, and provide another means of criticality detection to personnel allowed into the affected areas (i.e., portable detectors or alarm devices). Since both the post-maintenance testing and the quarterly surveillance are planned activities, the TSR LCO compensatory measures would have been in place before these activities take place.

The modification also adds a loss-of-power monitoring feature to the circuits powering the homs. Loss-of-power to the horn power circult will result in an alarm at the Central Control Building C-300 CAAS console and will be indicated as a trouble alarm associated with one of the clusters located in that building. This alarm will give immediate notification to operators of loss-of-power to the horns, which will contribute to a quicker determination of CAAS inoperability in the affected area.

USEC also incorporates previously granted CAAS audibility exclusion areas into the proposed SAR and TSR sections. By letter dated December 4,1998, NRC granted USEC CAAS audibility exclusion request for permit-required confined spaces and cell housing associated with cells that are running. In these exclusion areas, a " buddy system"is used to ensure that personnel working in these areas are notified to evacuate in the event of inadvertent criticality.

Implementation of the CAAS modification project will involve entering existing the CAAS LCO in the areas being modified, disconnecting the existing relays and associated equipment for the local and building horns, connecting the new relays and associated equipment, and performing operability testing on the new CAAS. USEC will perform operability testing using approved procedures and will meet all acceptance criteria prior to declaring the new CAAS operable. The final connection of the cluster detectors to the modified alarm system will be performed in only one area at a time. As a result, TSRs covering the new upgraded CAAS must be in place at '

the same time as TSRs covering the existing CAAS. Once USEC has .;ompleted the upgrade project and the new CAAS is operable in all of the buildings, it will remove TSRs related to the current CAAS audibility. Similarly, USEC will retain the description of the current CAAS in various SAR sections while incorporating the description of the new CAAS into those same l sections. Once USEC has completed the upgrade project and the new CAAS is operable in all of the buildings, it will remove the description of the current CAAS system from the SAR.

, The audibility acceptance criteria that the CAAS modification is intended to meet was previously l approved by the amended Certificate of Compliance on January 7,1999. Therefore, only the l TSR surveillances for the modification have not been previously reviewed and approved.

ANSI /ANS 8.31986," Criticality Accident Alarm System," recommends surveillances to ensure

3 that instrument responses to radiation are checked (detect the criticality), the audibility of the alarm is periodically measured, and the entire CAAS be tested in the course of drills. The current CAAS configuration surveillance requirement for testing the CAAS and building horns quarterly meets the ANSI requirements and that TSR surveillance remains the same for the CAAS modification. The only TSR surveillance change between the current CAAS and the CAAS modification is the surveillance for the air or nitrogen supply. The current CAAS relies on nitrogen pressure to sound the alarm horns for the required 120 seconds. The TSR surveillance for a nitrogen pressure of 900 pounds per square inch gauge (psig) was previously determined to be adequate to meet 120 seconds. The CAAS modification is relying on air pressure in accumulators located near the alarm horns. The proposed quarterly TSR surveillance verifies that the air pressure in the accumulators is adequate to sound the alarm horns for the required 120 seconds. The surveillance air pressure varies from 121 psig in the CAAS for the C-331/C-335 Tie-Line to 145 psig in the CAAS for the C-400 Building. The differences in the surveillance air pressures are due to differences in the number and size of accumulators and the number of horns.

ENVIRONMENTAL REVIEW lssuance of an amendment to the Certificate of Compliance GDP-1 to revise the Technical j Safety Requirements is subject to the categorical exclusion provided in 10 CFR 51.22(c)(19). i Therefore, neither an environmental assessment nor an environmental impact statement is l required for the proposed action. I CONCLUSION '

The CAAS audibility upgrade modifications will irnprove the auduny and reliability of the CAAS, which minimizes the consequence of criticality accidents. The upgraded CAAS TSR air pressure surveillance is the only surveillance change and that surveillance appears adequate to ensure the air pressure will sound the alarm horns for 120 seconds while ensuring adequate audibility. The modifications require that the TSRs covering the new upgraded CAAS and

! TSRs covering the existing CAAS must be in place at the same time. Similarly, the description of the current CAAS will be retained in various SAR sections while the description of the new CAAS is incorporated into those same sections. The staff concludes that the revision to the SAR and TSRs provides adequate safety and ensures, adequate TSR coverage during the modification, during the system changeover, and after the new system is operable. The staff ,

j recommends the approval of revisions to the CAAS audibility upgrade-related TSRs and SARs.

l The staff revievdd and approved the CAAS audibility criteria when it issued the Certificate of Compliance dated January 7,1999. By letter dated December 4,1999, the staff has also granted an exclusion from the CAAS audibility requirements for permit-required confined spaces and cell housings associated with cells that are running.

The Region lil inspection staff has no objection to this proposed action.

Principal Contributor Yen-Ju Chen Charles Cox

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