ML20195J063
| ML20195J063 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 11/18/1998 |
| From: | Cox C NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| Shared Package | |
| ML20195J051 | List: |
| References | |
| NUDOCS 9811240185 | |
| Download: ML20195J063 (5) | |
Text
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4 UNITED STATES l
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NUCLEAR REGULATORY COMMISSION t
WASHINGTON, D.C. 2055M001
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November 18, 1998
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70-7001 CERTIFICATE HOLDER:
United States Enrichment Corporation Paducah Gaseous Diffusion Plant Paducah, KY
SUBJECT:
COMPLIANCE EVALUATION REPORT: APPLICATION DATED SEPTEMBER 11,1998, NORMETEX PUMP HIGH DISCHARGE PRESSURE SYSTEM BACKGROUND By letter dated September 11,1998, the United States Enrichment Corporation (USEC) requested an amendment to the Certificate of Compliance for the Paducah Gaseous Diffusion Plant (PGDP). The request is to delete Technical Safety Requirements (TSRs) 2.3.2.1, "Normetex Pump Discharge Pressure," and 2.3.3.1, "Normetex Pump High Discharge Pressure System." The request also includes changes to related sections of the Safety Analysis Report (SAR) to support deletion of the TSR requirements.
The September 11,1998, amendment request submittal fulfills a commitment that USEC made in an August 28,1998, Request for Enforcement Discretion. The enforcement discretion request was to allow the facility to retum to normal operation by not enforcing compliance with actions required in TSR 2.3.3.1, "Normetex Pump High Discharge Pressure System," until submittal and approval of an amendment request to delete the TSR. A self-revealing event on August 26,1998 (Event Report 34693), identified that the Normetex Pump High Discharge Pressure System' would not always prevent exceeding the safety limit on the discharge expansion bellows. After an engineering review, the facility staff declared the five pumps inoperable on August 27,1998, and entered the action statement of TSR 2.3.3.1, placing the facility in recycle mode. USEC prepared and submitted a Request for Enforcement Discretion on August 28,1998, to allow returning the pumps to service with compensatory measures that allowed withdrawal operations at a restricted level. Following standard NRC procedures, the Director, Office of Nuclear Material Safety and Safeguards (NMSS) granted the enforcement discretion verbally on August 28,1998, based on the staff's determination that extended operations in recycle mode could introduce additional safety consequences without a corresponding safety benefit. The verbal affirmation was followed by a written Notice of Enforcement Discretion (NOED No. GDP 98-1) dated September 1,1998.
On October 18,1998, USEC made a second Request for Enforcement Discretion. That enforcement discretion request was to allow the facility to retum to normal operation by not enforcing compliance with the actions required in TSR 2.3.2.1, "Normetex Pump High Discharge Pressure," untilissuance of the amendment request to delete TSR 2.3.2.1 and TSR 2.3.3.1. On October 17,1998, a second event (Event Report 34926) similar to the August 26,1998, event caused the Building C-315 Normetex Pump No.1 discharge line expansion bellows to exceed 9811240185 981118 PDR ADOCK 07007001 C
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the TSR 2.3.2.1 safety limit. As in the August 27,1998, event, the facility staff declared all five pumps inoperable, placed the facility in the recycle mode and on October 18,1998, submitted the written request for enforcement discretion. Following standard NRC procedures, the Director, Office of Nuclear Material Safety and Safeguards (NMSS) granted the enforcement discretion verbally on October 18,1998, based on the staff's preliminary review of the amendment request i
and determination that extended operations in recycle mode could introduce additional safety I
consequences without a corresponding safety benefit. The verbal affirmation was followed by a written Notice of Enforcement Discretion (NOED No. GDP 98-2) dated October 20,1998.
l issuance of this amendment will terminate both NOED No. GDP 98-1 and NOED No. GDP 98-2.
DISCUSSION The Normetex pumps are positive displacement pumps used at the PGDP to compress the uranium hexafluoride (UFe) gas to a pressure above its triple point so the gas can then be cooled and condensed into a liquid. The pumps are used at the product (enriched) withdrawal facility and at the tails (depleted) withdrawal facility. The pumps have several automatic systems or interlocks that will shut down the pumps. The Normetex UFe Release Detection System is a safety system that shuts down the pumps when two detectors at the pump station detect a release of UFe. This safety system is credited in SAR Section 4.3.3.1.1 for limiting any release of UFe from the pumps to 250 pounds (Ibs). Operation of the detection system is covered by a TSR. A second safety system, Normetex Pump High Discharge Pressure System, shuts down the pumps on a high discharge pressure signal. The system is supposed to prevent a failure of the pump discharge line due to an overpressure event caused by the discharge block valve closing while the pump continues to run. The release from this failure is bounded by the 250 lbs mentioned above. A third system, identified as non-safety related, is an interlock on the pump discharge block valve that is also designed to shut down the pumps when the discharge block valve closes. A limit switch on the discharge block valve trips the pump upon valve closure and closes the pump's suction valve.
The amendment request proposes deleting TSR Safety Limit (SL) 2.3.2.1: "The Normetex withdrawal pump discharge bellows pressure shall not exceed 45 psia" and TSR 2.3.3.1 which establishes a limiting control setting, a limiting condition of operation, and surveillances to ensure SL 2.3.2.1 is not exceeded. Title 10 of the Code of Federal Regulations (CFR), Part 76.4 defines safety limits as "those bounds within which the process variables must be maintained for adequate control of the operation and that must not be exceeded in order to protect the integrity of the physical system that is designed to guard against the uncontrolled release of radioactivity."
Part 76.4 also defines limiting control settings as " settings for automatic alarm or protective devices related to those variables having significant safety functions." Limiting control settings is further defined in 10 CFR Part 76.87(d)(2) as "specified for a variable on which a safety limit has been placed." These definitions imply a safety significance criteria for determining what process variable be assigned safety limits.
Any failure in the Normetex pump discharge line is controlled by the Normetex UFe Release Detection System, as described in SAR Section 4.3.3.1.1, to limit any release of UFeto 250 lbs.
The same SAR section states that the failure of the discharge line from an overpressure event caused by the closure of the discharge block valve is of " negligible safety concem." That conclusion is further supported in the September 11,1998, amendment request which calculated that a maximum of 5 lbs of UF, would be released from the Normetex pump discharge block valve closure. When the discharge valve closes, an interlock shuts the suction valve limiting any release to the inventory of UF in the Normetex pump, which is a maximum of 5 lbs. Therefore, if
3 the 45 psia safety limit is exceeded due to the discharge block valve closing and results in a release, such a small release does not represent a safety significant hazard that warrants a safety limit. The uncontrolled release of radioactive materialis prevented by another TSR system, the Normetex UF Release Detection System. While the small release does pose a danger te workers in the immediate vicinity, protection of the worker from small releases is provided through the administrative controls listed in TSR 3.23, " Worker Protection From UF, Process Hazards."
The amendment request also proposes downgrading the classification of the Normetex Pump High Discharge Pressure System from a quality (Q) safety system to a non-safety (NS) safety system for the tails withdrawal facility pumps and to a nuclear criticality safety augmented quality (AQ-NCS) safety system for the product withdrawal facility pumps. The NS classification for the tails withdrawal facility is consistent with other automatic systems that have minor safety significance but do provide an equipment protection feature. The AQ-NCS classification for the product withdrawal facility pumps is consistent with the NCS program where features that are relied upon for meeting the double contingency principle in NCS shall be classified as AQ-NCS.
Criticality safety is a concern at the product withdrawal facility because uranium enriched to 1.0%
or higher of uranium-235 is withdrawn there. Therefore, a nuclear criticality safety approval (NCSA)is required by TSR 3.11.4 for operation of the facility. The NCSA for the product withdrawal facility requires the Normetex Pump High Discharge Pressure System for moderation control. Moderation controlis established by preventing the discharge pressure from exceeding 50 psia, the pressure at which hydrogen fluoride would condense and provide moderation control concerns in the condensers and accumulators downstream in the process. Pressure increases in the Normetex pump discharge line would be caused by either an increase in pump output or by i
the discharge block valve closing with the pump running or coasting down. An increase in the pump output could be caused by several factors, the most likely being an increase in the pump suction pressure. The discharge line pressure increase from an increase in the pump output would be slower than the rapid pressure spike caused by the discharge block valve closure. The facility staff's engineering analyses re-confirmed the system's ability to prevent the discharge pressure from the slower pressure rise from exceeding the NCSA limit of 50 psia. The Normetex pump would trip at 42 psia and there would be very little pressure rise with the entire volume of I
the discharge line downstream from the pump available for the volume of UFe that would be pumped during the pump coast down. Moderation control would still be maintained during the i
pressure surge from an inadvertent discharge block valve closure because the pressure surge would be limited to the piping between the pump and the block valve. As the block valve closed, the upstream piping would experience the pressure spike while the pressure in the downstream piping would decrease. Any condensed hydrogen fluoride would only be in the upstream section of piping and not downstream of the block valve in the condensers and accumulators. That condensed hydrogen fluoride would re-vaporize in the upstream piping after the pressure spike subsided.
The August 28,1998, Request for Enforcement Discretion committed USEC to upgrade the l
safety system classification of the Normetex pump discharge block valve interlock that trips the pump and shuts the suction valve when the discharge block valve goes shut. The commitment was to upgrade the safety system classification from NS to O. The upgrade in classification is intended to provide a substitute of the previously Q Normetex Pump High Discharge Pressure System with the new Q interlock system such that there remains a Q safety system to prevent high pressure rupture of the discharge line caused by the discharge block valve closure. The staff agrees that the safety system downgrade for the High Discharge Pressure System is
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appropriate given that the interlock is now the system for which credit is taken to limit the pressure surge upon inadvertent closure of the discharge block valve.
ENVIRONMENTAL REVIEW issuance of the requested amendment to the Paducah Certificate of Compliance (GDP-1) to delete the TSRs and revise the related sections in the SAR is subject to the categorical exclusion provided in 10 CFR 51.22(c)(19) and will not have a significant impact on the human environment. Therefore, in accordance with 10 CFR 51.22(b), neither an environmental assessment nor an environmentalimpact statement is required for the proposed action.
CONCLUSION The deletion of TSR SL 2.3.2.1 is warranted because of the lack of safety significance from a maximum 5 lb release of UFe. Workers' protection from such small releases is assured by adherence to the administrative practices required by TSR 3.23, " Worker Protection From UF, Process Hazards." With the deletion of TSR SL 2.3.2.1, the corresponding limiting control setting, limiting condition of operation, and surveillances of TSR 2.3.3.1 are not required. Any uncontrolled release of UF, is prevented by the Normetex UFe Release Detection System by limiting any release to 250 lbs. A release from the discharge block valve closure remains unlikely by substituting the Normetex discharge block valve interlock for the Normetex Pump High Diccharge Pressure System as the Q safety system for maintaining an available and reliable system to protect against a release of UF from an overpressure event. The AQ-NCS e
classification for the Normetex Pump High Discharge Pressure System in the product withdrawal facility is consistent with the NCS program. The SAR changes are consistent with the TSR changes and safety classification changes in the amendment request. On the basis of its review, the NRC staff concludes that this amendment does not adversely affect public health and safety or the environment.
The Region !!! Inspection staff has no objection to this proposed action.
Princioal Contributor Charlie Cox DISTRIBUTION:(ControlNo. 480S)
Docket 70-7001 NRC File Center PUBLIC KO'Brien, Rill SPB r#
NMSS dir. ofc. r#
FCSSr#
WTroskoski, FCOB PHiland, Rill
- See previous concurrence h
OFC 4SPB YSPB SPB SPB SPB NAME CCorij MHorn DHoadley MGalloway 7$
orW DATE 10/ /98 10/ 19 8 10/ /98 10/21/98 10 @ E C = COVER E = COVER & ENCLOSURE""
N = NO COPY l
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4 bONCLUSION The deletion of TSR SL 2.3.2.1 is warranted because of the lack of safety significance from a maxim 5 lb release of UF. Workers' protection from such small releases is assured by adherene o the administrative practices required by TSR 3.23, " Worker Protection From UF, Process Haz ds." With the deletion of TSR SL 2.3.2.1, the corresponding limiting control setting, limiting ndition of operation, and surveillances of TSR 2.3.3.1 are not required. Any uncontrolled relea e of UF, is prevented by the Normetex UF Release Detection System by s
I limiting any release td' 50 lbs. A release from the discharge block valve closure remains l
unlikely by substituting t Normetex discharge block valve interlock for the Normetex Pump High Discharge Pressure Syste s the Q safety system for maintaining an available and reliable system to protect against a re se of UF, from an overpressure event. The AQ-NCS l
classification for the Normetex P p High Discharge Pressure System in the product withdrawal I
facility is consistent with the NCS p sqram. The SAR changes are consistent with the TSR changes and safety classification changes in the amendment request. On the basis of its review, i
the NRC staff concludes that this amend nt does not adversely affect public health and safety or the environment.
The Region lli Inspection staff has no objection to t 's proposed action.
Princioal Contributor i
Charlie Cox i
l DISTRIBUTION:(ControlNo. 480S)
Docket 70-7001 NRC File Center PUBLIC KO'Brien. Rill SPBr#
KWinsberg,0GC NMSSr#
NMSS dir. ofc. r#
FCSS r#
WTroskoski, FCOB PHiland, Rill OFC SPB SPB SPB SP8 b
SPB NAME CCoxij MHorn DHoadley RPierson DATE 10/ /98 10/ 19 8 10/ /98 10B
/98 10/ /98 C = COVER E = COVER & ENCLOSURE N = NO COPY normcu. pad OFFICIAL RECORD COPY l
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