ML20198D982
| ML20198D982 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 12/31/1997 |
| From: | Toelle S UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | Pierson R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| GDP-97-0226, GDP-97-226, NUDOCS 9801080351 | |
| Download: ML20198D982 (5) | |
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December 31,1997 Mr. Robert C. Pierson SERIAL: ODP 97-0226 Chief, Special Projects 11 ranch Division of Fuel Cycle Safety and Safeguards, NMSS United States Nuclear Regulatory Commission Washington, D.C. 20555 0001 Paducah Gaseous Diffusion Plan'(PGDP)
Docket No.70-001 Compliance Plan Issue 44, Operational / Safety System Trip Redundancy
Dear Mr. Pierson:
Issue 44 of the Plan for Achieving Compliance With NRC Regulations at the Paducah Gaseous Diffusion Plant (Compliance Plan) contains a required action that states:
A review of system designs will be performed where operational trips and alarms coincide with the setpoints ihr safety syste.m actuation based on the same monitored parameter and the same equipment actuated. Where redundant operational and safety system actuations exist, corrective action will be identified that may include justification either for the redundancy or system madifications to climinate the redundancy. The results of this review will be submitted to the NRC for review and approval by December 31, 1997. If the review detennines that a system modification is required, this Compliance Plcn issue will be revised to establish a new completion date for compliance, in accordance with this Compliance Plan requirement, the subject system designs were reviewed to deteimine where operational trips may be redundant to safety system trips. The review was conducted by each individual system engineer for their assigned systems. The specific results of the reviews of each system are available on site at PGDP. Three systems were discovered to have operational trips or alamis that coincide with the setpoints for safety system actuation based on the same monitored parameter and the same equipment actuated. They are as follows:
1.
Nomietex liigh Discharge Pressure Trip. This safety-related trip actuates at 41 psia and has an operational trip at 39 psia. This system's design is considered justified, so no corrective actions are planned to eliminate the redundant pressure trip. Details of this justification are provided in Enclosure 1.
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l Mr. Robert C. Pierson December 31,1997 GDP 97 0226, Page 2 2.
Plant Air Trace Moisture Meter 'this system has two alarm settings, The safety related setting is at +5'F dew point and the operational setting is at -45'F dew point. This system's design is considered justified, so no corrective actions are planned to eliminate the redundant alarm. Details of this justification are provided in Enclosure 2.
3.
Free /cr/ Sublimer liigh-liigh Weight Trip.1his safety related trip has an operational trip that is designed to actuate at a set value below the safety related control setting. Nojustification for this condition relative to Compliance Plan issue 44 could be determined, therefore, it is planned to remove the redundant operational trip (see the list of new commitments in linclosure 3). contains a list of new commitments contained in this letter, as a result of these reviews. If you have any questionr or require additional information, please contact Russ Wells at (301) 564 3245.
Sincerely,
/3 S. A.
ll Steven A.Toelle Nuclear Regulatory Assurance and Policy Manager linclosures: As stated ec:
NRC llegion 111 Office NRC Resident inspector - PGDP NRC Resident inspector - PORTS DOE Regulatory Oversight Manager c
Enclostue 1 GDP 97-02.26 Page1of1 Normetex liigh Discharge Pressure Trip Issue: Normetex pumps use a 41 psia high discharge pressure trip to prevent exceeding the 42 psia LSSS associated with the 45 psia SL of the discharge expansion joint. Detection of this condition is via either of two pressure transmitteu that each feed a pressure switch. Actuation of chher pressure switch results in tripping of the main motor contactors, thereby shutting down the pump. Tbc pressure switches used are dual-setting. On one switch (C-310 only), the second setting is the 37 psia warning alarm. On the other switch, the second setting is the 39 psia Operational Trip, which also results in tripping the main motor contactors and shutting down the J
pump. Thus, both the 4I psia safety related trip and the 39 psia non safety-related trip use mostly the same components and carry out the same action.
Ilackground: The intent of the 41 psia trip is to prevent damage to the discharge expansicajoint following an event resulting in a blocked disc. trge line (failure of Discharge Block Valve, see I
SAR section 3.4.2). Research of the Norme.tx manufacturing data noted that the manufacturer E
recommended maximum continuous discharge pressure for UF, service is 2500 millibar (2.5 atmospheres or about 37 psia, hence the 37 psin waming alarm) to prevent fonnr+ien of L
so!id/ liquid UF in the pump or the seuing of the puniping spirals due to excese mal 6
expansion. The nem'nal set point "as-found" error for these devices is presenti, 6 'out 0.7 psi To avoid overlapping trip / alarm tolerance bands, an Operational Trip in support of the manufacturer's recommenuation is set above the warning alarm by 2 psia, or 39 psia. The exac reasons for the design are not available in system documentation, but the above reconstruction indicates that the 39 psia Operational Trip is not mere'y a lower setting of the safety-related trip, bm is there far protection of the pump under routine circumstances to present damage that, while not a safety concern, would nonetheless cost a considerable amount of money to repair (estimate 570K-$100K for spiral repair alone).
Action: Tne above discussion was inchided as a revision to the Normetex Pump description in Safety Analysis Report (SAR) Sections 3.4.2 and 3.5.2 by RAC 96C207, which was approved by the Plant Operating Review Committee (PORC). No further action is intended since the reason for, and presence of, the two trips wiil be detailed in *S SAR. It is not reasonable to consider the Operational Trip as " preventing" the Safety Trip un&r the design-base accident conditions.
Operational experience has shown in the past that, under a blocked discharge block valve scenario, the discharge pressure increases from system non mal (30 psia) to 42 psia in only a few revolutions of the pump. It is therefore not credible to arrest a rapid pressure increase with a 39 psia trip to " prevent" a 41 psia trip, since the coast-down of the pump alone could bring in tha hisc.er alarm and mandate reportabi ity, etc. Since this has actually happened several times in C-315 and C-310, experience dictates that receipt of"jnst" a 39 psia Operational Trip means only a very minor transient was present (slowly plugging line with freeze-out, operator error utessurizing pump during start-up, or loss of C-310 condenser veut header, to cite a few examples) that would not be expected to challenge the design base accident scenario.
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- Enclosure 2 -
GDP 97 0226 -
Page1of1-Plant Air Trace Moisture Meter Issue: The Moisture liigh and liigh liigh alarms are -45'F and +5'F dew point, respectively.
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The liigh alann (-45"F dew point) is for maintaining a Instrument Air quality level (NS) and the fligh liigh alarm (+5'F dew point) is for meeting the NSCA GEN 10-01 requirement
- (AQ-NCS). The alarms utilize the same equipment for actuation.
' Hackgrouad: In accordance with NSCA GEN-10-01, the upper limit for moisture in the instmment air system is 1300 ppm This is in effect during purging of cells with instrument air.
Calculation SPC-CSE 1935214, Rev.1, establishes the liigh-liigh air moisture alarm at'+5*F to provide necessary margin for this NSCA lin.:t. The NCSA states that the applicability for this requirement is associated with the purging or pressurization of off-stream or shutdown UF.
process gas equipment with Instrument Air.
The calculation, SPC-CSE-19352-14, Rey,1, also establishes a high air moisture alarm limit of
-45'F to maintain an operational moisture limit of 10 ppm in the air system. The basis for this t
, alarm s:tpoint is derived from ISA-S7.3-1975 (R1981), " Quality Standard for instrument Air",
Section 4.1.1. The intent of this alarm is to prevent possible long term damage to those components that use Instrument Air for control and ind: cation.
Action: As the above alarms are adequately documented and justified, there are no further actions required.
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- )l GDP 97-0226 Page1of1 Commitments Contained in this Submittal 1.
USEC will submit to NRC a Certificate Amendment Request (CAR) to revise PGDP Compliancc Plan issue 44 to include a Plan of Action and Schedule item to address the modification required to remove the DPC liigh-High Weight Trip iram the Freezer / Sublimer systems. The associated Compliance Plan revision will be submitted to the DOE for review and approval by January 30,1998. Once approved by DOE, the CAR will be submitted to NRC for review and approval.
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