ML20154P734
| ML20154P734 | |
| Person / Time | |
|---|---|
| Site: | Paducah Gaseous Diffusion Plant |
| Issue date: | 10/18/1998 |
| From: | John Miller UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | Paperiello C NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| GDP-98-0222, GDP-98-222, NUDOCS 9810230059 | |
| Download: ML20154P734 (11) | |
Text
{{#Wiki_filter:. _ - _ Y O p USEC A Global Energy Company JAMES H. MILLER DIR: (301) 564-3309 VICE PRESIDENT PRODUCTloN fax: (301)671-8279 October 18,1998 GDP 98-0222 Dr. Carl J. Paperiello Director, Office of Nuclear Material Safet-ad Safeguards Attention: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Paducah Gascous Diffusion Plant (PGDP) Docket No. 70-7001 Request for Enforcement Discretion
Dear Dr. Paperiello:
Pursuant to discussions held between USEC and NRC on October 18,1998, the purpose of this letter is to request enforcement discretion associated with the potential consequences of returning the Normetex Pumps to operation in the Product and Withdrawal Facilities. The enforcement discretion is necessary to allow cascade operations to return to normal pending the NRC review and approval of a Certificate Amendment Request submitted on September 11,1998. On October 17,1998, at 1730 CDT, No. I Normetex Pump in C-315 tripped while running on stream. A discharge pressure of approximately 50 psia was reached. This is greater than the / TSR Safety Limit of 45 psia. The apparent reason for the pump trip was the closing of the / discharge valve caused by solenoid valve failure. There is an interlock designed to shut down the pump if the discharge valve closes. The pump was shut down and isolated by this innrlock y and was declared inoperable pending investigation and a technical evaluation in compliance with TSR 1.6.1.2.c. The automatic closure of the pump suction and discharge block valves limits the amount of UF that can be released. The pump, when isolated, does not contain significant 6 amounts of UF. There was no release of UF. 6 6 This event was similar to an event that occurred on August 26,1998, involving No. 2 Normetex Pump. As a result of that event, PGDP requested enforcement discretion on August 28,1998, 9810230059 981010 PDR ADOCK 07007001 C PDR 20817-1818 '" ' U (d -{ g 6903 Rockledge Drive, Bethesda, MD enw Telephone 301-564-3200 Fax 301-564-3201 http://www.usec.com OfBces in I :~rmore, CA Paducah, KY Portsmouth, OH Washington, DC l
Dr. Carl J. Paperiello October 18,1998 GDP 98-0222, Page 2 and received verbal authorization on the same day with written approval following or. September 1,1998. PGDP's request relative to the August 26,1998, event was based on compensatory actions to manually control pressure on the pump suction to preclude exceeding 45 psia should the block valve fail close. This latest event shows that block valve failures vary such that closing times can be significantly different and those differences can affect the maximum pressure spike. ' Thus, the current compensatory measures are only partially effective. As a result of this second event, all Normetex Pumps were declared inoperable on October 17, 1998, plant withdrawal operations were stopped, and the cascade was placed in a Recycle mode. This is similar to the action PGDP took on August 27,1998. Based on USEC's October 18, 1998, verbal request for enforcement discretion, NRC has verbally authorized USEC to return PGDP to normal operation until 1800 Hours on October 20,1998, it is USEC's understanding that this authorization is based upon continuation of the compensatory actions previously put into place on August 28,1998. USEC is seeking enforcement discretion to return to normal plant operations as explained in Enclosure 1. Specifically, USEC is requesting discretion to operate without following the Safety Limit until the NRC completes their review of the proposed certificate amendment. Enclosure 1 provides the technicaljustification for this request in accordance with NRC Inspection Manual Chapter 9900. USEC believes an emergency situation exists (similar to the criteria described in 10 CFR 50.91 for Part 50 licensees). Thejustification of this emergency is explained in Enclosure 1. Should you have any questions regarding this matter, please contact Larry Jackson at (502) 441-6796 or Steve Toelle at (301) 564-3250. There are no new commitments contained in this submittal. l - Sincerely,
- s. G. u
- James H. Miller Vice President, Production
Enclosure:
Justification for Request for Enforcement Discretion cc: NRC Document Control Desk NRC Region III Office NRC Resident Inspector - PGDP Mr. Robert C. Pierson, NRC IIQ Mr. Randall M. DeVault, DOE
4 ENCLOSURE GDP 98-0222 Justification for Request for Enforcement Discretion I l
l l GDP 98-0222 l Page 1 of 6 JUSTIFICATION FOR NRC ENFORCEMENT DISCRETION 1. THE TSR VIOLATED. i l TSR 2.3.2.1, Normetex Pump High Discharge Pressure System, will be violated. We cannot j demonstrate that the Normetex Pump High Discharge Pressure System will always function to meet the TSR operability requirements (TSR 2.3.2.1) for the Normetex Pump discharge l bellows pressure. 2. THE CIRCUMSTANCES SURROUNDING THE SITUATION, INCLUDING ROOT CAUSES, NEED FOR PROMPT ACTION AND IDENTIFICATION OF ANY RELEVANT HISTORICAL EVENTS. i l _The circumstances leading up to this issue are documented in PGDP Event Notification l Worksheet No. 34926, dated October 18,1998. Specifically, the No.1 Normetex Pump in C-315 tripped while running on stream. A momentary discharge pressure of approximately l-50 psia was reached. This is greater than the TSR Safety Limit of 45 psia. The apparent reason for the pump trip was the closing of the discharge valve. There is an interlock designed to shut down the pump if the discharge valve closes. The pump was shut down and isoleted by this interlock and was declared inoperable pending investigation and a technical evaluation in compliance with TSR 1.6.1.2.c. The automatic closure of the pump suction and discharge block valves limits the amount of UF that can be released. The 6 pump, when isolated, does not contain significant amounts of UF. There was no release of 6 UF and no discernable damage to the bellows. 6 The cause of the valve actuation appears to be solenoid valve failure. The root cause of this failure is indeterminate at this time; however, an investigation will look into this failure. Current plant condition is that the Product and Withdrawal facilities are in Recirculation with the Normetex Pumps in Mode 3 (i.e., not operating). The No. I pump in C-315 will remain shutdown until the TSR required technical evaluation is complete. The balance of the Normetex Pumps will remain in Mode 3 until the NOED is approved. f l While in Recirculation, assay limits will increase significantly and the plant will have to l commence assay mixing to prevent exceeding an assay limit. Freon gas will start pocketing in C-310 and will increase to the point that surges in the cascade will result and cascade shutdown with inventory is required to prevent compressor damage. These Freon perturbations and potential shutdown with UF inventory are an undesirable occurrence. 6
1 l GDP 98-0222 Pap 2 of 6 j On August 26,1998, the No. 2 Normetex Pump in C-315 tripped while running on stream. A momentary discharge pressure of 46 psia was observed. The apparent reason for the pump trip was the closing of the discharge valve. As a result of that event, USEC requested i enforcement discretion on August 28,1998. On the same day, the NRC granted verbal discretion and followed this with written approval on September 1,1998. On September 11,1998, USEC submitted the follow up Certificate Amendment Request. That request is currently under review by the NRC. If approved as requested, this enforcement discretion request would be obviated. In 1991, one incident was recorded where the Safety Limit was marginally exceeded as indicated by an uncalibrated gauge. Other calibrated gauges did not detect or indicate the Safety Limit was violated. Based on this information, management concluded that no Safety Limit was violated. 3. TIIE SAFETY BASIS FOR TIIE REQUEST, INCLUDING AN EVALUATION OF THE SAFETY SIGNIFICANCE AND POTENTIAL CONSEQUENCES OF TIIE PROPOSED COURSE OF ACTION, INCLUDING ANY QUALITATIVE RISK ASSESSMENT. SAR 4.3.3.1.1 defines the accident scenarios for Normetex pump failures. The failure modes are defined as a fatigue failure of the discharge bellows or outlet piping and a discharge pressure rise which ruptures the pump discharge bellows. The Normetex pump high discharge pressure system (TSR 2.3.3.1) will detect a high pressure and initiate shutdown of the pump prior to the pressure exceeding the LCS of 42 psia which is intended to prevent exceeding the Safety Limit. A failure of the Normetex pump high discharge pressure system would result in a source tenn bounded by the fatigue failure scenario described below. The consequences of a fatigue failure are a UF release of 50 lb./ min for five minutes for a 6 conservative total of 250 lbs. This is categorized as an extremely low hazard in accordance with SAR Table 4.2-2. This rate was conservatively derived from a withdrawal rate of 70,000 lb. UF / day. The release time of five minutes is based upon the UF release 6 6 detection system - Normetex pump (TSR 2.3.4.3) detecting the release, shutting down the pump and closing the discharge valve. Due to the close proximity of the detector heads,2 minutes would be a more realistic release time. The safety significance of operation with the requested discretion would be no greater than that presented in SAR 4.3.3.1.1 for a failure of the Normetex pump high discharge pressure system. The worst case release would still be bounded by the actions of the Normetex PGLD sys.;m to 250 lb. UF. The actual release would be significantly less. Calculations 6
_.m. _.. _ _. _. ~ _ _ _ _. _ _.. _ - i GDP 98-0222 Page 3 of 6 i i indicate a release of 5 lbs of UF.. The initiating event of a discharge valve closure does not rely on the PGLD system to isolate or shutdown the pump. The actuation of the 42 psia trip shuts down the pump. Therefore, should a release occur at a pressure exceeding 45 psia, the pump has already tripped and would not continue to pump for the five minutes estimated by SAR 4.3.3.1.1. The issue will have no impact on the criticality safety of the product withdrawal operations. l The proposed operation will have no impact on the release scenario. Therefore, the criticality safety of a UF release is unchanged. NCSA 3974-05 relies on the system 6 pressure being less than 50 psia to maintain moderation control in the product withdrawal condensers, accumulators and cylinders. The initiating event of concern for this issue, discharge valve closure, isolates the Normetex pump and any high pressure from the i downstream product withdrawal system. The product withdrawal condensers, accumulators and cylinders are not exposed to the high pressure. Criticality is not a concern in tails withdrawal. I i 4.- Tile BASIS FOR THE CERTIFICATE HOLDERS CONCLUSION THAT THE NONCOMPLIANCE WILL NOT BE OF POTENTIAL DETRIMENT TO THE PUBLIC HEALTH AND SAFETY, THE ENVIRONMENT, SAFEGUARDS, OR SECURITY, AND THAT NEITIIER AN USQ NOR A SIGNIFICANT HAZARD CONSIDERATION IS INVOLVED. The proposed operation will not result in risk greater than previously analyzed in the SAR. The response in Question 3 shows the potential consequences are still bounded by the existing SAR analysis. The consequences presented in the S AR for the bounding analysis result in an extremely low hazard which is defined in SAR Table 4.2-2 as having no off-site impact, no health and safety concerns for workers at nearby facilities, and slight injury or 4 illness to operating personnel. Therefore, there is no potential detriment to the public or worker health and safety. It is important to note that two redundant safety systems exist to prevent undue consequences of the postulated failures in the SAR. They are the PGLD system and the Normetex Pump High Discharge Pressure system. Without the high discharge pressure system, the PGLD system will still keep releases within those presented in the accident analysis. The discovery of the Normetex Pump High Discharge System inability to prevent a Safety Limit violation was previously discussed in USEC letters GDP 98-0188, dated August 28, 1998 and GDP 98-0193, dated September 11.1998. These letters discussed that there is not 1
Enclosure i GDP 98-0222 Page 4 of 6 a significant increase in the probability of previously evaluated accidents nor any increase in the consequences. The elimination of the TSR as requested in the September 11,1998, Certificate Amendment Request does not significantly decrease the margin of safety. If one assumes 45 psia (the SL) has significance relative to the frequency of the IIPDS accident described in the SAR, then exceeding 45 psia could increase the frequency of an accident described in the SAR. Ilowever, vendor provided information shows that failures would not occur in the discharge bellows for pressures more than twice the Safety Limit. Thus, the determination that there is a USQ based on relatively small exceedances of the Safety Limit does not appear warranted and in any case the safety significance is minor. Based on the following conclusions, there is no Significant flazard Consideration:
- 1. The proposed operation has no impact on any effluents released offsite. The actual operation of the withdrawal systems will be such that there is no change in the effluents emitted from these operations.
- 2. The proposed operation will not result in an increase in individual or cumulative occupational radiation exposure. The exposure to in process radiation will be the same.
Any exposure from released UF is bounded by the SAR analyzed release of 250 lbs 6 UF. 6
- 3. The proposed operation will not result in a significant construction impact.
- 4. The SAR analysis has previously analyzed the accident of a failure of the Normetex high discharge pressure system. The proposed course of action is bounded by this SAR analysis. The consequences of a failure of the Normetex high discharge pressure system is still bounded by the SAR analysis. Therefore, there is no increase in the potential for, or radiological or chemical consequences from, previously analyzed accidents.
- 5. There is no possibility of a new or different kind of accident.
- 6. The SAR analyzed accident scenario associated with this issue is the failure of the Normetex pump high discharge pressure system. In this scenario, the PGLD system detects the release, shuts down the pump and closes the discharge valve. No significant margins of safety associated with these mitigating actions are impacted by the proposed operation.
- 7. The proposed changes will not result in an overall decrease in the effectiveness of the plant's safety, safeguards or security programs.
5. Tile BASIS OF TIIE CONCLUSION TIIAT TIIE NONCOMPLIANCE WILL NOT INVOLVE ADVERSE CONSEQUENCES TO TIIE ENVIRONMENT. l
GDP 98-0222 Page 5 of 6 The proposed operation has no impact on any effluents released offsite. The actual operation of the withdrawal systems will be such that there is no change in the effluents emitted from these operations. In addition, no other operational activity will lead to increased environmental consequences. . 6, ANY PROPOSED COMPENSATORY MEASURES. In the August 28,1998, enforcement discretion request, compensatory actions were proposed and implemented which were to help prevent safety limit violations. Recent events proved this to be difficult. Ilowever, the analysis performed tojustify the September 11,1998, amendment request concluded there were no increases in the consequences of the affected accidents. The analyzed accident in question is effectively bounded by another postulated accident. Additionally, there is no significant increase in the probability of a previously evaluated accident. Based on these arguments, continued implementation of compensatory actions are not necessary, 7. THE JUSTIFICATION FOR TIIE DURATION OF NONCONFORMANCE. On September 11,1998, USEC submitted an amendment request addressing the actions necessary for the ultimate resolution of this issue. The duration of this nonconformance will last until the NRC completes their action to approve the proposed amendment. 8. A STATEMENT TIIAT TIIE REQUEST HAS BEEN APPROVED BY THE PLANT OPERATIONS REVIEW COMMITTEE (PORC). The PGDP PORC approved this request for enforcement discretion on October 18,1998. 9. THE REQUEST MUST ADDRESS IlOW ONE OF THE NOED CRITERIA FOR APPROPRIATE PLANT CONDITIONS SPECIFIED IN SECTION B IS SATISFIED. Criteria B.3 in Manual 9900 - NOEDs for GDPs states: "For all operating conditions at the GDP, the NOED is intended to avoid total plant shutdown, without considering the full implication and without corresponding safety, safeguards, security or environmental benefit." Therefore, the granting of enforcement discretion would prevent a total plant shutdown and the introduction of additional risk caused by the abnormal evolution. In addition, USEC believes Criteria B.1 also applies to this situation. B.1 states: "For on-going operations at the GDP, the NOED is intended to: (a) avoid undesirable transients as a result of h cing compliance with the TSR/ certificate condition and, thus, minimize
GDP 98-0222 Page 6 of 6 potential safety, environmental, safeguards, or security consequences and operational risks; or,..." We believe the cascade perturbations due to Freon accumulation are undesirable risks.
- 10. IF A FOLLOW-UP TSR/ CERTIFICATE AMENDMENT IS REQUIRED, Tile NOED REQUEST MUSTINCLUDE MARKED-UP TSR PAGES. TiiE ACTUAL TSR/ CERTIFICATE AMENDMENT REQUEST MUST FOLLOW WITIIIN 48 IlOURS.
The proposed TSR change was submitted on September 11,1998. This additional enforcement discretion is requested while the NRC completes their review of this amendment request. I1. ANY OTilER INFORMATION TIIE STAFF DEEMS NECESSARY BEFORE MAKING A DECISION TO EXERCISE ENFORCEMENT DISCRETION. No other information has been requested by the StatTat this time. I . _, _ _ _}}