ML993160248
| ML993160248 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 11/04/1999 |
| From: | Pierson R NRC/NMSS/FCSS/FSPB |
| To: | Adkins J U.S. Enrichment Corp (USEC) |
| References | |
| -RFPFR, NRC-2021-00234 | |
| Download: ML993160248 (8) | |
Text
"UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001
November 4, 1999 Mr. James N. Adkins Vice President, Production United States Enrichment Corporation Two Democracy Center 6903 Rockledge Drive Bethesda, MD 20817
SUBJECT:
PORTSMOUTH 91-01 REPORT: SEPTEMBER 24,1999, LOSS OF MODERATION CONTROL EVENT
Dear Mr. Adkins:
This refers to the 4-hour reportable (Bulletin 91-01) event that occurred on September 24, 1999. Your event report indicated that a previously unanalyzed chemical compound, identified subsequently as UO2CI(OH)-2H 2 0, was discovered in the side purge piping that had an H/U of 5, which exceeded the maximum assumed H/U of 4 in the cascade. Your report also indicated this condition left the side purge cascade in a singly contingent state where only mass control remained. Based on information that has been provided in the event report, and our knowledge concerning the configuration and composition of deposits within the cascade, the Nuclear Regulatory Commission (NRC) staff does not believe that an immediate safety concern exists. Despite this, there remain actions that should be taken to ensure continued safety of the as-found condition, as well as longer-term concerns that may impact other areas of the plant.
Based on your report, it is my belief that the existence of this compound may also invalidate one of the main criticality safety bases of the plant, namely that H/U in the cascade cannot exceed a value of 4. I am not persuaded that the history and mode of formation of this compound is well-known or that the assumed process conditions (related to the Building X-326 fire) preclude its existence in other portions of the cascade. The existence of an unpredicted chemical form of uranium is itself a cause for concern. Consequently, it is not evident to me how mass control was established or maintained to prevent more than a safe mass from accumulating. Your report indicated that mass control was maintained because the deposit contained less than a safe mass of uranium, in the as-found condition. That a critical mass was not reached for this particular deposit does not m.eath.a-.asscontrol was maintained in this case.
In the near future, we plan to schedule a meeting with you to discuss the significance of the concerns that we have identified. At this meeting, you should be prepared to discuss the interim measures in place committed to in your September 24, 1999, event report and reiterated in a telephone conversation with Ms. Melanie Galloway of my staff on October 15, 1999. These measures include: (1) USEC will continue to maintain isolation of the equipment to ensure that additional mass cannot intrude from the outside; (2) USEC will not conduct operations, maintenance, or otherwise handle fissile material in the affected areas until completion of the associated NCSA; and (3) USEC will complete a root cause analysis. You should also be prepared to explain why this does not represent a unreviewed safety question, why you have assurance that the facility is in a safe condition at the current time, and what long term measures will be taken to resolve this issue.
James N. Adkins, USEC 2
Please submit answers to the following questions within 30 days of the date of this letter:
(1) What declared controls existed on the side purge system and remained in place to maintain mass control? (Include a discussion of controls to ensure that additional mass does not enter the area.) What engineered features (e.g., geometry control) remained after formation of the deposit to prevent a criticality accident? In particular, justify the assertion that criticality cannot occur without additional uranium mass.
(2) The deposit consisted of a previously unanalyzed uranium compound. What constitutes a safe mass for such an unanticipated material? If this is unknown, is the mass limit based on optimally moderated U-235?
(3) What is the impact of the invalidation of this assumed process condition (H/U _4) on the safety basis of the plant? How will the cascade safety basis including the certificate application be reevaluated to take this new information into consideration? When addressing this question, justify the maximum H/U ratio that can be credibly obtained in the cascade and provide the basis for why it cannot be exceeded. Include in this a description of any revisions that have been made or are planned to any NCSA/E (nuclear criticality safety approval/evaluation) as a result of this event.
(4) Please address the following issues related to the as-found condition: (1) where, when, and how the deposits were identified; (2) the mechanism of how the deposits were formed; (3) the source of chlorine in the deposit; (4) the total quantity of the compound UO2CI(OH).2H 20 formed during the fire, including how much total U-235 was contained in the deposits; and (5) how well the surrounding equipment is characterized.
(5) What assurance is there that similar compounds do not exist elsewhere in the cascade in greater than safe mass quantities, and what prevents their formation in the future?
(6) The likelihood of a fire in Building X-326 has been evaluated and documented in the SAR. Why was the chemical reaction that resulted from the fire and the formation of deposits with H/U >4 not also evaluated as a credible contingency?
Please contact the NRC Portsmouth Project Manager, Mr. Yawar Faraz, at (301) 415-8113, with any questions.
Sincerely,
Robert C. Pierson, Chief Special Projects Branch Division of Fuel Cycle Safety and Safeguards, NMSS
Docket: 70-7002 Certificate: GDP-2 James N. Adkins, USEC November 4, 1999 2
Please submit answers to the following questions within 30 days of the date of this letter:
(1) What declared controls existed on the side purge system and remained in place to maintain mass control? (Include a discussion of controls to ensure that additional mass does not enter the area.) What engineered features (e.g., geometry control) remained after formation of the deposit to prevent a criticality accident? In particular, justify the assertion that criticality cannot occur without additional uranium mass.
(2) The deposit consisted of a previously unanalyzed uranium compound. What constitutes a safe mass for such an unanticipated material? If this is unknown, is the mass limit based on optimally moderated U-235?
(3) What is the impact of the invalidation of this assumed process condition (H/U_<4) on the safety basis of the plant? How will the cascade safety basis including the certificate application be reevaluated to take this new information into consideration? When addressing this question, justify the maximum H/U ratio that can be credibly obtained in the cascade and provide the basis for why it cannot be exceeded. Include in this a description of any revisions that have been made or are planned to any NCSA/E (nuclear criticality safety approval/evaluation) as a result of this event.
(4) Please address the following issues related to the as-found condition: (1) where, when, and how the deposits were identified; (2) the mechanism of how the deposits were formed; (3) the source of chlorine in the deposit; (4) the total quantity of the compound UO 2CI(OH).2H 20 formed during the fire, including how much total U-235 was contained in the deposits; and (5) how well the surrounding equipment is characterized.
(5) What assurance is there that similar compounds do not exist elsewhere in the cascade in greater than safe mass quantities, and what prevents their formation in the future?
(6) The likelihood of a fire in Building X-326 has been evaluated and documented in the SAR. Why was the chemical reaction that resulted from the fire and the formation of deposits with H/U >4 not also evaluated as a credible contingency?
Please contact the NRC Portsmouth Project Manager, Mr. Yawar Faraz, at (301) 415-8113, with any questions.
Sincerely, signed by R. Pierson Robert C. Pierson, Chief Special Projects Branch Division of Fuel Cycle Safety and Safeguards, NMSS Docket: 70-7002 Certificate: GDP-2 Distribution:
Docket: 70-7002 N R 0 Center PUBLIC SPB r/f NMSS r/f FCSS r/f NMSS r/f D. Hartland, Reg Ill KO'Brien, RIll P. Hiland, Reg III P. Ting J. Davis L. Berg T. Sherr GASPB\\CSTresponse-90-01.wpd (*See previous concurrence)
OFC SPB E SPB 1 E _SPB E SPB 1 E SPEý
NAME *CTripp:al *YFaraz *DHoadley *MGalloway RPi,_r? on
DATE 10/6/99 10/7/99 10/12/99 10/12/99 I?e,.'A /99
C=COE E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY "James N. Adkins, USEC 2
(1) What declared controls existed on the side purge system and remained in place to maintain mass control? (Include a discussion of controls to ensure that additional mass does not enter the area.) What engineered features (e.g., geometry control) remained after formation of the deposit to prevent a criticality accident? In particular, justify the assertion that criticality cannot occur without additional uranium mass.
(2) The deposit consisted of a previously unanalyzed uranium compoujd:. What constitutes a safe mass for such an unanticipated material? If this is unkno r', is the mass limit based on optimally moderated U-235? /
(3) What is the impact of the invalidation of this assumed pro9cess condition (H/U<4) on the safety basis of the plant? How will the cascade safety basis including the certificate application be reevaluated to take this new informatioi into consideration? When addressing this question, justify the maximum H/U/ratio that can be credibly obtained in the cascade and provide the basis for why it caoriot be exceeded. Include in this a description of any revisions that have been made or are planned to any NCSA/E (nuclear criticality safety approval/evaluation) as a result of this event.
(4) Please address the following issues related to the as-found condition: (1) where, when, and how the deposits were identified;,(2) the mechanism of how the deposits were formed; (3) the source of chlorine in'the deposit; (4) the total quantity of the compound UO 2CI(OH)-2H 20 formed during the fire, including how much total U-235 was contained in the deposits; and (5) how wet the surrounding equipment is characterized.
(5) What assurance is there that similar compounds do not exist elsewhere in the cascade in greater than safe massj/uantities, and what prevents their formation in the future?
(6) The likelihood of a fire n Building X-326 has been evaluated and documented in the SAR. Why was the chemical reaction that resulted from the fire and the formation of deposits with H/U >4 not also evaluated as a credible contingency?
The information received to date indicates that USEC is not sufficiently cognizant of process conditions within the cascade, which raises regulatory and safety concerns. NRC disagrees with USEC that the safety significance is low since it appears to indicate lack of process understanding.
Please contact the NRC Portsmouth Project Manager, Mr. Yawar Faraz, at (301) 415-8113, with any questions.
Distribution:
Docket: 70-7002 NRC File Center PUBLIC SPB r/f NMSS r/f FCSS r/f NMSS r/f D. Hartland, Reg III KO'Brien, Rill P. Hiland, Reg Ill P. Ting J. Davis L. BergT. Sherr
G:\\SPB\\CST-response-90-01.wpd (*See previous concurrence)
NAME *CTripp:al *YFaraz *DHoadley *MGalloway RPierson
DATE 10/6/99 1 10/7/99 10/12/99 10/12/99 10/ /99
%, = $-UVvtm E = COUVERK & EN(CLOSURE N = NO COPY OFFICIAL RECORD COPY James N. Adkins, USEC 3
disagrees with USEC that the safety significance is low since it appears to indicate lack of process understanding.
Please contact the NRC Portsmouth Project Manager, Mr. Yawar Faraz-Z', at (301) 415-8113, with any questions.
Sincerely,,/
7//
Robýrt C. Pierson, Chief Division of Fuel Cycle Safety pecial Projects Branch
/and Safeguards, NMSS
Docket: 70-7002 Certificate: GDP-2
/
Distribution:
Docket: 70-7002 NRC File Center PUBLIC SPB r/f NMSS r/f FCSS r/f NMSS r/f D. Hartland, Reg III KO'Brien, Rill P. Hiland, Reg III P. Ting J. Davis L. Berg T. Sherr
G:\\SPB\\CS-\\response-90-01.wpd (*See previous concurrence)
OFC SP E 1 SB E SPB.[E SPB III
NAME *CTripp:al *YFaraz *DHoadley *MGalloway RPierson
DATE 10/6/99 10/7/99 10/12/99 10/12/99 10/ /99 C = COVER E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY 1.0i
James N. Adkins, USEC 3
wi 4 ore fly chalterize"leosits 'n t fý po~tjor!4f thecascýade-f deter ?i4th d tr b o~n, a~/~mQun}( fissile ?ayr,1 mp ete revision of Vaffected Nd.A/Es en X/,gide purge area,. and"(4) 3JSg-E( wilf-'
by -. ?'Please contact the NRC Po siouth Project Manager, Mr. Yawar Faraz, at (301) 415-8113, with any questions.
Sincerely,
Robert C. PiE erso9, Chief Special ProjE ct6 Branch Division of F uel Cycle Safety and Saf uards, NMSS
Docket: 70-7002 Certificate: GDP-2
Distribution:
Docket: 70-7002 NRC File Center 3LIC SPB r/f NMSS r/f FCSS r/f NMSS r/f 1, Reg III KO'Brien, Rill P. Hiland, Reg IIl P. Ting J. Davis Ir T. Sherr
G:\\SPB\\CST\\response-90-01.wpd
(*See previous concurrence)
NAME *CTrpp:al *YFaraz *DHoadley WMGalloway RPierson
DATE 10/6/99 10/7/99 10/12/99 10/12/99 10/ /99 C = COVER E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY James N. Adkins, USEC 3 ?' I
The information received to date indicates that USEC is not sufficiently cognizant bf process 1 conditions within the cascade, a condition which is a significant regulatory angcsafety concern. 7
process understanding. NRC disagrees with USEC that the safety significance is low since it appears to indicate lack of
In the near future, we plan to schedule a management meeting wi you to discuss the safety concerns that we have identified. In addition, we expect that yo.'will provide responses to the above questions for our detailed review within 30 days of the ddte of this letter. Please contact the NRC Portsmouth Project Manager, Mr. Yawar Faraz, at( 4 01) 415-8113, with any questions.
Sincerely,i
/ //
Robet C. Pierson, Chief SpOcial Projects Branch Division of Fuel Cycle Safety
,'and Safeguards, NMSS
Docket: 70-7002 Certificate: GDP-2
Distribution:
Docket: 70-7002 NRC File 'penter PUBLIC SPB r/f NMSS r/f FCSS r/f NMSS r/f? D. Hartland, Reg III KO'Brien, Rill P. Hiland, Reg III P. Ting J. Davis L. Berg T. Sherr
//
G:\\SPB\\CST~response-90-01.Wpl1 See previous concurrence OFC SPB sp13 TP SPIII3 spa
NAME_ CTripp:al* *YFaraz,y MyU-y ' RPierson DATE 10/6/99 10/7/99 10/ i/99 10/ )d!/99 10/ /99
C = COVER E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY K_..
James N. Adkins, USEC 3
The information received to date indicates that USEC is not sufficiently cognizant'6f process conditions within the cascade, a condition which is a significant regulatory ancafety concern.
NRC disagrees with USEC that the safety significance is low since it ap /ars to indicate lack of process understanding.
In the near future, we plan to schedule a management meeting 't'h you to discuss the safety concerns that we have identified. In addition, we expect that y u will provide responses to the above questions for our detailed review written 30 days of t date of this letter. Please contact the NRC Portsmouth Project Manager, Mr. Yawar Faraz, (301) 415-8113, with any questions.
Sincerel /
//
obert C. Pierson, Chief Special Projects Branch Division of Fuel Cycle Safety and Safeguards, NMSS
Docket: 70-7002 Certificate GDP-2 / S5/,/
Distribution: NR./ File Center SPB r/f.. FCSS r/f Docket: 70-7002 NMSS r/f -FE-"FCOB PUBLIC PTing, FCOB D. Hartland, Reg III P. Hiland, Reg IIl J. Davis, FCSS KO'Brien, Rill L. Berg, FSPB T. Sherr, FLIB v-
G:\\SPB\\CST\\response-90-01.wpd
- See previous concurrence OFC SPB SPB SPB Ii Z II
NAME CTripp:al' YFaraz LW DHoadley MWalloway RPierson
DATE 10/6/99 10/ -7 /99 10/ /99 10/ /99 10/ /99
C = COVER E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY