ML20211P209

Provides Staff Written Clarification of NRC Reporting Expectations of When Double Contingency Losses Should Be Reported to NRC IAW Bulletin 91-001, Reporting Loss of Criticality Safety Controls, & Suppl

ML20211P209
Person / Time
Site:	Portsmouth Gaseous Diffusion Plant, 07007001
Issue date:	09/09/1999
From:	Ten Eyck E NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Toelle S UNITED STATES ENRICHMENT CORP. (USEC)
References
IEB-91-001, NUDOCS 9909130163
Download: ML20211P209 (8)

Text

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• X September 9, 1999 Mr. Steven A. Toelle Nuclear Regulatory Assurance and Policy Manager United States Enrichment Corporation 6903 Rockledge Drive Bethesda, MD 20817-1818 i

SUBJECT:

CLARIFICATION OF REPORTING EXPECTATIONS IN ACCORDANCE WITH I BULLETIN 91-01 j

Dear Mr. Toelle:

)

in telephone conference calls on April 5 and 9,1999, with United States Enrichment Corporation l (USEC) staff, the Nuclear Regulatory Commission (NRC) staff provided clarification of the NRC's  !

expectations of when double contingency losses should be reported to NRC in accordance with Bulletin 9101, " Reporting Loss of Criticality Safety Controls," dated October 18,1991, and its supplement dated July 27,1993. We are providing you this clarification in written form (Enclosure). Adhering to the enclosed guidance would meet your commitment to Bulletin 91-01 and its supplement contained in the Portsmouth and Paducah Safety Analysis Reports.

Should you have any questions, please contact Melanie Galloway of my staff at (301) 415-7266.

Sincerely, Eliza th .

rfhEk, Director Division of Fuel Cycle Safety and Safeguards, NMSS

Enclosure:

As stated Distribution: - -'

Docket: 70-7001 and 70-7002 File Center PUBLIC NMSS r/f N l FCSS r/f SPB r/f SC HU CEiMR CDP)

G:\SPB\MAM\critclar.wpd (*See previous concurrence) oPC . SPR i_ _SPB E FCSS SPB UB SPB FCSS . FCSS /

NARAE 1I *D% NDaWs 'CT @ *DDa m *RPe w MWe J EOTeL DATE 7/ 15 /99 7/14 /99 7/ 20 /99 7/20 /99 7/ 20 /99 7/ 20 /99 9/8 9 9/ k /99 C = COVER E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY 9909130163 990909 ppR ADOCK0700g1 L

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\,,,,,/* September 9, 1999 Mr. Steven A. Toelle Nuclear Regulatory Assurance and Policy Manager United States Enrichment Corporation 6903 Rockledge Drive Bethesda, MD 20817-1818

SUBJECT:

CLARIFICATION OF REPORTING EXPECTATIONS IN ACCORDANCE WITH BULLETIN 91-01 I l

Dear Mr. Toelle:

In telephone conference calls on April 5 and 9,1999, with United States Enrichment Corporation (USEC) staff, the Nuclear Regulatory Commission (NRC) staff provided clarification of the NRC's expectations of when double contingency losses should be reported to NRC in accordance with Bulletin 91-01," Reporting Loss of Criticality Safety Controls," dated October l 18,1991, and its supples.ent dated July 27,1993. We are providing you this clarification in written form (Enclosure). Adhering to the enclosed guidance would meet your commitment to Bulletin 91-01 and its supplement contained in the Portsmouth and Paducah Safety Analysis Reports.

Should you have any questions, please contact Melanie Galloway of my staff at (301) 415-7266.

Sincerely,

'! [-

Elizab th O. T( yck, Directo i Division of Fue Cycle Safety and Safeguards, NMSS

Enclosure:

As stated )

L ,

1 CLARIFICATION OF THE NUCLEAR REGULATORY COMMISSION'S EXPECTATIONS REGARDING REPORTING LOSS OF CRITICALITY SAFETY CONTROLS In itsBulletin 91-01, " Reporting Loss of Criticality Safety Controls," dated October 18,1991, and its Supplement dated July 27,1993, the Nuclear Regulatory Commission (NRC) provided guidance to fuel cycle licensees on when the loss or degradation of criticality safety controls should be reported to the NRC. In certain cases, further clarification and discussion of this j guidance is warranted to achieve a full understanding of NRC's intent in the bulletin.

Accordingly, we provide the following points which parallel your Bulletin 91-01 reporting i guidance (attached) as discussed in the April 9 telecon.

1. If a controlis lost or degraded and the effect of this loss or degradation on the controlled parameter is unknown within the reporting times of Bulletin 91-01, then reporting is required. The fact that information is leamed subsequent to the reporting times of Bulletin 91-01 that the parameter was unaffected or the parameter remained within your i analysis is not relevant to a reportability determination. Therefore, retracting or j downgrading an earlier report based on this later information is not appropriate.

Retracting or downgrading a report is only appropriate when, during the reporting period, you determine that a control has been lost or degraded, and after the report is made, you leam that a control was not actually lost or degraded; for instance, if it is believed that a l component which serves as a parameter control has malfunctioned and the loss or degradation of this controlis reported in accordance with Bulletin 91-01 but then subsequently it is leamed that the component did not malfunction such that the l parameter was not lost or degraded, downgrading or retracting your original Bulletin 91-l 01 report would be appropriate. However, such a scenario would be a rare occurrence.

This situation would not apply though to the case where it is erroneously believed that a doubly contingent operation exists and the control for one of the contingencies is lost and then, subsequent to reporting, it is teamed that the operation is actually singly contingent, even if the loss or degiadation did not affect the single parameter being controlled. The reason that retracting or downgrading is not appropriate in this case is because the original assessment of the situation does not represent a full understanding of operations and the associated risk and thus the original report should stand.

2. A significant degradation or loss of control over a controlled parameter is reportable. If the term "significant" is not rigorously defined in an approved criticality document, and a control is lost or degraded to any degree, then the loss or degradation must be considered signifier.. A and must be reported. If the term "significant"is defined in an approved criticality document and a control is lost or degraded to a lesser degree than what is defined as significant and process stability is assured (such that further degradation is unlikely), only then may an event report not be made. However, if this determination is made after the reporting period is over, then the event may not be downgraded or retracted. It would be appropriate though to revise the report to include the updated information.

3. A lost or degraded controlis reportable even if the associated process conditions (process parameters) credited for double contingency are maintained. However, degradation or loss of a control need not be reported if it is within pre-defined criteria which indicates such degradation or loss is of low significance and when concurrently ENCLOSURE

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assurance of process stability exists, that is, that a state exists where the risk of criticality is not substantially greater than that associated with the state before the degradation occurred. Note that the guidance of Bulletin 91-01, Supplement 1 specifies that any significant degradation or loss of control should be reported within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

4. For the loss or degradation of control over a controlled parameter not to require reporting in accordance with Bulletin 91-01, the criticality safety analysis must clearly assess exactly that loss or degradation, must clearly define which controls apply to that loss or degradation and must demonstrate that such a loss or degradation does not result in a significant loss of criticality safety effectiveness. In addition, process stability as noted above must be demonstrated. Also as noted above, if these determinations are made after the Bulletin 91-01 reporting times, they become moot; reporting should have i occurred and would remain unchanged by subsequent determinations. Again, note that the guidance of Bulletin 91-01and its supplement specifies that any significant degradation or loss of control should be reported within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

5. Contrary to the statement otherwise, there is no assurance that the loss or degradation of t

a control where process conditions have been maintained does not cause a significant j safety hazard or threat to criticality. As previously noted, this would only be the case if i process stability is assured.

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6. Loss or degradation of control over a controlled parameter is important to NRC because NRC has concluded that the controls were chosen because of their significant contribution to averting a criticality. To the extent that it is believed that the loss or degradation of controls is not significant, consideration should be given to better define l controls through reassessing the analytical basis.

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04/0s/09 MON 14:39 TEL 614 897 4001 ports NCs SEcTIoN E0007 M'

'; UE2-RA-RE1030 Rev.2 Page 69a of 71 Appendix G (O 7{ BULLETIN 91-01 REPORTING GUIDANCE c;s.

Page1of1 The following provides guidance relative to the reporting of the loss of NCS controls under SAR 6.9, Table 1, reporting criteria A.2.c.(1) and A.4.a only.

This guidance should only be applied after an analysis of the condition relative to the affected NCSA to determine if the condition resulted in a violation of the double contingency principle.

The results of this analysis will be documented by NCS and provided to the PSS.

As always, if any uncertainty exist as to the reportability of the condition the NRC should be notified within the applicable reporting time limit. The report can be retracted later if appropriate justification can be provided. .

United States Enrichment Corporation (USEC) incorporated the reporting requirements of hTC Bulletin 91-01 into SAR Section 6.9, Table 1. Within these reporting criteria, NRC refers to the

" violation of the double contingency principle, as defined in ANSI 8.1." The ANSI 8.1, Ref. 4.2.2 definition is " Process designs should, in general, incorporate sufficient factors of safety to require at least two unlikely independent, and concurrent changes in process conditions before a criticality accident is possible." This def'mition is also included in SAR Section 5.2, " Nuclear Criticality Safety."

Under this criteria, reportmg would only be warranted when the double contingency principle has been violated. In the case where a control, specified in a Nuclear Criticality Safety Analysis (NCSA) is violated, but the process conditions credited for double contingency are maintained, the double contingency principle, as defined in the SAR and ANSI 8.1, is not violated and the control violation is not reportable.

Our NCSAs identify certain controls to help ensure that the process conditions relied upon to mamtam double contingency are not exceeded. The violation or loss of a control may or may not constitute exceedance of a process condition required for providing double contingency for the operation. In many cases the loss of an NCS control will not result in a violation of the double contingency principle, if the process condition does not change beyond what was analyzed as acceptable in the NCSE/A.

In addition, the violation of an NCS control where the process condition is maintained will not cause a significant safety hazard or threat to a criticality and would not warrant reporting to NRC under Bulletin 91-01.

s, . .

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t Mr. Steven A. Toelle Nuclear Regulatory Assurance and Policy Manager United States Enrichment Corporation 6903 Rockledge Drive Bethesda, MD 20817-1818

SUBJECT:

CLARIFICATION OF REPORTING EXPECTATIONS IN ACCORDANCE WITH

/

BULLETIN 91-01

Dear Mr. Toelle:

In telephone conference calls on April and 9,1999, with United States Enrichment Corporation (USEC) staff, the Nuclear RegulatoryCommission (NRC) staff provided clarification of the NRC's expectations of when double conti%ency losses should be reported to NRC in accordance with Bulletin 91-01, " Reporting Loss Criticality Safety Controls," dated October 18,1991, and its supplement dated July 27,19 . To provide you the greatest assistance and be as clear as possible, we are providing yo this clarification in written form (Enclosure). We would expect that your Bulletin 91-01 Re rting Guidance would be revised to incorporate this guidance.

^

Should you hav any q stions, please contact Melanie Galloway of my staff at (301) 415-7266.

/

/

Sincerely, Elizabeth Q. Ten Eyck, Director Division of Fuel Cycle Safety and Safeguards, NMSS Enclosur : As stated Distri tion:

Dock t: 70-7001 and 70-7002 File Center PUBLIC NMSS r/f FCSS r/f SPB r/f G:\SPB\MAM\critelar. wad (*See previous concurrence)

OFC SPB SPB E FCSS SPB UB SPB FCES FCSS NAME *MGalloway *DHoadley 'JDavis *CTripp *DDamon *RPerson MWeber E OTenEyck DATE 7/ 15 199 7/14 /99 7/ 20 19 9 7/ ?u 199 7/ 20 19 9 7/ 20 /99 7/ /09 71 19 9 l C = COVER E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY e#

1 l

Mr. Steven A. Toelle l Nuclear Regulatory Assurance l and Policy Manager United States Enrichment Corporation -

6903 Rockledge Drive < l Bethesda, MD 20817-1818 '

)

SUBJECT:

CLARIFICATION OF REPORTING EXPECTATIONSIN ACCORDANCE WITH BULLETIN 91-01

Dear Mr. Toelle:

In telephone conference calls on April 5 and 9,1999, wi United States Enrichment Corporation (USEC) staff, the Nuclear Regulatory Commission (N ) staff provided clarification of the NRC's expectations of when double contingency losses sh Id be reported to NRC in accordance with Bulletin 91-01, " Reporting Lost of Criticality SafetyAontrols," dated October 18,1991, and its supplement dated July 27,1993. To provide you the greatest assistance and be as clear as possible, we are providing you this clarification ' written form (Enclosure).

Should you have any questions, please con et Melanie Galloway of my staff at (301) 415-7266.

Sincerely,

/

Elizabeth Q. Ten Eyck, Director Division of Fuel Cycle Safety ,

and Safeguards, NMSS

Enclosure:

As stated i i

Distribution: l Docket: 70-7001 and 70-70 2 File Center PUBLIC NMSS r/f FCSS r/f SPB r/f l

G:\SPB\MAM\critelar.vod (*See previous concurrence)

OFC SPB Y SPB E/ FCSS . b_ SPB E UB E Sd rcSS rcSs  !

NAME 'T Iky *DHoadley JDevis CTripp DDamon R rson MWeber EOTenEyck DATE 7/ / 19 9 7/14 /9 7/ 2f 7/2h 199 7/ 10gg f 7f Y jgg yf fgg 7f fgg C = COVER E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY /Y/

F l Mr. Steven A. Toelle Nuclear Regulatory Assurance l and Policy Manager United States Enrichment Corporation 6903 Rockledge Drive Bethesda, MD 20817-1818

SUBJECT:

CLARIFICATION OF REPORTING EXPECTATIONS IN ACCORDANCE WITH BULLETIN 91-01

Dear Mr. Toelle:

In telephone conference calls on April 5 and 9,1999, with United States Eprichment Corporation (USEC) staff, the Nuclear Regnfatory Commission (NRC) staff provideplarification of the NRC's expectations of when double v.-4,tingency losses should be reported Jo NRC in accordance with Bulletin 91-01, " Reporting Loss of Criticality Safety Controls," dated October 18,1991, and its supplement dated July 27,1993. To provide you the greatest agsistance and be as clear as possible, we are providing you this clarification in written form nclosure).

Should you have any questions, please contact Melanie G loway of my staff at (301) 415-7266.

Sincerely, l

abeth O. Ten Eyck, Director ivision of Fuel Cycle Safety and Safeguards, NMSS

Enclosure:

As stated Distribution: '

l Docket: 70-7001 and 70-7002 File Center PUBLIC NMSS r/f l

FCSS r/f SPB r/f

/

G:\SPB\MAM\critelar.wpd  !

OFC SPB SPjL ' _[ b SPB FCSS FCSS NAME MGallowancal DHo RPierson MWeber EOTenEyck DATE 7 /99 7/ li /99 7/ /99 7/ /99 7/ /99 C = COVER E = COVER & ENCLOSURE N = NO COPY l OFFICIAL RECORD COPY l

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