ML20137C740
| ML20137C740 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 02/13/1997 |
| From: | Rifakes G 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-97-0014, GDP-97-14, NUDOCS 9703250104 | |
| Download: ML20137C740 (13) | |
Text
f0* f00 As United St-t:s Enrichment Corporation 2 Democracy Center 6903 Rockledge Dnve Bethesda, MD 20817 Tel: (301)S64-3200 Fax:(301) 564-3201 GEORGE P. RIFAKES Dir: (301) 564-3301 Executive VICE PRESIDENT, OPERATIONS Fax: (301) 571-3208 February 13,1997 Dr. Carl J. Paperiello SERIAL: GDP 97-0014 Director, Office of Nuclear Material Safety and Safeguards Attention: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Portsmouth Gaseous Diffusion Plant (PORTS)
Docket No. 70-7002 Certificate Amendment Request-Additional Hypothetical Criticatty Case for X-333 (SAR Section 4.1.1.2.3.5)
Dear Dr. Paperiello:
In accordance with 10 CFR 76.45, the United States Enrichment Corporation (USEC) hereby submits a request for mnendment to the Certificate of Compliance for the Portsmouth, Ohio Gaseous Diffusion Plant (GDP). This request is related to the 3% assay limit for the X-333 facility approved by the Nuclear Regulatory Commission (NRC) under Certificate of Compliance GDP-2 as documented in several sections of the USEC Certification Application, including SAR Section 3.1.4.3.5, SAR Table 3.1.1.6-1, TSR 2.2.3.8 (Seal Exhaust), TSR 2.2.3.9 (Evacuation Booster Station), TSR 2.3.3.2 (Freezer / Sublimer), and TSR 2.4.3.4 (Cold Recovery). A USEC review of the SAR performed to support the DOE approval of the 3% assay limit in X-333, which was obtained from DOE on November 8,1996, indicated that SAR Section 4.1.1.2.3.5 did not include a hypothetical criticality case to address the 3.0% assay limit. USEC is requesting NRC review of this Certificate Amendment Request (CAR) to add this hypothetical criticality case since this information had not been previously reviewed and approved by the NRC, thereby constituting an unreviewed safety question.
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Dr. " Carl J. Paperiello February 13,1997 GDP 97-0014 Page 2 As described in Enclosure 1, the additional hypothetical criticality case that needs to be added to SAR Section 4.1.1.2.3.5 reflects a total maximum worst case dose of 49.0 rem for a 50 minute duration. Ilowever, plant training / procedures and TSRs require that all personnel evacuate the area immediately upon hearing the Criticality Accident Alarm System (CAAS) alann, thereby significantly reducing the time spent in the area. Making an extremely conservative assumption that the time required to evacuate is approximately 10 minutes, the resultant maximum potential dose is actually 5.0 rem. Since the additional case is the same type of event as the case currently described in the SAR, there is no new potential for offsite effects.
While this event and its postulated dose of 49.0 rem (5.0 rem taking credit for the evacuation of ACR-1 in response to the CAAS alarm) has not been previously reviewed by the NRC, research indicates that the dose falls within the subclinical health effects range; and, therefore, would not cause any acute effects for exposed onsite personnel (see Enclosures). The lifetime cancer risk due to a 49.0 rem dose would not be significant, and is bounded by the allowable lifetime radiation dose for radiation workers. This conclusion is also supported by SAR Table A.1-6, which indicates that a dose of 50 rem results in "No deaths, but number of white blood cells drop below normal. If applied to male sex organs, may result in inhibition of sperm production." The same table indicates that a dose of 25 rems results in "No directly observable effects." Therefore, the dose due to the additional hypothetical criticality case for operation at 3% assay in X-333 does not pose a significantly greater threat to onsite personnel, and poses no additional threat to individuals located offsite. Note that the dose determined for the hypothetical criticality in X-333 at 3% assay is also much lower than that calculated for the hypothetical criticality event in X-330, which is 124 rem.
l 1 to this letter provides a detailed description and justification for the proposed changes. Enclosure 2 is a copy of the revised SAR pages. Enclosure 3 contains the basis for USEC's determination that the proposed change associated with this certificate amendment request is not significant; and is, therefore, acceptable. The amendment should become effective upon issuance.
Any questions related to this subject should be directed to Mark Lombard at (301) 564-3248.
Sincerely,
,h' V
George P. Rifakes Executive Vice President, Operations
Enclosures:
As Stated cc:
NRC Region 111 Office NRC Resident Inspector - PGDP NRC Resident inspector - PORTS Mr. Randall M. DeVault (DOE)
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OATH AND AFFIRMATION I, George P. Rifakes, swear and affirm that I am Executive Vice President, Operations, of the United States Enrichment Corporation (USEC), that I am authorized by USEC to sign and file with the Nuclear Regulatory Commission this Certificate Amendment Request for the i
Portsmouth Gaseous Diffusion Plant, that I am familiar with the contents thereof, and that the statements made and matters set forth therein are true and correct to the best of my knowledge, information, and belief.
/
George P. Rifal.es CATHERINE E. KEEL
- NOT/2YPUBE STATE G M l
MyComm1ntonExpiras Febrary41997 Subscribed to before me on this day of bl$
,1997.
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01001E;/aj Notary Public l
4 GDP 97-0014 Page 1 of 1 United States Enrichment Corporation (USEC)
Proposed Certificate Amendment Request Additional Hypothetical Criticality Case for X-333 (SAR Section 4.1.1.2.3.5)
Detailed Description of Change 1
l Analyses for X-330 and X-333 facilities in the DOE 1985 FSAR and the USEC SAR were
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based on modeling performed for similar process buildings at the Oak Ridge Gaseous Diffusion Plant (ORGDP).
Utilizing the ORGDP analyses for the X-333 facil.ty, the worst case hypothetical criticality as currently described in the SAR occurs in X-33-5, which is a distance of 240 feet from ACR-1.
It was calculated for this case that a criticality from a " dry accumulation" type criticality accident in Unit X-33-8 would result in a dose of 0.005 rem in the ACR-1.
Based on the enrichment gradient for the X-333 facility at the NRC and DOE approved maximum enrichment of 3%, the worst case criticality would occur at a distance of 40 feet from the ACR-1 in Unit X-33-6. While postulating all other conditions (i.e., ACR-1 configuration, dimensions, materials, etc.) to be the same as the analysis done which assumes a 1.2% assay in Unit X-33-8, the dose in the ACR is conservatively determined to be 49.0 rem. This dose assumes that a person would remain in the ACR for the entire duration of the pulse event, which is on the order of 50 minutes. By procedure, any individuals in the ACR-1 would evacuate immediately upon hearing the Criticality Accident Alarm System horn (s). Making an extremely l
conservative assumption that the time required to evacuate ACR-1 is approximately 10 minutes, the resultant maximum potential dose is actually 5.0 rem. Even a dose of 49.0 rem should not cause acute effects for exposed ACR-1 personnel. Table 15.1 of "The Health Physics and Radiological Health Handbook" quotes IAEA 881998 stating "from 0 to 250 rads: No clinical symptoms but a slightly increased frequency of chromosome aberrations may be detected in lymphocytes" (10 CFR Part 20 Table 1004(b).1, Quality Factors and Absorbed Dose Equivalencies provides the conversion of rads to rems; the highest and most conservative being 1 to 1) A 49.0 rem acute dose, while causing concern, should cause no immediate health l
effects. Also SAR Table A.1-6 states a dose of 50 rem results in "No deaths, but number of l
white cells drop below normal. If applied to male sex organs, may result in inhibition of sperm 6
production." The same table indicates that a dose of 25 rems results in "No directly observable effects." Any increase in lifetime cancer risk due to a dose of 49.0 rem would be slight, and is bounded by the allowable lifetime radiation doses for radiation workers. Since the additional case is the same type of event as the case currently described in the SAR, there is no new potential for offsite effects. As a result, the consequences from operation in X-333 at the 3%
j assay limit are not significant and are, therefore, acceptable. Note that the dose determined for the hypothetical criticality in X-333 at 3% assay is also much lower than that calculated for the hypothetical criticality event in X-330 at 5% assay, which is 124 rem.
The probability of a criticality for operation at 3% assay in the X-333 facility remains j
unchanged from that assumed for the current hypothetical criticality case in the SAR. Therefore, i
the overall risk from criticality in the X-333 enrichment cascade has not significantly increased j
as a result of this change because there is no increase in the probability of the event, and the potential effects to onsite workers due to consequences of the accident remain within the
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subclinical range.
GDP 97-0014 j
Page 1 of 5 l
Proposed Certificate Amendment Request Portsmouth Gaseous Diffusion Plant Letter GDP97-0014 Removal / Insertion Instructions Remove Page Insert Page VOLUME 2 Section 4.1.1.2.3.5 Section 4.1.1.2.3.5 Page 4.1-15/4.1-16 Page 4.1-15/4.1-15a Page 4.1-15b/4.1-16 i
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SAR-PORTS PROPOSED February 13,1997 RAC 96X0241 X-333 Buildine A hypothetical nuclear criticality for the X-333 Building was assumed to occur 240 feet from the l
control room which would place it somewhere in Unit X-33-8. Using the yield of 2 x 10" fissions for the first spike, an enrichment of 1.2% U-235, and a neutron leakage factor of 0.0360, the LD, dose 450 rems, will be reached in the area bounded by the symbol O as indicated in Figure 4.1.1-7. This is approximately 8 feet at the cell floor level. The dose expected to be received just inside the control room is approximately 0.005 rems. h should be noted that the primary difference between the X-330 calculation and the X-333 calculations is the neutron leakage factor.
Another hypothetical nuclear criticality for the X-333 Building is assumed to occur approximately 40 feet from the control room which would place it somewhere in Unit X-33-6. Using a yield of 2 x 10" fissions for the first event would give a dose of approximately 49 rem at a distance of 40 feet. It should be noted that this dose assumes that a person would remain in the ACR for the entire duration of the pulse event which is postulated to be on the order of 50 minutes. The CAAS system would actuate the evacuation alarms within 10 minutes of the initiation and the actual dose received in the ACR would be less than 5 rem.
4.1.1.2.3.6 Doses Calculated in Accordance with NRC Reculatory Guide 3.34. Revision 13 i
Table 4.1.14 contains calculated doses, in rems, that a person would receive from prompt gamma radiation and neutrons from a criticality accident with a fission burst of 2 x 10" fissions.* The doses are computed as a function of distance and shielding. As indicated in the table, the distance at which the LD, is reached is approximately 20 feet when no shielding is assumed.
4.1.1.2.3.7 Comparison of Dose Calculations Table 4.1.1-5 shows a comprison of the results obtained by using the three methods described in the previous paragraphs. Because of the numerous variables involved, this table, at best, provides a very general comparison of results. Various assumptions used are shown in the table. In most cases, very little credit is taken for shielding other than the concrete floor. Therefore, it is quite probab e that actual doses would be somewhat less.
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- A burst of 2 x 10" fissions is used for this comparison because it is roughly the same magnitude as the other accidents described in this section. It is recognized that NRC Regulatory Guide 3.34 defines the minimum accident of concern as a spike of I x 10" fissions with a total of 1 x 10" fissions over 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
However, this minimum accident would probably be more applicable for a power plant than an enrichment plant.
4.1-15
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SAR-PORTS PROPOSED February 13,1997 l
RAC 96X0241 i
i 4 l.1.2.3.8 Comnarisons of Hvoothetical Excursions with Other Criticality Experiments t.
j The comparisons shown in Table 4.1.1-5 use critical reactions with yields of approximately 2 x 10" fissions as the basis of comparison. Other criticality experiments have been conducted which indicate that i
the actual yield might be significantly less than 2 x 10" fissions. Therefore, the effects could be considerably less than those shown in Table 4.1.1-5. The most notable of these experiments were the French Le'corche' excursions, Consequences Radiologiques d'un Accident de Criticite (CRAC) experiments and low-assay solution criticality experiments performed at Los Alamos National Laboratory using a critical assembly named SilEBA (Solution llomogeneous Energy Burst in Air).*
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4.1-15a
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SAR-PORTS PROPOSED February 13,1997 RAC 96X0241 1
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1 Blank Page l
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4.1-15b
SAR-PORTS September 15,1995 Rev.1 The CRAC experiments were performed with highly enriched uranium solutions from 1968 through 1971 under the auspices of the French Atomic Energy Commission. In the CRAC experiments attention was directed toward the type of accident characterized by the typical radiation " spike." Figure 4.1.1-8 results graphically shows the characteristics of the spike. The fission yield of the spike was 4 x 10'6 fissions with an integrated yield of I x 10" fissions at 60 seconds. The spike shown in Figure 4.1.1-9 i
is somewhat similar to some of the excursions discussed in this section although the yield of the spike is somewhat less. The fission rate in the first spike would be sufficient to actuate the radiation alarms.
The SilEBA experiments were conducted at LANL using a solution with an enrichment of slightly less than 5 percent U-235. From the SIIEBA experiments, it was found that the pulse characteristics of a low-power, " slow-cooker" criticality accident are much different from those of the CRAC experiments.
A much longer period of time, about 30 minutes, was required for the pulse to develop. A typical first pulse experiment with SilEBA is shown in Figure 4.1.1-9. The pulse produced a total yield of 2.3 x 10'6 fissions after four hours. There is some similarity in the pulse shown here and the hypothetical excursion shown in Figure 4.1.1-4, although tne SHEBA pulse is considerably smaller. The radiation alarms were tested during the SHEBA experiments. It was determined that the alarms will actuate during this type of excursion; however, the reaction time is slower than the 0.5 seconds prescribed by the American National Standard ANSI /ANS 8.3-1979.
This brief comparison of the hypothetical excursions discussed in this section and the excursions experienced in the CRAC and SHEBA experiments indicates that doses calculated using bursts with a spike yield of 2 x 10" fissions is conservative and probably represents a worst-case situation.
4.1.1.2.4 Criticality Summary In general, if an accidental excursion were to occur, the likelihood of one or two fatalities accompanied by a few cases of radiation sickness would be high for personnel in the immediate area. It is conceivable that as many as eight fatalities (from a maintenance crew or fire fighting crew) could result, but the associated likelihood is very small. The radiation alanns are expected to emit signals before the peak fission rate is reached. This would initiate evacuation from the building and possibly reduce the dose received by personnel in the immediate area. A criticality can be considered a local event. There appears to be virtually no risk of fatality off-site in this type of event. Because of the containment provided by the process buildings, there would probably be no significant immediate radiological effects resulting from exposure to fission products formed during a criticality event.
The following conclusions can be drawn. The potential for criticality accidents, in terms of mass of uranium, moderation and configuration definitely exists in the cascade. In some cases, the margin of safety is dependent on administrative controls. For this reason, continued vigilance and conformance with the criticality safety criteria in use must be maintained to assure an adequate level of safety, in all cases, however, the likelihood of the identified accident sequences appears to be quite small, and would be classified as extremely low using Table 4-1. Because a criticality could result in the deaths of some employees, the consequence of a criticality would be classified as medium using Table 4-2. The overall risk to plant personnel is small in comparison with other occupational hazards. The risk to the public off site is negligible. Appendix C provides a more detailed discussion of the criticality hazards.
4.1 - 16
i GDP 97-0014 Page 1 of 4 United States Enrichment Corporation (USEC)
Proposed Certificate Amendment Request Additional Hypothetical Criticality Case for X-333 (SAR Section 4.1.1.2.3.5)
Significance Determination
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The United States Enrichment Corporation (USEC) has reviewed the proposed changes associated with this certificate amendment request and provides the following Significance Determination for consideration.
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- 1. No Sienificant Decrease in the Effectiveness of the Plant's Safety. Safecuards or Security Procrams The specific dose that an individual might receive based on a hypothetical criticality is not addressed in plant safety, safeguards or security programs contained in Volume 3 of the Application for United States Nuclear Regulatory Commission Certification for the Portsmouth Gaseous Diffusion Plant.
Therefore, there is no overall decrease in the effectiveness of there programs due to these changes.
- 2. No Sienificant Chance to Any Conditions to the Certificate of Compliance None of the Conditions to the Proposed Certificate of Compliance for Operation of Gaseous Diffusion Plants (GDP-2) specifically address the specific Jose that an individual might receive based on a hypothetical criticality. Thus, the proposed changes have no impact on any of the Conditions to the Proposed Certificate of Compliance.
- 3. No Sienificant Chance to Any Condition of the Approved Compliance Plan The changing of an assumed dose received by individuals that are near a criticality is not addressed by the Compliance Plan nor to any conditions of the Compliance Plan. Thus, the proposed changes have no impact on any condition of the approved Compliance Plan.
- 4. No Sienificant increase in the Probability of Occurrence or Conseauences of Previously Evaluated Accidents The shifl in the X-333 enrichment gradient for the case at 3% maximum assay versus the case currently described in SAR Section 4.1.1.2.3.5 does not change the cascade conditions necessary to initiate a criticality, nor did it change the physical configuration of the cascade.
Therefore, there is no change in the probability of the hypothetical criticality accident described in SAR Section 4.1.1.2.3.5. SAR Section 4.1.1.2.4, Criticality Summary, states "In all cases, however, the likelihood of the identified accident sequences appears to be quite small and would be classified as extremely low using SAR Table 4-1."
The hypothetical 1
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GDP 97-0014 Page 2 of 4 United States Enrichment Corporation (USEC)
Proposed Certificate Amendment Request Additional Hypothetical Criticality Case for X-333 (SAR Section 4.1.1.2.3.5)
Significance Determination criticality case at the 3% maximum assay would still be classified as extremely low probability. The PORTS plant has been analyzed for enrichments up to 97.6% and bounds the.X-333 case. It should also be noted that the overall risk from a criticality in the enrichment cascade has decreased from that described in the DOE 1985 FSAR due to the lower enrichments being processed (10% vs 97.6%).
There is no process equipment directly above ACR-1. The nearest potential location for a criticality is about 10 feet offset horizontally from the ACR-1, and the cell floor is about 32 feet above the operating floor. As a result, for operation at 3% assay the closest distance from the site of a potential critical reaction to the ACR-1 is about 40 feet. The concrete in the cell floor and ACR-1 roof is equivalent to 9 inches of concrete. Using the data in SAR Table 4.1.1-4, assuming a 2 x 10" fission event (which is conservative for a deposit type criticality scenario), and 9 inches of concrete shielding results in a dose of 49.0 rem at a distance of 40 feet. It should be noted that this dose assumes that individuals would remain in ACR-1 for the entire duration of the pulse event, which is postulated to be on the order of 50 minutes. Cascade personnel are trained and directed to immediately evacuate the area upon hearing the Criticality Accident Alarm System horn. Making an extremely conservative assumption that the time required to evacuate is approximately 10 minutes, the resultant maximum potential dose is actually 5.0 rem. While a dose of 49.0 rem is larger than the dose originally postulated in the ACR-1, there should be no acute effects to ACR personnel. The increase in lifetime cancer risk would be slight and is bounded by the alloxable lifetime radiation doses for radiation workers. Since the additional case is the same type of event as the case currently described in the SAR, there is no new potential for offsite effects. The maximum consequences as defined in SAR Table 4-2 would be classified as extremely low or negligible hazard level. The dose determined for the hypothetical criticality in X-333 at maximum 3% assay is also much lower than that calculated for the hypothetical criticality event in X-330 at 5% assay, which is 124 rem. Therefore, the increase in overall plant consequences from this change is acceptable.
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- 5. No New or DifTerent Type of Accident The difTerent types of criticality accidents that have postulated for the cascade have been previously analyzed for all enrichment levels, and, therefore, the change in consequences of a criticality at a higher enrichment does not result in any new or different types of accidents.
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GDP 97-0014 Page 3 of 4 United States Enrichment Corporation (USEC)
Proposed Certificate Amendment Request Additional Hypothetical Criticality Case for X-333 (SAR Section 4.1.1.2.3.5)
Significance Determination
- 6. No Sienificant Reduction in Marcins of Safety
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There is no substantial increase in the probability of a criticality as a result of the proposed change, nor have there been any new accident initiators identified. Therefore, there is no significant reduction in the margin of safety.
- 7. No Sienificant Decrease in the Effectiveness of any Procrams or Plans Contained in the i
Certificate Application j
i The specific dose that an individual might receive based on a hypothetical criticality is not addressed in plant safety, safeguards or security programs. Therefore, the effectiveness of these programs is unaffected by these changes.
- 8. The proposed chances do not result in undue risk to 1) nublic health and safety. 2) common defense and security. and 3) the environment.
A criticality is considered a local event. Due to the structure of the cascade building and the distance to the nearest public point, there would be no radiological effects resulting from exposure to fission products formed during a criticality event. As such, this change does not represent an undue risk to public health and safety and has no impact on plant effluents or physical security.
- 9. There is no chance in the types or sienificant increase in the amounts of any effluents that may be released offsite.
This change has no effect on the generation or disposition of effluents, therefore, does not change the types or amounts of effluents that may be released offsite.
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- 10. There is no sienificant increase in individual or cumulative occupational radiation exposure.
There is an increase in dose in the X-333 ACR-1 due to this change, however, the resultant dose is less than the dose postulated for a hypothetical criticality event in X-330 and the dose is less than that which would cause any acute effects for exposed personnel. This increase is, therefore, not significant. See Item 4 above.
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J GDP 97-0014 Page 4 of 4 l
United States Enrichment Corporation (USEC)
Proposed Certificate Amendment Request Additional Hypothetical Criticality Case for X-333 (SAR Section 4.1.1.2.3.5)
Significance Determination
- 11. There is no sienincant construction impact, This change does not involve a plant modi 6 cation, therefore, will not impact construction.
- 12. There is no sienificant increase in the notential for. or radiolouical or chemical consecuences from previously analyzed accidents.
With the addition of the subject hypothetical criticality to the SAR, there is an increase in dose in the X-333 ACR-1, however, the resultant dose is less than the dose postulated for a hypothetical criticality event in X-330 and the dose is less than that which would cause any acute effects for exposed personnel.
Therefore, the increase in consequences is not significant. See Item 4 above.
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