ML20138D402
| ML20138D402 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant, Paducah Gaseous Diffusion Plant |
| Issue date: | 04/07/1997 |
| From: | John Miller UNITED STATES ENRICHMENT CORP. (USEC) |
| To: | Pierson R NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| Shared Package | |
| ML20138D407 | List: |
| References | |
| GDP-97-0051, GDP-97-51, TAC-L30576, TAC-L32009, NUDOCS 9705010114 | |
| Download: ML20138D402 (14) | |
Text
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- I f 10 @ 2-United Stat:s Enrichment Corporation 1
2 Democracy Center L.S 6903 Rockledge Dnve Bethesda, MD 20817 Tel: (301)S64-3200 Fax: (301) 564-3201 United States Enrichinent Corimration JAMES H. MILLER Dir: (301) 564-3309 VicE PRESIDENT, PRODUCTION Fax: (301) 571-8274 1
April 7,1997 i
Mr. Robert C. Pierson, Chief SERIAL: GDP 97-0051 Special Projects Branch Division of Fuel Cycle Safety and Safeguards, NMSS Attention: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Paducah Gaseous Diffusion Plant (PGDP)
Portsmouth Gaseous Diffusion Plant (PORTS)
Docket Nos. 70-7001 and 70-7002 USEC Response to Request for AdditionalInformation (RAI)- Criticality Accident Alarm System (CAAS) Monitoring Exclusion Requests (TAC No.s L32009 and L30576) j
Dear Mr. Pierson:
In response to your request letter dated Febmary 28,1997, TAC No.s L32009 and L30576, requesting additional information on USEC's request for exclusion of areas within the USEC leased areas from CAAS monitoring, I am pleased to submit the enclosed information. provides a response to your staffs questions or requests concerning the Paducah GDP CAAS exclusion request. Enclosure 2 provides a response to your staffs questions or requests concerning the Portsmouth GDP CAAS exclusion request. Enclosure 3 lists new commitments contained in this correspondence.
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I.l ll ll ll llI.ll.i ll Offices in Paducah, Kentucky Portsmouth. Ohio Washington DC k
i NRC Document Control Desk April 7,1997
. GDP 97-0051 Page 2 I believe this additional information should enable you to complete the review and approval of our original requests dated April 9,1996 (PGDP), May 22,1996 (PORTS), and August 15,1996 (PGDP).
I would be pleased to discuss these responses with you. Please contact me at (301) 564-3309 or Ms.
Lisamarie Jarriel at (301) 564-3247, Sin
- ely, GN es H. Miller ice President, Production l
Enclosures cc: NRC Region III Office NRC Resident Inspector - PGDP NRC Resident Inspector - PORTS i
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ENCLOSURE 1 Response to NRC RAI Paducah Gaseous Diffusion Plant Docket 70-7001 (CATEGORY 1) FACILITIES WITH LESS THAN 15 GRAMS U AND (CATEGORY 2) AREAS WITH 235 URANIUM ENRICHED TO LESS THAN 1 %
For those defined areas that are to be excludedfrom coverage on the grounds that they "do not contain operations enriched to 1% or higher U-235, and 15 grams or more of U-235, " additionalinformation is requested. showing a commitment topractices sufficient to ensure that containers orpieces ofequipment with material exceeding these limits are not brought into these areas. Information showing that all individuals who might, even inadvertently, move special nuclear material are trainedin these measures?
USEC Resnonse USEC has demonstrated its commitment to identify and maintain the limitations for these facilities through the use of plant procedures, training, and surveillance.
Workers at the Paducah Gaseous Diffusion Plant go through a General Employee Training (GET) class.
GET training and/or testing is required every two years. This training includes general NCS training which informs the personnel ofcriticality safety concerns and the potential for criticality accidents. It also explains the differences between contamination areas and non-contamination areas. The contamination limit is more 235 restrictive than the 1% or higher U, and 15 grams or more 23'U limits.
Employees / workers are instructed that radioactive material is not to be removed from a contamination area.
The training emphasizes the NCS postings (which delineate the NCSA controls), Fissile Control Area markings (which identify areas under NCSA controls), and that only specially trained personnel are allowed to move or handle fissile material.
Personnel who are allowed to handle or direct the activities of workers who handle fissile /potentially fissile material (i.e. managers, handlers, design engineers, operators, etc.) are also required to complete much more detailed training. This training discusses the definition of fissile material, explains the parameters associated with criticality safety, and explains the application of these principles. In addition, this training covers personnel responsibilities related to criticality safety including obtaining the appropriate approvals prior to performing fissile material operations.
To ensure compliance with the NCS program requirements specified in the Procedures and Training Organization, walk-throughs and surveillances are performed by NCS, plant management, and the Safety, Safeguards, and Quality Organization. These walk-throughs and surveillances are performed in part to 2
ensure that operations involving uranium enriched to I wt percent or higher and 15 grams or more of 35g have been reviewed and approved by NCS, as well as to verify that conditions have not been altered to adversely affect NCS. This review and approval process includes compliance with CAAS requirements.
Response to NRC RAi Enclosure I to GDP 97-0051 Paducah Gaseous Difrusion Plant, Docket 70-7001 Page 2 of 5 4
(CATEGORY 3.a) CYLINDERS OF UF6 IN STORAGE YARDS IfamoimtsandenrichmentsofUFssufficient toproduce criticality are to be storedin these locations, then thefollowing information is requested 7he Paducah GDP document KWS-271 is referenced as the primary justajication that an accidental criticality is not a credible event in these cylinder storage situations. The f
arguments in KWS-27I that criticality is oflow likelihooddo notprovide a degree ofassurance high enough to warrant complete exclusionfrom CAAS coverage. Unless additionalinformation can be provided showing that cylinder damage producing holes larger than 1 inch diameter cannot occur, measures providing thefunction of the criticality monitoring described in 10 CFR 70.89 must be provided.
i USEC Resoonse In response to the above question, we have revised KY/S-271, " Justification For Excluding UF Cylinder 6
Accident Alarm Coverage." Revision 2 is attached for your review (Attachment 1). In this revision we i
changed pages 4, 6,14,19-25,32 and 33 by adding additional text on the drop test results and cylinder handling activities. As discussed in the original report submitted to the NRC, as well as this revision, if a t
cylinder breach occurred that was less than 1 inch in diameter, experimental data indicates that the breach would be sealed by the reaction products. The results of the added drop tests indicate that the probability 4
that a product cylinder would fail with a hole larger than 1 inch in diameter is considered extremely low.
We believe this additional information indicates that product cylinders will continue to provide UF6 containment under accident conditions more severe than could be postulated in the cylinder storage yards, and therefore, will address your concerns.
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~Not withstanding these results, an evaluation was conducted assuming a breach that was 6 inches in diameter in the top of the cylinder. The evaluation showed that more than 7 inches of rain would have to fall before i
the cylinder would be filled with 7.4 pounds of water (the amount needed to convert enough of the UF to 6
UO F to form a critical mass). Furthermore, a substantial mass of additional water is required for 2 2 j
moderation of the UO F under optimum condition. Severe storm data indicates that 5 inches of rain might 2 2 occur over a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> period once in 100 years. The frequency of a severe storm occurring following an event in which a cylinder is dropped and breached with a 6-inch diameter hole on the top of the cylinder is not considered credible.
l Ifit isproposed that a criticality monitoring qstem providing continuous coverage as described in 10 CFR 70.89 is notfeasible, thefollowing additionalinformation is requested:...
USEC Resnonse As discussed above, the re>ults of these drop tests indicate that product cylinders will continue to provide UF containment under accident conditions more severe than could be postulated in the cylinder yards. The 6
information presented substantiates the position that a cylinder accident during conditions that would provide sufficient moderation to cause a criticality is not credible, and therefore, CAAS coverage is not necessary, i
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Response to NRC RAI Enclosure I to GDP 97-0051
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Paducah Gaseous Diffusion Plant, Docket 70-7001 Page 3 of 5 Are allroadways along which movements ofspecialimclear material above a critically safe mass are made covered by the criticality monitoring system?
USEC Resnonse There are only two situations in which a single item containing more than a safe mass of fissile material is transported. A mass larger than the safe quantity is transported when product cylinders and equipment classified as " planned expeditious handling" (PEH) are transported. The transportation of these items are addressed in KY/G-558, Criteria for Transportation of Fissile Materials in Areas Without Criticality Accident Alarm Coverage at the Paducah Gaseous Diffusion Plant (Attachment 2).
Cylinders being transported on plant site have the right-of-way. Personnel have been informed of this (e.g.
GET training) and give equipment carrying cylinders a wide berth. Product cylinders are transported using specifically designed vehicles that are unlikely to incur damage in an accident. The plant speed limit is 25 mph and the cylinder vehicle speed limit is 15 mph for straight portions of the roadways and 5 mph for cornering, reducing the possibility of a vehicle accident. Drop test results (see Attachment 1) indicate that product cylinders will continue to provide UF containment under accident conditions, more conservative 6
than transportation accidents.
PEH equipment will be transported using two continuously monitored alarming radiation detectors.
Based on the arguments presented in this report, fixed CAAS coverage is not required for the roadways since it is not credible for a criticality to occur during the transport of a product cylinder and portable CAAS coverage is provided for the transport of equipment classified as PEH.
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Response to NRC RAI Enclosure I to GDP 97-0051 Paducah Gaseous Diirusion Plant. Docket 70-7001 Page 4 of 5 e
(CATEGORY 3.b) C-710 FACILITY DRAIN SYSTEM 1he C-710 Facility drain system empties imo the C 712 Acid Neutrali:ation Pit prior to discharge to sewer systems. 7he rationalefor exclusion of the C-712 Acid Neutrali:ation Pit by probabilistic analysis, is deficient in two respects. Additional information, which might adequately address the deficiencies, is identified below. The two deficiencies are: 1) the probabilistic analysis is deficient due to lack of independence, and 2) the criticality evaluation may not be sufficiently conservative.
- 1) Ihe probabilistic analysis argues that six independent human error events must occur to have a criticality (see Appendix E). Inadequate information is presented tojustify that these events are truly independent, since all 6 occur in the same room, Room 21. If the same personnel are involved as operators or supervisors, the events are not independent. Inprinciple, measures might be taken that wouldprovide such independence.
If such measures exist, please provide additional information demonstrating the independence ofthe discharges and ofthe supervisory monitoring of them. Please provide ha:ards analysis which attempts to identify ways in which independence might be defeated.
USEC Resoonse The Nuclear Criticality Safety Evaluation (NCSE) 1493-25, "NCS Evaluation for the Drain System in the C-710 Facility at the Paducah Gaseous Diffusion Plant," Revision 1, has been revised to address potential dependencies between events modeled in the original analysis (Attachment 3). The revised text takes no credit for the supervision detecting the error of an operator dumping fissile material into the drain system.
The location of the glass cold trap hydrolyzation process was clarified. This operation is not performed in the same laboratory that the tube and cylinder wash operations are performed. Since the tube and cylinder wash operations are performed in the same room the frequency of an operator violating the NCSA requirements and dumping large amounts of fissile material into the drain system was increased by an order of magnitude to account for this dependency. Appendix E of NCSE 1493-25 provides additional details.
- 2) The criticality evahtation argues that 426.8 Kg of uranium is necessary in orderfor the C-712 tank to be critical. 7he analysis appears not to have considered concentration of the uranium in a layer at the bottom of the tank. Rather it appears to have considered only the homogeneous distribution of uranium in a tankfidl ofwater. Since the smgle fxtrameter mass limitfor of5% enriched UOh is 1.64 Kg of contained
'"U (43 Kg U). It would appear that only slightly more than this, in an optimal configuration, might be critical. 7husfurther information is needed tojustify that 426 Kg is required to be critical in an unstirred tank receiving discharges that are not measured USEC Resnonse Appendix C of NCSE 1493-25 (i.e., Page 33 of Revision 1) addresses the formation of concentrated layers in the pit. The table presented in this appendix shows that 426.8 kgs of uranium will not go critical at any concentration in the pit. Referencing ARH-600 III.B.5-6 Critical Infinite Slab data supports the conclusions presented in this triole. Based on the flow rates and sample results presented in this report it is extremely conservative to even consider that the uranium would concentrate in layers. The relative uniform distribution of uranium is supported by the new sample results presented in Appendix E of the report.
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Response to NRC RAI Enclosure I to GDP 97-0051 Paducah Oaseous Diffusion Plant, Docket 70 7001 Page 5 of 5 l
The NCSA addressed this process upset in Section 4.2.5 where the largest mass of uranium which could be dumped to the system at one time was analyzed. In order for slightly more than 1.64 kg "U (i.e.,32.8 kgs 2
l of uranium at 5 wt. percent) to go critical, the uranium would have to be uniformly distributed at the optimum conce...itration in a sphere and fully reflected. In order to obtain this configuration the uranium would have to be dumped into the system all at once and allowed to diffuse uniformly in the shape of a l
sphere in the pit of water, However, the largest amount of material which could (i.e., under extreme accident conditions) be dumped into the system at one time is only 13.455 kgs of uranium. This is 60 percent of the maximum subcritical value established by PGDP (i.e., for an optimally moderated and reflected sphere) and only 45 percent of the value discussed in the NRC comment. Since this is the largest i
mass that could credibly be dumped into the system at one time and since there is no physical mechanism (i.e., input flow rate and tank design) for maintaining the uranium in an optimum configuration, a criticality is not possible for this accident scenario.
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ENCLOSURE 2 i
Response to NRC RAI Portsmouth Gaseous Diffusion Plant Docket 70-7002 I
j (SECTION 2) EXCLUSION OF NON-PROCESS BUILDINGS in Table 2 (p. 5) ofPOEF-lMUS-10 areas are specified that are to be excludedfrom coverage on the I
grounds that they "do not contain operations enriched to 1% or higher U-235, and 15 grams or more U-235. " Additional information is requested showing a commitment to practices sufficient to ensure that containers or pieces ofequipment with material exceeding these limits are not brought into these areas.
Information is needed showing that individuals who might, even inadvertently, move special nuclear materialare trainedin these measures.
I USEC Resoonse USEC has demonstrated its commitment to identify and maintain the limitations for these facilities through the use of plant procedures, training, and surveillance.
Workers at the Portsmouth Gaseous Diffusion Plant go through a General Employee Training (GET) class.
GET training and/or testing is required every two years. This training includes general NCS training which informs the personnel of criticality safety concerns and the potential for criticality accidents. It also explains the differences between contamination areas and non-contamination areas. The contamination limit is more 2
2 restrictive than the 1% or higher "U, and 15 grams or more "U limits.
l Employees / workers are instructed that radioactive material is not to be removed from a contamination area.
l The training emphasizes the NCS postings (which delineate the NCSA controls), Fissile Control Area markings (which identify areas under NCSA controls), and that only specially trained personnel are allowed to move or handle fissile material.
In addition to GET training there is job specific training. The groups (e.g Waste Management, Uranium Material Handling, Cascade Operations, Environmental Samplers and Lab personal) that move material between buildings receive additional training. This training stresses the imponance of transporting the fissile material from the point of receipt to its destination in a direct manner. It discusses the definition of
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fissile material, explains the parameters associated with criticality safety, and explains the application of these principles. In addition, this training covers personnel responsibilities related to criticality safety 3
including obtaining the appropriate approvals prior to performing fissile material operations.
To ensure compliance with the NCS program requirements specified in the Procedures and Training Organization, walk-throughs and surveillances are performed by NCS, plant management, and the USEC Safety, Safeguards, and Quality Organization. These walk-throughs and surveillances are performed in part j
to ensure that operations invoking uranium enriched to I wt. percent or higher and 15 grams or more of 2"U l
have been reviewed and approved by NCS, as well as to verify that conditions have not been altered to j
adversely affect NCS. This review and approval process includes compliance with CAAS requirements.
Response to NRC RAI to GDP 97-0051 Portsmouth Gaseous DifTusion Plant, Docket 70-7002 Page 2 of 6 j
(SECTION 3) EXCLUSION ON ROADWAYS FOR CERTAIN MATERIALS Is there a requirementfor Class 11 materials to be loaded and unloadedfrom transporting vehicles in areas covered by criticality alarms? Additional materials, diagrams, or images defining the type of objects that constitute Class 11materialshipments are requested. Additionaldescription of the structures which ensure
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the maintenance ofrequiredspacing during transport is requested. Information concerning the robustness ofthese spacing structures to normal vibrations and moderate mishaps is requested. What plans existfor measures to be taken by accident response teams to consider the possibility ofcriticality in the event of a major upset of the vehicle during transport of Class ll materials?
USEC Resnonse Class II materials are loaded and unloaded in areas with criticality alarm coverage. Fissile material containers before being loaded and after being unloaded from a vehicle are covered under other NCSA's (which are either building specific or general plant NCSA's). These NCSA's require criticality alarm coverage. Movement of fissile material between process buildings is controlled by NCSA-PLANT 043. A00.
This NCSA does not require criticality alarm coverage. This NCSA only covers the fissile material containers afler they are loaded into a vehicle.
Class 11 materials consist of the following small diameter containers:
Container Type Dimensions 744 G, Polyethylene Bottle ID: 4.32-in (max)
(DWG. DX-761-2340-M, Rev. 0)
Height : 50.4-in (max) i Wall Thickness: 0. I 25-in (+0.07, -0.00-in) 24-in Polybottle, Polyethylene Bottle ID: 5.0-in (max) i (DWG. BX-761-M373, Rev. 0)
Height : 24.0-in (max)
Wall Thickness: 0.I875-in (max)
GP Container, Polyethylene Bottle ID: 5.0-in (max)
(DWG. DX-761-2586-M, Rev. 0)
Height : 23.75-in (max)
Wall Thickness: 0.13-in (+/- 0.03-in)
Lid OD: 6.63-in (min)
CO-4 Polybottle, Polyethylene Bottle ID: 4.75-in (max)
(DWG. DX-761-2334-M) 1Icight : 9.0-in (max)
F Can, Tin Container ID: 5.25-in (max)
(DWG. DX-761-M-981)
Height : 24.0-in (max)
Wall Thickness: 0.015-in HYFER Can, Steel Container ID: 4.2813-in (max)
(Y-12 DWG: T2E800530A100) lleight : 10 0313-in (max)
Wall Thickness: 0.012-in Z-Can, Tin Container ID: 5.25-in (max)
(DWG. DX-761-2331-M) lleight : 15.0-in (max)
Wall Thickness: 0.015-in
Response to NRC RAI to GDP 97-005i Portsmouth Oaseous DiiTusion Plant, Docket 70-7002 Page 3 of 6 Class II materials are transported in the following vehicles:
Vehicle Allowed Containers Pickup trucks or vans with small diameter container Small diameter containers racks 5-inch UF6 cylinders 1S,2S, and small sample containers Pickup trucks or vans without small diameter container Dnuns or barrels racks 5-gallon containers 1S,2S, and small sample containers 8,10, and 12-inch UF6 cylinders on dollies B-25 boxes and 6x6x8 boxes contaminated components Barrellins and barreldollies Drums or barrels 20-position Step Van (Bread truck)
Small diameter containers 5-inch UF6 cylinders IS,2S, and small sample containers Drums or Barrels 24-position Step Van (Bread truck)
Small diameter containers 5-inch UF6 cylinders 1S,2S, and small sample containers Bicycles, sedans 1S,2S, and small sample containers Rail cars Large UF6 cylinders Forklins, mobile cans, straddle carriers Large UF6 cylinders (solid UF6 phase only)
B-25 boxes and 6x6x8 boxes Contaminated components With the exception of the specific configurations shown in Figures 1,2, and 3 (Attachment 6), racks on vehicles used for transporting small diameter containers provide a minimum of 23 inches center-to-center spacing. Some vehicles are also equipped with small racks that can be used for transporting 1S and 2S sample containers. These racks are located at the front of the pickup truck beds or along the walls of the Step Vans (bread tmeks) and provide a single row of positions for each rack. Position retention devices are used during the transport of multiple containers or pieces of equipment which require spacing. Position retention devices are defined as either mechanical devices, cords, straps, nets, or any other device, which when secured in place will preserve the intended spacing between containers during normal transport occurrences (e g., bumps in the road, minor collisions, etc.).
At the first indication that fissile material is involved, current practices have the Incident Commander establish a Command Post 500 feet away from the vehicle. Plant Security secures the area so plant personnel do not enter within a 500 foot radius. Radiation Technicians respond to the Command Post with radiation detection equipment to determine if a criticality has occurred. The Fire Department responds to the Command Post. The radiation detection equipment is monitored continuously during the operation until it has been determined that no fissile material is involved or until Criticality Safety Engineering has
Response to NRC RAI to GDP 97-0051 Portsmouth Gaseous DifTusion Plant, Docket 70-7002 Page 4 of 6 determined that the fissile material is in a " safe" configuration. The radiation detection equipment is continuously monitored to rninimize the radiation exposure to the responding personnel in the event of a criticality. If a criticality occurs during a response the Fire Department will retire to a safe distance and continue monitoring until it is safe to approach the accident.
IVith respect to transportation ofindividualitems or components that may contain greater than a safe mass of U-235, such as equipment classifiedfor Planned Expeditious Handling: IVhat commitment has been made, and what measures will be taken to ensure that such shipments will always be made under criticality alarm coverage? IVhat will be done of a criticality alarm covering the planned rout is temporally inoperative?
USEC Resnonse PEH equipment will be transported using two continuously monitored alarming radiation detectors.
TVith respect to Class lil, Large UF6 Cylinders, as long as no k>ading or unloading is done on these roadways, the primary concern is the possibility of cylinder chimage during transport. Is such transport done in such a way as to prechide cylinder damage as a result of vehicle accidents? Can the cylinders be droppedduring transport? IVhat worddbe the effect of a vehiclefuelfire on a cylinder? Il7y is criticality alarm coverage of these roadways notfeasible? What accident response measures would be taken in the event of vehiclefires and accidents?
USEC Resnonse Cylinders being transported on plant site have the right-of-way. Personnel have been informed of this (e.g.
GET training, the plant paper "The Open Line") and give equipment carrying cylinders a wide berth. When approaching equipment carrying a cylinder, drivers are to pull off to the side of the road. When following equipment cariying a cylinder, drivers are to follow no closer than 100 feet. The plant speed limit is set at 25 mph and 5 mph in the cylinder yards reducing the possibility of a vehicle accident.
The possibility of dropping a cylinder while being moved is unlikely. To minimize the possibility of dropping a cylinder, cylinder moving equipment that moves filled cylinders is inspected for proper operation on a per shift basis prior to use each shift. Drop test results (see Attachment 1) indicate that product cylinders will continue to provide UF containment under accident conditions, more conservative than 6
transportation accidents.
A vehicle fuel fire will not result in a criticality. A vehicle fuel fire of sufficient size will convert the solid UF into a liquid and then a gas. The increase in pressure due to the conversion ofliquid to gas will cause 6
the cylinder valve to open releasing gaseous UF. The gaseous UF will react with the moisture in the air 6
6 to form HF gas and UO F -
2 2 The roads adjacent to the process buildings are covered by the CAAS.
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Response to NRC RAI to GDP 97-0051 Portsmouth Gaseous DifTusion Plant, Docket 70-7002 Page 5 of 6 I
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- As with Class II materials, at the first indication that fissile material is involved, current practices have the i
Incident Commander establish a Command Post 500 feet away from the vehicle. Plant Security secures the j
area so plant personnel do not enter within a 500 foot radius. Radiation Technicians respond to the i
Command Post with radiation detection equipment to determine if a criticality has occurred. The Fire l
Department responds to the Command Post. The radiation detection equipment is monitored continuously during the operation untilit has been determined that no fissile material is involved or until Criticality Safety Engineering has determined that the fissile material is in a " safe" configuration. The radiation detection i
equipment is continuously monitored to minimize the radiation exposure to the responding personnel in the event of a criticality If a criticality occurs during a response the Fire Department will retire to a safe i
distance and continue monitoring until it is safe to approach the accident.
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Response to NRC RAI to GDP 97-0051 Portsrnouth Gascous Diffusion Plant, Docket 70-7002 Page 6 of 6 l
4 (SECTION 4) EXCLUSION OF CYLINDER OF UF6 IN STORAGE YARDS i
l TI.ere are amounts andenrichments of UF6 sufficient toproduce criticality in these locations. The Paducah GDP document KWS-271 is referenced as the primaryjustification that an accidental criticality is not credible event in these cylinder storage situations. The arguments in KWS-271 that criticality is low likelihood do not provide a degree ofassurance high enough to warrant complete exclusionfrom CAAS coverage. Utdess additionalinformation can be provided showing that cylinder damage producing holes larger than 1 inch diameter cannot occur, measures providing thefunction of the criticality monitoring describedin 10 CFR 70.89 must be provided.
USEC Resnong The Paducah GDP document KY/S-271 Revision 2 is referenced as the primary justification that an accidental criticality is not a credible event in outside cylinder storage yards. Revision 2 includes additional text on the drop test results and cylinder handling activities. As discussed in the original report submitted i
to the NRC, as well as this revision, if a cylinder breach occurred that was less than 1 inch in diameter, experimental data indicates that the breach would be sealed by the reaction products. The results of the added drop tests indicate that the probability that a product cylinder would fail with a hole larger than 1 inch in diameter is considered extremely low. We believe this additional information indicates that product cylinders will continue to provide UF containment under accident conditions more severe than could be 6
postulated in the cylinder yards, and therefore, will address your concerns.
Not withstanding these results, an evaluation was conducted assuming a breach that was 6 inches in diameter in the top of the cylinder. The evaluation showed that more than 7 inches of rain would have to fall before the cylinder would be filled with 7.4 pounds of water (the amount needed to convert the UF to UO F )-
6 2 2 Furthermore, a substantial mass of additional water is required for moderation of the UO F under optimum 2 2 condition. Severe storm data at PORTS indicates that 6.5 inches of rain might occur over a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> period once in 10,000 years. The frequency of a severe storm occurring following an event in which a cylinder is dropped and breached with a 6-inch diameter hole on the top of the cylinder is not considered credible.
Ifit isproposed that a criticality monitoring system providing continuous coverage as described in 10 CFR 70.89 is notfeasible, thefollowing additionalinformation is requested:
USEC Resnonse As discussed above, the results of these drop tests indicate that product cylinders will continue to provide UF containment under accident conditions more severe than could be postulated in the cylinder yards. The 6
information presented substantiates the position that a cylinder accident during conditions that would provide sufficient moderation to cause a criticality is not credible, and therefore, CAAS coverage is not necessary.
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Response to NRC RAI to GDP 97-0051 Page1of1 1
New Commitments Contained in this Correspondence No.
GDP Commitment Location 1
PORTS "PEH equipment will be transported using two continuously l
monitored alarming radiation detectors."
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