ML19345B399
| ML19345B399 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 11/21/1980 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8012010070 | |
| Download: ML19345B399 (5) | |
Text
6 i NSP NORTHERN STATES POWER COMPANY weu sexeou s, winu s sora ss4o,
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November 21, 1980 Direct 1r of Nuclear Reactor Regulation U S Nuclear Regulatory Commission Wash ingt on , DC 20555 Prairie Island Nuclear Cenerating Plant Docket No. 50-282 License No. DPR-42 50-306 DPR-60 Supplementa' Information - License Amendment Request Dated January 31, 1980 Attached are the answers to questions raised by the Chemical Enineering and Effluent Treatment Systems Branches related to the Prairie Island NGP Fuel Storage Facility modification that were sent to L 0 Mayer from R A Clark on November 5, 1980. Answers to questions from the Auxiliary Systems and Structural Engineering Branches will be contained in a subsequent le t t e r.
Should you have any additional questions please contact this of fice.
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L 0 Mayer, P Manager of Nuclear Support Se rvices LOM/TMP/bd cc: J G Keppler
- C Charnoff l MPCA Attn
- J W Ferman NRC Resident Inspector a- o' C) %T v
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I ATTACRMENT e
QUESTIONS AND RESPONSES Chemical Engineering Branch Question 1. In Section 5.4.2 (page 20) of the License Amendment Request for spent fuel storage, dated January 31, 1980, you stated that operating experience has shown that the greatest quantity of crud is released during movement of spent fuel assemblies.
Indicate the quantity of crud that is estimated to be released during each movement of spent fuel assemblies and any crud released during other storage pool operations. If there is crud released during other operations, indicate whether the filters will have to be changed more frequently or determine the need for increased installed filter capacity.
Response 1. Periodic radiochemical analysis of the spent fuelpoolcoolantgas showed a steady state activity level of approximately 1-2 X 10 uC/mi when no fuel handling is occuring. This activity level appears to be independent of the number of spent fuel assemblies scored in the pools. This activity level increases by a factor of 4 or 5 during refueling and spent fuel handling operations. The activity level returns to normal in less than one month. Other operations which increase the activity levels in the pool, that are not associated with refueling, are fuel assembly insert movements (such as thimble plugging devices and burnable poison rod assemblies) and spent fuel inspections. The frequency of these activities are independent of the number of assemblies scored in the pools and the increase in activity is less than that experienced at refuelings.
No other operations associated with the spent fuel pools is known to cause a " crud" release. It is not anticipated that the amount of " crud" released will increase in the future which would cause the need for more frequent filter changes or increased filter capacity.
Question 2. In Section C of Supplemental Information related to January 31, 1980 License Amendment Request, you indicated that if a pre-established limit of chlorides or fluoride is exceeded, the SEP demineralizer would be used, and that if the SFP ion exchange decontamination factor is unacceptable, the ion exchanger resin would be changed.
Provide the pre-established limits for chlorides and fluorides and the SFP ion exchanger decontamination f actors for various radioactive elements that are expected to be present in significant amounts in the spent fuel pool water. Provide the basis for establishing these values.
Response 2. The pre-eatablished limits for chlorides and fluorides are both 0.15 ppm. These limita are based on vendor supplied specifications for pool water. These are the same limits
(, that exist in the Tech Specs for the reactor coolant. Since l the spent fuel pool water is mixed with reactor coolant
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during refuelings, these limits are also maintained in the spent fuel pools. The SFP ion exchanger is normally kept in service when the spent Fuel cooling system is in operation.
Times when the SFP ion exchanger is not in operation include resin replacement and RWST purification prior to refuelings.
The plant chemists perform a weekly chemical analysis of the spent fuel pool water.
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These analyses include a measurement of the decontamina-tion f actor (DF) across the ion exchanger. Samples are drawn from r '
the inlet and outlet of the ion exchanger. A whole spectra activity measurement is made using a GeLi detector of both samples and a DF is determined. No specific isotopic DF's are determined.
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This weekly DF is trended and a determination on when to replace the resin is made by the Plant Chemist and Supervisor of Radiation Protection based on their best judgment.
Question 3. With respect to the In-Pool Surveillance Program, provide the 1
following:
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Question 3a The type of surveillance specimen with respect to mechanical ;
details, galvanic coupling effects and stressed materials.
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} Response 3a The surveillance sample consists of Boraflex sheet (8.25"x12"x I .125") enclosed in two stainless steel plates (9.625"x13.375" x.090" and 9.375"x13.125"x.024" respectively) . The stainless steel plates are tack welded along the three sides to encapsulate the r
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t Boraflex sheet. The top and four corners are lef t, open. The sample will be equipped with mounting hole and lif ting bail for ease in !
removal from the pool, f The stainless steel used is type 304 ASME SA 240 which. is the
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same material used in the storage tube. The Boraflex sheet will be of the same composition, produced by the same method and certified to the same criteria as the neutron absorber material used in the storage tube.
The material content of the Boraflex sheet has no known galvanic coupling reactions with the type of stainless steel used. Welding
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will be conducted at low heat input, minimizing residual stress.
^l The same welding methods is used in the f abrication of the fuel storage tubes will be used in assembly of the surveillance samples.
Residual stresses in the samples will be minimal.
l Question 3b The location of the sampiri in the pool with respect to whether they are exposed to gammc flux levels comparable to the absorber materials used in the racks.
Response 3b The surveillance samples will be hung in the pool in between two racks equipped with a sample holder plate. The first refueling following completion of the installation of the 4 storage racks fresh spent fuel assemblies will be placed adjacent to the sample holders. The gamma flux level of exposure of the Boraflex sheet in the samples will be about the same as the neutron absorber materials in the racks. The stainless steel plate will absorb a negligible amount of !
gamma radiation.
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Questien 3c Type of tests or examinations to be made on the samples with respect to corrosion, visual observations and weight gain or loss, etc.
Response 3c Each pre-irradiated and irradiated ' Boraflex sheet will be tested and examined to obtain the following data:
- Dimensions such as length, thickness and width
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- Hardness
- Dry weight
- Boron Carbide content The stainless steel plates will be visually examined for evidence of corrosion.
Question 3d Frequency of examinations.
Response 3d A sample will initially be withdrawn approximately 1 year after new racks are installed. Subsequent samples will be withdrawn at five year intervals.
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Question 3e How the program addresses item 1.5(1) of the OT Position for Review and Acceptance of Spent Fuel Storage and Handling Applications.
Response 3e on-site verification tests will be performed on all cells to ensure within 95% confidence limits that the neutron absorber material is in place in the fuel racks. These tests will consist of the insertion of a neutron source and detectors into the storage tube. This equipment is specifically designed for verification of neutron absorber in fuel racks.
Effluent Treatment Systems Branch Question 1. With regard to the cleanup loop in the spent fuel pool cooling and cleanup system;
- a. Other than during refueling, how of ten and for how long (on an annual basis) is it brought on line and used?
- b. What criteria are used for initiating 'and securing operation of the cleanup loop?
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Response 1. a. The spent fuel cooling system is maintained in operation
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except for brief periods of routine maintenance which
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average less than two weeks annually. The elecnup loop is in service and lined up for spent fuel pool cleanup whenever the scent fuel cooling system is in '
operation excer* follows. Prior to refueling on each unit the demi r is lined up for purification of the Refueling Wa ;e Tanks for approximately one month i each and the oop is isolated for approximately one day twice exchange resin in the demineralizer.
- b. No criteria ex: initiating or securing the cleanup
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loop since it ..mally in operation except as stated in part' a.
Question 2. When were the filters upstream of the spent fuel pit demineralizers installed, and what precipitated this change?
Response 2. The filters upstream of the spent fuel pool demineralizer were installed in June of 1979. These filters remove particulates in
! the spent fuel pool water so that particulates are not " filtered" out of the stream by the demineralizer -resin. This results in a
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slower rise in the differential pressure across the demineralizer, resulting in fewer resin changes due to low purification flow. Two .
benefits are derived from fewer resin changes; reduced volumes of L solid rad-waste and lower man-rem exposures from resin exchanges.
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