ML20215N495
| ML20215N495 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 07/31/1985 |
| From: | Oden D Battelle Memorial Institute, PACIFIC NORTHWEST NATION |
| To: | |
| Shared Package | |
| ML20215N487 | List: |
| References | |
| NUDOCS 8611060102 | |
| Download: ML20215N495 (46) | |
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EXTENDED FUEL STORAGE IN THE EXISTING ONSITE HUMBOLDT BAY UNIT NO. 3 STORAGE POOL.
a re m
D. R. Oden,
.. Project Manager Technical Contributors:
A. B. Johnson, Jr.
W. J. Bailey n; July 1985 Prepared for Pacific Gas & Electric Co.
San Francisco, California under BNW Contract 2311206920 and
. PG&E Contract 278-0024-85 l
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Battelle Pacific Northwest Laboratories Richland, Washington 99352 o209,hh$33 O
glOkOCW PDR l
r SUMfiARY Currently, 390 Zircaloy-clad fuel assemblies are stored in the Pacific Gas
& Electric (PG8E) Humboldt Bay Power Plant (HBPP) Unit No. 3 spent fuel pool.
The plant, which was shut down for the final time in 1976, is now entering a decommissioning phase termed " custodial safe storage (SAFSTOR)." All systems necessary to maintain plant safety will remain in service and will, in some I
cases, be upgraded.
Disposition of the nuclear fuel is a key consideration for SAFSTOR. The Nuclear Waste Policy Act of 1982 specifies that the utility is responsible for storage of the fuel until the federal government takes title in 1998. This report examines the technological and safety aspects of continued storage of the spent fuel in the HBPP Unit No. 3 spent fuel pool. The principal con-( siderations are 1) the technical basis for extended wet storage of Zircaloy-clad fuel and 2) how the technology applies to extended wet storage in the HBPP
{ Unit No. 3 pool.
BASIS FOR EXTENDED STORAGE OF ZIRCALOY-CLAD FUEL Wet storage technology has developed over the past 40 years. The
{ worldwide importance of wet storage technology has prompted several major assessments:
The conclusions of the International Nuc1 car Fuel Cycle Evaluation (INFCE) Working Group 6 were published in 1980.
A survey of world experience of storage of water reactor spent fuel in water pools was conducted jointly by the International Atomic
" Energy Agency (IAEA), Vienna, and the Nuclear Energy Agency (NEA),
Paris. The summary was published,in 1982.
A proposed rulemaking on the storage and disposal of nuclear waste (Waste Confidence Rulemaking) stated the position of the U.S. Depart-ment of Energy (DOE) (published in 1980). The position developed by ,
DCE served as a basis for the U.S. Nuclear Regulatory Commission (NRC) to evaluate confidence in existing technology and concepts for -
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interim storage and disposal of spent fuel and high-level waste. The i NRC comissioners ruled for confidence that spent fuel can be stored ,
in a reactor pool or other storage sf te for at least 30 years beyond ,
the expiration of that reactor's operating license. The Waste Confi-dence Decision was published in 1984 in the Federal Register.
The conclusions from these three studies are summarized in this report and lead to the general conclusion that wet storage of Zircaloy-clad fuel for several j decades (at least 50 years) will not compromise the health and safety of the -
public or the plant staff. This conclusion is supported by numerous technical investigations addressing extended wet storage of Zircaloy-clad fuel and behav-f or of spent fuel pool components, which are also summarized in this report. l Continuing surveillance of wet storage technology by an Electric Power Research Institute program and an IAEA program provide additional confidence.
Zircaloy-Clad Fuel Behavior in Wet Storage Wet storage of Zircaloy-clad fuel began in the late 1950s. Zircaloy-clad -
fuel discharged from the Shippingport reactor in 1959 is still in wet storage with periodic visual surveillance. In 1980, rods from the fuel were subjected to detailed nondestructive and metallurgical examination. The results were compared with published results from sibling rods examined 20 years earlier. 3 In 20 years of wet storage, there had been no significant change in rod diame- I ter, cladding burst strength, fission gas release, cladding hydrogen content, i
cladding defects, or cladding oxide thickness.
Studies were also conducted in Canada, the Federal Republic of Germany (FRG), and the United Kingdom (UK) on Zircaloy-clad fuel to investigate whether extended wet storage resulted in detectable degradation. In all cases, clad-ding degradation was not detected.
j A few cases have been reported inv.olving deterioration of stainless steel (SS) hardware. However, these cases involve pressurized water reactor (PWR) fuel of a different design than the HBFP boiling water reactor (BWR) fuel. No cases of hardware failure have been reported for BWR fuel. _
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Zircaloy corrosion rates at pool storage conditions have been too low to
, measure accurately. One estimate suggests that the cladding oxidation rate at i
HBPP pool storage conditions is less than 0.003 pm/yr. If this value is extra-polated to 100 years, the oxide growth will be less than 0.3 pm, which corre-sponds to less than 0.05% conversion of Zircaloy cladding to oxide.
Results of the investigations summarized above and the world survey of wet storage experience suggest that not even one out of several million Zircaloy-clad rods has failed by corrosion during wet storage that now exceeds '
I 25 years for some rods. The only detectable cladding degradation has occurred by mechanical damage to a few rods during fuel handling. In only one or two cases have these events resulted in detectable radiation releases. In all these cases, the releases have been minor.
Effect of Cladding Defects The storage behavior of Zircaloy-clad fuel with reactor-induced cladding defects has been investigated in the FRG, UK, and United States. For pe;fods of up to 8 years, the cladding defects did not enlarge or otherwise show evidence of deterioration. The amount of UO2 fuel exposed to the pool water appeared to remain essentially constant over the same period, suggesting very
. low UO 2 dissolution rates. Low amounts of radioactive species that leached from the exposed U02 made only minor additions to the inventory that entered the pools by periodic mixing with reactor coolant during refueling outages.
I t Detection of Cladding Degradation To date (1959 to 1985), there has been no evidence that Zircaloy-clad rods are degrading significantly in wet storage. If substantial aqueous cladding corrosion were to occur, it should be signaled by release of hydrogen from the reaction: Zr + 2H O2 + Zr02 + 2H2 . A few cases of aluminum corrosion in spent fuel pools have been detected by this means. If cladding breaches were to P
develop, they would be expected to result in release of helium fill gas and fission gas from rods with pressures exceeding the hydrostatic pressure in the pool. However, the cladding defect would be expected to be minute (approxi-mately 1 pm). Therefore, leaching of fission products from the UO fuel would 2
not be significant. -
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i crud Effects .
There is evidence that crud layers on some water reactor fuel tend to loosen in extended wet storage, which could result'in some crud spallation when the fuel is handled for shipping. However, not all ' fuel appears to be sus-ceptible. Crud that spalls while in reactor pools can be treated by the pool water treatment system. In some cases, loose material on pool floors has been removed with portable vacuum equipment. If properly assessed, the effects of crud loosening can be anticipated and mitigated. .
Behavior of Storage Pool Equipment The behavior of storage pool equipment has been investigated. The mate- .
rials generally include stainless steel, aluminum alloys, and a few cases of carbon steel. Corrosion-induced localized failures have occurred in SS piping at a few PWR spent fuel pools. SS liners have functioned in a large majority
'f of commercial spent fuel pools, with only minor leaks reported. Both SS and aluminum alloy racks have functioned successfully in spent fuel pools for periods exceeding 20 years. "
BASIS FOR EXTENDED STORAGE OF ZIRCALOY-CLAD FUEL IN THE HBPP UNIT NO. 3 FUEL STORAGE POOL Several considerations are addressed in this report:
- the HBPP pool history
- the HBPP fuel characteristics and how they relate to the world experience with wet storage of Zircaloy-clad fuel
- the HBPP fuel storage conditions and how they relate to the range of conditions in wet storage technology 1 a,
- expected behavior of the HBPP storage pool equipment e projected plans for management of the HBPP fuel storage facility over the expected storage period.
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HBPP Fuel Characteristics The 390 fuel assemblies stored in the HBPP Unit No. 3 pool have Zircaloy-2 cladding, Type 304 SS end fittings and spacers, and Inconel- X750 springs.
Zircaloy is also the construction material for the 140 fuel channels. The materials are typical of fuel assemblies stored in other BWR pools and some away-from-reactor (AFR) pools.
The range of wet storage residence times for fue'l now in the HBPP Unit ,
No. 3 pool is 9 to 14 years. By 1998, this range will have increased to 20 to 25 years. Zircaloy-clad fuel stored since 1959 is still in wet storage (26 years in 1985) and shows.no evidence of cladding degradation. To date, no BWR fuel has shown any evidence of degradation of SS components or deleterious effects of Inconel springs.
l Based on results of the world survey of wet storage experience and several examinations of Zircaloy-clad fuel after extended wet storage, Battelle-
} Northwest projects that no cladding defects will develop in the HBPP fuel, even if the fuel storage were to extend to the end of the proposed 30-year SAFSTOR period.
The burnup range for the HBPP fuel is 5,000 to 19,500 Mud /t. Zircaloy-clad BWR fuel with burnup levels up to 43,800 mwd /t has been in wet storage since 1982. BWR fuel with burnup levels up to 25,700 mwd /t has been in wet storage since 1973. Zircaloy-clad PWR fuel with burnup levels up to
- c. 55,000 mwd /t has been in wet storage since 1982. PWR fuel with burnup levels up to 33,000 mwd /t has been in wet storage since 1972. Thus, the burnup range for the HBPP fuel is below that for other Zircaloy-clad fuel now in wet storage.
I l' Estimates suggest that 58 HBPP fuel assemblies have rods with cladding defects. Other spent fuel pools have stored several hundred assemblies with defective cladding. In fact, some 2200 Zircaloy-clad fuel assemblies with one or more defective rods are currently in wet storage. Almost all are uncanned and have had only minor impacts on radioactivity inventories in the respective storage pools.
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Thermal releases from the HBPP fuel currently average 40 W/assenbly, compared with 450 W/ assembly per assembly for typical BWR fuel (28,000 mwd /t) 1 year after discharge. A PG8E analysis separate from this study indicates that heat generation rates for the HBPP fuel will not support temperatures that ,
- will substantially degrade the Zircaloy cladding even in the highly unlikely event that pool water is lost.
i The HBPP fuel assemblies are 4.5 in. square with 95-in. long rods; typical . ;
i BWR fuel dimensions are 5.5 in. square with 164-in. long rods.
j HBPP Pool Storage Conditions l- The HBPP Unit No. 3 pool water temperature is 19'C (66'F). Temperatures !
l in other fuel storage pools range from 15 to 55'C', depending on heat char-
} acteristics of stored fuel and the storage building characteristics.
- Recent pool water analyses indicate a pH of 5.5 to 6.5; conductivity of 3
) to 4 pmho/cm; less than detectable Cl , F , N0j, NO 3, P0 4,5 and S0" concen-trations; low or undetectable B, Ca, Fe, Na, and Zn concentrations; the Cu con-l<
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centration (0.3 ppm) is the highest. Recent radioactivity concentrations in the pool water are 1 x 10-4 pCi/cc. Based on these values, the HBPP pool water .
- purity control has been satisfactory.
9 HBPP Storage Pool Equipment The HBPP Unit No. 3 pool currently has the following components: o e pool walls - reinforced concrete (carboline coated) e pool liner - Type 304 SS .
e heat exchanger - Admiralty bronze
- e handling tools - aluminum / stainless steel. '
To the extent that visual inspections are possible (piping, heat exchan-ger, and visible areas of pool walls), all locetions appear to be in good c"on-dition. The condition of the pump is rated as fair, and it is being considered for possible replacement. , ,. l; i ;i
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r An aluminum alloy can stored in the pool since the early-to-mid 1960s was removed for inspection by the reactor staff; sections of the can also were sent to Battelle-Northwest for inspection. The aluminum did not appear to be pitted or have major corrosion in visual and microscope examinations of the surface.
The corrosion appeared to be similar to corrosion on aluminum components examined after 15 years in a deionized water pool; in that case, the oxide film was 8 to 20 pm thick on aluminum spacers in proximity to irradiated Zircaloy-clad fuel. The aluminum in the HBPP pool did not appear to be adversely '
[ affected by the exposure to the relatively low (0.3 ppm) copper concentration in the pool water. Even so, components in the pool water circulation system j that contain copper are being evaluated for removal and replacement with copper-free materials.
Recent visual examination of accessible carbon steel pipes did not indi-t cate any leaks. However, carbon steel is susceptible to corrosion in pool
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waters, suggesting that further evaluation of the pool piping system is war-1
(, ranted. The utility has indicated plans to inspect the recirculation system piping when the system is modified to remove the coolers and to route full l recirculation flow through a condensate demineralizer. Due to low levels of decay heat, it is no longer necessary to use heat exchangers to cool the spent l fuel pool.
Plans for HBPP Storage Facility Management During SAFSTOR s3 Review of the HBPP safety and environmental assessments indicates that i systems and procedures will remain in place to assure safe operation of the storage facility. The safety and monitoring plans are outlined in Appendix A.
Criticality, seismic, and safeguards aspects of fuel storage in the HBPP pool are addressed in other PG&E studies and are therefore not repeated in this study.
P CONCLUSIONS
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- Based on a world survey of wet storage experience and on specific examinations of Zircaloy-clad fuel after up to 20 years of wet stor-age, Battelle-Northwest projects that no cladding defects will -
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J develop in the HBPP fuel during the projected 30-year SAFSTOR period. .
Zircaloy cladding oxidation rates under pool storage conditions are ,
estimated to be less than 0.3 pm in 100 years.
- Based on studies.of Zircaloy-clad fuel with cladding defects and on ext.erience with storage of defective fuel, no significant impacts of ,
the defective rods now stored in the HBPP pool are expected during
- . the SAFSTOR period. Continued storage of the defective fuel in the uncanned condition is consistent with industry practice. -
Effects of crud on the HBPP fuel are not expected to be significant during the SAFSTOR period. When the fuel is moved, some crud spal- '
lation may be anticipated, based on' experience with other water reactor fuel after extended storage.
The HBPP pool temperature (19'C) is at the lower end of the range for reactor pools due to the relatively long fuel cooling period; thus, 1
i corrosion rates for the fuel and the pool storage equipment will be correspondingly minimized. U e
The current HBPP pool water chemistry includes Cl , F , N0j, NO3 ,
P0j, ands 0jlevelsthatarebelowdetectionlimits. Copper is the only significant cation, but the concentration is relatively low (0.3 ppm). Inspection of aluminum exposed to the pool water since '
the early-to-mid 1960s suggests that the low copper concentration has n not had a significant effect on aluminum corrosion. The utility a plans to upgrade the demineralizer system as part of SAFSTOR l preparations.
- A recent visual inspection of accessible HBPP pool components sug- ;
gests that they are in good condition. Experience with extended-i i
(>20 years) use of SS and aluminum components in other pools indi-cates good long-term durability. Exceptions include local corrosion of highly sensitized SS piping, which is not a consideration at the HBPP Unit No. 3 pool. Zircaloy fuel channels- and stellite materials "
l stored in the pool have good aqueous corrosion resistance. The pool water analysis suggests that corrosion rates, of copper components are , ;
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l i i low in the HBPP pool. Other experience indicates that carbon steel i ' corrosion rates are significant under storage pool water conditions, l
! suggesting that corrosion effects on the HBPP piping deserve further l consideration.
- In a sepirate PG&E study, it was concluded that in the event of a I complete loss of pool water the HBPP spent fuel cladding would remain l 6
intact due to the relatively low thermal release rates (estimated to l be 40 W, average per assembly). l t
- A review of HBPP Unit No. 3 SAFSTOR plans indicates that all plant functions necessary to maintain safe storage of the fuel in the HBPP pool will be in place.
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CONTENTS
SUMMARY
.................................................................. iii INTRODUCTION ............................................................. 1 TECHNICAL BASIS FOR WET STORAGE OF IRRADIATED WATER REACTOR FUEL ......... 3 MAJOR ASSESSMENTS OF WET STORAGE TECHNOLOGY ......................... 3 BEHAVIOR OF ZIRCALOY-CLAD FUEL IN EXTENDED WET STORAGE .............. 6 t
l BEHAVIOR OF FAILED FUEL ............................................. 8
- EFFECT OF CLADDING DEFECTS .......................................... 8 DETECTION OF CLADDING DEGRADATION ................................... 9
, P OOL COMP ON ENT BEHAV I OR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 s
CRUD EFFECTS ........................................................ 11
," BASIS FOR EXTENDED STORAGE OF ZIRCALOY-CLAD FUEL IN THE HBPP UNIT NO. 3 FUEL STORAGE POOL .................................................. 13 1
HBPP UNIT NO. 3 P0OL HISTORY ........................................ 13 CHARACTERISTICS AND HISTORY OF HBPP UNIT NO. 3 IRRADIATED FUEL ...... 17 I
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SUMMARY
OF HBPP UNIT NO. 3 P00L MATERIALS ........................... 18 PROJECTED PLANS FOR HBPP FUEL STORAGE OPERATIONS DURING SAFSTOR ..... 24
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REFERENCES .....................................'.......................... 25 l
APPENDIX A - SAFETY AND MONITORING PLANS AT THE HBPP UNIT NO. 3 POOL l DURING SAFSTOR .............................................. A.1 o
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7 FIGURES 1 Equipment Location - Ground Fl oor -)l an . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2 Equipment Location .................................................. 15 TABLES s
1 Summary of Spent Fuel Examinations to Define Status of Pool-Stored }
Fuel ................................................................ 7 1 2 Examples of Aluminum Alloy Fuel Racks in Spent Fuel Pools ........... 10 3 HBPP Uni t No. 5 Pool Hi story and Characteristics . . . . . . . . . . . . . . . . . . . . 16 4
HBPP Uait No. 3 Irradiated Fuel Characteristics . . . . . . . . . . . . . . . . . . . . . 19
..i 5 Summary of Materials in the HBPP Unit No. 3 Spent Fuel Pool ......... 21 .,1 6 HBPP Water Chemi stry Analy si s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 l A.1 Spent Fuel Storage Pool Water Chemistr During S AFSTOR . . . . . . . . . . . . . . . . . . . . . . .y and Activi ty
............................... A.5 A.2 Sp ent Fu el Mi scel l a neous Invento ry - 1984 . . . . . . . . . . . . . . . . . . . . . . . . . . . A.6 .s I
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INTRODUCTION
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. Currently, 390 irradiated spent fuel assemblies are stored in the Humboldt Bay Power Plant (HBPP) Unit No. 3 storage pool. Pacific Gas & Electric Co.
(PG&E) has announced plans to place the plant into a decommissioning stage called " custodial safe storage (SAFSTOR)." This report was prepared for PG8E by Battelle, Pacific Northwest Laboratories (a) and examines the technological and safety implications of continued storage of the spent. fuel in the HBPP Unit .
No. 3 spent fuel pool until the federal government accepts title to the fuel at j the end of the 30-year SAFSTOR period. The wet storage alternative at HBPP Unit No. 3 is examined from two standpoints: the technical basis for extended wet storage; and specific aspects of extended wet storage in the HBPP Unit No. 3 pool.
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r (a) Hereefter referred to as Battelle-Northwest or BNW.
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- TECHNICAL BASIS FOR WET STORAGE OF IRRADIATED WATER REACTOR FUE' 4
The technology for wet storage of irradiated fuel has developed since 1943. The first water-cooled power reactor fuel storage began in the late 1950s. Wet storage has emerged as the dominant worldwide fuel management method due to delays in reprocessing. The importance of wet storage technology has resulted in international studies of the technology. The U.S. Nuclear Regulatory Commission (NRC) developed a rulemaking that included a favorable position regarding the safety of wet storage.III The. wide use of wet storage over a 40-year period provides a definitive basis to assess the safety aspects.(1-12) Major assessments of wet storage technology are summarized below. The assessment of the safety of extended fuel storage in the HBPP Unit No. 3 spent fuel storage ~ pool is based on these summaries and on additional technical studies.
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MAJOR ASSESSMENTS OF WET STORAGE TECHNOLOGY
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The technology and safety of wet storage has been examined in several publications, including the following documents:
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International Nuclear Fuel Cycle Evaluation (INFCE).1980. Spent Fuel Management. Report of INFCE Working Group No. 6, STI/ PUB /534, IAEA, Vienna.(2) Conclusions related to wet storage experience include the following statements:
Based upon extensive operational' experience, the interim storage '
g of LWR and HWR spent fuel assemblies in water-filled storage pools
'l, can be considered a proven technology.
Experience exists with wet storage of LWR and HWR spent fuel for periods up to 20 years with low-burnup fuel. No significant diffi-culties are expected in projecting spent fuel behavior in wet storage for longer storage times and higher burnups. Nevertheless, observa-
? tion and investigation work should be continued to evaluate the behavior of high-burnup spent fuel assemblies during prolonged stor-age periods and to confirm the present positive experience....The wet, storage of LWR and HWR spent fuel, including the use of compact racks, can be regarded as a proven technology....
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- International Atomic Energy Agency. 1982. Storage of Water Reactor Spent Fuel in Water Pools - Survey of World Experience, IAEA Techni- l cal Report Series No. 218, Vienna.(3) To quote from the survey conclusions:
l There is a strong basis from the survey to conclude that water storage of spent nu: lear fuel is a mature, viable technology without major technological difficulties. There is a substantial basis to conclude from pool operator observations and from specific fuel examinations that Zircaloy-clad water reactor spent fuel has not '
degraded appreciably in up to 20 years....
Operational problems with spent fuel pool components have been r minor.
Spent fuel pool operations contribute small fractions to total.
radiation doses from nuclear reactor operations and make only minor contributions to volumes of low- and intermediate-level radioactive waste.
e Proposed Rulemaking on the Storage and Disposal of Nuclear Waste Statement of Position of the United States Department of Energy, ,
00E/NE-0007, April 1980;I4) Supp.1,I6) September 1980. The DOE study concludes that:
The abundant evidence shows that the adequacy and safety of extended storage of spent fuel in a water pool environment can be ;'
demonstrated today. The following points summarize the basis of this conclusion: .
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- 1. The technology of water pool storage of spent fuel is not only ;
available but is well established through more than 30 years of work at government and industrial facilities....
- 2. The regulatory framework, industry standards, and design i requirements for the water pool storage of spent fuel currently exist.
- 3. The licensing of water pool storage of spent fuel has been routinely practiced by the Commission and its predecessor agency ,
for nearly 20 years and is being practiced at the present time. '
- 4. Zircaloy-clad spent fuel has been stored under water for periods, of up to 20 years, ...with no evidence of degradation as a result of such storage. Studies of the corrosion aspects of water pool storage indicate that there are no obvious degrada-tion mechanisms which operate on the cladding at rates which ' I would be expected to cause failure in the time frame of 50 years ;;
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. or longer. Moveover, in the unlikely event that severe deterio-ration of the cladding were to develop, the spent fuel could be
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encapsulated to provide the necessary integrity for indefinite i storage.
, Because much of the experience in handling and storage of spent fuel has been gained at reactor sites and much of the technical data presented and discussed in this Statement was acquired in studies at reactor storage pools, there is no reason to doubt the technical adequacy of existing and planned reactor storage pools. Accordingly, i the Department submits that continued storage of spent fuel at reactor sites would be acceptable, even if such storage should be i required for. a period beyond the expiration of the reactor operating j license....
- NRC. August 31, 1984. " Waste Confidence Decisions." Federal Ragister 49(171):34,658-34,696.III After review of the DOE Statement of Position outlined above, the NRC commissioners ruled for confidence regarding extended wet storage of fuel at reactor pools, with the following statement:
1U ...if necessary, spent fuel generated in any reactor can be l
", stored safely and without significant environmental impacts for at ;
least 30 years beyond the expiration of that reactor's operating l licenses at that reactor's spent fuel storage basin, or at either I onsite or offsite independent spent fuel storage installations.
3 In summary, the comprehensive assessments of wet storage experience have lead to the conclusion that wet storage is a. safe technology. The technical
, basis is well established. The storage behavior of Zircaloy-clad spent fuel has been examined, including fuel with cladding defects. Effects of water storage on pool co.nponents (racks, piping, etc.) have been characterized. Wet
- w. storage technology has not been troublefree, but the problems have not been major. Problems such as dropped fuel assemblies, corrosion of piping welds at a few pressurized water reactor (PWR) pools, and swelling of dense racks do not apply to SAFSTOR at HBPP. Corrosion of carbon steel piping is an area that 7 will be addressed during preparations for SAFSTOR.
Wet storage technology has taken on major proportions worldwide. Several countries have recently directed their fuel management strategies to wet stor-age. Currently (1985), wet storage is the only licensed U.S. spent fuel l
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management option. In Sweden, the CLAB facility is designed to store Zircaloy-
' clad fuel for 40 years. Finnish fuel management involves wet storage in pools designed for a 60-year life; fuel storage is licensed for up to 40 years.
Several east European countries (Bulgaria, Czechoslovakia, and Hungary) are building large wet storage facilities. Large storage pools have recently been constructed in France and the United-Kingdom. Almost all of the world's reac-tors have fuel storage pools. This world commitment to wet storage technology grows from-independent assessments in numerous countries, leading to the con- ,
clusion that storage of water reactor fuel, even over periods up to 50 years, t is safe. I The following sections summarize several investigations:
- e storage behavior of Zircaloy-clad fuel in water for decades e storage behavior of Zircaloy-clad fuel with cladding defects e storage behavior of spent fuel pool component materials (aluminum, stainless steel). 1 J
BEHAVIOR OF ZIRCALOY-CLAD FUEL IN EXTENDED WET STORAGE Wet storage of Zircaloy-clad fuel began in the late 1950s. Zircaloy-clad '
fuel discharged from the Shippingport reactor in 1959 is still in wet storage with periodic visual surveillance. In 1980, rods from the fuel were subjected '
to detailed nondestructive and rsetallurgical examination (Table 1). The -
results were compared with published results from sibling rods examined ,
20 years earlier.UI In 20 years of wet storage, there had been no significant change in rod diameter, cladding burst strength, fission gas release, cladding !
hydrogen content, cladding defects, or cladding oxide thickness.
Studies were also conducted in Canada, the Federal Republic of Germany (FRG), and the United Kingdom (UK) on Zircaloy-clad fuel to investigate whether extended wet storage resulted in detectable degradation (Table 1). In all cases, cladding degradation was not detected.
A few cases have been reported involving deterioration of stainless steel (SS) hardware. However, these cases involved PWR fuel of a different design than the HBPP boiling water reactor (BWR) fuel. - - I' I
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l TABLE 1. Summary of Spent Fuel Examinations to Define Status of Pool-Stored Fuel (3)
Fuel Characteristics First Fuel: where Inspected / Burnup Water When How Fuel Type / Reactor by whom (mwd /t U ) Storage Examined Examined Remarks ZIrgjoy/UO/KWO/ 2 KWO pool /KWU Up to 1974 1975, NDT; eddy cur- No evidence that reactor-PWR 39,000 1977, rent; profilo- Induced defects are 1980 metry; visual changing; no evidence photography that intact cladding is degrading Zircoloy/UO /PWR(b) Windscale/UKAEA/BNFL 33,000 1972 1977 NOT/ hot cell No evidence of pool-2 Induced degradation Zircaloy/UO /BWR(b) Windscale/UKAEA/BNFL 20,000 1971 1977 NDT/ hot cell No evidence of pool-2 Induced degradation Zircaloy/UO /SGHWR Windscale/UKAEA/BNFL 1,900 1968 1977 Hot cell No significant degrada-2 y tion at reactor-Induced defects Zirealoy/UO /PHWR(b) Win dsca l e/UKAEA/BNFL 6,500 1966 1977 NDT/ hot cell No evidence of pool-2 Induced degradation Zipcaloy/UO 2/NRU gey Dam medAM W to M62 M78 - W M ot cell No e d ence of M -
NRX/ Douglas Pt./NPD ae,000 Induced degradation Zircaloy/UO /
2 Battelle/PNL/BCL 4,800 and 20 yr 1980 NDT/ hot cell No evidence of pool-Sh ippingport/PWR(d ) 18,000 and Induced degradation 16 yr (a) 28 rods are periodically examined; 10 with reactor-Induced defects,18 Intact.
(b) Proprietary.
(c) Approximately 140 rods are selected f or the Canadian surveillance program to be examined periodically through the year 2000 (d) Fuel examined under U.S. DOE program; to be placed in water storage for extended surveillanc9 4
Zircaloy corrosion rates at pool storage conditions have been too low to measure accurately. One estimate suggests that the cladding oxidation rate at HBPP pool storage conditions is less than 0.003 pm/yr.(8) If this value is extrapolated to 100 years, the oxide growth will be less than 0.3 pm, which corresponds to less than 0.05". conversion of Zircaloy cladding to oxide.
Results of the investigations sumarized above and the world survey of wet storage experience suggest that not even one out of several million Zircaloy-clad rods has failed by corrosion during wet storage that now exceeds 25 years -
for some rods. The only' detectable cladding degradation has occurred by mechanical damage to a few rods during fuel handling. In only one or two cases have these events resulted in detectable radiation releases. In all these '
cases, the releases have been minor.
In addition to the specific evidence for durability of Zircaloy-clad fuel in wet storage environments, there is further evidence that it has high aqueous "
corrosion resistance. Zircaloy-clad fuel remained in the Canadian Nuclear i
Power Demonstration (NPD) reactor for 16 years without failure.(3) Zircaloy- [
clad fuel remained in the Shippingport reactor for 17 years (12.3 years under reactor operating conditions), finally reaching an assembly-average burnup l exceeding 40,000 mwd /t.(3)
BEHAVIOR OF FAILED FUEL .
The vast majority of failed Zircaloy-clad fuel does not require special handling. The majority of pool coerators store fuel assemblies that contain defective fuel rods in the same fashion as intact fuel.(3) Defects in the fuel cladding have had little impact during wet storage, even when the fuel was not canned.(8-11,13) ;
Spent fuel with defective cladding has been stored, shipped, i and reprocessed, frequently on the same basis as intact fuel. I' i
EFFECT OF CLADDING DEFECTS The storage behavior of Zircaloy-clad fuel with reactor-induced cladding defects has been investigated in the FRG, UK, and United States.(8-11,13) For periods of up to 8 years, the cladding defects did not enlarge or otherwise show evidence of deterioration. Uranium oxide exposed to pool water over 5 to' ,
8 '
I
r i
i I
8 year:: has not dissolved sufficiently that fuel loss was detectable,
, suggesting very low rates of UO2 dissolution under wet storage condi-l! tions.(8,11,13) Low amounts of radioactive species tha't leached from the I
! exposed UO2 made only minor additions to the inventory that entered the pools by periodic mixing with reactor coolant during refueling ' outages.
DETECTION OF CLADDING DEGRADATION i
To date (1959 to 1985), there has been no evidence that Zircaloy-clad rods
! are degrading significantly in wet storage. If substantial aqueous cladding corrosion were to occur, it should be signaled by release of hydrogen from the reaction: Zr + 2H2 O + Zr02 + 2H 2 . A few cases of aluminum corrosion in spent fuel pools have been detected by this means. If cladding breaches were to e develop, they would be expected to result in release of helium fill gas and c fission gas from rods with pressures exceeding the hydrostatic pressure in the g pool. However, the cladding defect would be ' expected to be minute (~1 pm).
g Therefore, leaching of fission products from the UO2 fuel would not be significant.
i POOL COMPONENT BEHAVIOR The behavior of storage pool equipment has been investigated.(3,5,6) The materials generally include stainless steel, aluminum alloys, and a few cases of carbon steel. Corrosion-induced localized failures have occurred in SS piping at a few PWR spent fuel pools. SS liners have functioned in a large majority of commercial spent fuel pools, with only minor leaks reported. Both l
SS and aluminum alloy racks have functioned successfully in spent fuel pools 1
for periods exceeding 20 years. Table 2 summarizes several cases of extended t I
( usage of aluminum alloy racks. Several pools with aluminum components are still in service for times similar to aluminum rack residence in the HBPP Unit I
No. 3 pool; no serious deterioration has been detected in pools with deionized water. Copper ion contamination at sufficiently high concentrations can promote aluminum alloy corrosion.I14I The significance of chis observation is l t
! 9 i
TABLE 2. Examples of Aluminum Alloy Fuel Racks in Spent Fuel Pools (6)
Spent Fuel Pool Location Pool Chemi stry Time in Pool Remark s Studsvi k Studsvik, Sweden Delonized water 1964 to present No problems.
G.E.-Morris >b rr i s, I L, US A Delonized water 1972 to 1975 Corrosion at poor welds.I*I WAK Karlsruhe, GFR Delonized water 1969 to present(b) No cor osion af ter anodizing.
Yankee Rowe Rowe, MA, USA Boric acid (c) 17 yr; maximum Small amount of' pitting; good structural Integrity.
Three Mlle Island- Goldsboro, PA, USA Dnric acid 1974 to present No problems; Insulated from Unit 1 SS liner.
Maine Yankee Wi scasset, ME, USA Boric acid 1977 to present No problems.
Dyster Creek Toms River, NJ, USA Delonized water 7 yr(d) No probim.
NFS West Valley, NY, USA Delonized water 1965 to present No problems.
NRX Chalk River, Ontarlo, Canada Delonized water 1959 to present No problems.
RBOF Savannah River, SC, USA Delonized water 1963 to present No problems.
I FRSF *I ldaho Falls, ID, USA (f) 1963 to present Pitting corrosion.
4 (a) Most us tds were uncorroded; only poorly made welds corroded.
(b) In 1973 one-half of the aluminum racks were replaced with stainless steel ones.
(c) 800-ppm B maximum.
(d) Examination of locations on aluminum racks where they contacted SS pool liner revealed no significant crevice ;
corrosion. (
(e) Operated by Idaho National Engineering Laborato,ry (INEL). -
(f) Up to 730-ppm Ci and 590-ppm NO3 ; currently Cl = 360 ppm and NO3 = 430 ppm.
h
. . . . - . . . . 4 - -. ~~ ~ 4- ~ -- ~~~~ '
I addressed in the section on the HBPP storage pool. Carbon steel tends to form reddish-brown scales in spent fuel pool waters; this observation is also addressed in the HBPP pool section.
Although some operational problems involving pool components have occurred, these problems have had minimal impact; however, they do deserve the attention of storage pool designers, fabricators, and operators. The principal problems mentioned in Licensee Event Reports submitted to the NRC invcived pump seal failures and hose disconnections, minor leaks in spent fuel pool pipes and -
i liners, minor fuel assembly damage during handling, air overpressurization i damage during attempted cleaning of pool liner channels, piping and weld defects during fabrication, pipe breakage due to freezing during power outages, and corrosion-induced events in spent fuel pool piping.(3,6,8,12,13) In two recent events,(15,16) there was loss of pool water due to problems with ,
pneumatic pool seals (not a concern at HBPP).
CRUD EFFECTS
~
There is evidence that crud layers on some water reactor fuel tend to loosen in extended wet storage,(15) which could result in some crud spallation l
when the fuel is handled for shipping. However, not all fuel appears to be 1 susceptible. Crud that spalls while in reactor pools can be treated by the pool water treatment system. In some cases, loose material on pool floors has been removed with portable vacuum equipment. If properly assessed, the effects of crud loosening can be anticipated and mitigated.
L 11 l
I
i i
l I
. BASIS FOR EXTENDED STORAGE OF ZIRCALOY-CLAD FUEL IN THE HBPP UNIT NO. 3 FUEL STORAGE P00L ,
i Several considerations are addressed in this report:
- the liBPP pool history
- the HBPP fuel characteristics and how they relate to the world I
experience with wet storage of Zircaloy-clad fuel
- the HBPP fuel storage conditions and how they relate to the range of
,' conditions in wet storage technology
- expected behavior of the HBPP storage pool equipment e projected plans for management of the HBPP fuel storage facility over l the expected storage period.
HBPP UNIT NO. 3 POOL HISTORY Figures 1 and 2 show the spent fuel pool at HBPP Unit No. 3 in relation to
~
other reactor equipment and areas. Table 3 summarizes poal history and char-acteristics. The pool was constructed and filled prior to installing the I liner. The pool was drained for installation of the liner in June 1963. The l
pool was partially drained when the liner leak was discovered in-1966. The first fuel was placed in the pool in 1964. The first HBPP fuel had SS clad- l ding. Numerous fuel rods failed during reactor service, resulting in contami- l nation of the pool water. A large fraction of the radioactivity was removed by the pool cleanup system.
By 1971, all of the SS-clad fuel was removed from.the pool and was shipped
, for reprocessing. Since 1965, all fuel charged into the reactor has had
- Zircaloy-2 cladding.
, The crane has a capacity of 75 tons. It is inspected and certified annually and is load tested every 4 years. Currently, it is expected that 9 **
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REDT SECTION E-E FIGURE 2. Equipment 1.ocation A
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TABLE 3. HBPP Unit No. 3 Pool History and Characteristics First water in pool: 1963 First fuel in pool: 1964 Pool Size:
Length 28 ft Width 24 ft Depth (total) 36 ft at sump; 26 ft at racks Depth (wetted) 26 ft Water Volume 110,000 gal Shielding Depth 18 ft Cask Loading 36 ft
- Radiation dose to pool staff
- 5 to 10 mR/h at perimeter railing Radiation monitoring Currently - Air Continuous air monitor and periodic grab methods
- samples.
Pool water Grab samples.
Environs Stack gas monitoring; offsite environment monitoring program.
SAFSTOR - Air Same methods as indicated above, but Pool water sample and survey frequencies may differ.
Environs ;
Crane capacity: 75 tons l'-
Pool water temperature: 19'C (66*F)
. l
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the crane may be used during SAFSTOR. However, interlocks will be provided to prevent crane movement over the spent fuel pool during SAFSTOR.
I CHARACTERISTICS AND HISTORY OF HBPP UHIT NO. 3 IRRADIATED FUEL Table 4 summarizes characteristics of fuel stored in the HBPP Unit No. 3 spent fuel pool. The 390 fuel assemblies stored in the pool have Zircaloy-2
, cladding, Type 304 SS end fittings and spacers, and Inconel X750 springs.
Zircaloy is also the construction material for the 140 fuel channels. '
The materials are typical of fuel assemblies stored in other BWR and some away-from-reactor (AFR) pools.
The range of wet storage residence times for fuel now in the HBPP Unit No. 3 pool is 9 to 14 years. By 1998, this range will have increased to 20 to 25 years. Zircaloy-clad fuel stored since 1959 is still in wet storage (26 years in 1985) and shows no evidence of cladding degradation. To date, no BWR fuel has shown any evidence of degradation of SS components or deleterious m effects of Inconel springs.
Based on results of the world survey of wet storage' experier.ce(3) and several examinations of Zircaloy-clad fuel after extended wet stor-n age,(3,7,10,11,13) Battelle-Northwest projects that no cladding defects will develop in the HBPP fuel, even if the fuel storage were to extend to the end of the proposed 30-year SAFSTOR period.
The burnup range for the HBPP fuel is 5,000 to 19,500 mwd /t. Zircaloy-clad BWR fuel with burnup levels up to 43,800 mwd /t has been in wet storage since 1982. BWR fuel with burnup levels up to 25,700 mwd /t has.been in wet storage since 1973. Zircaloy-clad PWR fuel with burnup levels up to 55,000 mwd /t has been in wet storage since 1982. PWR fuel with burnup levels up to 33,000 mwd /t has been in wet storage since 1972. Thus, the burnup range e
for the HBPP fuel below that for other Zircaloy-clad fuel now in wet storage.
Estimates suggest that 58 HBPP fuel assemblies have rods with cladding defects. Other spent fuel pools have stored several hundred assemblies with defective cladding. In fact, as indicated earlier, some 2200 Zircaloy-clad
- 17 6
e
TABLE 4_. H8PP Unit No. 3 Irradiated Fuel Characteristics Fuel assembly materials:
Cladding - Zircaloy-2 End fittings - Type 304 SS
. Spacers - Type 304 SS Spacer spririgs - Inconel X750 Channels - Zircaloy-2 Fuel enrichments: 2.4% average Fuel batches stored in pool:-
No. of Assemblies No. of Charge Discharge Discharged an No. of Burnup, No. of Leaking Core No. Assemblies Date Date StoredinPoolga) Cycles mwd Assemblies (Type)
- 6 184 05-09-70 06-05-71 47 4 64,159 13: total 2(II),
m 7(III-1), 4(III-2) 7 184 08-26-71 08-25-72 48 4 61,952 7: total 4(III-1), .
3(III-2) i 8 172 10-06-72 09-01-73 51 4 57,504 16: total 14(III-1),
3(III-2) ,
9 172 10-02-73 10-30-74 28 4 69,033 11: total 16(III-2),
5(III-3) p 10 172 12-27-74 05-30-75 32 4 24,362 11: total 1(III-2), [
9(III-3), 1(III-4)
[
11 184 07-08-75 07-02-76 44 4 59,397 12-HF 1 4 b
e
, ,, ,f ,. _
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....A c - y - - _ --
TABLE 4. (contd)
No. of Assemblies No. of Charge Discharge Discharged an No. of Burnup, No. of Leaking Core No. Assemblies Date Date StoredinPoolpa) Cycles mwd Assemblies (Type) 12-HG 21 4 12-UD 46 3 12-XB 28 2 12-XC 44 1 390 (a) Total includes leaking assemblies.
g Fuel handling events: in 1975, one fuel assembly was dropped and several fuel rods separated from the assembly. Loose rods were retrieved and placed in special containers along with the fuel assembly.
Thermal characteristics (heat generation):
Average assembly - 60 W Total for 390 assemblies ~23 kW Fuel assembly age, extrapolated to 1998: Oldest - 33 years old (Type II, Core 2A, discharged December 1965)
Youngest - 23 years old (Core XC, discharged 1975)
\
e
fuel assembl!es with one or more defective rods are currently in wet storage.
Almost all are uncanned and have had only minor impacts on radioactivity inventories in the respective storage pools.
Thermal releases from the HBPP fuel currently average 40 W/ assembly, compared with ~850 W/ assembly for typical BWR fuel (28,000 mwd /t) 1 year af ter discharge. A PG&E analysis separate from this study indicates that heat generation rates for the HBPP fuel will not support temperatures that will ,
substantially degrade the Zircaloy cladding even in the highly unlikely event '
that pool water is lost.
The HBPP fuel assemblies are 4.5 in, square with 95-in. long rods; typical BWR fuel dimensions are 5.5 in. square and have 164-in. long rods.
The HBPP storage pool water chemistry and chemistry control measures are .
summarized in Table 5 for three periods: during reactor operations; during reactor shutdawn; during SAFSTOR. Table 6 summarizes results of anion and cation analyses on two recent (June 1985) water samples from the HBPP pool.
a Revied of the water chemistries and control procedures suggests that the pool chemistry cytrol has been typical of other BWR pools. The use of copper alloy componuts in the storage system (see following section) is reflected in the low, but detech,hle concentrations of copper ions in the pool water. The n i presence of carbcn steel piping has not resulted in significant dissolved iron in the pool water. The HBPP fuel storage facility appears to have consistently ,
involved a deionized water environment, similar to environments in AFR a7d other BWR pools.
}' l
SUMMARY
OF HBPP UNIT NO. 3 POOL MATERIALS l The HBPP Unit No. 3 pool wall is constructed of reinforced concrete coated on the inside surface with carboline. The walls are 2-1/2 to 3 ft thick, and the floor is 1 f t thick except over the suppression chamber where it is '
3-1/2 ft thick. The pool is lined with a SS liner such that there is a nominal 1/4-in gap between the liner and the concrete walls / floor. In 1966, a small leak developed in the liner. Since that time, the water level in the gap has been maintained below pool level and below groundwater level outside the pool ,
I 20 e
9 I
, TABLE 5. Summary of Materials in the HBPP Unit NO. 3 Spent Fuel Pool Parameter Reactor Operation Shutdown SAFSTOR j Pool chemistry control Delonized water Delonized water fIow (20 gpm); no flow (>100 gem) f ilter; skimmer, 7; pool vacuum, 7 Pool water pH Guideline 5.5 to 8.5 5.5 to 8.5 5.3 to 8.6 Typical 6 to 8 5.5 to 6.5 --
.j Makeup pH Guldeline 5.5 to 8.5 5.5 to 8.5 -
Typical 6 to 8 6 to 7 --
- Pool water conductiv-1 Ity, Mmho/cm Guldefine 5 5 10
, Typical 1 to 5 3 to 4 --
] Makeup water conduc-t i vi ty , Mmho/cm Guideline 5 5 --
Typical 1 to 3 - 1.5 --
Pool water chlorldy concentration, ppm ,)
Guideline 0.1 0.1 0.5(DI Typical <0.01 --
~
Makeup water chloride concentration, ppm Guideline 0.1 0.1 --
Typical <0.01 -- --
Pool water fluoride q concentration, ppm Guldeline Typical Makeup water fluoride concentration, ppm Gu ide li ne
,4 Typical Pool water turbidity, ppm Guideline 10 10 -
Typical <l.0 <1.0 --
Makeup water tur-bidity, ppm Guideline - -- --
Typical -- -- --
_I Typical radioactiv-Ity, mci /mL (cpm /mL)
Pool water (1x104 ) 1x10~4 0.1(c)
Makeup water (<5) 1x10-0 --
(a)' ppm - parts per million by weight.
( b) Chloride analysis required only If conductivity exceeds 3.0 Hamo/cm.
(c) Gross beta soluble activity (by proportional counter calibrated with ceslum-137). '
1 21 I
i b
- - ..s
a TABLE 6. HBPP Water Chemistry Analysis (a) ;
SFP-1 SFP-2 Species Oetection Limit 5/28/85(b) 6/6/85(b)
B 0.01 0.030 0.030 Ca 0.01 (0.01) 0.017 Cu 0.004 0.33 0.3$
Fe. 0.005 Undet. (0.005)
Li 0.004 0.012 Undet. #
Mn 0.002 0.004 Undet.
Na 0.01 0.08 0.1 Zn 0.02 ,
(0.02) 0.03 Species SFP-1 SFP-2 F- <0.1 <0.1 (0.08)
Cl- <0.1 <0.1 N0j <0.3 <0.3 5
P0 4 <0.4 <0.4 N0j <0.5 <0.5 -
S0j <0.5 <0.5 (a) Analysis conducted by Battelle-Northwest, Richland, Washington, June 1985. .4 (b) Water sampling dates at HBPP pool. "
to ensure that any leakage through the liner or through the concrete walls will be into the gap. The water from the gap is pumped to the Unit No. 3 -
radioactive waste collection system.
Recent tests conducted by PG8E determined the leakage rate into the gap to '
be approximately.2.6 gal / day. Of this, less than 0.12 gal / day is leakage from the spent fuel pool and the remaining 2.48 gal / day is from groundwater leaking into the gap. To determine if soil or groundwater contamination had occurred as a result of the pool leakage,11 groundwater monitoring wells were drilled.
9 22
1 I surrounding the pool in June 1984. Soil samples and groundwater samples did not show evidence that any significant contamination had occurred.
I The spent fuel pool heat exchanger tube material is Admiralty bronze. The fuel decay heat is sufficiently low that the heat exchanger is not needed and will be removed from the system during SAFSTOR.
Aluminum alloy pool components at several pools are still in service for a times similar to aluminum rack residence in the HBPP Unit No. 3 pool; and no significant deterioration has been detected in deionized water pools. The f presence of a copper alloy heat exchanger and pump components in the HBPP storage required some evaluation because copper ions can accelerate aluminum corrosion.Il4) As indicated earlier, BNO. staff examined sections from an aluminum can that has been exposed to HBPP pool water since the early-to-mid 1960. Visual and microscope examinations showed only a few shallow (up to
~5-mil) pits, suggesting that the relatively low copper ion concentrations in the pool water have not significartly affected aluminum integrity.
A pool cover will be installed at the beginning of SAFSTOR to keep objects from falling into the pool and to serve as a barrier for contamination control.
The HBPP fuel pool has carbon steel piping. Carbon steel is subject to formation of corrosion scales in spent fuel pool waters. To date, HBPP fuel pool operations have not been impacted by iron oxides rust blooms; disc, recent
, water analyses show low iron ion concentrations. When planned water circuit modifications are made, the piping system will be inspected to determine the degree of corrosion. Some pipe runs will be removed from service.
,_ In addition to the HBPP fuel and 140 Zircaloy fuel channels, other mate-rials are stored in the HBPP pool (Appendix A). It does not appear that they have caused significant turbidity or increases in pool water radiation concentrations.
9 23
1 PROJECTED PLANS FOR HBPP FUEL STORAGE OPERATIONS DURING SAFSTOR Appendix A provides a brief summary of HBPP plant systems, monitoring plans, and operator and radiation protection programs for the SAFSTOR period.
Review of the plans suggests that all plant systems necessary to conduct safe storage of the HBPP fuel will be in operation.
The proposal for the SAFSTOR period includes the following:
- administrative controls to prevent dropping objects into the spent
- fuel pool that might damage irradiated fuel assemblies e continued program for fire protection
- a proposal for modifications to eliminate the potential for an inadvertent criticality in the sper.t fuel pool e addition of a spent fuel pool cover to minimize dust and other contaminants from entering the spent fuel pool water and to minimize any spread of contamination from the pool
.i e provisions for emergency addition of water to the spent fuel pool in the event of pool damage and the primary makeup water supply is not available e a systematic monitoring program o preventative and corrective maintenance programs e operator training and certification e a records plan. ]
ll
~
9
- 24 ,
i
1 i
. REFERENCES I
I
~1. U.S. Nuclear Regulatory Commission. August 31, 1984. " Waste Confidence Decision." Federal Register 49(171):34658.
- 2. International Nuclear Fuel Cycle Evaluation (INFCE) Working Group No. 6.
1980. Spent Fuel Management. STI/ PUB /534, International Atomic Energy Agency, Vienna, Austria.
. 3. International Atomic Energy Agency. 1982. S*.orage of Water Reactor Spent Fuel in Water Pools - Survey of World Experience. Technical Report Series No. 218, STI/ DOC /10/218, ISBN 92-0-155182-7, Vienna, Austria.
I
- 4. U.S. Department of Energy. 1980. Proposed Rulemaking on the Storage and Disposal of Nuclear Waste / Statement of Position of the United States Department of Energy. 00E/NE-0007, Washington, D.C.
- 5. U.S. Department of Energy. 1980. Proposed Rulemaking on the Storage and Disposal cf Nuclear Waste / Cross-Statement of Position of the United States Department of Energy. DOE /NE-0007, Supp. 1, Washington, D.C.
- 6. Kustas, F. M., et al. 1981. Investigation of the Condition of Spent Fuel Pool Components. PHL-3513, Pacific Northwest Laboratory, Richland, Washington.
- 7. Bradley, E. R. , et al . 1981. Examination of Zircaloy-Clad Spent Fuel i 1
Af ter Extended Pool Storage. PNL-3921, Pacific Northwest Laboratory, Richland, Washington.
m 1 j
^
- 8. Johnson, A. B., Jr. 1977. Behavior of Spent Nuclear Feel in Water Pool '
Storage. BNWL-2256, Pacific Northwest Laboratory, Richland, Washington.
n
- 9. Johnson, A. B. , Jr. 1978. " Impacts of Reactor-Induced Cladding Defects \
on Spent Fuel Storage." In Proceedings of the NEA Seminar on Storage of '
Spent Fuel Elements, June 20-23, 1978, Madrid, Spain, pp. 235-253.
_ 10. Peehs, M., et al. 1978. " Behavior of Spent LWR Fuel Assemblies." In Proceedings of the NEA Seminar on Storage of Spent Fuel Elements, June 20-23, 1978, Madrid, Spain, pp. 223-234.
- 11. Peehs, M., et al. 1984. "Results of a Long-Term Wet Storage Demonstration Test with Intact and Operation Defective LWR Fuel Rods."
f Nuclear Eng. and Design 83(1):67-73.
- 12. Electric Power Pesearch Institute. 1984. Surveillance of LWR Spent Fuel in Wet Storage. EPRI NP-3765, Palo Alto, California.
- 13. Bailey, W. J., and A. B. Johnson, Jr. 1983. Wet Storage Integrity Update. PNL-4726, Pacific Northwest Laboratory, Richland, Washington. -
, 25 t
- 14. Uhlig, H. H. 1967. Corrosion and Corrosion Control. John Wiley & Sons, .
Inc., New York, 4th Printing, p. 300.
- 15. Connecticut Yankee Atomic Power Co. September 21, 1984. Letter to the U.S. Nuclear Regulatory Commission, " Licensee Event Report No. 84-013-00, Haddam Neck, Docket No. 50-213." Also see NUREG/CR-2000 (0RNL/NSIC-200),
4(1):8-9 (February 1985).
- 16. U.S. Nuclear Regulatory Commission. 1985. " San Onofre-2, Docket 50-361, LER 84-060." In Licensee Event Report (LER) Compilation, NUREG/CR-2000, ORNL/NSIC-200, 4(3):45-46. 3
- 17. Pacific Gas and Electric Co. July 1984. SAFSTOR Decommissioning Plan for g Humboldt Bay Power Plant, Unit No. 3. Docket No. 50-133, License g No. DPR-7.
- 18. Bechtel National, Inc. July 1984. ' Environmental Report far the Decommissioning of Humboldt Bay Power Plant, Unit No. 3. Docket No. 50-133, License No. DPR-7.
b
-1 1
r -
26 e
9 e
f b
. APPENDIX A i
SAFETY AND_ MONITORING PLANS AT THE HBPP UNIT NO. 3 POOL DURING SAFSTOR P9 6
I i
e f
9 I
se
i APPENDIX A SAFETY AND MONITORING PLANS AT THE HBPP UNIT NO. 3 P00L DURING SAFSTOR Safety and monitoring plans for HBPP Unit No. 3 during SAFSTOR are described in the application I17I for SAFSTOR decommissioning and in the
" environmental report.I18) It is important to this study to define how safety ,
j and environmental aspects of SAFSTOR apply to the fuel storage pool.
I PLANT SYSTEMS Plant systems related to the spent fuel pool area that will operate during SAFSTOR include the following:
e service systems, including the refueling building ventilation system, the spent fuel pool service system, the fire protection system, and electrical systems.
- waste disposal system, including the liquid and solid radioactive waste systems m o monitoring system, including the stack gas radiation monitoring sys-tem, the liquid waste system vent monitor, the process water monitor,
., area monitors, portable monitoring equipment, offsite environmental
_ monitoring stations, and spent fuel storage pool water level monitors.
The systems will be operated as required during the SAFSTOR period. Their f operation will be in accordance with approved procedures, and the operational g schedule will be of sufficient regularity to ensure adherence to the Unit No. 3 Technical Specifications. This oper-tional schedule may vary over the SAFSTOR
? period as conditions warrant.
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SPENT FUEL P0OL SYSTEMS Spent Fuel Storage Pool Service System The spent fuel storage pool service system consists of the equipment necessary to maintain water level and quality in the pool as well as equipment needed for handling and movement of spent fuel. Major components include the pool liner leakage pump and two fuel pool circulating water pumps.
Makeup water for the spent fuel storage pool is provided from the demine- ,
a ralized water system. The capacity of the demineralized water tank is ;
5,000 gal. Water to the demineralized water tank is normally supplied from i Units No. I and 2 condensate storage tanks. Emergency makeup to the spent fuel storage pool is available from the plant fire system.
Spent fuel storage pool water quality is maintained using either of two spent fuel pool circulating water pumps to circulate pool water through a ,
demineralizer.
The water level in the gap between the spent fuel pool liner and the con-crete wall is maintained using a liner gap pump that discharges to the turbine building drain tank.
Spent Fuel Storage Pool Water Level Monitors .,
Two water level indicating devices will be installed in the spent fuel
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storage pool. The outputs of these monitors will be indicated in the Control .,
Room. Annunciation (visual and audible) of low water level will be provided in the Control Room. One of these monitors will be an operating spare.
Spent Fuel Storage Pool Liner Gap Pump This pump is . located at an elevation +12 ft adjacent to the spent fuel storage pool. It takes suction on the gap between the fuel pool liner and the wall to maintain the water level below the groundwater level outside the build- ,
ing. Discharge is to the turbina building drain tank. The net effect is to maintain a head difference between groundwater.outside the building and water in the liner, providing for preferential inflow leakage into the liner from outside. This minimizes leakage of radioactive contaminants on the outside of the building. . -
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- Fuel Pool Circulating Water Pumps
, Two pumps are located on the ground floor (elevation +12 f t) in the i refueling building adjacent to the hatch into the new fuel storage vault.
Fuel Pool Coolers The fuel pool coolers are located adjacent to the fuel pool circulating water pumps in the Refueling Building. Their function was to remove decay heat 8 added to the pool water by the spent fuel. Due to the age of the spent fuel in ,
1 the pool, decay heat is low enough that the coolers are no longer required.
l The coolers will be removed from the spent fuel pool circulating water flow path during SAFSTOR.
Fuel and Channel Handling Tools These tools will be required for final removal of the spent fuel from the storage pool. The tools will be stored for the.SAFSTOR period pending their need for this purpose.
Spent Fuel Pool Bridge Crane This crane is used for movement of spent fuel within the spent Fuel stor- l age pool. It is mounted on the spent fuel pool bridge and will be required for
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final transfer of spent fuel to the shipping cask.
OPERATING LIMITS AND REQUIREMENTS
.. Retc . 'ng Building A thorough visual inspection of the refueling building will be conducted at least quarterly. Evidence of deterioration will be evaluated with regard to the function of the building as a weather enclosure, contanination control I
{ barrier, and radiation shield.
, Spent Fuel Storage Pool The water level in the spent fuel storage pool will be maintained at an elevation greater than 10 f t 6 in. The water level between the liner and the concrete walls will be maintained between elevation -12 in. and +9 in.
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The water quality in the spent fuel storage pool will be maintained within the ranges specified on Table A. If water quality limits are exceeded, action will be taken to restore the water quality within limits and an evaluation will ',
be conducted to determine the cause.
Spent fuel will only be handled under the following conditions:
- All handling will be accomplished using procedures approved by the Plant Staff Peview Committee (PSRC). ,
- Spent fuel handling operations will be under the direct supervision ,
of a member of the plant management staff who is a certified fuel l handler.
- At least one certified fuel handler will be present at the location of each fuel movement.
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ONSITE MONITORING The following monitors will be maintained through the SAFSTOR period:
- stack radiation monitor e continuous sampler in discharge canal
- fenceline dosimetry stations "
e groundwater monitoring wells "
Annual reports will include average and maximum values for total gamma, beta, alpha activity, and concentrations of indicator nuclides.
In the area of radwaste tr.eatment buildings routine surveys will be con-ducted to identify contamination and record dose rates. These surveys will be conducted quarterly or as needed to support waste management operations.
RADIOACTIVE INVENTORY IN THE HBPP SPENT FUEL POOL In addition to spent nuclear fuel' there is also a nonfuel radioactivity inventory in the spent fuel pool (see Table A.1).
The principal nonfuel materials include stellite rollers (cobalt-base" i alloy) and Zircaloy fuel channels. Both materials are highly resistant to cor-rosion at conditions in the HBPP Unit No. 3 fuel, pool. Therefore they will not j contribute significantly to the pool radioactivity level. 8 I
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TABLE A.1. Spent Fuel Storne . Memistry and Activity During :,M:,10?'
Parameter Acceptable Range pH 5.3 to 8.6 Chlorides (b) 0.5 ppm Conductivity 10.0 pmho/cm Gross beta soluble activity (c) 1.0 x 10~1 pc/d (a) Verification shall be accomplished by analysts of
.I samples taken at least once each month.
(b) Chloride analysis is only required if conductivity exceeds 3.0 pmho/cm (Reference NRC Regulatory Guide 1.56, Figure 2).
(c) By proportional counter calibrated with cesium-137.
I _ MAINTENANCE OF STRUCTURES, SYSTEMS, AND C0t1P0HENTS The maintenance program established for SAFSTOR will be a modified con-tinuation of the existing maintenance program at the plant and will include aspects for both preventive and corrective maintenance.
The preventive maintenance aspect will provide for a regularly scheduled series of inspections, tests, and services for structures, systems, and com-ponents. The frequency of preventive maintenance will be established on the basis of prior experience, ongoing operational use, plant conditions, and where applicable, Technical Specification requirenents. The objective of the preven-tive maintenance program will be to ensure continued reliable function of necessary structures, systems, and components equivalent to or better than the reliability existing at the beginning of the SAFSTOR period.
I OPERATOR TRAINING AND CERTIFICATION PROGRAM l During the SAFSTOR period, it is not expected that movements of spent reactor fuel will be made, except for special tests or inspections to monitor the fuel in storage. At some time durf ag the SAFSTOR period, fuel handling may be performed to transfer the spent fuel assemblies to DOE for disposal.
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TABLE A.2. Spent Fuel Pool Miscellaneous Inventory - 1984 '
Estimated Curie Content )
55 Fe 60 Co Other Total '
Component 63 Ni Nuclides -Curies Incoreingumentstrings(a) 90 98 69 <1 260
(<1 gram U)
Stellite rollers (b) <15 8,000 11 --
8,200 1 Canned waste -- -- -- -- --
Vacuum cleaner bags Miscellaneous debris Feedwater sparger(a,b) 1.1 1.2 0.83 <0.1 3.2 j Fuel channels (140)(b) 1,500 100 1,800 500 3,900 Sb-Be operating so'Jrces (2) I (a) Based on Reference.
,I (b) Based on neutron activation calculations and sample analysis.
A training and certification program will be implemented to maintain a staff that is properly trained and qualified to maintain the spent fuel, to g
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perform any fuel movements that may be required, and to maintain HBPP Unit ho. 3 in accordance with the possession-only license. This program will provide the training, proficiency testing, and certification of fuel handling personnel. A detailed description of the program is provided in Appendix III of the appifcation.Il2I The Operator Training and Certification Program ensures that people trained and qualified to operate HBPP Unit No. 3 will be available during the SAFSTOR period. This program is similar to that required by 10 CFR Part 72 Subpart I for Independent Spent Fuel Storage Facility Personnel. Licensee certification of personnel makes it unnecessary for the NRC to periodically conduct license examinations for persons involved in infrequent activities and '
prevents delays due to obtaining NRC fuel handler licenses for any evolutions .'
that may require fuel movements.
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RADIATION PROTECTION DEPARTilENT TRAINING PROGRAM
- A comprehensive program is presented to HBPP Unit No. 3 radiation and pro-I cess monitors (RPMs). The training consists of classroom training, on-the-job l training, and retraining to implement changes and improve skills. Course requirements include: i
- Nuclear Technology - basic nuclear and radiation protection theory.
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- Plant Design and Operation - plant layout, system functions, and .
equipment.
- Chemistry - analyses, calibration, and instrumentation.
- Radiochemistry - sample preparation, counting, and data reduction; I
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use and maintenance of instruments.
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- Emergency Plan and Procedures - emergency responsibilities, surveys, analysis, radiation protection during accident conditions, and envi-I ronmental monitoring.
RECORDS PLAN All records relative to the following areas shall be retained for the j duration of SAFSTOR:
o records of spent fuel inventory, transfers of fuel, and assembly histories e
records of' plant radiation and contamination surveys e
records of radioactivity in liquid and gaseous wastes released to the environment records of tests or experiments associated with the spent fuel storage records of changes made in operating procedures e
records of training and qualification for current members of the plant staff t
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- records of inservice inspections performed pursuant to the Technical :
Specifications
- minutes of meetings of the Plant Staff Review Committee and the General Office Nuclear Plant Review and Audit Committee e records of quality assurance (QA) activities required by the QA manual
- Records of reviews performed for' changes made to procedure or ,
equipment or reviews of tests and experiments pursuant to 10 CFR Part 50.59.
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