ML19339B155
| ML19339B155 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 10/14/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19339B145 | List: |
| References | |
| NUDOCS 8011060379 | |
| Download: ML19339B155 (12) | |
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NUCLE AR REGULATORY COMMISSION C
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SAFETY EVALUATI0ft BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 52 TO FACILITY OPERATING LICENSE NO. DPR-40 OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION, UNIT NO. 1 DOCKET NO. 50-285 Introduction By letter dated March 14, 1978, Omaha Public Power District (OPPD) submitted an application to amend the Fort Calhoun Station, Unit No.1 Technical Specifi-cations in the area of charcoal ventilation system flow rates for the spent fuel pool area and the safety injection (SI) pump rooms, Following staff review of this applicction, questions were asked of OPPD which resulted in further analyses and a revision to the application being submitted by letter dated March 6, 1979.
In early 1980, the staff became aware that there was sorre misunderstanding regarding the use of the term " operable" as it applies tu single failure criterion for safety. systems in power reactors Technical Specifications.
In an effort to remove this misunderstanding and to clarify NRC requirements, the staff sent a letter (dated April 10,1980) to all Power Reactor Licensees informing them of our requirements and requesting that they speci y and clarify these requirements in their Technical Specifications. OPPD responded to this request by letter dated August 5, 1980.
Discussion and Evaluation I.
VENTILATION SYSTEM FLOW RATES Section 9.10 of the Fort Calhoun Unit No.1 FSAR discussed the design function of the charcoal filters which are installed in the controlled access area ventilation system:
" Charcoal filters are installed in normally bypassed ducts at the exhaust of the three compartments where the safety injection and spray pumps and suction piping are situated.
These filters could be remote-manually brought on to line in the event of an accidental release of activity in these rooms during a plant emergency in particular during the recirculation period following a DBA (see Section 6.2)."
"A charcoal filter is also installed in a normally bypassed section of the return ductwork drawing air from the spent fuel storage pool area.
During spent fuel handling, the filter will be brought on the line to absorb gaseous iodines in the unlikely event of a fuel handling incident resulting in the release of large quantities of radio-activity (Section 14.18)."
8011060377-
- -__-__ By letters dated March 14 and April 28, 1978, and March 6, 1979, the Omaha Public Power District (the licensee) requested that Table 3-5 of Section 3.2 (Equipment and Sampling Tests) of the Technical Specifications for Fort Calhoun Station Unit 1 (Ft. Calhoun) be amended to reduce the air flow rate surveillance requirements for the spent fuel pool area ventilation (SFPAV) and the safety injection pump room ventilation (SIPRV).
The licensee requested that Specifications 10.b.3.b and 10.c.3.b
. Table 3-5 be changed to reduce the magnitude of the volume flow rate required to be passing through the charcoal filters in the two ventilation systems. The volume flow rates now required to be passing through the SFPAV and SIPRV are the design flow rates (+10%) for the systems.
The following information was given in the letter dated March 14,1978, from the licensee.
The design flow rates for the charcoal filters in the SFPAV and SIPRV are 12,800 cfm and 5,500 cfm, respectively.
The number of stand-ard charcoal filter cells in the SFPAY and SIPRV are 12 and 6, respectively, and each standard charcoal filter cell is rated at 1,000 cfm. These venti-lation systems have been adjusted for optimum performance; but the design rates given in the station Technical Specifications have not been achieved.
The maximum volume flow rates obtainable without exter. ive modifications of these ventilation systems are 4,400 cfm for the SIPRV and 10,400 cfm for the SFPAV.
The charcoal filters are installed in these ver.tilation systems to reduce the amount of radiciodine released from the station to the enviroament dur-ing accident conditions.
Reducing the flow rate through the charcoal fil-ters will increase the efficiency of the charcoal to remove airborne radio-iodine. However, the volume air flow must be sufficient to collect all the radiciodine released during the accident. The licensee stated that both ventilation systems have been balanced to (nsure negative pressures in the areas serviced by these ventilation systems. He states that testing has verified that the proposed volume flow rates maintain the safety injection /
spray pump rooms and the spent fuel storage pool area at negative pressures relative to the surroundings.
He further states that the proposed range of volume flow rates for the SFPAV and SIPRV allow some variation in performance of the ventilation system while not allowing such low volume rates that the negative pressures would be eliminated.
The licensee has reported the low measured flow rates in the SFPAV and SIPRV in Licensee Event Reports (LERs)78-041 (1/2/79) and 78-041 (1/30/79).
In LER 78-041, the licensee stated that the volume flow rates were chosen prior to the selection of the charcoal filter units for the SFPAV and SIPRV.
We have reviewed and evaluated he proposed changes to Specifications 10.b.3.b and 10.c.3.b of Table 3-5 of.the Technical Specifications for Fort Calhoun Station. These specifications are for the charcoal filters in the spent fuel pool area ventilation system (SFPAV) and the safety injection pump room ventilation system (SIPRV), respectively.
The two ventilation systems were designed to collect radioactivity re-leased during accidents and pass this radioactivity through charcoal fil-ters. The SFPAV would collect radioactivity released from the sper,t fuel pool during a fuel handling or cask drop accident. The SIPRV would collect radioactivity released into the safety injection pump rooms during a LOCA. This. radioactivity would come from ECCS leakage outside containment from safety injection and containment spray pumps pumping water from the containment sump during the recirculation mode.
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i The licensee has run tests measuring air flow to determine that the two ventilation systems at the proposed air flow rates will collect the ra-dioactivity released during accidents as they were designed to do.
Each safety injection pump room is an enclosed area with a single opening, a door (which would be clesed during a LOCA) and a supply air duct.
Air is supplied to and exhausted from the room to cool the high and low pressure safety injection pumps and the containment spray pump in the room.
The ventilation system has been balanced to have the safety injection pump room at a negative pressure.
The door is a fire barrier and plant pro-cedures require it to be shut or there be a person present to shut the door in case of a fire or an accident.
The licensee has run tests measuring air flow into the rooms when the doors are partially open_ to verify that the proposed volume flow rates for the SIRPV would maintain the room at negative i
pressures relative to the surroundings. The doors were partially opened to have measurable flow rates into each room.
Based on this, we conclude that the SIRPV should collect the. radioactivity released into the room.
The spent fuel pool is located in the Auxiliary Building.
The ventilation supply ducts for the area are located below the operating floor level and the exhaust ducts are located at floor level around the pool. The licen-see has run tests measuring the air flow in the building. The air flow is toward the exhaust ducts arranged around the pool.
Based on this, we conclude that the SFPAV should collect the radioactivity released from the pool.
The potential consequences of a po'stulated Loss-of-Coolant Accident (LOCA) and Fuel Handling Accident are give'n in Table 1.
The assumptions to cal-culate the potential consequences for these accidents are given in Tables 2 and 3.
The potential consequences for the postulated ECCS leakage outside containment and the Fuel Handling Accident are given with and without char-coal filtration. The potential consequences of the postulated accidents are well within the exposure guidelines of 10 CFR Part 100 and are, therefore, acceptable.
The licensee does not measure the negative pressure in the Fuel Handling Building and in the safety injection pump room when its respective ventila-tion system is operating. The licensee has measured that the air flow in each area when its ventilation system is operating is such that the radio-activity released to each area should be collected and filtered.
Because of this and because the potential consequences of the postulated accidents without charcoal filtration.of the radioactivity released from the spent fuel pool and to the safety injection pump room are well within the exposure guidelines of 10 CFR Part 100, we conclude that these air flow tests are adequate.to show that the ventilation systems will maintain a negative
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pressure in the appropriate areas and that the radioactivity will be collected and filtered.
No additional tests are needed. Based on this, we conclude that the proposed Technical Specification changes are acceptable as written, i
l The licensee does not have a technical specification which limits the leak-age from the high and low pressure safety injection pumps and the contain-ment spray pumps outside containment.
For long term cooling of the core and r
the containment, a continuous source of borated water is provided by recir-culating containment sump water. Recirculation is automatically initiated In by lcw water level in'the safety injection and refueling water tank.
the recirculation mode, the high-pressure safety injection pumps and the con-tainment spray pumps take suction directly from the containment sump and pump the water back into containment.
The low-pressure safety injection pumps
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may also be used to inject cooled water when the system pressure permits.
Leakage from these pumps drains to the pump room sump. From there it is pumped to the radioactive liquid waste disposal system for processing.
This leakage during a LOCA will contribute to the potential consequences of the accident. The potential consequences given in Table 1 are for 10 gph leakage from these systems outside containment.
By letter dated June 25, 1980, the licensee presented the results of leak rate tests performed as required by NUREG-0578, Item 2.1.6.a, " Integrity of Systems Outside Containment Likely to Contain Radioactive Materials".
These tests showed a maximum total leak rate of 489 cc/hr for all systems of consideration. Since this leak rate is well below the 10 gph assumed in.the staff's analyses and since the staff, as part of the continuing review of the TMI accident, is considering the necessity of either Technical Specification limits or license condition requirements to ensure acceptably low leakage rates from these systems, we find the present procedures to be acceptable pending a generic resolution.
One of the primary functions of the safety injection pump room ventila-tion system is to provide adequate cooling for the safety injection /
containment spray pump motors.
Design flow rates for the two safety injection / spray pump room filters and for the' spent fuel storage pool area filter are 5500 cfm per filter and 12,800-cfm, respectively. Accordingly, the plant's Technical Specifications require that these design flow rates be periodically verified.
However, although the ventilation system at Fort Calhoun Station has been adjusted for optimum performance, the design flow rates have not been achieved. The maximum flow rates obtainable without extensive modification of the ventilation system are 4400 cfm for each safety injection / spray pump room filter and 10,400 cfm for the spent fuel storage pool area filter.
(See References 3 and 4.)
The Omaha Public Power District submitted an application for Amendment of Facility Operating License, dated March 13, 1978 (Reference 1),
requesting the NRC to revise Technical Specifications for the Fort Calhoun Station to permit use of reduced air flow rates in the spent fuel pool area and the safety injection pump room.
The temperature of the safety injection pump room must be limited in order to assure the safe operation of the pumps. The bearings for the safety injection / containment spray pump motors are the limiting factors in determining the maximum allowable room temperature. The manufacturer has recommended that the motors not be operated with room ambient temperatures greater than 122'F (Reference 2).
The licensee has performed two separate analyses to predict the maximum temperature in the safety injection pump room.
Both analyses assume all four ECCS pumps operating in each of the pump rooms for the first 30 minutes following a LOCA. One spray and one HPSI pump operate from 30-50 minutes and one HPSI pump operates indefinitely after 50 minutes (Reference 6).
. The first analysis performed by the licensee was a transient analysis CONTRANS has using Combustion Engineering's CONTRANS computer code.
been reviewed by the NRC staff and has been found acceptable for calculating containment pressure / temperature responses.
This analysis The CONTRANS analysis predicted the long term sump water temperature.
assumed that the ECCS pumps and the recirculation piping that carried the hot sump water were the only heat sources in the safety injection The heat sinks were the concrete floors and walls. Without pump room.
taking credit for the ventilation system and assuming natural convective heat transfer, the CONTRANS analysis predicted a maximum temperature of 117 F during the first 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br />.
By this time, the shutdown cooling system is put into operation, which cools the sump water and in turn lowers the safety injection pump room temperature.
The second analysis performed by the licensee was a steady state calcu-lation which assumed that the sump water temperature did not drop below f
165 F (this was the temperature predicted by CONTRANS 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> af ter the LOCA).
The steady state calculation predicted that if a minimum ventilation flow rate of 1500 cfm exists, the safety injection pump room temperature will remain below the maximum allowable 122 F.
Since the proposed Technical Specifications will require a minimum ventilation flow rate of 3000 cfm for the safety injection pump room, the analysis appears conservative.
The analyses performed by the licensee to calculate the maximum safety injection pump room temperature appears to be conservative.
No credit was taken for either the shutdown cooling heat exchangers or the containment building air cooling and filtration system.
Both of these systems would remove energy from the containment system and would tend to lower the sump water temperature thus reducing the pump room tempera ture.
The steady state calculation which took credit for the ventilation flow rate made the conservative assumption that the tempera ture of the ventilation flow was 95*F.
There were two assumptions in the licensee's analyses that the staff questioned.
In the transient analysis performed with the CONTRANS computer code, the instantaneous mixing partition model was used.
While this flashing model maximizes the peak calculated containment pressure, it tends to minimize the sump water temperature thus lowering the heat load in the safety injection pump room.
In addition, while the licensee assumed a natural convective heat transfer coefficient of 2.0 BTU /hr-ft
- F to the pump room's heat sinks, a lower convective 2
heat transfer coefficient of 1.7 BT /hr-ft
- F was assumed from the 2
recirculation piping (heat source).
In a confirmatory analysis, the staff performed the steady state calculation assuming a constant sump water temperature of 200"F and a uniform convective heat transfer coefficient of 2.0 BTU /hr-ft
- F.
Our calculations verified that the 2
minimum proposed ventilation flow rate of 3000 cfm will be sufficient to cool the pump's motor bearings.
To further ensure the integrity of the ECCS pumps, the licensee is in the process of installing temperature detectors, with readout and alarms, in the control room to monitor the safety injection Jump room temperature.
In the event that additional cooling is needed for the pump rooms, two actions can be taken.
If activity levels are low enough, portable
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fans and blowers can be brought into the area.
Otherwise, operator t
action can be taken fram the control room to rebalance the ventilation system (i.e., clearing off vc..tilation flow to non-essential areas) in order to provide increased cooling.
Based on our review of the licensee's submittals, we conclude that the safety injection pump room temperature has been adequately addressed and that the proposed Technical Specifications are accepteble, j
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Table 1 POTENTIAL CONSEQUENCES OF POSTULATED ACCIDENTS Potential Consequences in Rem Exclusion Area Low Population Boundary (910m)
Zone (4800m)
Whole Whole Thyroid Body Thyroid Body Loss-of-Coolant Leakage Through Containment 39 1.5 5
0.5 Leakage Outside Containment With charcoal filtration 4
0.5 28 0.2 Without charcoal filtration 30 0.6 28 0.3
(*)
(*)
(*)
(*)
Purging i
i Fuel Handling In Spent Fuel Pit With charcoal filtration 15
.4 2
.4 Without charcoal filtration 100
.4 13
.4
- Negligible - less than 0.1 rem i
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4 Table 2 LOSS-0F-COOLANT ACCIDENT - ASSUtiPTIONS 1500 ftWt Core Power Level 3.0 years Operating Time Containment Leak Rate (0-24 hours) 0.10%
( 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) 0.05%
Fraction of Core Inventory Available for Leakage 25%
Iodine Noble Gases 100%
Iodine Composition - Elemental 91%
- Particulate 5%
- Organic 4%
Minimum Site Boundary Distance 910m Low Population Zone Distance 4800m 3
X/Q Values (sec/m )
5.0 x 10-4 0-2 hr. at 910 meters 6.3 x 10-5 0-8 hr. at 4800 meters 8-24 hr. at 4800 meters 1.3 x 10-5 24-96 hr. at 4800 meters 4.3 x 10-6 96-120 hr. at 4800 meters 9.3 x 10-7 Building Effective Cross Sectional Area 760m2 Containment Parameters Containment Volume 1.05 x 10 ft3 6
Containment Charcoal Filters (one unit)
O to 30 days Elemental Iodine Removal Coefficient 5.14/hr Particulate Iodine Removal Coefficient 5.14/hr Organic Iodine Removal Coefficient 1.70/hr Flow Rate 100,000 cfm Removal Efficiency elemental iodine 90%
particulate iodine 90%
methyl iodine 30%
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4 Containment Parameters Containment Purge (Hydrogen Purge) 23 to 30 days 250 cfm Flow rate Removal Efficiency elemental iodine 90" particulate iodine 90%
methy! iodine 70%
55 min. to 30 days ECCS Leakage Outside' Containment l
20 gal /hr l
Leakage 350,000 gal.
i Volume in Sump 50% of core inventory Iodine in Sump Fraction of leakage which Flashes 10%
Removal Efficiency i
s-90.
Elemental iodine 0".
Methyl iodine Particulate iodine 90.
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Table 3 FUEL HANDLING ACCIDENTS - ASSUMPTIONS 1500 MWt Power Level Operating Time 3 years 1.65 Peaking Factor Number of Fuel Assemblies Damaged 1
Number of Fuel Assemblies in Core 133 Shutdown Time Before Start of Refueling 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Activity Release From Pool Regulatory Guide 1.25 Charcoal Filtration of Radiciodine 851:
3 x/Q Values (sec/m )
5.0 x 10-4 0-2 br. at 910 0-8 hr. at 4800 meters 6.3 x 10-5 8-24 hr. at 4800 meters 1.3 x 10-5 24-96 hr. at 4800 meters 4.3 x 10-6 96-720 hr. at 4800 meters 9.3 x 10-7 Building Effective Cross Sectional Area 670m2 l
II. CLARIFICATION OF OPERABLE By letter dated April 10, 1980, the NRC requested all Power Reactor Licensees to upgrade their Technical Specifications to clarify the term operable as it applies to the singla failure criterion for safety systems. OPPD submitted a license amendment request by letter dated August 5,1980, to provide this clarification in the Fort Calhoun Station's Technical Specifications.
The proposad specifications differ from the guidance provided in the allowable time for placing the reactor in the hot shutdown condition (subcritical at operating temperature and pressure). OPPD proposed a six hour time limitation whereas the guidance specified a one hour limit.
~ is proposed difference would allow adequate time for the licenseu to conauct a controlled and orderly shutdown through a boration method, which is the normal method employed at the Fort Calhoun Station.
The boration method results in a maximum rampdown rate of approximately 20 percent per hoir.
Since the staff's requirement is based on an orderly shutdown and since it.
is.not the intent to require extraordinary actions which could possibly have adverse effects, the staff agrees that the proposed time limitation is accep-table.
Since this proposal was submitted in. response to the staff's request and is in conformance with that request, except for the agreed to deviation noted above, we find the proposed additional requirements to be acceptable.
Environmental Consideration We have determined that the amendment does not authorize a change in effluent types or-total amounts nor an increase in. power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendment involves an action which is insigni-ficant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of the amendment.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a signi-ficant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Date: October 14, 1380
References 1.
Letter from Omaha Public Power District to U.S.N.R.C., dated March 13,1978.
2.
Letter from Omaha Public Power District (T.E. Short) to U.S.N.R.C.
(Director, NRR), dated March 6,1979.
3.
Ft. Calhoun LER #77-033 submitted February 15, 1978.
4.
Ft. Calhoun LER #78-041, Revision 1, submitted January 30, 1979.
5.
Letter from Omaha Public Power District (W.C. Jones) to U.S.N.R.C.
(Director, NRR), dated September 6,1979.
6.
Letter from Omaha Public Power District (T.E. Short) to U.S.N.R.C.
(Director, NRR), dated May 24, 1979.
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