CY-98-129, Provides Supplemental Info to 980629 Response to 2.206 Petition Questions on Spent Fuel Cooling Methods.Util Pending Commitment Made within Ltr Stated

Provides Supplemental Info to 980629 Response to 2.206 Petition Questions on Spent Fuel Cooling Methods.Util Pending Commitment Made within Ltr Stated

ML20154L433
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	10/14/1998
From:	Heider K CONNECTICUT YANKEE ATOMIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
2.206, CY-98-129, NUDOCS 9810190297
Download: ML20154L433 (8)

Text

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CONNECTICUT YANKEE AT O MIC POWER COMPANY HADDAM NECK PLANT 362 INJUN HOLLOW ROAD e EAST HAMPToN. CT 06424-3099 October 14,1998 Docket No. 50-213 CY-98-129 Re: 10 CFR 2.206 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C 20555 Haddam Neck Plant Supplemental Response to 2.206 Petition Questions Soent Fuct Pool Cooling Methods The purpose of this letter is for Connecticut Yankee Atomic Power Company (CYAPCO) to provide supplemental information to its response to 2.206 petition questions originally provided by letter dated June 29,1998W, on behalf of the Haddam Neck Plant. The initial request for additional information was contained in an NRC letter dated May 28,1998(2) ,

Additional information, subsequently requested verbally by the NRC, is provided in this letter on the spent fuel pool cooling methods and cooling fan noise test results.

Attachment 1 to this letter restates the NRC questions and provides CYAPCO's supplemental response.

The following is CYAPCO's pending commitment made within this letter:

CY-98-129-01 Procedure AOP 3.2-59, " Loss of Spent Fuel Cooling" will be revised to \

provide the operators guidance on when to open and when to l subsequently close the SFB doors and roof hatch. The procedure will also direct the operators to request that airborne radioactivity surveys be performed when the SFB doors and roof hatch are opened.

] t.. O (1) CYAPCO Letter CY-98-103, from R. A. Mellor, to the U.S. Nuclear Regulatory Commission, " Response to 2.206 Petition Questions Spent Fuel Pool Cooling Methods",

dated June 29,1998.

(2) NRC Letter from Thomas L. Fredrichs, to Russell Mellor, " Request for Information - 2.206 Petition Regarding Spent Fuel Cooling Methods", dated May 28,1998.

9910190297 981014 PDR ADOCK 05000213 W PM ,

U. S. Nucl:cr Regulatory Commission-i-

CY-98-129/Page 2 L

If there are any question regarding this submittal, please contact Mr. G. P. van Noordennen at (860) 267-3938.

Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPANY For: Russell A. Mellor Vice President - Operations and Decommissioning By: M 'e KeI1n'eth J. Heider '

Decommissioning Director Attachment cc: H. J. Miller, NRC Administrator, Region I i

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l T. L. Fredrichs, NRC Project Manager, Haddam Neck Plant W. J. Raymond, NRC Senior Resident inspector, Haddam Neck Plant E. Wilds, Director, CT DEP Monitoring and Radiation Division l

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. Docket Number 50-213 CY-98-129 s

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i Attachment 1 1 Haddam Neck Plant .

Supplemental Response to 2.206 Petition Questions Spent Fuel Pool Cooling Methods l

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i October 1998

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U. S. Nuclaar Regulatory Commission f ' CY-98-129/ Attachment 1/Page 1 l

.Question 1 .

. 1 Do you intend to use ventilation through open doors and roof hatches of the spent fuel g building (SFB) to cool the spent fuel pool (SFP) in the event forced cooling is unavailable? )

if yes, answer questions 2 through 6. If no, answer nuestion 6.

{s.

Response 1 -  ;

I Yes. However, as discussed below, the need to open the SFB doors and roof hatch is j' extremely unlikely.

i' The heat energy in the st_ored spent fuel is released to the SFP water continuously. Part of this energy is released to the air above the SFP by evaporation of pool water. This occurs l' regardless of whether or not forced cooling is operating. The amount of water that

[ ' evaporates is a function of pool water temperature, air flow over the pool and the relative 3 humidity of the' air flowing over the pool. Vapor generated by evaporation of pool water is

normally removed from the EFB by an exhaust fan into the discharge line of the Primary Auxiliary Building (PAB) purge fans. The PAB purge fan discharge line leads to the plant L stack, which is monitored for radiation.

L 1

The SFP island at the Haddam Neck Plant (HNP) will be comprised of two redundant SFP

_ cooling subsystems.- Each SFP cooling subsystem will provide forced cooling for the SFP.

Each subsystem of the SFP cooling system will include a SFP cooling loop, an intermediate

!. . cooling loop and a spray cooling loop. The redundant subsystems of the SFP cooling loop and the intermediate cooling loop will have the capability to be crosstied, at the component level, to the other train to provide additional flexibility. Currently, all of the SFP cooling system equipment, as well as the SFB exhaust fan, can be powered from the EG-2B emergency diesel generator, which is independent from any off-site power supply. However,

. during phase ll of the SFP island project, a new diesel and switchgear will be installed to power SFP cooling loads in the event of loss of offsite power. Multiple failures of components would have to occur to result in the normal SFP island method of forced cooling not being available.

i l The intermediate loops have hose connections so that other sources of water can be used to

, cool the SFP heat exchangers. Temporary hoses and fittings are available on-site to make i- the backup cooling connection. Backup sources of water available include the fire system j which has a diesel engine driven pump that is not dependent on off-site power.

Should all the above permanent and temporary backup forced cooling equipment become unavailable, or all available power be lost to the SFP cooling pumps for an extended period of time, the heat energy from the fuel will cause the SFP temperature to rise until the heat

removed from the SFP from evaporation is equal to the heat addition. This is calculated to L occur prior to the SFP reaching 170 F and would result in a maximum evaporation rate of

] approximately four gallons per minute. It is estimated to take approximately 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> to

reach the existing Technical Specification pool temperature limit of 150 F, given an initial

0. S. Nucinar Regulatory Commission CY-98-129/ Attachment 1/Page 2 temperature in the SFP of 110 F. During this time, normal SFB ventilation, which will continue to direct the released vapor to a monitored stack, would continue to be used, if available.

The need to open the SFB doors and roof hatch, is extremely unlikely. It would take the long term loss of a number of normal and alternate spent fuel pool cooling methods to reach this point. Only during an event that would result in an extended loss of forced cooling, which would cause the fuel pool temperature to exceed the technical specification limit of 150 F, would the plant operators take action to open the SFB doors and roof hatch and allow the vapor to flow directly to the atmosphere outside the building. The Haddam Neck Plant has never experienced a loss of SFP cooling event that challenged the 150 degree SFP temperature limit in all its years of operation and it is not likely that this will occur in the future.

A review of past losses to spent fuel cooling either from a loss of off-site power or component malfunction confirm that cooling would be restored well within the estimated 50 hour5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> time frame.

The Defueled Emergency Plan will require the declaration of an " Unusual Event"if an uncontrolled heatup of the SFP occurs such that the bulk pool temperature exceeds 150 F. As such, the NRC will be notified and communications established under the Defueled Emergency Plan process. All action taken from that point on would be provided under associated supporting plant procedures with the NRC cognizant of the situation.

Make-up water to replenish the evaporated water is discussed in the response to question 2.

Monitoring of the vapor pathway is discussed in the response to question 4.

Question 2 l As the SFP water level drops, particulate material may deposit on the SFP walls. How has your dose consequence evaluation accounted for the potential release of particulate material?

Response 2 With the SFP isolated from the Reactor Cavity, the postulation of a continuous drop in water level within the SFP is not part of the Haddam Neck Plant's design basis. The Haddam Neck technical specifications require the SFP water level to be maintained at least 20 feet above the stored fuel. Alarms are present which will notify the operators if the water level above the top of the fuel would go above 20' 9" or below 20' 4" With the water level maintained above 20 feet, there will be no significant buildup of additional particulate matter to deposit on the spent fuel pool walls and thus, no new source of particulate activity would be released from the SFB.

U. S. Nuclear Regulatory Commission CY-98-129/ Attachment 1/Page 3 There_ are multiple sources of makeup water available ranging from demineralized water stored in multiple on-site tanks to river water. The tanks are the Demineralized Water Storage Tank (DWST), Primary Water Storage Tank (PWST), and the Recycled Primary Water Storage Tank (RPWST). However, the DWST is the designated seismically qualified make-up source. Two makeup sources (DWST and River Water) are available without the use of the off-site electric power supply, Assuming the maximum evaporation rate is approximately four gallons per minute, a minimum of three days supply of demineralized water is maintained on-site in a seismically qualified tank. If offsite power is available, the demineralized water supply can be replenished within 3 days. If offsite power is not available, alternate means of obtaining demineralized water would be evaluated. However, river water will also be available as a makeup supply, as necessary.

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The committed effective dose equivalent to an offsite member of the public due to potential -

. release of particulate radioactivity from the walls of the SFP, in the unlikely event of an uncontrolled loss of pool level to 13 feet above the top of the fuel assemblies, is approximately 1.1 E-3 mrem. The analysis which supports this dose equivalent includes many conservative assumptions regarding the transport of radioactive material from the contamination on the walls of the SFP to the environment. For example, the analysis assumes a release of material to the environment through an unfiltered pathway via an open roof vent. Additionally, the analysis assumes that an individualis present at the site boundary -

for the entire 2 week period during this postulated release condition. Two weeks is chosen as a conservative maximum amount of time it would take to restore the system or component which is postulated to fail. This analysis clearly indicates that the offsite dose to members of the public from this postulated release is bounded by the design basis accidents described in the HNP Final Safety Analysis Report.

In the highly unlikely event that an uncontrolled decrease in fuel pool level was 4

experienced with an inability for any of the makeup sources to replenish it, an Unusual Event would be declared. As such, the NRC would be notified and communications established under the Defueled Emergency Plan process. All action taken from that point on would be in accordance with associated supporting plant procedures with the NRC cognizant of the situation. Consideration would be given to close the SFB doors and roof hatch if the fuel would no longer be adequately shielded by water. It is estimated that 10 feet of water above the fuel would be needed to provide adequate shielding to plant emergency personnel. The 10 foot water depth exceeds the minimum water depth of 8 feet for shielding one year old fuel as specified by ANS!/ANS-57.7-1988, "American National Standard Design Criteria for an Independent Spent Fuel Storage installation (Water Pool Type)".

Question 3 What are the dose consequences of cooling the SFP by ventilating the SFB through open doors and the roof hatch under normal conditions and postulated design basis events?

_ . _ . . . _ . _ _ _ . _ _ _ _ _ . _ _ _ . _ _ _ . _ _ . _ . . . ~ . _ _ _ ._

U. S. Nuctur R gulatory Commi:sion CY-98-129/ Attachment 1/Page 4 Response 3 There is no normal condition under which the SFP is cooled by ventilating the SFB through

. open doors and the roof hatch.-

l l In the highly unlikely event of only evaporative cooling of the pool, the calculated total dose at the site boundary from the evaporation of the pool water for a fourteen day event is approximately 0.253 mrem. The analysis supporting this dose assumes a 5 gallon per minute evaporation rate. Tritium is the only radionuclide considered and the evaporated l water is discharged through the building roof vent unfiltered.

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Dose from particulate radioactivity discussed in answer to question 2 is not expected since the makeup water quantities are minimal and there are multiple methods of makeup.

l However, if the particulate dose (1.1 E-3 mrem) was added to the evaporation dose (0.253 mrem), the total dose would be only slightly increased to approximately 0.2541 mrem for a fourteen day event.

- Question 4 l 'What is your procedure for monitoring and quantifying a release of radioactive materials via I pathways through the open doors and roof hatch?

r Response 4 CYAPCO personnel would obtain samples using procedure RPM 2.5-12, " Airborne Radioactivity Surveys." The samples would be analyzed using plant procedures CHDP 2.3-14, ." Operation of the Canberra Genie Gamma Spectroscopy System" and CHDP 2.4-6,

" Tritium Analysis", to determine the specific activity of the released vapor. Total released activity would be determined using CHDP 6.4-2," Gaseous Discharge Data Handling (Hand Calculation)" and CHDP 6.4-4, " Particulate Discharge Data Handling (Hand Calculation)." As decommissioning progresses, these procedures will evolve and may be revised to support changing plant needs.

Question 5 L What action will be taken in the event that high radiation levels are detected emanating from the SFB, while the SFB is being ventilated through open doors and the roof hatch?

Response 5 I In the event high radiation levels are detected emanating from the SFB, while the SFB is being ventilated through open doors and the roof hatch, and consistent with our response to l question 2, consideration would be given to close the SFB doors and roof hatch. The SFB

ventilation system effluent would be manually diverted to a filter if the ventilation system is

!- operable.

U. S. Nucl ar Rtgulatory Commission CY-98-129/ Attachment 1/Page 5 High levels of. radiation will not be released during this ventilation evolution since there is no mechanism for causing this type of release. Spent fuel will remain covered and cooled through established makeup sources and evaporative cooling. The only activity that could create a noticeable radiation release would be a fuel handling accident. However, AOP 3.2-59, " Loss of Spent Fuel Cocling", requires that work in progress in the spent fuel pool (including fuel handling) be stopped untilloss of cooling is resolved. Procedure NOP 2.15-3, " Spent Fuel Building Ventilation System Operation" contains a precaution that the SFB Exhaust Ventilation System shall be in service, with the exhaust fan suction aligned through the charcoal filter, when initiating fuel movement operations or crane movement above the spent fuel pool. In addition, technical specifications related to fuel handling require the fuel building ventilation to be in service. In any event, the accident analysis for the fuel handling accident in the SFB does not assume the ventilation system is operating during the event. Even without taking credit for ventilation, the off-site doses during this accident are well below the EPA Protective Action Guidelinesm as discussed in CYAPCO's letter dated May 30,1997(2)

Question 6 How will local noise levels be affected by the modified SFP cooling system?

Response 6 Noise levels have been monitored during testing for the new cooling system and were found to be well within Department of Environmental Protection (DEP) regulations. CYAPCO procured fans with reduced noise emission specifically to address this potential issue. Noise levels from the coolers located at the HNP are low because CYAPCO has only 4 fans which operate at a slow speed of 900 rpm. Operation at this slow speed reduces the noise.

CYAPCO has had an extensive sound level survey performed to verify that the noise level of the modified SFP cooling system will be in compliance with the DEP regulations. The contractor performing the survey not only confirmed that the noise levels were wel! within the DEP regulations, but stated that they believed the acoustic irnpact on the community would be negligible.

(1) EPA 400-R-92-001," Manual of Protective Actions Guides and Protective Actions for Nuclear Incidents," US EPA,1991.

(2) CYAPCO letter CY-97-047 from T. C. Feigenbaum to U. S. Nuclear Regulatory Commission, "Defueled Emergency Plan and Request For Exemption From 10CFR50.54(q) For Offstie Response," dated May 30,1997.