ML20217N977
| ML20217N977 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 03/02/1998 |
| From: | NORTHERN STATES POWER CO. |
| To: | |
| Shared Package | |
| ML20217N974 | List: |
| References | |
| NUDOCS 9803090365 | |
| Download: ML20217N977 (10) | |
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License Amendment Request Dated March 2,1998 Soent Fuel Pool Soecial Ventilation System Technical Soecifications EXHIBIT A:
Description of the Proposed Change, Reasons for Requesting the Change, Safety Evaluation, and Significant Hazards Determination PROPOSED CHANGE AND REASONS FOR CHANGE NSP proposes to delete the requirements relating to crane operations in paragraph 2 of Technical Specification 3.8.D, Spent Fuel Pool Special Ventilation System. Paragraph 2 applies to operation with one ventilation train inoperable, while paragraph 3 applies to operation with both ventilation trains inoperable.
This proposed change will eliminate confusior, with respect to the applicability of this specification. Literal compliance with this specification as written could preclude movement of any loads within the spent fuel pool enclosure. The original design and license did not intend for the imposition of such a restriction. The original TS 3.8.D specification' did not limit or in any manner apply to crane operations other than spent fuel handling operations.
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On March 17,1986, NSP submitted a license amendment request that resulted in the NRC
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issuance of License Amendments 91/84. This amendment revised TS 3.8.D to conform with i
the guidance of the current Standard Technical Specifications. The Standard Technical Specifications in effect at that time included provisions for limiting crane operations with loads over spent fuel when the spent fuel pool special ventilation system is inoperable.
Prairie Island Technical Specifications thus incorporated these restrictions. There were no plant conditions, issues or physical changes that necessitated these additional limitations.
Requiring the spent fuel pool special ventilation system to be operable at all times is not consistent with the system design bases. Tw spent fuel pool enclosure roof slot doors and large access doors must be open to move loads into the enclosure or through the enclosure into the auxiliary building central court area. Testing shows, that when these doors are open, the spent fuel pool special ventilation system can not maintain a negative pressure within the enclosure. Therefore, both spent fuel pool special ventilation system trains i
become inoperable whenever large loads are moved into or through the spent fuel pool enclosure.
This proposed change will establish plant load handling requirements consistent throughout the plant. Prairic Island has other cranes that are capable of handling heavy loads in the
' Prior to License Amendments 91/84, TS 3.8.D stated: "From and after the date that one train of the Spent Fuel Pool Special Ventilation System is made or found inoperable for any reason, fue' Wdling operations are permissible only during the succeeding seven days (unless such train is made operable) provided that the redundant train is verified to be operable daily."
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vicinity of safety related equipment or irradiated fuel. These other cranes are not covered by l
Technical Specifications but are controlled through plant procedures implementing commitments to NUREG-061-2. The current Technical Specifications for spent fuel pool special ventilation system operability are not required to ensure that crane operations in the fuel pool enclosure are safe. The use of plant procedures, that implement the commitments to NUREG-0612, and procedures, that govern the use of protective covers over the spent fuel pool, ensure that these operations can be safely performed.
The installation of a single-failure-proof crane and spent fuel pool protective covers have reduced the probability that a heavy load might drop and cause damage to irradiated fuel.
This probability is very small and does not merit technical specification limitations on heavy load handling in the spent fuel pool enclosure. In 1992 NSP installed a single-failure-proof auxiliary building crane that meet the design criteria of NUREG-0612 " Control of Heavy Loads at Nuclear Power Plants." Prairie Island has also upgraded the west hoist on the spent fuel pool bridge crane to meet the design criteria of NUREG-0612. Spent fuel pool protective covers
- are also installed to prevent dropped loads from falling into the spent fuel pool. As discussed in USAR Section 10.2.1, these covers will prevent loads, that weigh up to 24,800 pounds and drop no more than 6 inches, from falling into the spent fuel pool.
This proposed change will provide consistency between the paragraphs of TS 3.8.D. An application for amendment by Northern States Power Company, dated May 7,1997, as supplemented May 30, July 29, and September 12,1997, proposed changes to the 3
paragraphs of TS 3.8.D. The change granted for TS 3.8.D.3 removed limitations on crane operations inside the spent fuel pool enclosure when both trains of the Spent Fuel Pool Special Ventilation System are inoperable. The change granted for TS 3.8.D.1 specified that both trains of the Spent Fuel Pool Special Ventilation System were only required to be operable during the movement of irradiated fuel.d SAFETY EVALUATION The spent fuel pool enclosure is a Class I reinforced concrete building with 12 to 18 inch thick walls and roof. The enclosure is an integral part of the spent fuel pool structure, covers the new fuel pit and both spent fuel storage pools, and is completely contained within the auxiliary building. The enclosure contains a small pool, Spent Fuel Pool 121, centered under the slot doors and a large pool, Spent Fuel Pool 122, at its east end. The enclosure's At the time of the spent fuel pool rerack project the NRC approved the installation and use of spent fuel pool protective covers.
- The May 7,1997 proposed change to TS 3.8.D.2 was denied because the NRC staff concluded that the proposed change was not consistent with the current TS. This amendment request puts forth a different proposal, which addressas the issues identified in the September 15,1997 Safety Evaluation as the basis for the previous denial.
- Previously the Spent Fuel Pool Special Ventilation System was required to be operable at all times.
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roof slot doors and large access doors must be open to move loads either into the spent fuel pool enclosure or through the enclosure into the auxiliary building central court.
The spent fuel pool special ventilation system provides a negative pressure in the spent fuel pool enclosure after the detection of high radiation. This system contains two completely redundant trains. The Updated Safety Analysis Report (USAR) Figure 5.2-10 shows a simplified system flow diagram typical of each train.
The normal ventilation system for the spent fuel pool area contains radiation monitors in the exhaust ducts. A high radiation signal isolates the normal ventilation system and activates both redundant trains of the fuel pool special ventilation system. Both trains take suction from the spent fuel pool enclosure, while each exhaust into a different Unit's containment inservice purge system.
The proposed change to TS 3.8.D.2 will not modify the spent fuel pool special ventilation system operability conditions required during irradiated fuel movement. This change will only remove limitations on crane operations inside the spent fuel pool enclosure. The proposed change will maintain the plant in a safe condition because:
The spent fuel pool special ventilatian system will continue to mitigate the consequences of a dropped spent fuel assembly and attached fuel handling tool as postulated in the plant design basis fuel handling accident.
5 Prairie Island procedures that implement commitments to NUREG-0612 requirements for the control of heavy loads address all loads heavier than that assumed in the fuel handling accident analysis.
The consequences of a fuel handling accident established the design basis for the spent fuel pool special ventilation system. The analysis of this accident assumed that an irradiated fuel assembly with its attached tool drops directly onto another irradiated fuel assembly rupturing the cladding of all the fuel rods in one assembly.' These conservative assumptions produced bounding environmental consequences. The analysis of this accident also assumed that the redundant train of the spent fuel pool special ventilation system remained functional after a single disabling failure occurred in the other train. The accident analysis applied the assumptions provided in Safety Guide 25 and calculated site boundary doses within the limits permitted in 10CFR100.
8 Procedures also allow for the handling of some heavy loads in conjunction with the use of spent fuel pool protective covers.
Analyses of this impact showed that the resulting buckling loads on the fuel rods would be below the critical buckling loads and the cladding stresses would be below the yield stress. No cladding is expected to rupture as a result of the impact.
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The proposed change to TS 3.8.D.2 will continue to impose a limitation on the movement of irradiated fuel when one spent fuel pool special ventilation system trains is not operable.
Such a limitation is consistent with the design basis of the plant and with the requirements of 10CFR50.36.
7 Pralrie Island procedures provide two NRC approved means of handling heavy loads within the spent fuel enclosure; single-failure-proof cranes and spent fuel pool protective covers.
The evaluation criteria of NUREG-0612 Section 5.1 eliminate any requirement to analyze the effects of a dropped heavy load, when such load is handled in accordance with the procedure requirements, rigging and single-failure-proof crane criteria in NUREG-0612.
Prairie Island has implemented tha heavy load handling requirements of NUREG-0612, so the consequences of a heavy load drop are removed from consideration. Therefore, the need for operability of the spent fuel pool special ventilation system to mitigate the consequences of a heavy load drop does not exist.
In support of Prairie Island's spent fuel pool reracking modifications, NSP obtained NRC approval to use protective covers over the spent fuel pools containing irradiated fuel. Plant operating procedures implement NRC commitments governing the installation and use of these covers. Handling heavy loads in accordance with these prescribed procedures prevents dropped heavy loads from falling into the spent fuel pool. Since this removes the initiating event for a radiological release, there is no need for the spent fuel pool special ventilation system to be operable.
The proposed change to TS 3.8.D.2 will remove the crane load handling limitation from consideration in conjunction with spent fuel pool special ventilation system operability. The removal of such a limitation is consistent with the design basis of the plant and with the requirements of 10CFR50.36. The proposed change does not adversely affect the health and safety of the public.
DETERMINATION OF SIGNIFICANT HAZARDS CONSIDERATIONS
- 1. The proposed amendment will not involve a significant increase in the probability or f
consequences of an accident orevioustv evaluated.
The proposed change does not affect any system that is a contributor to initiating events for previously evaluated anticipated operational occurrences and design basis accidents.
l Therefore, the proposed change will not increase the probability of any previously evaluated accident.
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' Use of these two means of handling heavy loads within the spent fuel enclosure are now required as a License Condition imposed upon Amendment 130 to DPR-42 and Amendment 122 to DPR-60.
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The, proposed change does not impact the required availability of the.,. ant fuel pool special ventilation system during spent fuel handling operations to mitigate the consequences of a fuel handling accident.
The proposed change does impact the required availability of the spent fuel pool special ventilation system during heavy load handling operations. However, this system is not required to mitigate the consequences of a heavy load dropping onto a spent fuel assembly. Such a requirement is not applicable at Prairie Island, because the heavy loads in the spent fuel pool enclosure are either handled with single-failure-proof cranes, rigging and plant procedures implementing Prairie Island commitments to NUREG-0612, or handled with spent fuel pool protective covers in place as described in the Prairie Island USAR. The use of a single-failure-proof crane with rigging and procedures that implement the requirements of NUREG-0612 assures that the potential for a heavy load drop is extremely small and therefore consideration of the effects of heavy load drops is 8
not required. Spent fuel pool covers prevent dropped loads from falling into the spent fuel pool and therefore consideration of the effects of heavy load drops is also not required. These actions taken to reduce the accident initiator probabilities to insignificant magnitudes negate any theoretically small increase in the consequences of a postulated heavy load drop accident resulting from the removal of a requirement to have one train of the spent fuel pool special ventilation system operable during crane operations. It is concluded in summary that the proposed change does not involve a significant increase l
In the consequences of any accident previously evaluated.
- 2. The proposed amendment will not create the possibility of a new or different kind of accident from any accident oreviously analyzed.
The proposed change does impact the required availability of the spent fuel pool special ventilation system during heavy load handling operations. Load drop events over spent fuel are well understood and have been thoroughly evaluated. The proposed change will not create any new accident scenarios or create the possibility of a new or different kind of accident from any accident previously analyzed.
- 3. The orocosed amendment will not involve a significant reduction in the margin of safety.
The proposed change does not impact the required availability of the spent fuel pool special ventilation system during spent fuel handling operations to mitigate the consequences of a fuel handling accident as described in the USAR. As a result the safety margin inherent in the 10CFR100 dose limits is not reduced.
The proposed change does impact the required availability of the spent fuel pool special j
ventilation system during heavy load handling operations. However, this system is not l
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- The covers do have a limit on the weight load they are analyzed to withstand.
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required to mitigate the consequences of a heavy load dropping onto a spent fuel assembly becauce the potential for a load drop is extremely small. Provision of single-failure-proof equipment and compliance with the other requirements of NUREG-0612 provides a defense-in-depth approach to assure the safe handling of heavy loads which would otherwise be demonstrated to be safe by the deterministic analysis of the radiological effects of dropped heavy loads.
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Considering the above evaluation and pursuant to 10CFR50.91, Northern States Power Company has determined that operation of the Prairie Island Nuclear Generating Plant in accordance with the proposed license amendment request does not involve a significant hazards consideration as defined by Nuclear Regulatory Commission regulations in 10CFR50.92.
ENVIRONMENTAL ASSESSMENT j
Northern States Power Company has evaluated the proposed change and determined that:
- 1. The change does not involve a significant hazards consideration,
- 2. The change does not involve a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, and
- 3. The change does not involve a significant increase in individual or cumulative
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occupational radiation exposure.
Accordingly, the proposed change meets the eligibility criterion for categorical exclusion set forth in 10CFR51.22(c)(9). Therefore, pursuant to 10CFR51.22(b), an environmental assessment of the proposed changes is not required.
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EXHIBIT B License Amendment Request Dated March 2,1998 Spent Fuel Pool Special Ventilation System Technical Specifications l
Appendix A, Technical Specification Pages Marked Up Page (shaded material to be added, strikethrough material to be removed) i l
i TS.3.8-4 i
4 TS.3.8-4 REY 220 9/15/97 3.8.C.
Small Spent Fuel Pool Restrictions No more than 45 recently discharged assemblies shall be located in the small pool (pool No. 1).
D.
Spent Fuel Pool Special Ventilation System 1.
Both trains of the Spent Fuel Pool Special Ventilation System shall be OPERABLE during movement of irradiated fuel assemblies in the spent fuel pool enclosure (except as specified in 3.8.D.2 and 3.8.D.3 below).
2.
With one train of the Spent Fuel Pool Special Ventilation System inoperable, fu:1 h: dling ep:::ti n: :nd ::::: :p:::ticn: ith 1:n ':
zer p::t fu:1 (I nci d:%i?tisH14sisiQbRisissdiiffid$is%
pas M ipply the spent fuel ho65~eh$1bsuhe i$ l 5f$ pertNIs$1ble during the following 7 days, provided the redundant train is demonstrated OPERABLE prior to proceeding with th::: Operation:
thE!inovemsnEis.
3.
With both trains of the Spent Fuel Pool Special Ventilation System inoperable, suspend movement of irradiated fuel assemblies in the spent fuel pool enclosure.
4.
The provisions of specification 3.0.C are not applicable.
E.
Suent Fuel Pool Storace 1.
Fuel Assembly Storage a.
The combination of initial enrichment, burnup and decay time of each spent fuel assembly stored in the spent fuel pool 1 shall be within the unrestricted range of Figures TS.3.8-1 or TS.3.8-2, as applicable, or fuel assemblies shall be stored in accordance with Specification 5.6.A.1.e.
b.
If the requirements of 3.8.E.1.a are not met, immediately l
initiate action to move any noncomplying fuel assembly to an acceptable location, c.
The provisions of Specification 3.0.C are not applicable.
2.
Spent Fuel Pool Baron Concentration a.
The spent fuel pool boron concentration shall be = 1,800 ppm when fuel assemblies are stored in the spent fuel pool.
b.
If the spent fuel pool boron concentration is not within limit, then immediately:
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- 1. Suspend movement of fuel assemblies in the spent fuel pool, and 2.
Initiate action to restore spent fuel pool boron concentration to within limit.
c.
The provirions of Specification 3.0.C are not applicable.
1 EXHIBIT C License Amendment Request Dated March 2,1998 Spent Fuel Pool Special Ventilation System Technical Specifications Appendix A, Technical Specification Pages Revised Page TS.3.8-4 i
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9 TS.3.8-4 C
3.8.C.
Small Spent Fuel Pool Restrictions No more than 45 recently discharged assemblies shall be located in the small pool (pool No. 1).
D.
Spent Fuel Pool Special Ventilation System 1.
Both trains of the Spent Fuel Pool Special Ventilation System shall be OPERABLE during movement of irradiated fuel assemblies in the spent fuel pool enclosure (except as specified in 3.8.D 2 and 3.8.D.3 below).
2.
With one train of the Spent Fuel Pool Special Ventilation System I
inoperable, the movement of irradiated fuel assemblies in the spent fuel enclosure is permissible during the following 7 days, provided the redundant train is demonstrated OPERABLE prior to proceeding with the movements.
3.
With both trains of the Spent Fuel Pool Special Ventilation System inoperable, suspend movement of irradiated fuel assemblies in the spent fuel pool enclosure.
4.
The provisions of specification 3.0.C are not applicable.
E.
Scent Fuel Pool Storace 1.
Fuel Assembly Storage n.
The combination of initial enrichment, burnup and decay time of each spent fuel assembly stored in the spent fuel pool shall be within the unrestricted range of Figures TS.3.8-1 or TS.3.8-2, as applicable, or fuel assemblies shall be stored in accordance with Specification 5.6.A.1.e.
j b.
If the requirements of 3.8.E.1.a are not met, immediately j
initiate action to move any noncomplying fuel assembly to an i
acceptable location.
c.
The provisions of Specification 3.0.C are not applicable.
2.
Spent Fuel Pool Boron Concentration i
a.
The spent fuel pool boron concentration shall be a 1,800 ppm when fuel assemblies are stored in the spent fuel pool.
j b.
If the spent fuel pool boron concentration is not within limit, then immediately:
- 1. Suspend movement of fuel assemblies in the spent fuel pool, and 2.
Initiate action to restore spent fuel pool boron concentration to within limit.
The provisions of Specification 3.0.C are not applicable.
c.