Represents the number of common stock shares subject aggregate of sponsor surrendered.

No definition available.

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of shares of the company that are subject to forfeiture represented as a percentage of issued and outstanding stock as a result of partial exercise of over-allotment option.

+ References

No definition available.

+ Details

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Namespace Prefix:	svsvu_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the maximum number of common stock shares subject to forfeiture.

+ References

No definition available.

+ Details

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Namespace Prefix:	svsvu_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of shares of the company that were no longer subject to forfeiture.

+ References

No definition available.

+ Details

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Namespace Prefix:	svsvu_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The period of time after completion of a business combination during which the shares or warrant may not be transferred.

+ References

No definition available.

+ Details

Name:	svsvu_RestrictionsOnTransferPeriodOfTimeAfterBusinessCombinationCompletion
Namespace Prefix:	svsvu_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares transferred to others during the period.

+ References

No definition available.

+ Details

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Namespace Prefix:	svsvu_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The period of time after a business combination which must elapse before consideration of the share price condition for transfer of shares.

+ References

No definition available.

+ Details

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Namespace Prefix:	svsvu_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The threshold period for not to transfer, assign or sell any of the shares or warrants, after the completion of the initial business combination.

+ References

No definition available.

+ Details

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Namespace Prefix:	svsvu_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold trading days to transfer assign or sell any shares or warrants after completion of initial business combination

+ References

No definition available.

+ Details

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Namespace Prefix:	svsvu_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The share price threshold that must be achieved in order to waive the restriction on transfer of shares during a restricted period after a business combination.

+ References

No definition available.

+ Details

Name:	svsvu_TransferAssignOrSellAnySharesOrWarrantsAfterCompletionOfInitialBusinessCombinationStockPriceTrigger
Namespace Prefix:	svsvu_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockSharesOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=svsvu_SpringValleyAcquisitionCorpMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	srt_TitleOfIndividualAxis=srt_DirectorMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassBMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=us-gaap_OverAllotmentOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
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Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=svsvu_SponsorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_BeneficialOwnerMember
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Related Party Transactions - Founder Shares (Details) - SPRING VALLEY ACQUISITION CORP - USD ($)				1 Months Ended	3 Months Ended
	Oct. 22, 2020	Sep. 30, 2020	Aug. 21, 2020	Sep. 30, 2020	Mar. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Aug. 31, 2020	Aug. 22, 2020
Related Party Transaction [Line Items]
Common stock, shares subject to forfeiture, as a percent of issued and outstanding shares (as a percent)			20.00%		20.00%
Shares subject to forfeiture					750,000
Stock price trigger to transfer, assign or sell any shares or warrants of the company, after the completion of the initial business combination (in dollars per share)			$ 12.00		$ 12.00
Threshold trading days for transfer, assign or sale of shares or warrants, after the completion of the initial business combination					20 days
Restrictions on transfer period of time after business combination completion					1 year
Threshold period after the business combination in which the 20 trading days within any 30 trading day period commences			30 days		30 days
Threshold period for not to transfer, assign or sell any of their shares or warrants after the completion of the initial business combination			150 days		150 days
Each of the Company's directors
Related Party Transaction [Line Items]
Number of shares transferred				120,000
Class B ordinary share
Related Party Transaction [Line Items]
Common shares, shares outstanding		5,750,000		5,750,000	5,750,000	5,750,000	5,750,000	5,750,000
Over-allotment option \| Class B ordinary share
Related Party Transaction [Line Items]
Shares subject to forfeiture			750,000
Shares no longer subject to forfeiture			750,000		750,000
Founder Shares \| Class B ordinary share
Related Party Transaction [Line Items]
Restrictions on transfer period of time after business combination completion			1 year
Sponsor \| Class B ordinary share
Related Party Transaction [Line Items]
Consideration received			$ 25,000
Shares issued			7,187,500
Number of shares surrender	1,437,500
Common shares, shares outstanding									5,750,000
Sponsor \| Founder Shares \| Class B ordinary share
Related Party Transaction [Line Items]
Threshold trading days for transfer, assign or sale of shares or warrants, after the completion of the initial business combination			20 days
Beneficial Owner \| Each of the Company's directors
Related Party Transaction [Line Items]
Number of shares transferred		40,000		40,000
Beneficial Owner \| Class B ordinary share
Related Party Transaction [Line Items]
Consideration received	$ 0		$ 25,000
Shares issued			7,187,500
Number of shares surrender	1,437,500
Common shares, shares outstanding	5,750,000